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European workshopon epitaxialgraphene and 2D materials

June 15th-19th, 2014Primošten, Croatian Adriatic coast

Booklet ofabstracts

European workshop on epitaxial graphene and 2D materials

15-19 June, 2014 Primošten, Croatia

Booklet of abstracts

Organizer: Institut za fiziku, Zagreb, Croatia

Co-organizer: Institut Néel - CNRS/UJF, Grenoble, France

Scientific Committee: Johann Coraux Institut Néel, Grenoble Yuriy Dedkov Technische Universität Dresden and SPECS GmbH Roman Fasel Empa, Dübendorf Thomas Greber Physik-Institut, Universität Zürich Rosana Larciprete CNR-ISC, Roma Silvano Lizzit Sincrotrone Trieste, Trieste Thomas Michely Universität zu Köln, Cologne Alexei Preobrajenski MAX-Laboratory, Lund Raoul van Gastel University of Twente, Enschede Local organizing Committee: Hrvoje Buljan Prirodoslovno matematički fakultet, University of Zagreb Davor Čapeta Prirodoslovno matematički fakultet, University of Zagreb Ida Delač Marion Institut za fiziku, Zagreb Marko Kralj Institut za fiziku, Zagreb Predrag Lazić Institut Ruđer Bošković, Zagreb Marin Petrović Institut za fiziku, Zagreb Iva Šrut Rakić Institut za fiziku, Zagreb Tomislav Vuletić Institut za fiziku, Zagreb Sponsored by: Oxford Instruments | Centre National de la Recherche Scientifique | Ministry of Science, Education and Sports of the Republic of Croatia | Centre de Compétences en Nanosciences Grenoble | Nanosciences Foundation Grenoble | Mesa+ Institute | SPECS Surface Nano Analysis | American Elements (best contributed talk prize) | Mantis deposition | Nature Communications | Nevac (best poster prize) Publisher: Institut za fiziku, Zagreb, Croatia Year: 2014 Editors: Marko Kralj, Johann Coraux, Hrvoje Buljan ISBN 978-953-7666-10-1

Sunday 15th Monday 16th Tuesday 17th Wednesday 18th Thursdaty 19th9:00 – 9:20 J. Osterwalder B. LeRoy T. Wehling9:20 – 9:40 J. Knudsen chair - E. Molinari chair - M. Kralj chair - J. Knudsen

9:40 – 10:00 chair - P. Liljeroth C. Sanchez-Sanchez N. Atodiresei F. Calleja10:00 – 10:20 V. Vonk P. Jelinek H. González-Herrero L. Giovanelli10:20 – 10:40 A. J. Martínez-Galera J. Landers F. Huttmann A. Garcia-Lekue10:40 – 11:00 A. Shikin O. Ourdjini J. A. Martín-Gago A. Varykhalov11:00 – 11:30 Coffee break Coffee break Coffee break Coffee break11:30 – 11:50 I. Gierz A. Kis E. Molinari A. Fedorov11:50 – 12:10 chair - T. Wehling chair - B. LeRoy chair - I. Gierz M. M. Ugeda12:10 – 12:30 S. Ulstrup M. Farmanbar H. Buljan chair - S. Lizzit

12:30 – 12:50 D. Menzel P. Lacovig M. Svec Concluding remarks12:50 – 14:00 Lunch Lunch Lunch Lunch14:00 – 14:20 Free time Free time P. Liljeroth14:20 – 14:40 chair - A. Kis

14:40 – 15:00 R. Fasel15:00 – 15:20 M. Kralj Y. Liu W. Jolie15:20 – 15:40 chair - R. Larciprete chair - R. Fasel K. Simonov15:40 – 16:00 Arrival M. Sicot J. A. Rodriguez-Manzo M. Fonin16:00 – 16:20 E. Voloshina J. Wofford16:20 – 16:40 Coffee break Coffee break Excursion16:40 – 17:00 C. Busse L. Magaud17:00 – 17:20 S. Vlaic C. Herbig17:20 – 17:40 D. Pacilè17:40 – 18:00 Opening P. Lazić Roundtable18:00 – 18:20 P. Sutter18:20 – 18:40 chair - T. Michely Free time Free time18:40 – 19:00 Welocme drink19:00 – 20:00 Diner Diner Diner20:00 – 22:00 Poster Session 1 Poster Session 2 Gala

Contents

1 Invited talks 3

Sutter- Controlled Synthesis of 2D Alloys and Heterostructures . . . . . . . . . . . . . . . 4Knudsen- Heterogeneous catalysis on transition metals atop and below graphene . . . . . 5Gierz- Non-equilibrium Dirac carrier dynamics in graphene investigated by time- and

angle-resolved photoemission spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . 6Kralj- Exploring and exploiting intercalation of epitaxial graphene . . . . . . . . . . . . . 7Osterwalder- Boron nitride and graphene on single-crystal substrates: CVD growth of

heterostructures and �lm transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Ki²- Single-Layer MoS2 � 2D Devices, Circuits and Heterostructures . . . . . . . . . . . . 9Liu- Controllable synthesis of graphene and its electronic properties . . . . . . . . . . . . 10LeRoy- Imaging and Spectroscopy of Graphene Heterostructures . . . . . . . . . . . . . . 11Molinari- Illuminating graphene nanoribbons . . . . . . . . . . . . . . . . . . . . . . . . . 12Liljeroth- Scanning probe experiments on atomically well-de�ned graphene nanostructures 13Wehling- Adsorbates and many body e�ects in two dimensional materials . . . . . . . . . 14Ugeda- Observation of giant bandgap renormalization and excitonic e�ects in a monolayer

transition metal dichalcogenide semiconductor . . . . . . . . . . . . . . . . . . . . . 15

2 Contributed talks 16

Vonk- Atomic Structure of Graphene-Support Interfaces . . . . . . . . . . . . . . . . . . . 17Martinez Galera- Tailoring Graphene with nanometer accuracy . . . . . . . . . . . . . . . 18Shikin- Spin current formation at the Graphene/Pt interface for magnetization manipu-

lation in deposited magnetic nanodots . . . . . . . . . . . . . . . . . . . . . . . . . . 19Ulstrup- Direct View on the Ultrafast Carrier Dynamics of Massless and Massive Dirac

Fermions in Mono- and Bilayer Graphene . . . . . . . . . . . . . . . . . . . . . . . . 20Menzel- Ultrafast charge transfer to graphene monolayers: Substrate coupling, local den-

sity of states, �nal state dimensionality, and two-step processes. . . . . . . . . . . . . 21Sicot- Tuning Electronic Properties of Epitaxial Graphene by Copper Intercalation . . . . 22Voloshina- Crystallographic and electronic structure of graphene on the pseudomorphic

Cu/Ir(111) substrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Busse- H2O on graphene - cluster formation caused by hydrophobicity . . . . . . . . . . . 24Vlaic- Elementary processes and factors in�uencing the intercalation between graphene

and iridium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Pacilè- Novel mismatched graphene-ferromagnetic interfaces . . . . . . . . . . . . . . . . . 26Lazi¢- Graphene spintronics: Spin injection and proximity e�ects from �rst principles . . 27Sanchez-Sanchez- On-Surface Synthesis of BN/Graphene Hybrid Structures . . . . . . . . 28Jelinek- Silicene vs. ordered 2D silicide: the atomic and electronic structure of the Si-

(√

19×√

19)R23.4°/Pt(111) surface reconstruction . . . . . . . . . . . . . . . . . . . 29Landers- Convergent Fabrication of a Perforated Graphene Network with Air-Stability . . 30Ourdjini- Role of the surface structure in the polymerization of molecular precursor in

graphene nanoribbons: DBBA on the reconstructed 1x2-Au(110) surface . . . . . . . 31Farmanbar- Tuning the Schottky barrier heights at MoS2|metal contacts: a �rst-principles

study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Lacovig- Epitaxial Growth of Single-domain Hexagonal Boron Nitride . . . . . . . . . . . 33Rodriguez-Manzo- Toward Sensitive Graphene Nanoribbon�Nanopore Devices by Prevent-

ing Electron Beam-Induced Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

1

CONTENTS 2

Wo�ord- Graphene growth by molecular beam epitaxy using high-quality, epitaxial nickel�lms on MgO(111) as substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Magaud- Cleaning graphene: what can be learned from quantum/classical molecular dy-namics simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Herbig- Ion Irradiation of Metal-Supported Graphene: Exploring the Role of the Substrate 37Atodiresei- Graphene-surface interfaces from �rst-principles simulations . . . . . . . . . . 38González-Herrero- Graphene tunable electronic tunneling transparency: A unique tool to

measure the local coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Huttmann- Tuning the van der Waals Interaction of Graphene with Molecules by Doping 40Martin-Gago- Sublattice localized electronic states in atomically resolved Graphene-Pt(111)

edge-boundaries and its relation with the Moiré patterns . . . . . . . . . . . . . . . . 41Buljan- Uncovering Damping Mechanisms of Plasmons in Graphene . . . . . . . . . . . . 42Svec- High-quality single atom N-doping of graphene/SiC(0001) by ion implantation . . . 43Fasel- Electronic and optical properties of atomically precise graphene nanoribbons . . . . 44Jolie- Con�nement of Dirac Electrons on Graphene Quantum Dots . . . . . . . . . . . . . 46Simonov- Formation and growth dynamics of graphene nanoribbons: in�uence of substrate

reactivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Fonin- Probing the Electronic Properties of Epitaxial Graphene Flakes on Au(111) . . . . 48Calleja- Adding magnetic functionalities to epitaxial graphene by self assembly on or below

its surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Giovanelli- Magnetic Coupling and Single-Ion Anisotropy in Surface-Supported Mn-based

Metal-Organic Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Garcia-Lekue- Electron scattering and spin polarization at graphene edges on Ni(111) . . 52Varykhalov- Behavior of Dirac and massive electrons in superlattices of bare and quasifree-

standing graphene on Fe(110) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Fedorov- Observation of a universal donor-dependent vibrational mode in graphene: key

to superconductivity in graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3 Posters 55

Bignardi- Dual character of excited charge carriers in graphene on Ni(111) . . . . . . . . . 56Dombrowski- Dirac Electron Scattering In Caesium Intercalated Graphene . . . . . . . . . 57Endlich- Investigations into the dynamical properties of graphene on Ir(111) . . . . . . . . 58Lisi- Exploring the intercalation process of Cobalt under Graphene . . . . . . . . . . . . . 59Sipahi- Spin polarization of Co(0001)/graphene junctions from �rst principles . . . . . . . 60Varykhalov- Highly spin-polarized Dirac fermions at the graphene-Co interface . . . . . . 61Themlin- Surface umklapp in ARPES : Seeing through 2D overlayers . . . . . . . . . . . . 62Usachov- Dopant-controlled and substrate-dependent electronic properties of graphene . . 63Lazi¢- Graphene on Ir(111), adsorption and intercalation of Cs and Eu atoms . . . . . . . 64Lin- Controllable nitrogen doping of graphene via a versatile plasma-based technique . . . 65Magaud- Graphene and Moirés . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66�rut Raki¢- E�ects of uniaxial structural modulation on graphene's electronic structure . 67Svec- Fulerenes on Graphene Held Together by van der Waals Interaction . . . . . . . . . 68Acun- The instability of silicene on Ag(111) . . . . . . . . . . . . . . . . . . . . . . . . . . 69Farwick zum Hagen- Graphene Flakes embedding in hexagonal Boron Nitride . . . . . . . 70Uder- Cold Tip SPM - A new generation of variable temperature SPM for spectroscopy . 71Svec- Butter�y Hydrogen Dimers on G/SiC(0001). . . . . . . . . . . . . . . . . . . . . . . 72�apeta- Contacting graphene with liquid metals . . . . . . . . . . . . . . . . . . . . . . . 73Shinde- Electronic properties of edge modi�ed zigzag graphene nanoribbons . . . . . . . . 74Järvinen- Self-assembly and orbital imaging of metal phthalocyanines on graphene model

surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Petrovi¢- Wrinkles of graphene on Ir(111) - internal structure and long-range ordering . . 77Schröder- Etching of Graphene on Ir(111) with Molecular Oxygen . . . . . . . . . . . . . 78Martin Recio- Unusual Moire Patterns on Graphene on Rh(111) . . . . . . . . . . . . . . 79Papagno- Hybridization of graphene and a Ag monolayer supported on Re(0001) . . . . . 80

Index 81

Chapter 1

Invited talks

3

CHAPTER 1. INVITED TALKS 4

Controlled Synthesis of 2D Alloys and Heterostructures

Invited talk

Sutter, Peter

Contact: [email protected]

Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973(USA)

The ability to tailor materials properties by alloying or in heterostructures with controlledinterfaces has become one of the foundations of modern materials science. Two-dimensional (2D)crystals, such as graphene, hexagonal boron nitride, and a family of metal dichalcogenides representa new class of systems that o�er unique opportunities for materials integration. Mixed phases(`alloys') and heterostructures of di�erent 2D crystals promise tunable electronic structure andchemical reactivity and raise fundamental questions on interface formation, alloying, strain, andpolarity in a new context at reduced dimensionality. I will discuss recent advances in developing thesynthesis and processing of alloys and heterostructures of 2D materials on metal substrates, derivedprimarily from real-time observations by surface electron microscopy, complemented by scanningprobe microscopy and in-situ spectroscopy. Focusing on the integration of graphene with hexagonalboron nitride, I will highlight progress toward meeting key challenges in the controlled formation of2D alloys and heterostructures: the continuous blending of immiscible 2D systems; precise thicknessand stacking control in superlattices; and the creation of monolayer heterostructures with nanoscalecharacteristic dimensions and atomically sharp line interfaces. Our combined �ndings establish apowerful toolset for the scalable fabrication of 2D alloys and heterostructures for research andapplications.


Heterogeneous catalysis on transition metals atop and belowgraphene

Invited talk

Knudsen, Jan (1); Grånäs, Elin (2); Gerber, Timm (3); Andersen, Mie (4); Arman, MohammadA. (2); Schulte, Karina (6); Stratmann, Patrick (3), Schnadt, Joachim (2); Feibelman, Peter J. (5);Hammer, Bjørk (4); Andersen, Jesper N. (1); Michely, Thomas (3)


(1) Division of Synchrotron Radiation Research and the MAX IV Laboratory, Lund University(2) Division of Synchrotron Radiation Research, Lund University(3) Physikalisches Institut, Universität zu Köln(4) Interdisciplinary Nanoscience Center and Department of Physics and Astronomy, Aarhus

University(5) Sandia National Laboratories, Albuquerque, United States(6) MAX IV Laboratory, Lund University

Graphene (Gr) supported arrays of nanoparticles with extremely narrow size distribution andgraphene covered transition metal surfaces are attractive model systems for systematic studies ofgas adsorption and reactivity on nanoparticles and for studying con�nement e�ects, respectively.First, I will discuss how Pt-clusters binds to Gr grown on Ir(111) and how this is visible in X-rayPhotoelectron spectroscopy spectra (XPS). Subsequently, I will discuss molecular adsorption on thePt-clusters. Focusing on CO adsorption I will show that small clusters (< 10 atoms) sinter throughSmoluchowski ripening while larger clusters remain stable with respect to sintering [1,2]. Followingadsorption on clusters atop Gr, I will discuss con�nement e�ects and show that it is possible toperform a catalytic reaction under Gr and discuss how Gr a�ects the chemistry. I will presentan extensive atomic scale picture of intercalated H2-, O2- and CO-structures sequentially formedunder Ir(111) supported Gr when gas is dosed in situ at UHV and ambient conditions based onXPS, Scanning Tunneling Microscopy, and Density Functional Theory [3, 4]. Finally, I will comparethe water - and CO2 formation reaction on the Gr-Ir(111) system. Without Gr either H2 or COreact with chemisorbed oxygen and form H2O or CO2, which desorb directly. With Gr present theCO2 formation reaction is una�ected while the water formation reaction is signi�cantly changedleading to trapped H2O and OH under Gr.

References

[1] Knudsen et al., Phys. Rev. B, 85, 035407 (2012)[2] Gerber et al., ACS nano, 7, 2020 (2013)[3] Grånäs et al., ACS nano, 11, 9951 (2012)[4] Grånäs et al., Journal of Physcial Chemistry C, 117, 16438 (2013)


Non-equilibrium Dirac carrier dynamics in graphene investi-gated by time- and angle-resolved photoemission spectroscopy

Invited talk

Gierz, Isabella (1); Mitrano, Matteo (1); Bromberger, Hubertus (1); Petersen, Jesse C. (2);Cacho, Cephise (3); Chapman, Richard (3); Springate, Emma (3); Stöhr, Alexander (4); Köhler,Axel (4); Link, Stefan (4); Starke, Ulrich (4); Cavalleri, Andrea (1)


(1) Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany(2) Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, United King-

dom(3) Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell, United Kingdom(4) Max Planck Institute for Solid State Research, Stuttgart, Germany

The optical properties of graphene are made unique by the linear band structure and the vanish-ing density of states at the Dirac point. Even in the absence of a band gap, a relaxation bottleneckat the Dirac point allows for saturable absorption [1] and even population inversion with potentialapplications for lasing at arbitrarily long wavelengths [2]. Furthermore, e�cient carrier multipli-cation by impact ionization has been discussed in the context of light harvesting applications [3].We have excited epitaxial graphene mono- and bilayers at various wavelengths from the visible tothe mid-infrared range and investigated the response of the electronic structure with time- andangle-resolved photoemission spectroscopy.

We �nd that for excitation at 1.3µm direct interband transitions occur, resulting in distinctchemical potentials for valence and conduction band at earliest times. However, there are no indi-cations for carrier multiplication [4]. For excitation below 2µe, where µe is the chemical potential,free carrier absorption results in a hot electronic distribution [4]. Finally, when tuning the pumpwavelength resonant to the infrared active in-plane lattice vibration in bilayer graphene at 6.3µm,we observe a decrease of the fast relaxation time usually associated with electron � optical phononcoupling, demonstrating a control of the electronic properties of graphene on the femtosecond timescale using tailored light pulses.

References

[1] Q. Bao et al., Adv. Funct. Mater. 19, 3077 (2009).[2] T. Li et al., Phys. Rev. Lett. 108, 167401 (2012).[3] T. Winzer et al., Nano Lett.10, 4839 (2010).[4] I. Gierz et al., Nat. Mater. 12, 1119 (2013).


Exploring and exploiting intercalation of epitaxial graphene

Invited talk

Kralj, Marko


Institute of Physics, Bijeni£ka cesta 46, 10000 Zagreb

The magic of the electronic, mechanical and optical properties of graphene can be exploited inapplications. In particular, with the zero density of states at the Fermi energy and linear bandsaround it, it is easy to change the Fermi surface of graphene by the adsorption either "on top" or"underneath" graphene where typically charge transfer processes take place. In epitaxial graphenesystems deposition of atoms and molecules often leads to intercalation where species are pushedbetween graphene and its support. Besides the common e�ect of the charge donation, the interca-lation can a�ect the binding interaction and more subtle properties of graphene, e.g. magnetism.In fact, properties of many layered materials, including copper- and iron-based superconductors,dichalcogenides, topological insulators, graphite and epitaxial graphene, can be manipulated byintercalation. Intercalation involves complex di�usion processes along and across the layers butthe microscopic mechanisms and dynamics of these processes are not well understood. To resolvethis issue in great detail, we study the intercalation and entrapment of alkali atoms under epitaxialgraphene on Ir(111) in real and reciprocal space by means of LEEM, STM, ARPES, LEED andvdW-DFT, and �nd that the intercalation is adjusted by the van der Waals interaction, with thedynamics governed by defects anchored to graphene wrinkles [1]. Moreover, the high uniformity andquality of strongly n-doped graphene allows us to reveal the quasiparticle properties in graphene,some of which are still debated.

References

[1] M. Petrovi¢, et al., Nature Commun. 4, 2772 (2013).


Boron nitride and graphene on single-crystal substrates: CVDgrowth of heterostructures and �lm transfer

Invited talk

Osterwalder, Juerg (1); Roth, Silvan (1); Cun, Huanyao (1); Hemmi, Adrian (1); Bernard, Carlo(1); Matsui, Fumihiko (2); Kaelin, Thomas (1); Greber, Thomas (1)


(1) Department of Physics, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzer-land

(2) Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST),Ikoma, Nara 630-0192, Japan.

Chemical vapor deposition (CVD) performed under ultra-high vacuum conditions on single-crystal metal surfaces enables the growth of large-area and high-quality graphene and hexagonalboron nitride (h-BN) single layers. Aiming towards a platform technology for graphene-basedelectronic devices, our group follows two di�erent approaches.

On the one hand, we explore the CVD parameter space of precursor pressure and temperaturein order to go beyond the self-saturating single-layer growth, or to grow heterostacks of the twomaterials. On Cu(111) a graphene layer could be grown on a pre-deposited single layer of h-BNwhen using 3-pentanone as a precursor at a pressure of 2.2 mbar [1]. On Rh(111) the same procedureleads to an incorporation of carbon into the metal surface layers, while a graphene layer is formedonly upon a second high-pressure dose [2]. In both cases the heterostructures show clear structuraland spectroscopic signatures of graphene on h-BN but are far from defect-free.

The second approach is based entirely on single-layer growth that leads to much lower defectdensities, and subsequent transfer of the layers onto a di�erent substrate. First results on h-BN�lms transferred onto oxidized silicon wafers will be presented.

References

[1] S. Roth et al., Nano Lett. 13, 2668 (2013).[2] S. Roth, PhD Thesis, Department of Physics, University of Zurich (2013).


Single-Layer MoS2 � 2D Devices, Circuits and Heterostructures

Invited talk

Ki², Andras

Contact: andras.kis@ep�.ch

Electrical Engineering, EPFL, Lausanne, Switzerland

After quantum dots, nanotubes and nanowires, two-dimensional materials in the shape of sheetswith atomic-scale thickness represent the newest addition to the family of nanoscale materials.Monolayer MoS2, a direct-gap semiconductor is a typical example of new graphene-like materialsthat can be produced using the adhesive-tape based cleavage technique. The presence of a bandgap in MoS2 allowed us to fabricate transistors that can be turned o� and operate with negligibleleakage currents [1]. Furthermore, our transistors can be used to build simple integrated circuitscapable of performing logic operations and amplifying small signals [2]. We have also successfullyintegrated graphene with MoS2 into heterostructures to form �ash memory cells [3] that could beused to extend the scaling of this type of devices. Next, I will show photodetectors based on MoS2that have a sensitivity surpassing that of similar graphene devices by several orders of magnitude.Incorporating MoS2 in van der Waals heterostructures can open the way to an extremely diverserange of materials where di�erent layers cam be mixed and matched to di�erent functionalities.This is not only limited to two-dimensional materials: classical 3D semiconductors with saturateddangling bonds can also be integrated with 2D semiconductors, as I will show on the example ofp-Si/n-MoS2 heterostructures that behave as diodes and can be used to achieve light emission andenergy harvesting in a broad energy range[4].

References

[1] B. Radisavljevic et al., Nat. Nanotechnol. 6, 147 (2011).[2] B. Radisavljevic, M. B. Whitwick and A. Kis, ACS Nano 5, 9934 (2011).[3] S. Bertolazzi, D. Krasnozhon and A. Kis, ACS Nano 7, 3246 (2013).[4] O. Lopez-Sanchez et al., ACS Nano (2014).


Controllable synthesis of graphene and its electronic properties

Invited talk

Liu, Yunqi


Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China

Controllable synthesis of graphene is a pre-requirement both for basic research and practicalapplications of graphene. In addition to the mechanical cleavage, several e�cient methods for thepreparation of graphene have been developed in recent years, including epitaxial technique, chemicalmethods (especially, bottom-up chemical synthesis) and chemical vapor deposition (CVD). Amongthem, CVD on metal crystals is widely used in the large-scale synthesis of graphene �lms, and morethan 5 mm single crystals of monolayer and bilayer graphene have been reported on copper. The�nal goal for the controllable synthesis is to obtain even larger size, monolayer (or layer numbersare in control) and single-crystal structure.

On the other hand, research on electronic properties of graphene is one of the most importanttopics of graphene. Similar to silicon, which has become a main material for microelectronics,processes three fundamental electric behaviors: metallic, semiconducting and insulating. Carbon isanother sample to have such a unique property. This might be the physical base why some scientistsproposed that the carbon-based electronics will replace the silicon-based electronics in the future.However, to realize this, it seems, there is still a long way to go.

In this presentation, I will report a few recent results [1-10] on synthesizing graphene in acontrollable manner, and studies on its electronic properties.

References

[1] Jianyi Chen, et al., Adv. Mater. 26, 1348 (2014).[2] Lifeng Wang, et al., Adv. Mater. 26, 1559 (2014).[3] Lili Jiang, et al., Adv. Mater. 25, 250 (2013).[4] Dacheng Wei, et al., Nature. Commun. 4, 1374 (2013).[5] Bin Wu, et al., NPG Asia Mater. 5, e36 (2013).[6] Jianyi Chen, et al., Adv. Mater. 25, 992 (2013).[7] Liping Huang, et al., Small 9, 1330 (2013).[8] Dacheng Wei, et al., Acc. Chem. Res. 46, 106 (2013).[9] Dechao Geng, et al., J. Am. Chem. Soc. 135, 6431 (2013).[10] Lang Jiang, et al., J. Am. Chem. Soc. 135, 9050 (2013).


Imaging and Spectroscopy of Graphene Heterostructures

Invited talk

LeRoy, Brian


University of Arizona, 1118 E. 4th St, Tucson AZ 85721 USA

Two-dimensional materials such as graphene and transition metal dichalcogenides are beingextensively studied for potential electronic and optical applications. Recently it has become possibleto create heterostructures of these materials in order to create designer bandstructures. Spatiallyresolved information is crucial to understand the properties of these heterostructures. Using acombination of scanning probe microscopy and optical spectroscopy, we have probed the localelectronic properties of graphene heterostructures. These systems consist of a monolayer of graphenein contact with other materials ranging from insulators to two-dimensional semiconductors such asMoS2 and topological insulators. By using boron nitride, a wide band gap insulator as a substrate,we observe an improvement in the electronic properties of graphene as well as a moire patterndue to the misalignment of the graphene and boron nitride lattices [1]. We �nd that the periodicpotential due to the boron nitride substrate creates new Dirac points in graphene leading to changesin its electronic properties [2]. We have recently demonstrated how the stacking con�gurationof graphene structures can be modi�ed with an electric �eld inducing a metal to semiconductortransition [3]. Lastly, our latest results on graphene-topological insulator and graphene-transitionmetal dichalcogenide heterostructures will be discussed.

References

[1] J. Xue et al., Nature Materials 10, 282 (2011).[2] M. Yankowitz et al., Nature Physics 8, 382 (2012).[3] M. Yankowitz et al., Nature Materials advance online publication 28 April 2014, doi:10.1038/nmat3965.


Illuminating graphene nanoribbons

Invited talk

Molinari, Elisa (1,2); Cardoso, Claudia M. (1); Ferretti, Andrea (1), Wang, Shudong (1), Prezzi,Deborah (1), Ruini, Alice (1,2)


(1) CNR-Istituto Nanoscienze, S3 Center Modena, Italy(2) University of Modena and Reggio Emilia, FIM Department, Modena, Italy

Graphene nanostructures have striking properties related to lateral con�nement, that can open aband gap in the graphene bands and make them suitable for digital (opto-)electronics. Key featuresconnected to the tunability of electronic and optical properties were predicted [1], and full atomiccontrol of GNR geometry was recently demonstrated on gold [2].

We study the electronic and optical excitations of armchair GNRs by ab-initio calculations,including substrate e�ects and many-body interactions through the so-called GW-BSE scheme, andcompare them with scanning tunneling (STS), X-ray and re�ectance di�erence spectroscopy (RDS)experiments [1,3-5]. The results reveal sizable band gaps and parabolic band dispersions near the topof the valence band, while optical spectra are dominated by strongly anisotropic excitonic features.We investigate the spectral evolution of the ribbon during its bottom-up fabrication starting fromits molecular precursors through the polymerization phase, thus clarifying the build-up of quasi-1Dexcitons in the act of the ribbon formation.

Excellent agreement is found with experimental data [3-5], indicating that this scheme can pro-vide quantitative predictions for GNRs and a powerful tool for characterization. We �nally discussmodulated GNRs and design quantum-dot like con�ned systems that lead to novel nanostructuredesigns with controlled couplings.

References

[1] e.g. D. Prezzi et al, Phys. Rev. B77, 041404 (2008); Phys. Rev. B84, 041401 (2011).[2] J. Cai et al, Nature 466, 470 (2010).[3] P. Ru�eux et al, ACS Nano 6, 6930 (2012).[4] R. Denk et al, Nature Commun, in press (2014).[5] A. Batra et al, to be published (2014).


Scanning probe experiments on atomically well-de�ned graphenenanostructures

Invited talk

Liljeroth, Peter

Contact: peter.liljeroth@aalto.�

Department of Applied Physics, Aalto University School of Science, PO Box 15100, 00076 Aalto,Finland

The electronic properties of graphene edges have been predicted to depend on their crystallo-graphic orientation. However, studying them experimentally remains challenging due to the di�-culty in realizing clean edges without disorder. I will discuss two systems that allow construction ofwell-de�ned graphene edges: graphene nanoribbons (GNRs) obtained through a bottom-up process1and interfaces between graphene and hexagonal boron nitride (h-BN) in an epitaxial monolayer.We have synthesized atomically well-de�ned GNRs through on-surface polymerization [1] that havearmchair edges along the long axis of the ribbon and zigzag (ZZ) ends along the short axis. Theelectronic states of the GNRs close to the Dirac point are located at the ZZ ends of the nanoribbons.In addition to the electronic structure of the GNRs, I will discuss contacting the GNR to a metalliclead by a single chemical bond by controllably removing individual hydrogen atoms from the ZZends of the GNR [2]. Extended ZZ graphene edges can be passivated and stabilized using hexago-nal boron nitride (h-BN). ZZ-terminated, atomically sharp interfaces between graphene and h-BNis an experimentally realizable, chemically stable model systems for graphene ZZ edges. We haveexplored the structure of the graphene- (h-BN) interfaces with both scanning tunnelling microscopyand numerical methods and show them to host localized electronic states similar to those on thepristine graphene ZZ edge [3].

References

[1] J. Cai et al., Atomically precise bottom-up fabrication of graphene nanoribbons, Nature 466,470 (2010).

[2] J. van der Lit et al., Suppression of electron-vibron coupling in graphene nanoribbons con-tacted via a single atom, Nature Comm. 4, 2023 (2013).

[3] R. Drost et al., Electronic states at the graphene-hexagonal boron nitride zig-zag interface,submitted.


Adsorbates and many body e�ects in two dimensional materi-als

Invited talk

Wehling, Tim


Institute for Theoretical Physics and Bremen Center for Computational Material Sciences, Uni-versity of Bremen, 28359 Bremen, Germany

Two dimensional materials combine pronounced surface e�ects with distinct many body inter-actions. Both a�ect material properties decisively, as they determine excitations and boundariesbetween di�erent electronic as well as structural phases. Here, we discuss three examples of howinteractions a�ect material properties. First, we consider chemically functionalized graphene andshow how doping triggers adsorbate phase transitions including tendencies towards sublattice sym-metry breaking [1]. Regarding the electrons in layered materials, local "Hubbard interactions"generally compete with large non-local Coulomb interactions. We will discuss the "two-faced" na-ture of these non-local interactions: while they contribute to strong renormalizations of electronicexcitations, non-local Coulomb terms turn out to weaken ground state electronic correlations fre-quently [2]. This is helpful in the context of phonon mediated superconductivity in materials likedoped transition metal dichalcogenides [3].

References

[1] T. Wehling, B. Grundkötter-Stock, B. Aradi, T. Niehaus, T. Frauenheim, Charge dopinginduced phase transitions in hydrogenated and �uorinated graphene, arXiv:1312.2276 (2013).

[2] M. Schüler, M. Rösner, T. O. Wehling, A. I. Lichtenstein, M. I. Katsnelson, Hubbard modelsfor materials with nonlocal Coulomb interactions: graphene, silicene and benzene, Phys. Rev. Lett.111, 036601 (2013).

[3] M. Rösner, S. Haas, T. O. Wehling, Phase Diagram of Electron Doped Dichalcogenides,arXiv:1404.4295 (2014).


Observation of giant bandgap renormalization and excitonice�ects in a monolayer transition metal dichalcogenide semicon-ductor

Invited talk

Ugeda, Miguel M. (1); Bradley Aaron J. (1); da Jornada, Felipe (1,2); Shi, Sufei (1); Zhang, Yi(3,4); Qiu, Diana (1,2); Hussain, Zahid (3); Shen, Zhi-Xun (4,5); Wang, Feng (1,2); Louie, StevenG. (1,2); Crommie, Michael F. (1,2)


(1) Department of Physics, University of California at Berkeley, Berkeley, California 94720,USA

(2) Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, USA

(3) Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley,CA 94720, USA(4) Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory,

Menlo Park, CA 94025, USA(5) Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics,

Stanford University, Stanford, CA 94305, USA

Atomically-thin transition metal dichalcogenide (TMD) semiconductors have generated greatinterest recently due to their remarkable physical properties. For example, reduced screening in 2Dhas been predicted to result in dramatically enhanced Coulomb interactions that should cause gi-ant bandgap renormalization and excitonic e�ects in single-layer TMD semiconductors [1, 2]. Herewe present a direct experimental observation of extraordinarily high exciton binding energy andbandgap renormalization in a single-layer of semiconducting TMD [3]. We determined the bindingenergy of correlated electron-hole excitations in monolayer MoSe2 grown on bilayer graphene (BLG)using high-resolution scanning tunneling spectroscopy (STS) and photoluminescence spectroscopy.We have measured both the quasiparticle electronic bandgap and the optical transitions of mono-layer MoSe2/BLG, thus enabling us to obtain an exciton binding energy of 0.55 eV for this system,a value that is orders of magnitude larger than what is seen in conventional 3D semiconductors. Wehave corroborated these experimental �ndings through ab initio GW and Bethe-Salpeter equationcalculations which show that the large exciton energy arises from enhanced Coulomb interactionsthat lead to a dramatic blue-shifting of the quasiparticle bandgap. These results are of fundamentalimportance for room-temperature optoelectronic nanodevices involving 2D semiconducting TMDsas well as more complex layered heterostructures.

References

[1] H. P. Komsa, A. V. Krasheninnikov, Physical Review B. 86, 241201 (2012).[2] D. Y. Qiu, et al., Physical Review Letters. 111, 216805 (2013).[3] Miguel M. Ugeda, et al., Submitted. (2014).

Chapter 2

Contributed talks

16

CHAPTER 2. CONTRIBUTED TALKS 17

Atomic Structure of Graphene-Support Interfaces

Contributed talk

Vonk, Vedran (1); Polman, Krista (3); Franz, Dirk (1); Stierle, Andreas (1); Conrad, Ed (2);Vlieg, Elias (3)


(1) DESY Nanolaboratory, Hamburg, Germany(2) The Georgia Institute of Technology, Atlanta, USA(3) Radboud University, Nijmegen, The Netherlands

For most applications, graphene is not free-standing but is supported by another material.This requires to understand the details of the atomic structure and characteristic defects of thegraphene-support interface. We will elucidate two di�erent graphene-based structures, both studiedby synchrotron x-rays. Surface x-ray di�raction allows it to `see all the way through', which makes itpossible to study the buried interface of graphene and its support. A new scattering scheme, makinguse of high-energy x-rays in combination with area detectors, is shown to enable fast non-destructivecharacterization in a pressure range up to ambient conditions [1]. Our study of ultrathin furnace-grown epitaxial graphene (EG) on SiC(000-1) shows that the interface consists of approximately2 layers of atoms, which are partly in registry with the SiC substrate and partly disordered [2].Furthermore, it is shown that EG has mostly AB-type stacking, see Figure. Two-dimensional arraysof nearly identical nanoparticles with a very narrow size distribution enable systematic studies ofthe catalyst's size-e�ect on conversion reactions [3]. We will show the results of in-situ investigationsof Pt, Rh and PtRh nanoparticles kept in environments relevant for catalytic CO conversion. Anewly devised high energy scattering scheme enables to record large portions of reciprocal space ina relatively fast time frame, by which means in-situ measurements during chemical reactions arepossible (see Fig).

References

[1] J. Gustafson, M. Shipilin et al. Science 343, 758-761 (2014).[2] V. Vonk, K. Polman et al. (in preparation).[3] D. Franz, S. Runte et al. Phys. Rev. Lett. 110, 065503 (2013).

(left) SXRD data analysis of EG on SiC(000-1) shows that it has mostly AB-type stacking. (right)High-energy x-ray di�raction pattern of Pt nanoparticles grown on graphene-Ir(111) support. The

main di�raction rods are indexed corresponding to the substrate, the satellite rods by G.


Tailoring Graphene with nanometer accuracy

Contributed talk

Martínez-Galera, Antonio J. (1,2); Brihuega, Iván(1,3); Gutiérrez-Rubio, Ángel (1); Stauber,Tobias(1,3); Gómez-Rodríguez, José M. (1,3)


(1) Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049Madrid, Spain

(2) Present address: II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937Köln, Germany

(3) Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049Madrid, Spain

The selective modi�cation of pristine graphene represents an essential step to fully exploit itspotential. Two main routes are usually followed to modify graphene properties. On one hand,bottom up approaches have demonstrated to be very e�cient to change the overall electronic struc-ture of graphene [1-3]. On the other hand, with top down approaches it is possible to induce suchchanges on a local scale [4,5]. Here we merge bottom-up and top-down strategies to tailor graphenewith nanometer accuracy. Speci�cally, we have developed a perfectly reproducible nanolithographictechnique that allows, by means of an STM tip, to modify with 2.5 nm accuracy the electronic prop-erties of graphene monolayers epitaxially grown on Ir(111) surfaces. This method can be carriedout also on micrometer sized regions and the structures so created are stable even at room tem-perature. As a result, we can strategically combine graphene regions presenting large di�erencesin their electronic structure to design graphene nanostructures with tailored properties. Therefore,this novel nanolithography method could open the way to the design of nanometric graphene-baseddevices with speci�c functionalities.

References

[1] R. Balog, B. Jorgensen, et al., Nature Materials 9, 315-319 (2010).[2] S. Rusponi, M. Papagno, et al., Physical Review Letters 105, 246803 (2010).[3] T. Ohta, A. Bostwick, et al., Science 313, 951-954 (2006).[4] M. M. Ugeda, I. Brihuega, et al., Physical Review Letters 104, 096804 (2010).[5] L. Tapaszto, G. Dobrik, et al., Nature Nanotechnology 3, 397-401 (2008).

Figure 1. Upper panel illustrates the nanopatterning process, with a schematic STM tip drawn ontop of a real experimental image. Lower panel shows a 95x35 nm2 STM image with the �nal result

after writing the word �graphene�.


Spin current formation at the Graphene/Pt interface for mag-netization manipulation in deposited magnetic nanodots

Contributed talk

Shikin, Alexander


(1) Ulianovskaya, 1 St-Petrsburg State University Peterhof, St-Petersburg 198504 Russia

Controllable manipulation of magnetization without external magnetic �eld only by appliedelectrical current attracts enhanced attention due to possibility of creation of new generation mem-ory and quantum logic devices. Recently, a perspective idea was proposed related to using thespin torque generated by spin current developed in low-dimensional Rashba system with strongspin-orbit interaction [1]. Magnetic switching driven by spin-orbit torque is considered more ef-fective than the switching by external magnetic �eld that can allow design of spintronics deviceswith greater energy e�ciency and reduced dimensions. In the talk this idea is applied to analy-sis of using the spin current developed at the Graphene/Pt interface characterized by enhancedspin-orbit interaction for induced magnetization of Ni-nanodots arranged atop due to the spin-orbittorque e�ect. We report the results of experimental and theoretical investigations of spin electronicstructure of the Graphene/Pt interface and demonstrate a large induced spin-orbit splitting (∼80-200meV) of the graphene π-states with formation of non-degenerated Dirac cone spin states nearthe Fermi level. It makes possible separation of electrons at the Fermi level with opposite orientedspins. We propose the idea, how this spin structure can be used for the spin current formation andfor creation of spintronics device allowing to switch a magnetization of the attached FM-nanodotsby the induced spin-orbit torque e�ect [2].

References

[1] I.M. Miron et al., Nature Materials, 9, 230 (2010).[2] A.M. Shikin et al., ArXiv:1312.6999 (2013).


Direct View on the Ultrafast Carrier Dynamics of Massless andMassive Dirac Fermions in Mono- and Bilayer Graphene

Contributed talk

Ulstrup, Søren, (1); Johannsen, Jens C., (2); Cilento, Federico, (3); Miwa, Jill A., (1); Crepaldi,Alberto, (3); Zacchigna, Michele, (4); Cacho, Cephise, (5); Chapman, Richard, (5); Springate,Emma, (5); Mammadov, Samir, (6); Fromm, Felix, (6); Raidel, Christian, (6); Seyller, Thomas,(6); Parmigiani, Fulvio, (3,7); Grioni, Marco, (2), King, Phil D. C., (8); Hofmann, Philip, (1)


(1) Aarhus University, 8000 Aarhus C, Denmark(2) EPFL, 1015 Lausanne, Switzerland(3) Sincrotrone Trieste, 34149, Trieste, Italy(4) IOM-CNR Laboratory TASC, 34012 Trieste, Italy(5) STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom(6) Technical University of Chemnitz, 09126 Chemnitz, Germany(7) University of Trieste, 34127 Trieste, Italy(8) University of St. Andrews, Fife KY16 9SS, United Kingdom

Understanding of the ultrafast carrier dynamics in mono- and bilayer graphene is essential forexploiting these materials in future electronic and optoelectronic devices [1]. The hallmarks of thesematerials are their low energy Dirac spectra consisting of massless and massive Dirac Fermions,respectively. With the advent of high harmonic laser-based time- and angle-resolved photoemission(TR-ARPES) it is now possible to record movies that directly capture the momentum-resolved out-of-equilibrium properties of these Dirac particles with femtosecond time resolution [2,3]. Here, wecharacterize the dynamic processes around the Dirac point in epitaxial mono- and bilayer grapheneusing TR-ARPES, addressing the timescales of hot carrier scattering processes in both systems. Forbilayer graphene, we are able to disentangle the dynamics in the two conduction band sub-statesand �nd that the gap in the lower sub-state plays a crucially important role, leading to a remarkablydi�erent relaxation dynamics compared to monolayer graphene.

References

[1] F. Bonaccorso, Z. Sun et al., Nat. Photonics, 4, 611 (2010).[2] J. C. Johannsen, S. Ulstrup et al., Phys. Rev. Lett., 111, 027403 (2013).[3] I. Gierz, J. C. Petersen et al., Nat. Mater. 12, 1119 (2013).

Measuring the ultrafast dynamics of (A) massive, and (B) massless Dirac Fermions using time-and angle-resolved photoemission. Excited electron-hole pairs are induced by an IR pump pulse.Dynamic processes such as electron-phonon scattering are then probed with a high harmonic XUV

probe pulse.


Ultrafast charge transfer to graphene monolayers: Substratecoupling, local density of states, �nal state dimensionality, andtwo-step processes.

Contributed talk

Menzel, Dietrich, (1); Lacovig,Paolo, (2); Kostov, Krassimir L., (3); Larciprete, Rosanna, (4);Lizzit, Silvano, (5)


(1) Physik-Department E20, Technische Universität München, 85748 München, Germany(2) Elettra Sincrotrone Trieste, S.S.14 km 163.5, 34149 Trieste, Italy(3) Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 So�a,

Bulgaria(4) Institute of Complex Systems, 00133 Roma, Italy(5) Elettra Sincrotrone Trieste, S.S.14 km 163.5, 34149 Trieste, Italy

The ultrafast electron dynamics at graphene monolayers (Gr ML), in particular the chargeexchange with adsorbates and substrates, is of importance for photochemistry and electrochemistryof Gr. In order to improve its understanding, we carry out a program to use the so-called corehole clock (CHC) method [1,2] with adsorbed Ar to determine the charge transfer time constants(CTT) at Gr ML with strongly varied substrate coupling. Our �rst results, reported at EWEG2013 and meanwhile published [3], showed strong dependence of the CTT on the dimensionality ofthe CT �nal state, and on the coupling strength to the substrate. Qualitatively the results followexpectations, with CT to various decoupled Gr ML being slowest (∼16 fs), and Gr on transitionmetals (e.g. Ru) much faster (up to 6x) and depending on the local coupling for corrugated Gr/Ru.However, CT on physisorbed Gr/Pt(111) is still more than twice as fast than on decoupled Gr,and new data on strongly coupled Gr/Ni(111) and on (slightly corrugated) Ir(111) are somewhatpuzzling. The following points will be discussed: that the results on transition metals do not simplyfollow the coupling strength due to e�ects of the local density of states at the relevant energy; whythe physisorbed Gr ML on metals show much faster CT than decoupled Gr, and what e�ects couldslow down the CT into two-dimensional decoupled Gr ML. Further improved understanding willrequire detailed calculations which are under way.

References

[1] For an extensive review, see P.A. Brühwiler, O. Karis, and N. Martensson, Rev. Mod. Phys.74, 703 (2002).

[2] For a recent survey, see D. Menzel, Chem. Soc. Rev. 37, 2212 (2008).[3] S. Lizzit et al., ACS Nano 5, 4359 (2013), DOI: 10.1021/nn-4008862.


Tuning Electronic Properties of Epitaxial Graphene by CopperIntercalation

Contributed talk

Sicot, Muriel,(1); Fagot-Revurat, Yannick, (1); Vasseur, Guillaume,(1); Kierren, Bertrand,(1);Malterre, Daniel,(1)


(1) Université de Lorraine, Institut Jean Lamour, UMR 7198, B.P. 239 F-54506, Vand÷uvrelès Nancy, France

Structural and electronic properties of epitaxial graphene grown on Ir(111) after intercalation ofabout one monolayer of copper has been investigated by low energy electron di�raction (LEED), X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy/spectroscopy (STM/STS)and angle-resolved photoemission spectroscopy (ARPES) at 80 K [1]. Studies of structural prop-erties have shown that copper is mostly intercalated at step edges (see area 2 in Figure) and alsoforms intercalated nanoislands of about one atomic layer high on terraces (area 1). We show thatgraphene-covered Cu layer grows pseudomorphically on Ir surface. Cu penetration under graphenemodi�es drastically graphene electronic properties i.e. results in electron doping shifting the Diracpoint by more than 500 meV and opening an energy gap at K point as shown by ARPES measure-ments. Under submonolayer intercalation, we observe strong bias dependency of STM topographs.It can be explained by the drastic modi�cations of local density of states upon Cu intercalationsuch as the attenuation of the Rashba type surface state of Ir as shown by ARPES and STSmeasurements.

References

[1] M. Sicot et al., submitted

STM/STS of Gr/Cu (0.3 ML) /Ir(111)


Crystallographic and electronic structure of graphene on thepseudomorphic Cu/Ir(111) substrate

Contributed talk

Voloshina, Elena (1); Vita, Hendrik (2); Böttcher, Stefan (2); Horn, Karsten (2); Ovcharenko,Roman (1); Kampen, Thorsten (3); Thissen, Andreas (3); Dedkov, Yuriy (3)


(1) Institut für Chemie, Humboldt-Universität zu Berlin, 10099 Berlin, Germany(2) Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany(3) SPECS Surface Nano Analysis GmbH, Voltastraÿe 5, 13355 Berlin, Germany

Understanding the nature of the interaction at the graphene/metal interfaces plays a critical rolefor the correct description of graphene-based electron- and spin-transport devices. Here, severalfactors, such as doping level or/and hybridization of the electronic states of graphene and themetal around the Fermi level de�ne the properties of such interfaces. Starting from p-doped nearlyfree-standing graphene on Ir(111), we tailor its properties via intercalation of one monolayer ofCu. The crystallographic and electronic structures of the resulting n-doped nearly free-standinggraphene layer on the lattice mismatched pseudomorphic Cu/Ir(111) substrate were studied bymeans of scanning probe microscopy (STM and 3D NC-AFM) and photoelectron spectroscopyin combination with state-of-the-art density functional theory calculations. These results allowunderstanding the general mechanisms that are responsible for the modi�cation of the electronicstructure of graphene at the Dirac point (doping and the band-gap opening) in such systems.


H2O on graphene - cluster formation caused by hydrophobicity

Contributed talk

Busse, Carsten, (1); Standop, Sebastian, (1); Michely, Thomas (1)


(1) II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany

An understanding of the interaction between water and graphene is necessary to assess thestability of this material under ambient conditions, but also to elucidate basic mechanisms ingraphene-based supercapacitors where the interaction of the carbon sheet with the water basedelectrolyte is a key factor for electron transport. Here, we study the adsorption of H2O on graphenegrown epitaxially on Ir(111) combining the complementary experimental techniques of scanningtunneling microscopy (STM) and thermal desorption spectroscopy (TDS). Water adsorbed at lowtemperatures (20 K) and coverages (< 3 ML) does not wet graphene, but forms a dense packedlattice of three-dimensional droplets aligned in the gr/Ir(111) moiré. Higher coverage and/or higherdeposition temperature result in coalescence of theses droplets, i.e. a closed water adlayer. Thekinetic parameters (order of desorption process, desorption barrier, exponential prefactor) are de-termined for the two phases. The formation of the droplet lattice is driven by the low and spatiallyvarying binding energy between graphene and H2O.


Elementary processes and factors in�uencing the intercalationbetween graphene and iridium

Contributed talk

Vlaic, Sergio, (1,2); Kimouche, Amina, (1,2); Coraux, Johann, (1,2); Santos, Benito, (3); Lo-catelli, Andrea, (3); Rougemaille, Nicolas, (1,2)


(1) Univ. Grenoble Alpes, Inst. NEEL, 25 rue des Martyrs, F-38042 Grenoble, France(2) CNRS, Inst NEEL, 25 rue des Martyrs, F-38042 Grenoble, France(3) Elettra � Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5 in Area Science Park, I-34149

Basovizza, Trieste, Italy

Intercalation of foreign species between graphene and its substrate is one of the most usedmethods to manipulate graphene's properties and to induce new ones, in a �nely controlled manner.It has allowed one, for instance, to fully decouple graphene from its substrate (H intercalation [1])and to manipulate the ferromagnetism of an intercalated Co layer [2]. Even though intercalation hasbeen known since the 1980's, it has only been recent that pathways explaining how intercalationinitiates have been pursued. To date only a few have been identi�ed: graphene edges [3] andpre-existing point defects [4] as well as at the intersection between graphene wrinkles [5]. Realtime monitoring of the intercalation of cobalt between graphene and Ir(111) with the help of low-energy electron microscopy, has provided us with greater insight. We discovered unanticipatedintercalation pathways, unveiled the processes energetics and how both depend on the graphene-substrate interaction. More speci�cally, we found that intercalation does not require the pre-existence of point defects inside the graphene lattice to proceed, but can occur at curved regions,such as those found at graphene wrinkles and on top of substrate step edges (Fig.1 a) and b)).Curved region intercalation is found to be in competition with edge intercalation (Fig.1 c)). Weshow that these two processes and their relative occurrence can be controlled by temperature andthe interaction of graphene with the substrate.

References

[1] C. Riedl, C. Coletti, et al., Phys. Rev. Lett. 103, 246804 (2009).[2] N. Rougemaille, A.T. N'Diaye, et al., Appl. Phys. Lett. 101, 142403 (2012).[3] P. Sutter, J. T. Sadowski, et al. J. Am. Chem. Soc. 132, 8175 (2010).[4] M. Sicot, P. Leicht, et al., ACS Nano 6, 151 (2012).[5| M. Petrovi¢, I. �rut Raki¢, et al., Nat. Commun. 4, 2772 (2013).

Schematic representation (left) and LEEM image (right) of Co intercalation between graphene andIr(111) at the substrate step edges (a), at graphene wrinkles (b) and at the graphene free edges (c).

Darker areas under the graphene sheet correspond to the intercalation regions.


Novel mismatched graphene-ferromagnetic interfaces

Contributed talk

Pacilé, D., (1, 2); Lisi, S., (3); Papagno, M., (1, 2); Ferrari, L., (2, 4); Sheverdyaeva, P.M., (2);Moras, P., (2); Leicht, P., (5); Krausert, K., (5); Zielke, L., (5); Fonin, M., (5); Dedkov, Yu. S.,(6);Mittendorfer, F., (7); Doppler, J.,(7); Garhofer, A. (7); Betti, M. G., (3); Mariani, C. (3); Redinger,J., (7); Carbone, C., (2)

Contact: daniela.pacile@�s.unical.it

(1) Dipartimento di Fisica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy(2) Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Trieste, Italy(3) Dipartimento di Fisica, Università di Roma �La Sapienza�, Piazzale Aldo Moro 5, I-00185

Roma, Italy(4) Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Roma, Italy(5) Fachbereich Physik, Universität Konstanz, 78464 Konstanz, Germany(6) SPECS Surface Nano Analysis GmbH, Voltastrasse 5, 13355 Berlin, Germany(7) Institute of Applied Physics and Center for Computational Materials Science, Vienna Uni-

versity of Technology, 1040 Vienna, Austria

The low-energy excitations in graphene depend on the interaction strength with the metal thatserves as support [1, 2]. By varying the support itself or by intercalation of foreign atoms it ispossible, through electron hybridization and structural modi�cations, to tailor graphene electronicproperties [3]. Variable interaction strengths can thus provide an additional control over the prop-erties of graphene and may open new �elds of applications. We will present the structural andelectronic properties of novel mismatched systems obtained by intercalation of one-single ferromag-netic (FM=Ni, Co) layer on graphene/Ir(111). Upon intercalation the FM lattice is resized tomatch the Ir-Ir lattice parameter, resulting in a mismatched graphene/FM/Ir(111) system [4, 5].By performing scanning tunneling microscopy measurements and density functional theory calcu-lations we prove that the intercalated Ni layer strongly increases the local interaction for speci�cadsorption sites and induces a strong rumpling of the graphene �lm. Angle-resolved photoemissionspectroscopy studies on graphene/FM/Ir(111) systems show a clear transition from nearly-free-standing to strongly-hybridized character of the graphene �lm. The comparison between graphenegrown on bulk Ni and Co and the novel systems allow us to get insight into the graphene-metalinteraction.

References

[1] M. Papagno at al., ACS Nano 6, 199 (2012.[2] M. Papagno at al., ACS Nano 6, 9299 (2012).[3] M. Papagno et al., Phys. Rev. B 88, 235430 (2014).[4] D. Pacilé at al., Phys. Rev. B 87, 035420 (2013).[5] R. Decker et al., Phys. Rev. B 87, 041403(R)(2013).

a) Constant energy image of G/Ni/Ir taken at binding energy of 3 eV with a photon energy of 70eV. b) STM overview showing the morphology of graphene with a partially intercalated Ni

submonolayer. The corrugation in the optimized structure of G/Ir and G/Ni/Ir, and C1s corelevels, are superimposed.


Graphene spintronics: Spin injection and proximity e�ects from�rst principles

Contributed talk

Zutic, Igor, (1); Sipahi, Guilherme, (1,2); Lazi¢, Predrag (3); Kawakami, Roland, (4)

Contact: zigor@bu�alo.edu

(1) University at Bu�alo, State University of New York, Bu�alo, NY 14260, USA(2) Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Brazil(3) Rudjer Boskovic Institute, PO Box 180, Bijenicka c. 54, 10 002 Zagreb, Croatia(4) The Ohio State University, Columbus, Ohio 43210, USA

Ferromagnet/graphene (F/Gr) junctions o�er a number of desirable spin-dependent properties.In such structures graphene can provide e�ective spin-�ltering or replace a tunnel barrier, havingan advantage of low resistance and a small number of defects [1]. F/Gr junctions display magneticproximity e�ects and a robust spin injection, larger than in other materials [2]. Both phenomenainduce a magnetic moment in graphene, which in the �rst case already occurs spontaneously in equi-librium, while the second case represents a nonequilibrium process [3]. First-principles methods arekey to assess the properties of F/Gr junctions and relate them to the desired performance, but thecomputational cost is often too high. By focusing on magnetologic gates [4] and Ni(111)/graphenejunctions, we include van der Waals interactions from �rst principles, crucial for their detailedunderstanding. We formulate a computationally-inexpensive model to study spin injection andproximity e�ects [5]. By presenting spin polarization maps, we establish a versatile tool to tailorthe desired spin-dependent properties for graphene spintronics which suggest a wealth of opportu-nities, not limited to magnetically storing and sensing information, but also including processingand transferring information [4].

References

[1] O. M. J. van 't Erve et al., Nature Nanotech. 7, 737 (2012).[2] W. Han, et al., Phys. Rev. Lett. 105, 167202 (2010).[3] I. Zutic et al., Rev. Mod. Phys. 76, 323 (2004).[4] H. Dery et al., IEEE Trans. Electron. Dev. 59, 259 (2012).[5] P. Lazic et al., submitted to Phys. Rev. B, preprint.

Spin polarizations, PN , PNv, PNv2 for a reference bulk Ni. Inset: Magnetic moment resolved oneach atom in the computational cell (C1,C2,Ni1,..,Ni5) for TOP-FCC Ni/graphene con�guration.Orbital projections of the atomically-resolved DOS spin polarization. Total spin polarizations.


On-Surface Synthesis of BN/Graphene Hybrid Structures

Contributed talk

Sanchez-Sanchez, Carlos, (1); Müller, Matthias, (2); Bettinger, Holger F., (2); Brüller, Sebas-tian, (3); Müllen, Klaus, (3); Talirz, Leopold, (1); Pignedoli, Carlo, (1); Ru�eux, Pascal, (1); Fasel,Roman, (1)


(1) Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse129, CH-8600 Dübendorf, Switzerland

(2) Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076Tübin-gen, Germany

(3) Max Planck Institute for Polymer Research, 55128 Mainz, Germany.

The absence of an electronic band-gap is a major obstacle to the fabrication of e�cient graphene-based switching devices. Di�erent strategies, including top-down structuring and chemical mod-i�cations, have been proposed to transform graphene into a semiconductor [1]. However, mostof these strategies lack accurate atomic control on the �nal structures, which can be achieved bybottom-up strategies based on the surface-assisted colligation and transformation of suitably de-signed precursor monomers, proved to yield atomically precise surface-supported nanoarchitectures.Fullerenes, nanodomes and nanographenes have been synthesized via Surface-Assisted Cyclodehy-drogenation (SACDH). Furthermore, the combination of SACDH with surface-catalyzed Ullmanncoupling has been used for the synthesis of atomically precise graphene nanoribbons and porousgraphene, where electron con�nement yields the appearance of a band-gap [2,3]. We will show howthe combination of SACDH and Ullmann coupling on metallic surfaces under ultra-high vacuumconditions allows for the formation of 2D BN/graphene hybrid networks, which are unavailablevia traditional solution-based chemistry. We �nd that scanning tunneling microscopy images anddensity functional theory calculations allow the identi�cation of the position and orientation of theborazine rings. Our proof-of-concept study opens the door towards the design and synthesis ofatomically precise heterostructures by tailoring of precursor monomers.

References

[1] D. Jariwala, A. Srivastava et al. http://arxiv.org/ftp/arxiv/papers/1108/1108.4141.pdf[2] J. Mendez, M. F. Lopez, et al., Chem. Soc. Rev., 40, 4578-4590 (2011).[3] J. Björk and F. Hanke, Chem. Eur. J. 20, 928 � 934 (2014).

Small-scale STM images of the 1,2:3,4:5,6-Tris(2,2´-biphenylylene)borazole monomer (a) before(b) and after (c) complete cyclodehydrogenation. b) (100Å x 100Å) I=150pA, U=-1.5V c) (100Å

x 100Å) I=100pA, U=-1.5V.


Silicene vs. ordered 2D silicide: the atomic and electronicstructure of the Si-(

√19 ×

√19)R23.4°/Pt(111) surface recon-

struction

Contributed talk

Svec, Martin, (1); Hapala, Prokop, (1); Ondracek, Martin, (1); Blanco-Rey, Maria, (2); Merino,Pablo, (3); Mutombo, Pingo, (1); Chab, Vladimir, (1); Martin Gago, Jose Angel, (3); Jelinek,Pavel, (1,4)


(1) Institute of Physics of the AS CR, Cukrovarnická 10, 162 00 Praha, Czech Republic(2) Donostia International Physics Center, P. Manuel de Lardizabal 4, 20018 Donostia-San

Sebastian, Spain(3) CSIC-ICMM, C/Sor Juana Ines de la Cruz 3, E-28049 Madrid, Spain(4) Graduate School of Engineering, Osaka University 2-1, Yamada-Oka, Suita, Osaka 565-

0871, Japan

Many research groups, encouraged by pioneering works reporting growth of silicene 2D sheets onAg surfaces [1], have directed their attention to other noble metal surfaces [2]. On the other hand,it is well known that Si forms binary alloys with the majority of the transition metals. In orderto resolve the �silicene vs. silicide� dispute and to understand precisely the atomic structure of thereal surface phases, we provided an extensive comparison of the experimental data with di�erentatomistic models including silicene. We used a set of complementary experimental techniquessupported by the state-of-the-art theoretical analysis. We present detailed investigation of theatomic and electronic structure of Si-(

√19×

√19)R23.4°/Pt(111) surface reconstruction by means

of STM, nc-AFM, SRPES, LEED-IV and ARUPS, ; supported by theoretical calculations - DFT,STM simulation, IV-LEED simulation and k-space electronic band projection. We proposed anatomistic model consisting of ordered Si/Pt surface alloy, which �ts very well to experimentalevidence. To make our conclusions more relevant, we extended our consideration to similar system- the Si-(

√7×√

7)R19.1°/Ir(111) [2]. Also here our 2D ordered silicide model made of characteristicmetal/Si tetramers is thermodynamically more favorable than a silicene 2D sheet grown on top ofIr(111) surface. These �ndings indicate generality of our model and they render unlikely anyformation of silicene or germanene on nobel metal surfaces.

References

[1] A. Kara et al, Surf. Sci. Rep. 68, 1 (2012).[2] L. Meng et al Nano Lett. 13, 685 (2013).

(a) and (b) Top and side view of predicted model structure. (c) A scheme of the twisted Kagomestructure adopted by the system in the presence of the Si3Pt tetramers. (d) high-resolution STM

topography, a simulated STM image (both at -20mV) and the model.


Convergent Fabrication of a Perforated Graphene Network withAir-Stability

Contributed talk

Landers, John (1); Coraux, Johann (1); Bendiab, Nedjma (1); Lamare, Simon (2); Magaud,Laurence (1); Chérioux, Frédéric (2)


(1)University of Grenoble Alpes, Institut NEEL, F-38042 Grenoble, France CNRS(2)Institut FEMTO-ST, Université de Franche-Comté, CNRS, ENSMM, 32 Avenue de l'Observatoire,

F-25044 Besançon, France

The synthesis of 2D nanostructures on crystalline substrates has emerged in recent years [1] asone of the most actively pursued topics in nanotechnology [2-3]. 2D porous frameworks synthesizedunder ultra high vacuum (UHV) have drawn special attention due to the di�erent properties thatthey may possess compared to their hermetic counterparts like the ability to open a bandgap, andthe occurrence of magnetic �at bands [4]. Of particular interest are e�orts towards a fully carbonbackbone, such as porous graphene, through covalent self assembly, where the pore size and shapecan be uniformly controlled. This strategy is a versatile way to produce di�erent assemblies, forinstance the long-sought graphene antidot lattice [4], and in applications where size selectivity iscrucial (e.g. catalysis or optical absorption). Nevertheless, their applicability is limited by theirstability at higher temperatures (up to 700K) and atmospheric pressure (exposure to air). Wereport a new convergent synthesis based on a triple aldolisation that we use to create networks ofporous graphene on Au(111) [5]. Using scanning tunneling microscopy (STM), Raman spectroscopyand density functional theory (DFT), we show that a porous graphene network covers the surfaceand identify intermediate states in the growth process. Finally, we have successfully demonstratedthat the network is stable at higher pressures, including argon backed pressures of 10−5 mbar, andremains intact after exposure to air.

References

[1] L. Grill, M. Dyer et al. Nat. Nanotechnol. 2, 687 (2007).[2] M. Bieri, M. Treier et al. Chem. Commun. 46, 6919 (2009).[3] Y. Q. Zhang, N. Kepcija et al. Nat. Commun. 3, 1286 (2012).[4] T.G. Pedersen, C. Flindt et al. Phys. Rev. Lett. 100, 136804 (2008).[5] J. Landers, J. Coraux et al. ACS Nano. (2014). (submitted)

(Left) Scanning tunnel microscopy (STM) topograph of a fully conjugated carbon networksynthesized on Au(111). (Right) Density functional theory (DFT) calculations showing the stablestructure on Au(111). Middle inset shows the reaction based on a novel convergent approach via

triple aldolisation.


Role of the surface structure in the polymerization of molecu-lar precursor in graphene nanoribbons: DBBA on the recon-structed 1x2-Au(110) surface

Contributed talkOurdjini, Oualid, (1); Massimi, Lorenzo, (1); Betti, Maria Grazia, (1); Mariani, Carlo, (1);

Cavaliere, Emanuele, (2); Gavioli, Luca, (2); La�erentz, Leif (3); Grill, Leonhard, (3)(4)Contact: [email protected](1) LOwtemperature Ultraviolet Spectroscopy laboratory Dipartimento di Fisica, Universita di

Roma La Sapienza Piazzale Aldo Moro 2, I-00185 Roma, Italy(2) Interdisciplinary Laboratories for Advanced Materials Physics (i-LAMP) Dipartimento di

Matematica e Fisica Università Cattolica del Sacro Cuore via dei Musei 41, 25121 Brescia, Italy(3) Fritz-Haber-Institute of the Max-Planck-Society, Department of Physical Chemistry, Fara-

dayweg 4-6, 14195 Berlin, Germany(4) Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Aus-

triaGraphene nanoribbons (GNRs) can be obtained by two-step surface-assisted covalent coupling of

the 10,10'-dibromo-9,9'-bianthryl (DBBA) precursors on metal surfaces [1,2]. The Au(111) metallicsubstrate induces the dehalogenation and cyclodehydrogenation reaction steps associated to GNRssynthesis at elevated substrate temperatures [1] (475K-675K). An appropriate choice of the substratecould improve the GNRs growth by lowering the polymerization temperature. We have studied thesurface chemistry of the DBBA molecules on the anisotropic 1x2-reconstructed Au(110) surfaceby temperature-programmed X-Ray Photoelectron Spectroscopy (XPS) and Scanning TunnelingMicroscopy (STM). The channel geometry of the Au(110) o�ers an ideal template to investigate thein�uence of the surface structure on the DBBA assembling and to control the GNRs orientation. TheC-Br bond associated to the dehalogenation reaction step is activated at room temperature withoutadditional activation energy. The cyclodehydrogenation reaction occurs between 425K-515K. Thesequential step process occurs at lower substrate temperatures (315K-510K) than Au(111) whilepreserving the hierarchical GNRs growth process. Preliminary STM results show the formation ofGNRs with a reduced length, probably due to the low molecular mobility of DBBA on Au(110).These results bring new insights into the catalytic e�ect and the role of anisotropic metallic surfaceson the GNRs synthesis.

References

[1] J. Cai et al, Nature, 466 (2010).[2] S. Linden et al, Physical Review Letter, 108, 216801 (2012).

Temperature-programmed HR-XPS of the a) Br 3d core level and b) C1s core level of the10,10'-dibromo-9,9'-bianthryl (DBBA) precursors on Au(110); c) Schematic model and STM

images of GNRs formation.


Tuning the Schottky barrier heights at MoS2|metal contacts: a�rst-principles study

Contributed talk

Farmanbar, Mojtaba ; Brocks, Geert


(1) Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University ofTwente, P. O. Box 217, 7500 AE Enschede, The Netherlands

Molybdenite consists of layers of covalently bonded MoS2 with weak van der Waals interactionsbetween the layers, which enable exfoliation of a single layer(SL) of MoS2 through micromechanicalcleavage, similar to graphene. Indeed experiments on SL-MoS2 have demonstrated a high cur-rent on/o� ratio at room temperature in �eld e�ect transistors(FETs) [1]. Application of MoS2in electronic devices requires making contacts with metal electrodes. Such metal-semiconductorcontacts generally lead to Schottky barriers for charge carrier injection, which may hamper thedevice performance [2]. In this paper we study the Schottky barriers at SL-MoS2|metal interfacesby �rst-principles density functional theory (DFT) calculations. For conventional semiconductorssuch as Si, the Schottky barrier height (SBH) at the metal-semiconductor interface is often onlyweakly dependent on the metal species, and the Fermi level is pinned inside the semiconductor bandgap. We show that Fermi level pinning is absent for clean interfaces with SL-MoS2. Adsorption ofMoS2 onto a metal substrate gives rise to a potential step across the interface whose size dependson the metal species. The SBHs can then be tuned by selecting metal with appropriate work func-tions, and the SBH for electrons can be reduced to zero using metals with moderate work functions(<4.8), such as Ag or Cu. Only for high work function metals, such as Au, Pd, or Pt, the SBH issubstantial, which is in agreement with experiment [3,4].

References

[1] B. Radisavljevic, A. Radenovic et al. Nature, 6, 147 (2011).[2] N. R. Pradhan, D. Rhodes et al. Appl. Phys. Lett, 102, 123105 (2013).[3] W. Chen, E. J.G. Santos et al. Nano Lett, 13, 509 (2013).[4] S. Das, H. Chen et al. Nano Lett, 13, 100 (2010).

(a) The structure of a SL-MoS2. (b) The top view of a SL-MoS2 on Au (111) substrate. (c) TheSchottky barrier height (SBH) at SL-MoS2|metal interfaces as a function of the work function of

the clean metal surface.


Epitaxial Growth of Single-domain Hexagonal Boron Nitride

Contributed talk

Lacovig, Paolo, (1); Orlando, Fabrizio, (2,3); Larciprete, Rosanna (4); Baraldi, Alessandro,(2,3); Lizzit, Silvano (1);


(1) Elettra-Sincrotrone Trieste S.C.p.A., AREA Science Park, S.S. 14 km 163.5, 34149 Trieste,Italy

(2) Physics Department and CENMAT, University of Trieste, Via Valerio 2, 34127 Trieste,Italy

(3) IOM-CNR, Laboratorio TASC, AREA Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy(4) CNR-Institute for Complex Systems, Via Fosso del Cavaliere 100, 00133 Roma, Italy

The rising interest of the scienti�c community in graphene (GR), motivated by its fascinatingproperties and wide range of potential applications, has triggered substantial interest also on othertwo-dimensional (2D) atomic crystals and, in particular, on hexagonal boron nitride (h-BN) [1],which provides a superior insulating platform for high-performance GR devices [2]. However, anumber of challenges still awaits the scienti�c community before the full potential of 2D atomiccrystals can be exploited, such as the development of reliable methods for the growth of high-quality GR and h-BN single layers. For instance, it is still challenging to obtain large h-BN singlecrystalline domains because of the formation of rotated phases that give rise to grain boundaries andother 1D defects [3,4]. A deeper understanding of the h-BN growth mechanism is therefore highlydesirable in order to �nd the optimum approach to grow high-quality �lms. Here, we investigatethe structure of h-BN grown on Ir(111) by chemical vapor deposition (CVD) of borazine [5]. Usingsynchrotron radiation photoelectron spectroscopy and photoelectron di�raction, we show that it ispossible to control the formation of rotated h-BN domains and, under proper conditions, to formh-BN monolayers with single orientation. Our results provide new insight into the strategies forproducing high-quality h-BN sheets.

References

[1] M. Corso et al., Science 303, 217 (2004).[2] C. R. Dean et al., Nature Nanotechnology 5, 722 (2010).[3] W. Auwärter et al., Surface Science 545, L735 (2003).[4] G. Dong et al., Physical Review Letters 104, 096102 (2010).[5] F. Orlando et al., The Journal of Physical Chemistry C 115, 157 (2012).


Toward Sensitive Graphene Nanoribbon�Nanopore Devices byPreventing Electron Beam-Induced Damage

Contributed talk

Matthew Puster, Julio Rodriguez-Manzo, Adrian Balan, Marija Drndic


(1)Department of Physics and Astronomy University of Pennsylvania Philadelphia, PA 19104United States of America

Graphene-based nanopore devices are promising candidates for next-generation DNA sequenc-ing. Here we fabricated graphene nanoribbon�nanopore (GNR-NP) sensors for DNA detection.Nanopores with diameters in the range 2�10 nm were formed at the edge or in the center ofgraphene nanoribbons (GNRs), with widths between 20 and 250 nm on silicon nitride membranes.GNR conductance was monitored in situ during nanopore formation inside a transmission electronmicroscope (TEM). GNR resistance increases linearly with electron dose and GNR conductance andmobility decrease by a factor of 10 or more when GNRs are imaged at relatively high magni�cationwith a broad beam prior to making a nanopore. By operating the TEM in scanning TEM (STEM)mode, in which the position of the converged electron beam can be controlled with high spatialprecision via automated feedback, we prevent electron beam-induced damage and make nanoporesin highly conducting GNR sensors. This method min- imizes the exposure of the GNRs to thebeam resulting in GNRs with unchanged sensitivity after nanopore formation [1].

References

[1] Matthew Puster, Julio A. Rodriguez-Manzo, Adrian Balan, and Marija Drndic "TowardSensitive Graphene Nanoribbon-Nanopore Devices by Preventing Electron Beam Induced Damage"ACS Nano 7 (12), 11283-11289, 2013, DOI: 10.1021/nn405112m.

Illustration of a single DNA molecule passage in solution through a nanopore drilled in a graphenenanoribbon fabricated on top of a thin silicon nitride membrane.


Graphene growth by molecular beam epitaxy using high-quality,epitaxial nickel �lms on MgO(111) as substrates

Contributed talk

Wo�ord, Joseph, (1); Oliveira, Myriano, (1); Schumann, Timo, (1); Jenichen, Bernd, (1); Jahn,Uwe, (1); Fölsch, Stefan, (1); Lopes, Joao Marcelo, (1); Riechert, Henning, (1)

Contact: wo�[email protected]

(1) Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7 10117 Berlin, Deutschland.

The novel properties of graphene give it many potential applications, all of which will requireimprovements in graphene synthesis. Here we present a study of graphene grown by molecularbeam epitaxy (MBE) on single-crystalline, epitaxial Ni(111) �lms on MgO(111) substrates. Theexceptional surface quality of the Ni �lms � combined with the sub-monolayer precision of MBE� has allowed the observation of growth phenomena which might otherwise have been obscured.Raman spectroscopy and scanning tunneling microscopy (a) both indicate that the graphene is ofvery high crystalline quality, and Raman also reveals the inhomogeneous thickness common in �lmsgrown on Ni. We examine these variations using scanning electron microscopy (SEM), and discoverthat the thicker regions of graphene develop as elongated ribbons, and that these ribbons coincidewith step-edge clusters in the surface of the Ni substrate (b). SEM also shows well-de�ned angularfeatures along the perimeter of the thicker regions. The in�uence of Ni surface morphology on thedeveloping graphene �lm indicated by these two facts suggests a �growth from below� mechanism,where any subsequent graphene layers develop at the interface between the Ni substrate and thepreviously deposited graphene [1,2]. Finally, our experiments suggest that the graphene thicknessmay be manipulated using a tailored Ni substrate, potentially allowing bi- and multi-layer structuresto be engineered into majority monolayer �lms.

References

[1] S. Nie, et al., ACS Nano, 5, 2298 (2011).[2] S. Nie, et al., New J. Phys., 14, 093028 (2012).

Scanning tunneling microscope (a) and scanning electron microscope (b) images of graphenegrown on Ni-MgO(111) by molecular beam epitaxy. The thicker regions of the graphene �lm

coincide with step-clusters in the Ni substrate.


Cleaning graphene: what can be learned from quantum/classicalmolecular dynamics simulations

Contributed talk

Magaud, Laurence,(1); Delfour, Laure,(1); Davydova, Alessandra,(2); Despiau-Pujo, Emilie,(2);Cunge, Gilles,(2)


(1) Institut Néel, CNRS/UJF,Grenoble,France(2) LTM, CNRS/UJF-Grenoble1, CEA Grenoble, France

During graphene growth or the successive steps needed to create devices, hydrocarbon radicalsoften adsorb on graphene samples and alter their transport properties [1]. Cleaning grapheneis then of primary importance. One promising route for this is the use of a hydrogen plasma.The goal of the present study is to assist the development of graphene cleaning experiments andto understand the mechanisms of CH3 groups � a �rst approximation to resist residues left ongraphene after processing- removal from graphene by a H2 plasma. For this, quantum and classicalmolecular dynamics simulations have been performed for varying energies of an incident hydrogenatom sent on a methyl group adsorbed on graphene. For increasing energies, successive processeshave been found at 0K: re�ection, etching, sputtering. The e�ect of temperature on these processeshas then modeled and predictions will be compared to experimental data [2]. Quantum Moleculardynamics results are obtained at 0K in the NVE ensemble using the code VASP [3]. Classical MDcalculations based on the well tested C-H REBO [4,5] potential have also been performed to enablelonger dynamics and to test the e�ect of graphene temperature.

References

[1] Y.Ahn, et al. Appl. Phys. Lett. 102, 091602 (2013).[2] L.Delfour et al. submitted to Phys. Rev B[3] G.Kresse and J.Hafner, Phys. Rev. B 47, 558 (1993).[4] E.Despiau-Pujo et al, J. Appl. Phys. 113, 114302 (2013).[5] D. W. Brenner et al., J. Phys.: Condens. Matter 14, 783 (2002).

Figure 1: molecular dynamics simulation of a H atom sent on a methyl group adsorbed ongraphene. At 1 eV (bottom left) a CH4 molecule is formed and escapes from graphene. At 4 ev(right) the CH4 molecule forms and then breaks into a H atom and a CH3 group. Both leave

graphene.


Ion Irradiation of Metal-Supported Graphene: Exploring theRole of the Substrate

Contributed talk

Herbig, Charlotte, (1); Åhlgren, Harriet, (2); Simon, Sabina, (1); Kotakoski, Jani, (2, 3);Krasheninnikov, Arkady V., (2, 4); Michely, Thomas, (1)


(1) II. Physikalisches Insitut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany(2) Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki, Finland(3) Department of Physics, University of Vienna, Boltzmanngasse 5, 1190 Wien, Austria(4) Department of Applied Physics, Aalto University, P.O. Box 11100, 00076 Aalto, Finland

The investigation of ion irradiation e�ects on 2D materials is an emerging subject, triggeredby graphene's (Gr) potentials in applications. Though the �eld is still in its infancy, alreadynew phenomena caused by ion irradiation of 2D layers were discovered [1-3]. For supported Grthe e�ect of the substrate on ion beam damage and annealing is important. We investigate thebehavior of high quality, epitaxially grown Gr, weakly coupled to Ir(111), to low energy noble gas ionirradiation by scanning tunneling microscopy (STM), molecular dynamics simulations, and densityfunctional theory (DFT). For a freestanding layer, sputtered atoms leave the layer either in forwardor backward direction. For metal-supported Gr, only C atoms carrying backward momentum aresputtered while a large fraction of atoms carrying forward momentum are trapped in between theGr layer and the substrate. As evident from STM and DFT, trapped C atoms form nm-sized Grplatelets at the interface upon annealing at 1000K, assisted by substrate defects (see �gure). Theincorporation into the Gr layer is suppressed due to high migration barriers, while di�usion intothe Ir is energetically unfavorable. By measuring the area fraction of the platelets, we obtain thetrapping yield, i.e., the number of trapped C atoms per incident ion. Interestingly, compared tothe sputtering yield, the trapping yield for Gr on Ir(111) displays a distinctly di�erent dependenceon the ion beam angle of incidence.

References

[1] Standop et al., Nano Lett., 13, 1948 (2013).[2] Akcöltekin et al., Appl. Phys. Lett., 98, 103103 (2011).[3] Åhlgren et al., Phys. Rev. B, 88, 155419 (2013).

STM topograph of a graphene platelet at the graphene/Ir(111) interface emerging after ionirradiation at room temperature under normal incidence and subsequent annealing at 1000 K.

Image size is 13 nm x 12 nm.


Graphene-surface interfaces from �rst-principles simulations

Contributed talk

Atodiresei, Nicolae


(1) Dr. Nicolae Atodiresei Peter Grünberg Institut and Institute for Advanced SimulationForschungszentrum Jülich Leo-Brandt-Straÿe D-52425 Jülich, Germany

In order to construct a functional graphene-based electronic component it is essential to gain afundamental theoretical understanding of the graphene-electrode interface which in turn essentiallycontrols the transport properties of the graphene-based device. Of course, the geometrical, electronicand magnetic structure of a graphene-surface interfaces are determined by the adsorbate-substrateinteraction. Depending on the strength of the graphene-surface interaction, one can distinguishbetween the (i) strong (weak) chemisorption implying a direct overlap of the graphene and surfaceelectronic states, (ii) a physisorption due to the long range van der Waals interactions and (iii) anelectrostatic interaction due to an electron transfer between graphene and its supporting substrate.We will present a theoretical systematic study that explains how the subtle interplay betweenthe chemical, electrostatic and the weak van der Waals adsorption mechanisms determines thegeometry, electronic and magnetic structure of graphene adsorbed on substrates with di�erentchemical reactivities. Such �rst-principles calculations are applied to unravel the electronic andmagnetic properties of the adsorbed graphene on surfaces and can provide not only the basic insightsneeded to interpret surface-science experiments but are also a key tool to design graphene-substratesystems with tailored properties that can be integrated in graphene-based devices.

References

[1] K. V. Raman, A. M. Kamerbeek, N. Atodiresei, A. Mukherjee, T. K. Sen, P. Lazic, V.Caciuc, R. Michel, D. Stalke, S. K. Mandal, S. Blügel, M. Munzenberg, J. S. Moodera, �Interfaceengineered templates for molecular spin memory and sensor devices�, Nature 493, 509 (2013).

[2] S. Schumacher, T. Wehling, P. Lazic, S. Runte, D. Förster, C. Busse, M. Petrovic, M. Kralj,S. Blügel, N. Atodiresei, V. Caciuc, T. Michely, �The backside of graphene: manipulating adsorptionby intercalation�, Nano Letters 13, 5013 (2013).

[3] M. Petrovic, I. �rut, S. Runte, C. Busse, J. T. Sadowski, P. Lazic, I. Pletikosic, Z.-H Pan,M. Milun, P. Pervan, N. Atodiresei, R. Brako, D. �okcevic, T. Valla, T. Michely, M. Kralj, �Themechanism of caesium intercalation of graphene�, Nature Communications 4, 2772 (2013).

[4] R. Mazzarello, Y. Li, D. Subramaniam, N. Atodiresei, P. Lazic, V. Caciuc, C. Pauly, A.Georgi, C. Busse, T. Michely, M. Liebmann, S. Blügel, S.; Pratzer, P.; Morgenstern, M., �Absenceof magnetic edge states at zigzag edges of graphene on Ir(111)�, Advanced Materials 25,1967 (2013).

[5] R. Decker, J. Brede, N. Atodiresei, V. Caciuc, S. Blügel, R. Wiesendanger, �Atomic-scalemagnetism of cobalt-intercalated graphene�, Physical Review B 87, 041403 (2013).


Graphene tunable electronic tunneling transparency: A uniquetool to measure the local coupling.

Contributed talk

González Herrero, Héctor, (1); Martínez Galera, Antonio Javier, (2); Moreno Ugeda, Miguel,(3); Craes, Fabian, (2); Fernández Torre, Delia, (4); Pou, Pablo, (4); Pérez, Rubén, (4); GómezRodríguez, José María, (1); Brihuega, Iván, (1)


(1) Dept. Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid,Spain

(2) II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany(3) Department of Physics, UC Berkeley, Materials Science Division, Lawrence Berkeley Na-

tional Laboratory,366 Birge Hall,Berkeley, CA 94720, USA(4) Dept. de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid,

E-28049 Madrid ,Spain

Graphene grown on metals has proven to be an excellent approach to obtain high qualitygraphene �lms [1,2]. However, special care has to be taken in order to understand the interac-tion of graphene with the substrate, since it can strongly modify its properties even in apparentlyweakly coupled systems [3].

Here, we have grown one monolayer graphene on Cu (111) by using a new technique consistingin the thermal decomposition of low energy ethylene ions irradiated on a hot copper surface [4].By means of low temperature STM/STS experiments, complemented by density functional theorycalculations, we have obtained information about the structural and electronic properties of ourgraphene samples with atomic precision and high energy resolution. Our work shows that dependingon the STM tip apex and the tunnel parameters we can get access to either the graphene layer,the copper surface underneath or even both at the same time, see Figure 1. This fact provides aunique tool to investigate the local coupling between the graphene layer and the metal underneath.Moreover, this approach can also be applied to investigate the interaction of point defects in thegraphene layer with the underlying substrate [5].

References

[1] J. Wintterlin and M. L. Bocquet, Surf. Sci., 603, 1841(2009).[2] X. S. Li et al., Science, 324, 1312 (2009).[3]I. Brihuega, P. Mallet et al., Phys. Rev. Lett., 109, 196802 (2012).[4] A.J. Martínez-Galera, I. Brihuega et al., Nano Letters, 11, 3576 (2011).[5]M. M. Ugeda, D. Fernández-Torre et al., Phys. Rev. Lett., 107, 116803 (2011).

Same 60x60 nm2 terrace measured with di�erent tunneling conditions. a) the moire pattern of thegraphene layer is observed. b) the standing-waves patterns associated with the Cu(111) surface

state below the graphene layer are observed. Both images are measured at 6K.


Tuning the van derWaals Interaction of Graphene with Moleculesby Doping

Contributed talk

Huttmann, Felix, (1) Martínez-Galera, Antonio J., (1) Atodiresei, Nicolae, (2) Caciuc, Vasile,(2) Blügel, Stefan, (2) Wehling, Tim O., (3) Michely, Thomas, (1)


(1) II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany(2) Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich,

52428 Jülich, Germany(3) Bremen Center for Computational Material Science (BCCMS), Universität Bremen, Am

Fallturm 1a, 28359 Bremen, Germany

Strong n-doping of graphene on its epitaxial substrate can be introduced via intercalation ofhighly electropositive elements such as Cs and Eu, and has recently been shown to lead to reducedbinding energy for electropositive, ionic adsorbates [1].

Here, we explore tuning of graphene's van der Waals (vdW) interaction with adsorbates viadoping. Employing an all in-situ surface science approach, we �nd by scanning tunneling microscopyand thermal desorption spectroscopy a signi�cantly higher binding energy on n-doped as opposed toundoped graphene for the vdW-bonded molecules benzene and naphthalene. This is just oppositeto the case of electropositive, ionic adsorbates. Based on the model character of these simple pi-conjugated molecules [2], we propose that the strength of the van der Waals interaction is modi�edby doping. The experimental results are compared to density functional calculations, including vander Waals interactions.

References

[1] S. Schumacher et al., Nano Lett. 13, 5013 (2013).[2] S. D. Chakarova-Käck et al., Phys. Rev. Lett. 96, 146107 (2006).


Sublattice localized electronic states in atomically resolved Graphene-Pt(111) edge-boundaries and its relation with the Moiré pat-terns

Contributed talk

Merino, Pablo (1); Rodrigo, Lucia (2); Pinardi, Anna (3); Méndez, Javier (3); López, Maria (3);Martinez, Ignacio (3); Pou, Pablo (2); Pérez, Ruben (2); Martín-Gago, Jose A. (3)


(1) Centro de Astrobiología INTA-CSIC, Carretera de Ajalvir, km.4, E-28850, Madrid, Spain(2)Dpto. de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-

28049, Madrid, Spain(3)Instituto de Ciencias de Materiales de Madrid CSIC, C. Sor Juana Inés de la Cruz 3, E-

28049 Madrid, Spain

Understanding the connection of graphene with metal surfaces is a necessary step for developingatomically-precise graphene-based technology. Combining high resolution STM experiments andDFT calculations we have unambiguously unveiled the atomic structure of the boundary betweena graphene zigzag edge and a Pt(111) step. On this surface, the steps are nucleation lines and wehave shown that the graphene edges minimize their strain by inducing a 3-fold edge-reconstructionon the metal side. DFT calculations and atomically resolved STM images show the existence ofan unoccupied electronic state, which is exclusively localized in the C-edge atoms of a particulargraphene sublattice. Moreover, we have depicted a model that shows the relation between thedi�erent Moiré orientations and the direction of the interface-edage

References

[1] P. Merino et al. ACS nano 5 ,5627-5634 (2011).

STM image showing an atomically resolved Graphene-Pt(111) edge-boundary.


Uncovering Damping Mechanisms of Plasmons in Graphene

Contributed talk

Buljan, Hrvoje (1); Jablan, Marinko (2); Solja£ic, Marin (3);


(1) Department of Physics, Faculty of Science, University of Zagreb, Bijeni£ka c. 32, 10000Zagreb, Croatia

(2)ICFO - The Institute of Photonic Sciences, Mediterranean Technology Park, Av. CarlFriedrich Gauss 3, 08860 Castelldefels (Barcelona), Spain

(3) Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue,Cambridge MA 02139, USA

The development of nanophotonics depends on our ability to con�ne and control light at scalesmuch smaller than the wavelength of light. One, and perhaps the only viable path towards this goal,is to use surface plasmons - collective excitations of electrons and light at the interface of a conductorand a dielectric [1]. Plasmon wavelength can be much smaller than the wavelength of light in air atthe same frequency of the wave, which enables smaller di�raction limit in the plane of propagationand exponentially strong con�nement (at the scale of the plasmon wavelength) perpendicular tothe plane of propagation. However there is a tradeo-o�: The strong subwavelength con�nement oflight is generally accompanied with large losses resulting in small propagation lengths of plasmonicexcitations, imposing a large obstacle to development of nanophotonics. When graphene | a singlesheet of carbon atoms organized in a honeycomb lattice with its extremely interesting electricaland optical properties was isolated on a dielectric substrate [2], graphene plasmons became a veryhot topic of research in the nanophotonic community due to their strong con�nement of light,the possibility of control via gate voltage, and potentially smaller losses than in the previouslyused systems [3]. The understanding of plasmon losses in graphene is of key importance for theirpotential use in nanophotonics [3]. There are a number of possible damping pathways for plasmonsin graphene, which we discuss in light of the recent experiments [4-6] where plasmon grapheneproperties were studied. First we point out that Landau damping can be eliminated by doping(e.g., back-gate doping) of graphene. Second we discuss scattering from phonons and electron-electron scattering beyond random-phase approximation. Finally we address the role of impuritiesand attempt to provide the intrinsic limits on plasmon damping [7]. Some other advantages ofgraphene plasmons as the possibility of operation in a broad frequency range (including THz) willbe discussed.

References

[1] W.L. Barnes, A. Dereux, and T. W. Ebbesen, Nature 424, 824, (2003).[2] K.S. Novoselov et al., Science 306, 666, (2004).[3] M. Jablan, H. Buljan, and M. Solja£i¢, Phys. Rev. B 80, 245435 (2009).[4] H. Yan et al., Nature Nanotechnology 7, 330 (2012).[5] J. Chen et al., Nature 487, 77 (2012).[6] Z. Fei et al., Nature 487, 82 (2012).[7] M. Jablan, M. Solja£i¢, and H. Buljan, Phys. Rev. B 89, 085415 (2014).


High-quality single atom N-doping of graphene/SiC(0001) byion implantation

Contributed talk

Telychko, Mykola, (1); Mutombo, Pingo, (1); Ondracek, Martin, (1); Hapala, Prokop, (1);Berger, Jan, (1); Spadafora, Evan, (1); Jelinek, Pavel, (1,2); Svec, Martin, (1)


(1) Institute of Physics of the AS CR, Cukrovarnická 10, 162 00 Praha, Czech Republic(2) Graduate School of Engineering, Osaka University 2-1, Yamada-Oka, Suita, Osaka 565-

0871, Japan

Proper functionalization of graphene, in particular substitutional doping, has received enhancedinterest these days. Nitrogen doping [1,2] is probably one of the most extensively studied routes totune the electronic properties of pristine graphene. Despite of these advances still there is a lackof a method, which provides high-quality N-doped graphene with nitrogen exclusively located atsubstitutional con�guration and without introduction of additional undesired impurities.

Here we report a straightforward method to produce high-quality nitrogen-doped graphene onSiC(0001) using direct nitrogen ion implantation and subsequent stabilization at temperaturesabove 1300K with no additional defects. In addition, we demonstrate that double defects, whichcomprise of two nitrogen defects in a second-nearest-neighbor (meta) con�guration, can be formedin a controlled way by adjusting duration of bombardment. We also explain atomic STM contrastof single N-doped in terms of the quantum interference, which provides more information aboutelectron transport in N-doped graphene.

References

[1] L. Zhao et al Science 333, 999, (2011).[2] J.C. Meyer et al Nature materials, 10, 209 (2011).

A pair of 9x9nm2 current maps of graphene with substitutional N-defects, exhibiting the two mostexperimentally observed atomically-resolved contrasts: (left) a hollow-triangle contrast and (right)

full-triangle contrast. The insets show registration of the defects with the graphene lattice.


Electronic and optical properties of atomically precise graphenenanoribbons

Contributed talk

Cai, Jinming, (1); Pignedoli, Carlo A., (1); Talirz, Leopold, (1); Söde, Hajo, (1); Denk, Richard,(2); Hohage, Michael, (2); Zeppenfeld, Peter, (2); Feng, Xinliang, (3); Müllen, Klaus, (3); Wang,Shudong, (4); Prezzi, Deborah, (4); Ferretti, Andrea, (4); Ruini, Alice, (4,5); Molinari, Elisa, (4,5);Liang, Liangbo, (6); Meunier, Vincent, (6); Ru�eux, Pascal, (1); Fasel, Roman, (1)


(1) Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf,Switzerland

(2) Institute of Experimental Physics, Johannes Kepler University, 4040 Linz, Austria(3) Max Planck Institute for Polymer Research, 55128 Mainz, Germany(4) CNR-Istituto Nanoscienze, S3 Center, 41125 Modena, Italy(5) Department of Physics, Mathematics, and Informatics, University of Modena and Reggio

Emilia, 41125 Modena, Italy(6) Department of Physics, Rensselaer Polytechnic Institute, Troy, NY 12180, United States of

America

Graphene nanoribbons (GNRs) � narrow stripes of graphene � are predicted to be semicon-ductors with an electronic band gap that sensitively depends on the ribbon width. For armchairGNRs (AGNRs) the band gap is inversely proportional to the ribbon width, with an additionalquantum con�nement-related periodic modulation which becomes dominant for AGNRs narrowerthan 3 nm. This allows, in principle, for the design of GNR-based structures with speci�c andwidely tunable properties, but requires structuring with atomic precision. Recently, we have shownthat a surface-assisted synthetic route using speci�cally designed precursor monomers allows forthe fabrication of ultra-narrow graphene nanoribbons with the needed precision [1].

Here, we will report on detailed experimental investigations of their structural, electronic andoptical properties [1-5]. For the case of AGNRs of width N=7 (7-AGNR), the electronic bandgap and band dispersion have been determined with high precision [2,3]. Optical characterizationhas revealed important excitonic e�ects [4], which are in good agreement with expectations forquasi-one-dimensional graphene systems. The versatility of the bottom-up approach also allows forthe fabrication of substitutionally doped GNRs and heterostructures [5]. First attempts at �elde�ect transistor fabrication and characterization reveal serious challenges in patterning and contactfabrication that are related to the nanoscale dimensions of individual AGNRs.

References

[1] J. Cai et al., Nature, 466, 470 (2010).[2] P. Ru�eux et al., ACS Nano, 6, 6930 (2012).[3] L. Talirz et al., J. Am. Chem. Soc. 135, 2060 (2013) ; H. Söde et al., submitted.[4] R. Denk et al., submitted.[5] J. Cai et al., submitted.


Ultra-narrow armchair graphene nanoribbons investigated in this work.


Con�nement of Dirac Electrons on Graphene Quantum Dots

Contributed talk

Jolie, Wouter (1); Craes, Fabian (1); Petrovic, Marin (2); Atodiresei, Nicolae (3); Caciuc, Vasile(3); Blügel, Stefan (3); Kralj, Marko (2); Michely, Thomas (1); Busse, Carsten (1)


(1) II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany(2) Institut za �ziku, Bijenicka 46, 10000 Zagreb, Croatia(3) Peter Grünberg Institut (PGI) and Institute for Advanced Simulation (IAS), Forschungszen-

trum Jülich and JARA, 52425 Jülich, Germany

Graphene Quantum Dots (GQD) are a model system to observe quantum size e�ects due tothe con�nement of electronic states to their small area. The observation [1-4] of these states onepitaxial GQDs on Ir(111) has led to a debate: Are the standing wave patterns arising from theDirac electrons of graphene or from the free electron-like surface state of Ir(111)? Since bothbands have similar slopes in a wide k-range, no clear identi�cation can be made. We solve thisproblem by intercalating oxygen between graphene and Ir(111). We show with angle-resolvedphotoemission spectroscopy (ARPES) that the oxygen suppresses the surface state and e�ectivelydecouples graphene. Density functional theory supports this �nding, showing an increased distancebetween graphene and its substrate while hybridization between the states is absent. We observespatial con�nement on GQDs with scanning tunneling microscopy. We analyze the states with arelativistic particle-in-a-box model and �nd a linear dispersion relation in agreement with ARPES.This is the �rst clear observation of the con�nement of graphene's Dirac electrons since a dispersivesurface state is ruled out. We record additional graphene signatures - a dip in the density ofstates and standing wave patterns arising from intervalley scattering, underlining the decoupling ofgraphene on our substrate.

References

[1] D. Subramaniam et al., Phys. Rev. Lett. 108, 046801 (2012).[2] S. K. Hämäläinen et al., Phys. Rev. Lett. 107, 236803 (2011).[3] S.-H. Phark et al., ACS Nano 5, 8162 (2011).[4] S. J. Altenburg et al., Phys. Rev. Lett. 108, 206805 (2012).

(a) STS-spectra recorded on graphene, revealing the energies of the con�ned states. (b) STM andSTS images of the GQD, the later measured at the three energies highlighted by three blue verticallines in the spectra in (a). The di�erently shaded dots indicate where the spectra were detected.


Formation and growth dynamics of graphene nanoribbons: in-�uence of substrate reactivity

Contributed talk

Simonov, Konstantin, (1), (2), (3); Vinogradov, Nikolay, (1), (2), (4); Vinogradov, Alexander,(3); Generalov, Alexander,(2), (3), (5); Zagrebina, Elena, (3); Mårtensson, Nils, (1),(2); Cafolla,Attilio (6); Carpy, Tomas, (6); Cunni�e, John, (6); Preobrajenski, Alexei, (2)


(1)Department of Physics, Uppsala University, Box 530, 75121, Uppsala, Sweden(2)MAX-lab, Lund University, Box 118, 22100, Lund, Sweden(3)V.A. Fock Institute of Physics, St. Petersburg State University, 198504, St. Petersburg,

Russia(4)European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, B.P. 220, FR-38043, Greno-

ble Cedex, France(5)Institute for Solid State Physics, Dresden University of Technology, DE 01062, Dresden,

Germany(6)School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland

Atomically precise armchair graphene nanoribbons (AGNRs) can be fabricated via thermallyinduced polymerization of 10,10'-dibromo-9,9'-biantracene (DBBA) on metal surfaces [1]. Thoughthe growth mechanism of GNRs on Au(111) is roughly known, the e�ect of substrate on growthand structure of the GNRs remains to be established. In this talk we focus on the process ofAGNRs growth on Au(111), Ag(111) and Cu(111) by means of core-level spectroscopies (Fig.1,a,b)used in combination with scanning tunnel microscopy (STM) (Fig.1,c). At room temperature (RT)the DBBA molecules remain intact on Au(111), while on Cu(111) full dehalogenation occurs andtilted polymer chains start to appear. On Ag(111) the DBBA molecules are partially dehalogenatedat RT, thus leading to distinctive features in GNRs formation. On inert Au(111) dehalogenationcompletes at 200◦C with the formation of polyantracene chains. Further annealing of the Au(111)substrate leads to the formation of 7-AGNRs at 400◦C, while on the Ag(111) and Cu(111) surfacesthe formation of GNRs takes place at 350◦C and 250◦C, respectively. On Cu(111) the orientationof GNRs appears to be governed by a strong ribbon-substrate interaction which is not observedfor weakly-bonded GNRs on Au(111) (Fig.1,c). Moreover, we demonstrate that on Cu(111) thepresence of atomic Br does not disrupt the growth of GNRs. In general, core-level spectroscopiesare shown to be highly informative for understanding the details of GNR formation.

References

[1] J. Cai et.al., Nature, 466, 470 (2010).

Fig.1 (a)Temperature evolution of Br 3d PE spectrum on Au(111) and Ag(111);(b)Br 3d PEspectra and corresponding C K-edge NEXAS, recorded after deposition at RT;(c)STM images of

GNRs on Au(111), Ag(111) and Cu(111).


Probing the Electronic Properties of Epitaxial Graphene Flakeson Au(111)

Contributed talk

Fonin, Mikhail (1); Leicht, Philipp (1); Gragnaniello, Luca (1); Tesch, Julia (1); Zielke, Lukas(1); Bouvron, Samuel (1); Voloshina, Elena (2); Hammerschmidt, Lukas (3); Marsoner Steinkasserer,Lukas, (3); Paulus, Beate (3); Dedkov, Yuriy S. (4)


(1) Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany(2) Institut für Chemie, Humboldt Universität zu Berlin, 12489 Berlin, Germany(3) Institut für Chemie und Biochemie, Freie Universität Berlin 14195 Berlin, Germany(4) SPECS Surface Nano Analysis GmbH, 13355 Berlin, Germany

Con�nement of electrons in graphene quantum dots and nanoribbons represents an exciting �eldof research, owing to predicted peculiar electronic and magnetic properties [1,2]. Recent attemptswith the purpose of measuring the properties of graphene nano dots on Ir(111) have revealeddetrimental edge bonding of graphene to the employed iridium substrate. We have developed anin-situ fabrication method of graphene nano �akes (GNFs) on the Au(111) noble metal surface. Weshow that this system is well-suited for scanning tunneling microscopy (STM) investigations of theelectronic properties of epitaxial GNFs.

We show that the prepared GNFs can be easily displaced across terraces at room temperatureby scanning with appropriate tunneling parameters if �akes are initially detached from the Auterraces, underlining negligible graphene-Au bonding. Furthermore, unreconstructed and singlehydrogen terminated graphene edges are observed by STM as con�rmed by the accompanying DFTcalculations. The electronic properties of the graphene �akes can be accessed via quasi-particleinterference mapping at low temperatures (10 K). Owing to the distinctly di�erent positions ofgraphene scattering processes compared to Au surface state backscattering in the Fourier trans-forms, we can unambiguously distinguish between graphene and Au electronic contributions. Ourmeasurements show a linear dispersion for larger graphene �akes with Dirac point shifted towardsthe unoccupied states.

References

[1] K. Nakada, M. et al.; Phys. Rev. B 54, 17954 (1996).[2] O. V. Yazyev; Rep. Prog. Phys. 73, 056501 (2010).

3D STM representation of quasi-freestanding graphene �ake on Au(111) showing herringbonereconstruction and moiré as well as quasi-particle interference at edges


Adding magnetic functionalities to epitaxial graphene by selfassembly on or below its surface

Contributed talk

Garnica, Manuela (1,2); Calleja, Fabian (1); Vázquez de Parga, Amadeo L. (1,2); Miranda,Rodolfo (1,2)


(1)Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Canto-blanco 28049, Madrid, Spain

(2)Dep. Física de la Materia Condensada, Universidad Autónoma de Madrid, Cantoblanco28049, Madrid, Spain

By growing epitaxially graphene on Ru(0001)or Ir(111) under Ultra High Vacuum conditions [1]and adsorbing molecules on it or intercalating heavy atoms below it, we show how to add magneticfunctionalities to graphene.The graphene monolayer on Ru(0001) is spontaneously nanostructuredforming an hexagonal array of nanodomes with a periodicity of 3 nm [2] and localized electronicstates [3]. Cryogenic Scanning Tunnelling Microscopy and Spectroscopy and DFT simulationsshow that isolated TCNQ molecules deposited on gr/Ru(0001) acquire charge from the substrateand develop a sizeable magnetic moment, which is revealed by a prominent Kondo resonance. Themagnetic moment is preserved upon dimer and monolayer formation. The self-assembled molecularmonolayer develops spatially extended spin-split electronic bands with only the majority band�lled, thus becoming a 2D organic magnet whose predicted spin alignment in the ground state isvisualized by spin-polarized STM at 4.6 K [4]. The intercalation of an ordered array of Pb atomsbelow graphene grown on Ir(111) results in the appearance a series of equally spaced, sharp peaksin the di�erential conductance, as revealed by laterally resolved Tunnelling Spectroscopy. The Pbenhances the, usually negligible, spin-orbit interaction of graphene. The spatial variation of thespin-orbit coupling when going from graphene intercalated with Pb to the graphene on Ir(111)creates a pseudo-magnetic �eld that originates pseudo-Landau levels [5]

References

[1] A.L. Vázquez de Parga et al, Phys. Rev. Lett. 100, 056807 (2008).[2] B. Borca et al, Phys. Rev. Lett. 105, 036804 (2010).[3] D. Stradi et al, Phys. Rev. Lett. 106, 186102 (2011).[4] M. Garnica et al, Nature Physics 9, 368 (2013).[5] F. Calleja et al, submitted


Magnetic Coupling and Single-Ion Anisotropy in Surface-SupportedMn-based Metal-Organic Networks

Contributed talk

Giovanelli, Luca, (1); Savoyant, Adrien, (1); Abel, Mathieu, (1); Maccherozzi, Francesco, (2);Ksari, Younal, (1); Koudia, Mathieu, (1); Hayn, Roland, (1); Choueikani, Fadi, (3); Otero, Edwige,(3); Ohresser, Philippe, (3); Themlin, Jean-Marc, (1); Dhesi, Sarnjeet, S., (2); and Clair, Sylvain(1)


(1) Aix-Marseille Université, CNRS, IM2NP UMR 7334, F-13397 Marseille, France(2) Diamond Light Source, Didcot, OX11 0DE, United Kingdom(3) Synchrotron SOLEIL, L'orme des Merisiers, Saint-Aubin - BP48, 91192 Gif-sur-Yvette

CEDEX, France

π-conjugated macrocycles such as phthalocyanines hosting a single transition metal atom haveshown great versatility in producing 2D magnetic arrays. This includes the possibility to modifythe magnetic state of the central metal atom through ferromagnetic (FM) coupling to the substrateand by adsorption of smaller molecules [1]. An alternative approach for the synthesis of magneto-organic nanostructures consists in manipulating the magnetic properties of transition metal atomsthrough selective bonding to functional ligands in surface-supported, self-assembled metal organicnetworks [2,3]. In the present study the electronic and magnetic properties of Mn coordinatedto 1,2,4,5-tetracyanobenzene (TCNB) have been investigated by combining STM and XMCD per-formed at low temperature (3 K). When formed on Au(111) and Ag(111) substrates the Mn-TCNBnetworks display similar geometric structures. Magnetization curves reveal FM coupling of the Mnsites with similar single-ion anisotropy energies, but di�erent coupling constants. Low-temperatureXMCD spectra show that the local environment of the Mn centers di�ers appreciably for the twosubstrates. Multiplet structure calculations were used to derive the corresponding ligand �eld pa-rameters con�rming an in-plane uniaxial anisotropy. The observed interatomic coupling is discussedin terms of superexchange as well as substrate-mediated magnetic interactions.

References

[1] C. Wäckerlin et al., Angew. Chem. Int. Ed. 52, 1 (2013).[2] T. R. Umbach et al., Phys. Rev. Lett. 109, 267207 (2013).[3] N. Abdurakhmanova et al., Phys. Rev. Lett. 110, 027202 (2013).


Angular dependence of XAS and XMCD over the Mn L2,3 edge for Mn-TCNB/Au(111). T=3 K.B=6 T. θ = 0◦ correspond to normal incidence and θ = 70◦ to grazing incidence. The bottom

curves are obtained by ligand �eld multiplet calculations.


Electron scattering and spin polarization at graphene edges onNi(111)

Contributed talk

Garcia-Lekue, Aran, (1,2); Balashov, Timofey, (3); Olle, Marc, (3); Ceballos, Gustavo, (3);Arnau, Andres, (1,4,5); Gambardella, Pietro, (3,6,7); Sanchez-Portal, Daniel, (1,4); Mugarza, Aitor,(3)


(1) Donostia Internatioal Physics Center (DIPC), San Sebastian, Spain(2) IKERBASQUE, Basque Foundation for Science, Bilbao, Spain(3) Catalan Institute for Nanoscience and Nanotechnology (ICN2), Barcelona, Spain(4) Materials Physics Center CFM-MPC, CSIC-UPV/EHU, San Sebastian, Spain(5) University of the Basque Country, UPV/EHU, San Sebastian, Spain(6) Instituciò Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain(7) Swiss Federal Institute of Technology, ETH Zurich, Switzerland

The interaction of graphene with a metal often perturbs its unique electronic properties. How-ever, this interaction can also be positively exploited to engineer graphene-metal hybrid structureswith novel electronic and magnetic properties.

In this work, we investigate graphene nanoislands grown on Ni(111) by local tunneling spec-troscopy measurements combined with spin-polarized ab initio electronic structure calculations[1,2]. We �nd that the electron scattering at the graphene edges is spin- and edge-dependent. Thisbehavior is attributed to the strong distortion of the electronic structure at the interface, whichopens a gap and spin-polarizes the Dirac bands of graphene. Moreover, we demonstrate that edgescattering is strongly structure dependent, with asymmetries in the re�ection amplitude of up to30% for reconstructed and unreconstructed zig-zag edges. These results suggest a lateral 2D spin�ltering for graphene layers, similar to that occurrind across the interface [3].

References

[1] A. Garcia-Lekue et al., Phys. Rev. Lett. (in press)[2] M. Olle et al. Nano Lett. 12, 4431 (2012).[3] V. M. Karpan et al. Phys. Rev. Lett. 99, 176602 (2007).

(a) Topographic (Vb = 0.1V) and constant current dI/dV map showing the interference pattern ofthe S1 surface state scattered from graphene islands. Setpoint current: I = 0.3 nA. Image size: 30x 37 nm2. (b) Dispersion relation obtained from the standing wave periodicity. A parabolic curve

is included.


Behavior of Dirac and massive electrons in superlattices of bareand quasifreestanding graphene on Fe(110)

Contributed talk

Varykhalov, Andrei, (1); Sanchez-Barriga, Jaime, (1); Marchenko, Dmitry, (1); Hlawenka, Peter,(1); Rader, Oliver, (1);


(1) Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II,Albert-Einstein-Strasse 15, 12489 Berlin, Germany

The Dirac electrons forming the π band in graphene have peculiar properties distinct from other,massive quasiparticles. A prominent example is Klein tunneling, theoretically predicted [1] as wellas observed in transport experiments on p-n junctions [2]. In the present contribution we addressthe band structure of a one-dimensional graphene superlattice on Fe(110) [3] studied by angle-resolved photoemission. Unlike the famous case of graphene/Ir(111) which displays intense replicabands with large and extended minigaps in the Dirac cone [4,5], neither band replicas nor minigapsare observed for the π band of graphene on Fe(110). However, the control experiment consisting ofthe measurement of the σ bands from the same system reveals intense σ band replicas shifted inmomentum space according to the superlattice periodicity. We discuss this surprising result withthe help of theoretical investigations. In the second part of the presentation we report electronicproperties of quasifreestanding graphene on Fe(110) achieved by intercalation of Au. Characteriza-tion of its band structure by means of angle- and spin-resolved photoemission shows that interactionwith Au causes remarkable changes of replica bands, charge doping and spin structure of the Diraccone.

References

[1] M. I. Katsnelson et al., Nat. Phys. 2, 620 (2006).[2] A. F. Young, P. Kim, Nature Phys. 5, 222 (2009).[3] N. A. Vinogradov et al., Phys. Rev. Lett. 109, 026101 (2012).[4] I. Pletikosi¢ et al., Phys. Rev. Lett. 102, 056808 (2009).[5] E. Starodub et al., Phys. Rev. B 83, 125428 (2011); J. Sanchez-Barriga et al., Phys. Rev.

B 85, 201413(R)(2012).

ARPES from bare graphene/Fe(110). (a) Dirac cone measured for k‖ perpendicular to theone-dimensional ripples shows no replica bands; (b) and (c) σ band sampled at di�erent photon

energies along the ripples displays pronounced replicas (white arrows).


Observation of a universal donor-dependent vibrational modein graphene: key to superconductivity in graphene

Contributed talk

A., Fedorov (1,2,4); D., Haberer (1); C., Struzzi (2); N., Verbitskiy (3); M., Knupfer (1); B.,Büchner (1); D., Usachov (4); O., Vilkov (4); L., Pettaccia (2); A., Grüneis (1,2,3)

Contact:

(1) IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany(2) Köln Universität, Richmodstr. 10, 50667 Köln, Germany(3) Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy(4)Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria(5) St. Petersburg State University, Ulianovskaya 1 St. Petersburg 198504, Russia

The fundamental interplay of electrons and phonons mediates superconductivity in the conven-tional superconductors and also plays an important role for many properties of undoped cuprates.Angle resolved photoemission (ARPES) has become an important tool which allows to probeelectron-phonon coupling (EPC) as a kink in the spectral function of a material. EPC induced su-perconductivity was found in many other carbon-related materials like intercalated graphite (GIC)[1], fullerene crystals [2], nanotubes [3] and boron [4] doped diamond, however any report aboutsuperconductivity in graphene is still absent. In order to investigate the possible superconductingpairing mechanism in doped graphene, we performed a comprehensive study of alkali and earth-alkaline doped quasi-free-standing graphene using high resolution ARPES measurements of thespectral function [5]. Following detail analysis of the experimentally determined self-energies, whichallows us to extract the underlying Eliashberg functions and ascribe the measured �ne structureto peaks in the phonon dispersion relation of graphene. An unexpected low-energy peak appearsfor all dopants with an energy and intensity that depend on the dopant atom. We show that thispeak is the result of a dopant-related vibration. The low energy and high intensity of this peak arecrucially important for achieving superconductivity, with Ca being the most promising candidatefor realizing superconductivity in graphene.

References

[1] N.B. Hannay, T.H. Geballe, B.T. Matthias, K. Andres, P. Schmidt, and D. MacNair, Phys.Rev. Lett. 14, 225 (1965).

[2] S.P. Kelty, C.-C. Chen, and C. M. Lieber, Nature 352, 223 (1991).[3] Z.K. Tang et al., Science 292, 2462 (2001).[4] E.A. Ekimov, et al., Nature 428, 542 (2004).[5] A.V. Fedorov, N.I. Verbitskiy, D. Haberer, C. Struzzi, L. Petaccia, D. Usachov, O.Y. Vilkov,

D.V. Vyalikh, J. Fink, M. Knupfer, B. Buchner & A. Grüneis, Nature Communications, 5, 3257(2014).

Chapter 3

Posters

55

CHAPTER 3. POSTERS 56

Dual character of excited charge carriers in graphene on Ni(111)

Poster

Bignardi, Luca, (1); Haarlammert, Thorben, (1); Winter, Carsten, (1); Montagnese, Matteo,(2); van Loosdrecht, Paul, (2); Voloshina, Elena, (3); Rudolf, Petra, (4); Zacharias, Helmut, (1)


(1) Physikalisches Institut, University of Münster, Wilhelm-Klemm Str. 10, 48149 Münster,Germany

(2) II. Physikalisches Institut, University of Köln, Zülpicher Str. 77, 50937 Köln, Germany(3) Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin,

Germany(4) Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG

Groningen, The Netherlands

The dynamics of excited charge carriers at the graphene/Ni(111) interface has been investigatedby means of time-resolved, two-photon photoemission spectroscopy, employing fs-XUV pulses withan energy of 39.2 eV produced by high harmonics generation. Due to the interplay of substrate andadsorbate band structures, the dependence of the lifetimes on the energy of the excited carriers wasfound to be similar to that of Ni 3d electrons measured for clean Ni up to 1 eV above the Fermilevel, while it resembled that of graphite from 1 eV above the Fermi level onwards. This result issuggested to be the e�ect of the peculiar electronic structure of the interface, which still possessesfeatures belonging to the pristine graphene layer, such as a residual saddle point.


Dirac Electron Scattering In Caesium Intercalated Graphene

Poster

Daniela, Dombrowski, (1); Sven, Runte, (1); Fabian, Craes, (1); Jürgen, Klinkhammer, (1);Marin, Petrovi¢, (2); Marko, Kralj, (2); Thomas, Michely, (1); Carsten, Busse, (1)


(1) II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany(2) Institut za Fiziku, Bijeni£ka 46, 10000 Zagreb, Croatia

With Fourier-transform scanning tunneling microscopy (FT-STM) one can directly image the2D Fermi contour of a surface by analysing charge carrier scattering patterns arising at defects [1].This enables the determination of a dispersion relation E(k) in STM [1]. We apply FT-STM toa closed caesium intercalated graphene layer [2]. The caesium layer electronically decouples thegraphene from the metallic substrate. This allows the detection of long-range scattering patternsarising, e.g. from intervally-scattering. Defects in the intercalated layer such as domain boundariesact thereby as the necessary scatterers. The trigonal warping of the Dirac cone is already visibleat the Fermi level, because of the strong n-doping due to the intercalated caesium (see picture).We analyse the dispersion relation in the range accessible for FT-STM and compare it with E(k)determined by angular resolved photoemission spectroscopy (ARPES). With FT-STM we also canmap anisotropies in the scattering patterns to the local symmetry of the scatterers and the structureof the sample. Finally, we discuss the suppression of speci�c scattering vectors due to pseudo-spinconservation [3].

References

[1] L. Petersen et al., Physical Review B, 57, 6858 (1998).[2] M. Petrovi¢ et. al, Nature Communications, 4, 2772 (2013).[3] P. Mallet et al., Physical Review B, 86, 045444 (2012).

Scattering patterns arising at defects in a closed caesium intercalated graphene layer. The trigonalwarping of the Dirac cone is clearly visible.


Investigations into the dynamical properties of graphene onIr(111)

Poster

Endlich, Michael (1); Miranda, Henrique (2,3); Molina-Sánchez, Alejandro (2,3); Wirtz, Ludger(2,3); Kröger, Jörg, (1)


(1) Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany(2) Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxem-

bourg(3) Institute for Electronics, Microelectronics, and Nanotechnology [IEMN], CNRS UMR 8520,

Dept. ISEN, F-59652 Villeneuve d'Ascq Cedex, France

The phonon dispersion of singly oriented graphene on Ir(111) was determined by angle-resolvedinelastic electron scattering and density functional calculations. Kohn anomalies of the highestoptical phonon branches were observed at the Γ and K point of the surface Brillouin zone. Whilethe Kohn anomaly at Γ is virtually identical to the Kohn anomaly observed from graphite andpredicted for pristine graphene (Fig. a), the Kohn anomaly at K is weakened (Fig. b). Thisobservation is rationalized in terms of a decrease of the electron-phonon coupling due to screeningof graphene electron correlations by the metal substrate. The measured dispersion curves furtherexhibit replica, which are rationalized in terms of phonon backfolding induced by the graphenemoiré superlattice.

Dispersion of (a) the LO phonon in the vicinity of Γ and of (b) the TO phonon close to K.


Exploring the intercalation process of Cobalt under Graphene

Poster

Lisi, Simone, (1); Di Bernardo, Iolanda, (1); Mariani, Carlo, (1); Pacilé, Daniela, (2); Betti,Maria Grazia, (1)


(1) Dipartimento di Fisica, Università di Roma �La Sapienza�, Piazzale Aldo Moro 5, I-00185Roma, Italy

(2) Dipartimento di Fisica, Università della Calabria, 87036 Arcavacata di Rende [CS], Italy

The structural and electronic properties of graphene (Gr) can be in�uenced by its interactionwith the surrounding environment [1,2] and by modifying the underlying support by adatoms in-tercalation [3,4]. Graphene shows interesting magnetic properties in contact with a ferromagneticmetal, as observed when deposited on Ni(111) [5]. The engineering of permanent magnetic mo-ments in non-magnetic graphene can be achieved by intercalation of magnetic adatoms and it canopen a novel route to design light and �exible magnetic materials. We present a photoemission andabsorption spectroscopy study of Co intercalation in high quality graphene sheets grown on Iridium(111) surface. Core levels photoemission from C1s, Ir4f and Co3p, before and after Co intercalation,shows a homogeneous di�usion of Co adatoms during the intercalation, up to a completion of amismatched corrugated Co monolayer. CK and CoL2,3 edges, together with core levels, unravela mixing of Co with graphene, with C-Co hybridized character, in contrast to the low interactingGr/Ir(111) [2]. Further Co intercalation releases the mismatch of graphene. CoL2,3 absorptionedges reveal a di�erent response, as a function of Co thickness. Graphene can tailor the assemblingof magnetic FePc molecules when deposited on its top [2]. The presence of the Co-intercalated layerinduces interesting electronic response, as deduced by preliminary photoemission results.

References

[1] A. Bostwick et al., Nature Physics, 3, 36 (2007)[2] M. Scardamaglia et al., The Journal of Physical Chemistry C, 117, 3019 (2013)[3] D. Pacilé et al., Physical Review B, 87, 035420 (2013).[4] J. Coraux et al., The Journal of Physical Chemistry Letters 3, 2059 (2012)[5] M. Weser et al., Applied Physics Letters, 96, 012504 (210)


Spin polarization of Co(0001)/graphene junctions from �rstprinciples

Poster

Sipahi, Guilherme, (1,2); Zutic, Igor, (1); Atodiresei, Nicolae (3); Kawakami, Roland, (4); Lazic,Predrag (5)


(1) University at Bu�alo, State University of New York, Bu�alo, NY 14260, USA(2) Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Brazil(3) Peter Grünberg Institut and Institute for Advanced Simulation, Jülich, Germany(4) The Ohio State University, Columbus, Ohio 43210, USA(5) Rudjer Boskovic Institute, PO Box 180, Bijenicka c. 54, 10 002 Zagreb, Croatia

Junctions comprised of ferromagnets and nonmagnetic materials are one of the key buildingblocks in spintronics [1]. With the recent breakthroughs of spin injection in ferromagnet/graphenejunctions it is possible to consider spin-based applications that are not limited to magnetoresistivee�ects [2,3]. However, for critical studies of such structures it is crucial to establish accurate predic-tive methods that would yield atomically resolved information on interfacial properties. By focusingon Co(0001)/graphene junctions and their electronic structure, we illustrate the inequivalence ofdi�erent spin polarizations [4]. We show atomically resolved spin polarization maps [4] as a usefulapproach to assess the relevance of Co(0001)/graphene for di�erent spintronics applications.

References

[1] I. Zutic et al., Rev. Mod. Phys. 76, 323 (2004).[2] H. Dery et al., IEEE Trans. Electron. Dev. 59, 259 (2012).[3] O. M. J. van 't Erve et al., Nature Nanotech. 7, 737 (2012).[4] Sipahi et al., J. Phys. Cond. Matter, in press.


Highly spin-polarized Dirac fermions at the graphene-Co in-terface

Poster

Marchenko, Dmitry, (1); Varykhalov, Andrei, (1), Sanchez-Barriga, Jaime, (1); Carbone, Carlo(2); Rader, Oliver (1)


(1) Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II,Albert-Einstein-Strasse 15, 12489 Berlin, Germany

(2) Istituto di Struttura della Materia�Consiglio Nazionale delle Ricerche, Basovizza, 34149Trieste, Italy

The interface of graphene with ferromagnets is most interesting for spintronics. Grapheneepitaxially grown p(1x1) on Co(0001) shows an intact Dirac cone [1]. A strong hybridization ofthe upper Dirac cone with Co3d states is present but it occurs away from the K-point. We showby spin- and angle-resolved photoemission that these ingredients are balanced to such an extentthat the intact Dirac cone is strongly spin polarized with a spin polarization of 60% of the Diracpoint. The polarization is of minority spin meaning an antiparallel coupling of graphene andCo magnetic moments. Wave-vector dependent measurements exclude a spin-orbit contributionto the spin polarization, and the ferromagnetic alignment is veri�ed by reversal of the remanentmagnetization. The importance of the spin polarization at the interface for spin �ltering is pointedout since previously a bu�er layer of noble metals has been required for obtaining spin-�lteredintact Dirac cones. In addition, the use of the present results for possible combination with strongspin-orbit e�ects is pointed out.

References

[1] A. Varykhalov et al., Phys. Rev. X 2, 041017 (2012).

Spin-resolved photoemission at the K-point of graphene/Co(0001). (a) and (b) are for oppositemagnetization directions. (c) spin asymmetries from (a) (blue) and (b) (green). Zero asymmetrylevel is indicated as dashed line. (d-f) Same but for 23° away from K. Photon energy is 62 eV.


Surface umklapp in ARPES : Seeing through 2D overlayers

Poster

Giovanelli, Luca, (1); Bocquet, François C., (2); Amsalem, Patrick, (3); Abel, Mathieu, (1);Salomon, Eric, (4); Koch, Norbert, (3); Petaccia, Luca (5); Goldoni, Andrea (5); Themlin, Jean-Marc, (1)


(1) Aix-Marseille Univ., IM2NP, UMR CNRS 7334, Marseille, France(2) Peter Grünberg Institut (PGI-3), Functional Nanostructures at Surfaces, Forschungszentrum

Jülich, 52425 Jülich, Germany(3) Humboldt-Universität zu Berlin, Institut für Physik, D-12489 Berlin, Germany(4) Aix-Marseille Univ., PIIM, F-13397, Marseille, France(5) Elettra Sincrotrone Trieste, Strada Statake 14 km 163.5, I-34149 Trieste, Italy

Atomically-thick 2D materials can be synthesized e.g. from atomic or molecular precursorson well-de�ned single-crystal metal surfaces acting both as a catalyst and structural template[1,2,3]. Angle-resolved photoemission (PE), which provides a direct access to the overlayer 2D bandstructure, is a prominent tool to study the electronic properties of these extended 2D nanostructuresand epitaxial 2D crystals. However, the identi�cation of genuine features of the overlayer is oftencomplicated by the simultaneous contribution of both the adsorbate and the substrate to the overallPE spectral shape. In particular, electronic states of the substrate may get folded back in k spacethrough scattering by the ordered overlayer, leading to additional substrate-related features, ane�ect also known as surface-umklapp. Going through several examples of 2D overlayers on metalsurfaces, it is shown that, once back-folded, the clean surface contribution of localized and weaklydispersing d-states is completely washed away: ARPES spectra then mimic that of a substratepoly-crystal [4]. By employing low photon-energy photoemission and �rst-principle calculations,we show how a 2D ordered overlayer made of ZnPc molecules can be used as a di�raction lattice toe�ectively probe the Ag band structure (Fig. 1) [5]. In conclusion, the recognition of the ubiquitousrole of surface-umklapp e�ects should help disentangling genuine adsorbate features from substratecontributions.

References

[1] M. Corso et al,. Science, 303, 217 (2005).[2] J. Lobo-Checa et al., Science 325, 300 (2009).[3] L.Porte et al., Int.J.Nanotechnol., 9, 325 (2012).[4] L. Giovanelli et al., Phys. Rev B, 87, 035413 (2013).[5] F. Bocquet et al., 84, 241407(R) (2011).

Fig.1 (a) ARPES image of 1ML ZnPc/Ag(110) around normal emission with hν=9 eV; red andblue EB(?e) dispersion curves correspond to sp di�racted photoelectrons; the dashed lines locatethe HOMO and LUMO of ZnPc. (b) ARPES image of clean Ag(110); the green lines origin from

the sp direct transitions.


Dopant-controlled and substrate-dependent electronic proper-ties of graphene

Poster

Usachov, Dmitry, (1); Fedorov, Alexander, (1); Vilkov, Oleg, (1); Vyalikh, Denis V., (1,2)


(1) Faculty of Physics, St. Petersburg State University, 198504, St. Petersburg, Russia(2) Institute of Solid State Physics, Dresden University of Technology, 01062 Dresden, Germany

Many research e�orts are focused at elaboration of methods for tuning the graphene propertiesfor its better performance in electronic applications. One of the promising approaches is dopingwith heteroatoms. In particular, nitrogen-doped graphene (N-graphene) is a perspective materialfor batteries, supercapacitors, Pt-free fuel cells, electrochemical sensors, etc. However, the impact ofnitrogen on the graphene electronic properties substantially depends on its local chemical bonding.Thus, the bonding type must be precisely controlled. Recently we have proposed an approach forthe large-scale N-graphene synthesis with the post-synthesis tuning of dopant bonding [1]. Herewe uncover the dependence of the N-graphene electronic structure and charge transfer on thetype and concentration of impurities, and discuss the kinetics and mechanism of interconversionbetween di�erent nitrogen bonding con�gurations. Another successful approach for controllingthe graphene properties is surface alloying of di�erent atoms underneath graphene. It providespossibility for varying the strength of graphene bonding to substrate and allows tuning of thesubstrate composition and properties [2]. Here we demonstrate this approach by several recentexamples, including formation of graphene contacts with di�erent metal silicides, widely used insilicon-based electronics. This provides a further step towards integration of graphene with theexisting silicon technology.

References

[1] D. Usachov, et al., Nano Lett., 11, 5401 (2011).[2] O. Vilkov, et al., Sci. Reports, 3, 2168 (2013).


Graphene on Ir(111), adsorption and intercalation of Cs andEu atoms

Poster

Lazi¢, Predrag (1); Damir, Sokcevic (1); Radovan, Brako (1); Petrovi¢, Marin (2); �rut Raki¢,Iva (2); Kralj, Marko (2); Milun, Milorad (2); Pervan, Petar (2); Pletikosi¢, Ivo (2); Atodiresei,Nicolae (3); Caciuc, Vasile (3); Bluegel, Stefan (3); Michely, Thomas (4); Runte, Sven (4); Busse,Carsten (4); F. Foerster, Daniel (4); Schumacher, Stefan (4); Wehling, Tim, O. (5, 6); Valla, Tonica(7); Pan, Z.-H. (7); Sadowski, J. T. (8)


(1) Rudjer Boskovic Institute, Zagreb, Croatia(2) Institut za �ziku, Bijeni£ka 46, 10000 Zagreb, Croatia(3) Peter Grünberg Institut & Institute for Advanced Simulation, Forschungszentrum Jülich and

JARA 52425, Julich, Germany(4) II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany(5) Institut für Theoretische Physik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen,

Germany(6) Bremen Center for Computational Material Science (BCCMS), Universität Bremen, Am

Fallturm 1a, 28359 Bremen, Germany(7) Department of Condensed Matter Physics & Materials Science, Brookhaven National Lab,

Upton, New York 11973, USA(8) Center for Functional Nanomaterials, Brookhaven National Lab, Upton, New York 1197

Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) willbe presented. Graphene on Ir(111) surface is an interesting system because graphene has almostpristine electronic structure in it due to its weak bonding character to iridum surface. The bond-ing is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphenegets doped and and nature of binding changes - especially in the case when the atoms intercalate.Density Functional Theory calculations with standard semilocal functionals (GGA) - fail to repro-duce experimental �ndings even qualitatively. Only when the newly developed nonlocal correlationfunctional is used (vdW-DF) which includes van der Waals interactions, are the calculations inagreement with experiment, revelaing the mechanism of graphene delamination and relaminationwhich is crucial for intercalation and trapping of atoms under the graphene.

References

[1] M. Petrovic et al., Nature Comm. 4, 2772 (2013).[2] S.Schumacher et al., Nano Letters 13, 5013 (2013).


Controllable nitrogen doping of graphene via a versatile plasma-based technique

Poster

Lin, Yu-Pu, (1) ; Ksari, Younal, (1) ; Prakash, Jai, (1) ; Giovanelli, Luca, (1) ; Themlin,Jean-Marc, (1)


(1) Aix-Marseille Université, CNRS, IM2NP, UMR 7334, 13397 Marseille, France

The e�ective chemical doping of graphene, able to in�uence its electronic and chemical proper-ties, is actively pursued [1]. Indeed, the N-doped graphene has been reported to exhibit superiorperformance over the pristine material in several applications (�eld-e�ect transistors, batteries, fuelcells, and super-capacitors) [2-5]. However, methods to realize a reliable and controlled dopinghave still to be mastered. In this work, we present an e�ective, versatile plasma-based method forthe nitrogen-doping of graphene grown on 6H-SiC(0001). Using a tunable hybrid plasma source,graphene monolayers are exposed to a stream of N ions and/or to a neutral �ow of thermalized Nspecies. The electronic doping levels of the N-doped graphene (NG) are revealed through the analy-sis of the pi* states dispersion using angle-resolved inverse photoemission spectroscopy (ARIPES).It shows that low-energy N ions (5 35 eV) cause an n-type doping (up to 0.4 eV, �g.1b) with amajority of graphitic (substitutional) N (up to 8.7%, �g.1a,c), as revealed by XPS (NG-ion spec-trum below). In contrast, neutral N species rather form pyridinic-N in the presence of defects(NG-atom spectrum). In brief, we show that the bonding environment of N atoms in graphenecan be easily controlled using a versatile plasma-based technique, which will certainly be of greatinterest for the processing of future graphene-based nano-devices using widespread technologies likeplasma-processing.

References

[1] H. Liu, Y. Liu, and D. Zhu, Journal of Materials Chemistry, 21, 3335 (2011).[2] D. Wei, Y. Liu, Y. Wang, et al. Nano Letters, 9, 1752-1758 (2009).[3] M. D. Stoller, S. Park, et al. Nano Letters, 8, 3498 (2008).[4] D. Pan, S. Wang, et al. Chem. Mater., 21, 3136 (2009).[5] H. M. Jeong, J. W. Lee, et al. Nano Letters, 11, 2472 (2011).

Figure 1. (a) The three major doping con�gurations of N in graphene: Pyridinic-N, Pyrrolic-Nand Graphitic-N. (b) Linear extrapolation of the π states obtained by ARIPES for pristine

graphene (PG), NG-ion and NG-atom with respect to k|| along Γ-K. (c) N 1s XPS spectra of thestudied NG samples.


Graphene and Moirés

Poster

Bhatti, Asif Iqbal (1); Ferhat, Karim (1); Lançon, Frédéric (2); Ralko, Arnaud (1); Coraux,Johann (1); Magaud, Laurence (1)


(1) Institut Néel, CNRS and UJF, Grenoble, France(2) LSIM, INAC,CEA Grenoble, Grenoble, France

Graphene outstanding properties are related to its honeycomb lattice and any perturbation tothis sp2 lattice can induce drastic changes [1]. Here we address the case of moiré superperiodsimposed to graphene. Their origins can be multiple: interaction with a substrate such as a metalsurface, h-BN or SiC [2,3], rotated graphene bilayers [4] and defects network. The strength of theinteraction can range from very weak van der Waals interaction to the local formation of strongcovalent bonds. All these cases will be discussed on the basis of ab initio calculations coupled toan e�ective potential description. Superperiods can induce important modi�cations of the elec-tronic structure of graphene: loss of the linear dispersion and of the Dirac cones in the case ofvery strong interaction but also additional Dirac cones, gap opening, van Hove singularities, local-ization and con�nement e�ects for weaker coupling. Graphene morphology also strongly dependson the strength of the interaction and the lattice mismatch, resulting in corrugations with variableamplitude and formation of wrinkles [5].

References

[1] Pedersen, T. et al. Phys. Rev. Lett. 100, 136804 (2008).[2] C.Tonnoir et al, Phys. Rev. Lett.111, 246805 (2013).[3] F.Varchon et al, Phys. Rev.B 77, 235412 (2008).[4] G.Trambly de Laissardière et al, Phys.Rev.B86,125413 (2012).[5] H. Hattab et al, Nano Lett. 12, 678 (2012).

Figure: Graphene on rhenium, side view that shows a strong corrugation (left); Band structureand density of states of a twisted graphene bilayer with a rotation angle of 7°.


E�ects of uniaxial structural modulation on graphene's elec-tronic structure

Poster

�rut Raki¢, Iva, (1); Mik²i¢ Trontl, Vesna, (1); Pervan, Petar, (1); Craes, Fabian, (2); Jolie,Wouter, (2); Busse, Carsten, (2); Lazi¢, Predrag, (3); Kralj, Marko, (1)


(1) Institut za �ziku, Bijeni?ka cesta 46, 10000 Zagreb, Croatia(2) II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany(3) Institut Ru�er Bo²kovi¢, Bijeni£ka cesta 54, 10000 Zagreb, Croatia

Engineering of graphene's electronic structure presents a vital course in graphene research due tospeci�c requirements in crucial applications such as electronics or optoelectronics. In this work weutilize the fact that structural modi�cations of graphene, in particular the ones involving strain, leadto changes of its electronic structure. Our approach, linked to strain engineering, is based on growinggraphene on a stepped surface Ir(332). Graphene on Ir(332) causes severe surface restructuringresulting in new mesoscopic features consisting of wide (111) terraces bounded by step bunchesdominantly of (133) orientation. We have studied this system by means of STM, STS, ARPES andDFT. ARPES averaged on a scale of micrometer, shows an anisotropy of the Fermi velocity as wellas a slight n-doping. In addition, STS spectra and maps visualize electronic states localized on�at terraces, step bunches or step edges, showing distinction depending on a direction of graphenebending. More detailed examination of step bunches reveals an additional electronic substructurelikely mediated by local changes in van der Waals interaction with the substrate. Finally, vdW-DFTresults, based on models involving characteristic (111), (133) and (332) structures, are presented.Our �ndings demonstrate a viable route to alter epitaxial graphene's electronic structure by meansof strain and van der Waals interaction.


Fulerenes on Graphene Held Together by van der Waals Inter-action

Poster

Svec, Martin, (1); Merino, Pablo, (2), Dappe, Yannick, (3); Gonzalez, Cesar, (1); Jelinek, Pavel,(1,4); Martin Gago, Jose Angel, (2)


(1) Institute of Physics of the AS CR, Cukrovarnická 10, 162 00 Praha, Czech Republic(2) CSIC-ICMM, C/Sor Juana Ines de la Cruz 3, E-28049 Madrid, Spain(3) Service de Physique de l'Etat Condensé, DSM/IRAMIS/SPEC, CEA Saclay, France(4) Graduate School of Engineering, Osaka University 2-1, Yamada-Oka, Suita, Osaka 565-

0871, Japan

In this contribution, we concentrate on the interactions occurring between fullerenes and asingle-layer epitaxial graphene grown on SiC(0001). Using the variable temperature scanning tun-neling microscopy (STM) and advanced theoretical simulations, we found the cohesion among thefullerenes stronger than the binding to the surface despite the presence of a superlattice corrugation.The fullerenes arrange into planar islands at 40K with a 4x4 periodicity, held together exclusively bythe van der Waals forces, which is manifested by collective movement of the islands upon manipula-tion with the scanning probe. This has been con�rmed by extensive density functional calculationstaking into account the van der Waals contribution. Furthermore, the most energetically favorablecon�guration evaluated by the theory corresponds to the experimentally observed internal orien-tation of the fullerenes in the 4x4 reconstruction. The orientation of the molecule was determinedby matching the experimental to simulated STM images considering a moving fullerene attachedto the probe, that was the origin of a changing intramolecular contrast.

References

[1] M. �vec et al, Phys. Rev. B. 86, 121407(R) (2012).

3D representation of 20x20 nm2 empty states STM topography of C60 islands on a) SLG taken at600mV, 100pA and b) (6x6)-SiC(0001) recorded at 1000mV, 100 pA. Both images were obtained

at 40 K.


The instability of silicene on Ag(111)

Poster

Acun, Adil ; Poelsema, Bene ; Zandvliet, Harold ; van Gastel, Raoul


(1) Physics of Interfaces and Nanomaterials MESA+ Research Institute Faculty of Science andTechnology Carré � CR 2.209 University of Twente PO Box 217 7500 AE Enschede The Netherlands

Graphene, a carbon allotrope with a 2D honeycomb structure has opened the door to a newera in material science. The discovery of graphene has sparked the search to a silicon version ofgraphene, referred to as silicene. Here we have used low energy electron microscopy to directlyvisualize the formation and stability of silicene layers on a clean Ag(111) substrate. We have foundthat silicene layers are intrinsically unstable against the formation of an sp3-hybridized, bulk-likesilicon structure. The irreversible formation of this bulk-like structure is initiated by thermal Siadatoms that are produced by the silicene layer itself. The same instability prevents the formationof a fully closed silicene layer or a thicker bilayer, rendering the future large-scale fabrication ofsilicene layers on Ag substrates unlikely.

References

[1] Acun et al., Appl. Phys. Lett., 103, 263119 (2013).


Graphene Flakes embedding in hexagonal Boron Nitride

Poster

Farwick zum Hagen, Ferdinand; Zimmermann, Domenik; Michely, Thomas; Busse, Carsten


(1) II. Physikalisches Institut, Universität zu Köln, Zülpicher Straÿe 77, 50937 Köln, Germany

Many special properties of graphene, as for example the high carrier mobility and the spin-polarized edge state, are suppressed in any real world sample due to the interaction with theenvironment. A possible remedy is embedding graphene in hexagonal boron nitride (hBN) whichprovides a promising combination of geometric match and electronic mismatch [1]: It is isostructuralwith a small lattice mis�t of only 1,8% [2], yet at the same time a wide band gap insulator. In thisstudy we analyse embedding of nm-sized graphene quantum dots in a monolayer of hBN. Usingscanning tunneling microscopy (STM) the morphology of graphene hBN hybrid structures on Ir(111)is investigated. The materials are synthesised via temperature program growth (TPG) and chemicalvapor deposition (CVD) growth processes using ethylene and borazine as precursor gases. We studydi�erent samples in dependence on growth conditions, such as temperature, pressure, gas dose andmethod. The analysis of highly resolved STM images focuses on the phase boundaries, followingthe question whether heterogeneous or homogeneous nucleation takes place. Finally these hybridstructures are exposed to oxygen in order to investigate structural coherent junctions between hBNand graphene.

References

[1] Geim, A. K.; Novoselov, K. S. The rise of graphene. Nature Mater. 6, 183�191 (2007).[2] Liu, L. et al., Structural and electronic properties of h-BN. Phys. Rev. B 68, 104102 (2003).


Cold Tip SPM - A new generation of variable temperatureSPM for spectroscopy

Poster

Troeppner, Carsten (1); Atabak, Mehrdad (1); Koeble, Juergen (1); Uder, Bernd (1)


(1) Oxford Instruments Omicron NanoScience, 65232 Taunusstein, Germany

We present design and �rst results of a new generation of variable temperature scanning probemicroscope (SPM) that has been developed to enhance the performance in tunneling spectroscopyat lower and variable temperatures. The new microscope for ultra high vacuum is based on anew stage design using a �ow cryostat compatible for cooling with liquid nitrogen or helium. Incontrast to earlier established designs of variable temperature SPM's [1-3] where only the sample iscooled, this new SPM also cools the scanner with tip. This is realized by a new developed compactmicroscope stage with thermal shields and a cooling management system. With the new designwe achieve lower temperatures and improve drift by more than an order of magnitude comparedto previous variable temperature stages. Sample temperatures down to 10 K (with helium) and 95K (with nitrogen) have been achieved. The temperature stability is better than 5mK / min and athermal drift of 1 pm/s was achieved. During cooling the mechanical z stability is better than 3pm. These conditions enhance spectroscopy measurement capability. �Loop o�� times of up to 10 sper single spectroscopy curve have been measured. The new �ow cryostat also allows for changingbetween nitrogen cooling and helium cooling in less than 90 min during a running experiment.Pre-cooling with nitrogen during the starting phase of an experiment also reduces running costs forliquid helium.

References

[1] Omicron, "VT SPM" (1995)[2] RHK, "Variable Temp BEETLE"[3] SPECS, "Aarhus SPM"


Butter�y Hydrogen Dimers on G/SiC(0001).

Poster

Merino, Pablo (1), Martinez, Jose Ignacio (1), Svec, Martin (2), Jelinek, Pavel (2,3); MartinGago, Jose Angel (1), de Andres, Pedro (1)


(1) CSIC-ICMM, C/Sor Juana Ines de la Cruz 3, E-28049 Madrid, Spain(2) Institute of Physics of the AS CR, Cukrovarnická 10, 162 00 Praha, Czech Republic(3) Graduate School of Engineering, Osaka University 2-1, Yamada-Oka, Suita, Osaka 565-

0871, Japan

Hydrogen adsorbates on graphene [1] are a prominent model of graphene functionalization andhave important consequences in astrochemistry and material science among others. Here we addressthe �rst stages of hydrogen deposition on graphene grown on SiC(0001) with a combined exhaustivetheoretical-experimental approach with advanced calculation including for the �rst time the full(6√

3x6√

3)R30◦ unit cell of the G/SiC(0001) and high resolution scanning tunneling microscopyimages resolving simultaneously the graphene lattice and the hydrogen adsorbates. The atomic scaledetermination of the most stable geometry, the butter�y-shaped dimer, will be discussed under thiscombined approach and we will unclose the intrinsic di�culties in determining the exact atomicstructure for the hydrogen dimers, trimers and small 2D-clusters on graphene.

References

[1] L. Hornekær et al. Phys. Rev. Lett. 96, 156104 (2006).

High resolution STM images of hydrogen small dimers on SLG. a) V=-0.3V, I=1nA, 3.8x3.8nm2.b) Image where the atomic graphene grid has been superimposed and a simple interpretation of

where the hydrogen atoms might be chemisorbed have been over imposed.


Contacting graphene with liquid metals

Poster

�apeta, Davor (1); Jurdana, Mihovil (1); Plodinec, Milivoj (2); Kralj, Marko (3)


(1) University of Zagreb, Faculty of Science, Department of Physics, Bijeni£ka 32, 10000 Za-greb,Croatia

(2) Ru�er Bo²kovi¢ Institute, Bijeni£ka cesta 54, 10000 Zagreb, Croatia(3) Institut za �ziku, Bijeni£ka 46, 10000 Zagreb, Croatia

Characterization and device fabrication of graphene and related 2D materials requires form-ing reliable electrical contacts. Standard methods such as e-beam and photolithography are timeconsuming, require expensive equipment and usually contaminate samples with resist and processchemicals residues. "Soldering" with indium is clean, but requires heating so it is not compatiblewith heat sensitive substrates. We show that mercury and gallium-indium eutectic, metal and alloyliquid at the room temperature, form electrical contacts to CVD graphene on common dielectricsubstrates. Since mercury doesn't wet graphene, SiC, SiO2 or polymers, mercury contact ("mercuryprobe") is temporary and can be removed after measurement without damaging graphene. This en-ables rapid testing of graphene quality and uniformity during di�erent stages of device fabrication.Gallium-indium alloy forms permanent semi-solid contacts that are highly resistant to stretchingand bending. Glass capillary �lled with GaIn can be used as a fountain pen for "drawing" con-tacts using micromanipulator or by hand. Both methods take only minutes to implement, don'tcontaminate graphene with residue and require only basic equipment.


Electronic properties of edge modi�ed zigzag graphene nanorib-bons

Poster

Shinde, Prashant (1); Baumgartner, Marion (1); Passerone, Daniele (1); Pignedoli, Carlo (1)


(1) Swiss Federal Laboratories for Materials Science and Technology, EMPA, Überlandstrasse129, 8600 Dübendorf, Switzerland

Graphene nanoribbons (GNRs), quasi-one dimensional graphene derivatives, are promising ma-terials for electronic devices [1-2]. The electronic properties of GNRs strongly depend on thegeometry of the edges. Structural perfection [3-4], during growth and post processing, is of keyimportance: occurrence of defects at the edges could be detrimental for the expression of peculiarproperties predicted in theory [5]. On the basis of DFT simulations we discuss here the e�ect ofedge modi�cations on the electronic and magnetic properties of zigzag GNRs. We explore the char-acteristics of the electronic band structure with a focus on the nature of localized states. Ribbonswith cove edges (see e.g. Fig. (a)) show partially �at bands at the Fermi energy and the frontierstates are localized around the cove defects. The non-magnetic ribbons with even (odd) width, N,are always metallic (semiconducting). The origin of alternating even/odd behavior is the staggeredcove position. For wide ribbons, N > 9, the ground state is found to be antiferromagnetic. Anotherclass of ribbons, exhibiting a pentagonal ring at the zigzag backbone (Fig. (b)), have antiferro-magnetic ground state with spin polarized states localized at the edges. The HOMO (LUMO) hasmaximum intensity in between (on) the pentagons. We discuss e�ectiveness of edge modi�ed designof GNRs as an appropriate mechanism to tune electronic and magnetic properties of zigzag GNRsfor potential applications in nanoelectronics.

References

[1] Dutta, S. et. al, J. Mater. Chem. 20, 8207 (2010).[2] W. Y. Kim, K. S. Kim Nature Nanotech. 3, 408 (2008).[3] Cai J. et al. Nature, 466, 470 (2010).[4] Ru�eux P. et al. ACS Nano, 6, 6930 (2010).[5] Huang B. et al. Phys. Rev. B, 77, 153411 (2008).


Zigzag graphene nanoribbons: The cove defects in anti-zigzag con�guration (top panel, N odd), thezigzag con�guration (middle panel, N even). The bottom panel shows ZGNR with pentagon as a

topological defect at the zigzag backbone.


Self-assembly and orbital imaging of metal phthalocyanines ongraphene model surface

Poster

Järvinen, Päivi; Hämäläinen, Sampsa K; IJäs, Mari; Harju, Ari; Liljeroth, Peter

Contact: paivi.jarvinen@aalto.�

(1) Aalto University, Department of Applied Physics

Metal phthalocyanines (MPc) consist of a coordinated metal ion surrounded by an organicmacrocycle of alternating carbon and nitrogen atoms. As both the central metal ion and themacrocycle can be modi�ed, the electronic properties and self-assembly of these molecules can betuned over a broad range. The use of arrays of MPcs on graphene has been suggested for tuning theelectrical properties of graphene [1]. While the self-assembly of MPcs has been extensively studiedon metal substrates, systematic studies of the symmetry of molecular assemblies and energeticposition of the molecular orbitals on graphene are lacking.

Here, we study the e�ect of central ion and macrocycle substitution on the self-assembled MPcstructures on epitaxial graphene by low-temperature scanning tunnelling microscopy (STM). Weinvestigate the energetic positions and symmetries of molecular orbitals by scanning tunneling spec-troscopy (STS) experiments and density functional theory (DFT) calculations. We focus on cobaltphthalocyanine (CoPc), copper phthalocyanine (CuPc) and fully �uorinated cobalt phthalocyanine(F16CoPc) on G/ Ir(111) substrate as model systems. Our results shed light on the molecularordering and the energies of molecular orbitals with respect to the graphene Dirac point for the dif-ferent MPcs. This information will be crucial for using molecular overlayers to modify the electronicproperties of graphene.

References

[1] P. Järvinen et al. �Molecular self-assembly on graphene on hexagonal boron nitride and SiO2substrates�, Nano Letters, 13, 3199-3204, (2013)

STM images show self-assembled structures of CoPc, CuPc, and F16CoPc.


Wrinkles of graphene on Ir(111) - internal structure and long-range ordering

Poster

Petrovi¢, Marin, (1); Sadowski, Jerzy T. (2); �iber, Antonio, (2); Kralj, Marko, (1)


(1) Institut za �ziku, Bijeni£ka 46, 10000 Zagreb, Croatia(2) Center for Functional Nanomaterials, Brookhaven National Lab, Upton, New York 11973,

USA

Wrinkles are an intrinsic feature of many epitaxial graphene systems and transferred graphenein devices. For graphene/Ir(111), wrinkles have been reported several times up to now [1,2,3], buta more comprehensive study on their long-range ordering as well as description of their internalstructure are still missing. In this work, STM was used to reveal the structure of individual wrinklesof graphene/Ir(111) which extends beyond simple half-pipe model. Once graphene is delaminatedfrom iridium, the van der Waals interaction leads to complex folded structures. By using LEEM, wewere able to characterize the long-range order of graphene's interconnecting wrinkles network. Forthe aligned R0 graphene, we found a clear relation between the direction of extension of wrinklesand high symmetry directions of the iridium substrate. We also show that such network can beapproximated by a Voronoi diagram which greatly facilitates its characterization. In contrast, nosuch ordering is observed on R30 rotational domains of graphene/Ir(111), indicating reduced bindingto the substrate. Most prominent features of wrinkles, including characteristic intra- and inter-wrinkle length-scales are explained using phenomenological, scaling theoretical arguments based onthe interplay of adsorption and elastic energies of a constrained graphene sheet. Our �ndings arerelevant for the control and technological implementation of wrinkled graphene.

References

[1] N'Diaye, A. T. et al. New J. Phys. 11, 113056 (2009).[2] Hattab, H. et al. Nano Lett. 12, 678 (2012).[3] Petrovi¢, M. et al. Nat. Commun. 4, 2772 (2013).


Etching of Graphene on Ir(111) with Molecular Oxygen

Poster

Schröder, Ulrike A., (1); Grånäs, Elin, (2); Gerber, Timm, (1); Arman, Mohammad A. (2);Schulte, Karina (3); Andersen, Jesper N.,(2,3); Knudsen, Jan, (2,3); Michely, Thomas, (1)


(1) II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77 50937 Köln, Germany(2) Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Swe-

den(3) MAX IV Laboratory, Lund University, Box 118, 221 00 Lund, Sweden

Carbon combustion is important for many applications, but so far, it is not very well understoodon the atomic level. High quality graphene(Gr) on Ir(111) exposed to molecular oxygen provides awell-de�ned system, and therefore gives a unique possibility to study the role of defects in etching ofgraphitic materials, and develop a detailed understanding of the etching mechanism. Using scanningtunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and thermal desorptionspectroscopy (TDS), we �nd that the mechanism governing the onset of etching depends on whetherit is Gr islands or a closed Gr �lm that are attacked by oxygen. For Gr islands, etching sets in at550 K. O2 dissociates on the bare Ir(111). Real time STM measurements reveal that O then attacksGr via the edges. Free edges are preferentially etched, compared to Gr edges bound to Ir steps.From TDS we obtain the ratio of CO2/CO formed during etching. It depends on the amount ofO present at etching sites. Perfectly closed Gr �lms are remarkably stable against oxygen etching,which �rst sets in around 700 K. At this temperature, 5-7 defects stemming from the Gr growthprocess act as nucleation points for etching, presumably because O2 dissociation is facilitated there.At higher etching temperatures, large hexagonal etch holes are visible in the STM: Zigzag edgesare more stable against etching than armchair edges. In contrast to Gr islands, signi�cantly moreCO than CO2 is produced.

STM images of perfectly closed 1 ML Gr exposed to molecular oxygen at a) 700 K and b) 750 K.a) Left: 5-7 defect. Right: small etchhole nucleating at a 5-7 defect. Image size 20 nm x 40 nm.

b) Large hexagonal etchholes. Image size 265 nm x 265 nm.


Unusual Moire Patterns on Graphene on Rh(111)

Poster

Martin-Recio, Ana (1); Martinez-Galera, Antonio J. (1,2); Gomez-Rodriguez, Jose M. (1)


(1) Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid,Madrid, Spain

(2)Present address: Physikalisches Institut, Universitat zu Koln, Zulpicher Str. 77, Koln, Ger-many

The growth of graphene on transition metals by means of di�erent procedures has been highlystudied in recent years [1] in order to understand the interactions between them. These interactionsdo not only change the electronic properties of graphene, but also its geometrical structure whichleads to moire periodic superstructures. It has been found that, if the graphene-metal interaction islow enough, more than one moire lattice is stable for the same graphene-metal system [2,3]. In thecase of graphene on Rh(111), this interaction is not considered to be low [1]. Therefore, only onerelative orientation of the carbon atom lattice with the Rh(111), leading to only one moire pattern,has been described [4,5]. It is the (12x12)C aligned with (11x11)Rh(111) moire. In this study, wereport on the growth of graphene on Rh(111) and the formation of several di�erent moire structures.The experiments were performed in ultra-high vacuum (UHV) by means of variable temperaturescanning tunneling microscopy (VT-STM). Graphene monolayers were grown on Rh(111) singlecrystals in UHV via chemical vapor deposition (CVD) of low pressure ethylene (C2H4). In ourSTM measurements we observed the usual (12x12)C on (11x11)Rh(111) moire (�g.1a) which wasfound in previous works [4,5], but also several other rotational graphene domains (�g.1b). Theseunusual structures, corresponding to smaller periodicities than the normal (12x12)C moire, havebeen modeled through atomic resolved data.

References

[1] M. Batzill, Surf. Sci. Reports 67, 83 (2012).[2] M. M. Ugeda, D. Fernandez-Torre, I. Brihuega, P. Pou, A.J. Martinez-Galera, R. Perez, and

J.M. Gomez-Rodriguez, Phys. Rev. Lett. 107, 116803 (2011).[3] A. J. Martinez-Galera, I. Brihuega, and J. M. Gomez-Rodriguez, Nano Letters 11, 3576

(2011).[4] B. Wang, M. Ca�o, et al., ACS Nano 4, 5773-5782 (2010).[5] E. N. Voloshina, Yu. S. Dedkov, et al., Appl. Phys. Lett. 100, 241606 (2012).

Figure 1. (a) 10x10 nm2 STM image of the (12x12)C moire with its model. V=-0.4V, I=2nA; (b)15x15 nm2 image of two di�erent moires: the usual moiré on the right-top, and a new one on the

left-bottom. Comparing the angles in both �akes, a model for the new structure is obtained.V=-0.3V, I=19nA.


Hybridization of graphene and a Ag monolayer supported onRe(0001)

Poster

Papagno, Marco, (1,2); Moras, Paolo (1); Sheverdyaeva, Polina (1); Doppler, Jorg (3); Garhofer,Andreas, (3); Mittendorfer, Florian (3); Redinger, Josef (3); Carbone, Carlo (1);

Contact: marco.papagno@�s.unical.it

(1) Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Trieste, Italy(2) Dipartimento di Fisica, Universitá della Calabria, 87036 Arcavacata di Rende (Cs), Italy(3) Institute of Applied Physics and Center for Computational Material Science, Vienna Uni-

versity of Technology, Gusshausstrasse 25/134, A-1040 Vienna, Austria.

A detailed understanding of the chemical interaction between graphene and a metal substrateis a major prerequisite for tailoring the electronic properties of graphene, because it allows tuningthe electronic states of graphene by changing the support or via the intercalation of alloy materials[1]. For instance, for graphene adsorbed on Ni, Rh, Ru and Re the hybridization between thecarbon and metal atoms leads to a loss of the linear dispersion of the graphene bands. In thesecases the electronic properties can be restored by intercalation of noble-metal atoms, as evidencedby several angle-resolved photoemission spectroscopy (ARPES) studies [2, 3]. The intercalatednoble-metal layers not only act as spacers, but also reduce the hybridization between the metal dorbitals and graphene π band. To shed more light on the role of the intercalated �lm we investigatedthe electronic structure of graphene supported on Re(0001) before and after the intercalation ofone-monolayer Ag with ARPES experiments and density functional theory (DFT) calculations [4].In this study, we show that even as the noble-metal �lm leads to a decoupling of the substrate,the electronic states of the intercalated layer still hybridize with the graphene layer and inducea band gap in the graphene π band. The results clearly indicate that the electronic structure ofgraphene adsorbed on a noble-metal layer can still deviate signi�cantly from the structure of anideal, unsupported graphene sheet.

References

[1] M. Batzill, Surf. Sci. Rep. 67, 83 (2012).[2] C. Enderlein, Y. S. Kim, A. Bostwick, E. Rotenberg, and K. Horn, New J. Phys. 12, 033014

(2010).[3] A. Varykhalov, M. R. Scholz, T. K. Kim, and O. Rader, Phys. Rev. B 82, 121101(R) (2010).[4] M. Papagno, P. Moras, P. M. Sheverdyaeva, J. Doppler, A. Garhofer, F. Mittendorfer, J.

Redinger, and C. Carbon, Phys. Rev. B 88, 235430 (2013).

Index

Åhlgren, 37

Abel, 50, 62Acun, 69Amsalem, 62Andersen, 5, 78Arman, 5, 78Arnau, 52Atabak, 71Atodiresei, 38, 40, 46, 60, 64

Böttcher, 23Büchner, 54Balan, 34Balashov, 52Baraldi, 33Baumgartner, 74Bendiab, 30Berger, 43Bernard, 8Betti, 26, 31, 59Bettinger, 28Bhatti, 66Bignardi, 56Blügel, 40, 46Blanco-Rey, 29Bluegel, 64Bocquet, 62Bouvron, 48Brüller, 28Bradley, 15Brako, 64Brihuega, 18, 39Brocks, 32Bromberger, 6Buljan, 42Busse, 24, 46, 57, 64, 67, 70

Cacho, 6, 20Caciuc, 40, 46, 64Cafolla, 47Cai, 44Calleja, 49Capeta, 73Carbone, 26, 61, 80Cardoso, 12Carpy, 47Cavaliere, 31

Cavalleri, 6Ceballos, 52Chérioux, 30Chab, 29Chapman, 6, 20Choueikani, 50Cilento, 20Clair, 50Conrad, 17Coraux, 25, 30, 66Craes, 39, 46, 57, 67Crepaldi, 20Crommie, 15Cun, 8Cunge, 36Cunni�e, 47

da Jornada, 15Dappe, 68Davydova, 36de Andres, 72Dedkov, 23, 26, 48Delfour, 36Denk, 44Despiau-Pujo, 36Dhesi, 50Di Bernardo, 59Dombrowski, 57Doppler, 26, 80Drndic, 34

Endlich, 58

Fölsch, 35Fagot-Revurat, 22Farmanbar, 32Farwick zum Hagen, 70Fasel, 28, 44Fedorov, 54, 63Feibelman, 5Feng, 44Ferhat, 66Fernández Torre, 39Ferrari, 26Ferretti, 12, 44Foerster, 64Fonin, 26, 48Franz, 17

81

INDEX 82

Fromm, 20

Gómez Rodríguez, 39Gómez-Rodríguez, 18Gambardella, 52Garcia-Lekue, 52Garhofer, 26, 80Garnica, 49Gavioli, 31Generalov, 47Gerber, 5, 78Gierz, 6Giovanelli, 50, 62, 65Goldoni, 62Gomez-Rodriguez, 79González Herrero, 39Gonzalez, 68Grüneis, 54Grånäs, 5, 78Gragnaniello, 48Greber, 8Grill, 31Grioni, 20Gutiérrez, 18

Hämäläinen, 76Haarlammert, 56Haberer, 54Hammer, 5Hammerschmidt, 48Hapala, 29, 43Harju, 76Hayn, 50Hemmi, 8Henning, 35Herbig, 37Hlawenka, 53Hofmann, 20Hohage, 44Horn, 23Hussain, 15Huttmann, 40

IJäs, 76

Järvinen, 76Jablan, 42Jahn, 35Jelinek, 29, 43, 68, 72Jenichen, 35Johannsen, 20Jolie, 46, 67Jurdana, 73

Köhler, 6Kaelin, 8Kampen, 23Kawakami, 27, 60

Kierren, 22Kimouche, 25King, 20Kis, 9Klinkhammer, 57Knudsen, 5, 78Knupfer, 54Koch, 62Koeble, 71Kostov, 21Kotakoski, 37Koudia, 50Kröger, 58Kralj, 7, 46, 57, 64, 67, 73, 77Krasheninnikov, 37Krausert, 26Ksari, 50, 65

López, 41Lacovig, 21, 33La�erentz, 31Lamare, 30Lançon, 66Landers, 30Larciprete, 21, 33Lazic, 27, 60, 64, 67Leicht, 26, 48LeRoy, 11Liang, 44Liljeroth, 13, 76Lin, 65Link, 6Lisi, 26, 59Liu, 10Lizzit, 21, 33Locatelli, 25Lopes, 35Louie, 15

Müllen, 28, 44Müller, 28Méndez, 41Mårtensson, 47Maccherozzi, 50Magaud, 30, 36, 66Malterre, 22Mammadov, 20Marchenko, 53, 61Mariani, 26, 31, 59Marsoner Steinkasserer, 48Martín-Gago, 41Martínez Galera, 39Martínez-Galera, 18, 40Martin Gago, 29, 68, 72Martin-Recio, 79Martinez, 41, 72Martinez-Galera, 79

INDEX 83

Massimi, 31Matsui, 8Menzel, 21Merino, 29, 41, 68, 72Meunier, 44Michely, 5, 24, 37, 40, 46, 57, 64, 70, 78Miksic Trontl, 67Milun, 64Miranda, 49, 58Mitrano, 6Mittendorfer, 26, 80Miwa, 20Molina-Sánchez, 58Molinari, 12, 44Montagnese, 56Moras, 26, 80Moreno Ugeda, 39Mugarza, 52Mutombo, 29, 43

Ohresser, 50Oliveira, 35Olle, 52Ondracek, 29, 43Orlando, 33Osterwalder, 8Otero, 50Ourdjini, 31Ovcharenko, 23

Pérez, 39, 41Pacilé, 26, 59Pan, 64Papagno, 26, 80Parmigiani, 20Passerone, 74Paulus, 48Pervan, 64, 67Petaccia, 62Petersen, 6Petrovic, 46, 57, 77Pettaccia, 54Pignedoli, 28, 44, 74Pinardi, 41Pletikosic, 64Plodinec, 73Poelsema, 69Polman, 17Pou, 39, 41Prakash, 65Preobrajenski, 47Prezzi, 12, 44Puster, 34

Qiu, 15

Rader, 53, 61

Raidel, 20Ralko, 66Redinger, 26, 80Rodrigo, 41Rodriguez-Manzo, 34Roth, 8Rudolf, 56Ru�eux, 28, 44Ruini, 12, 44Runte, 57, 64

Söde, 44Sadowski, 64, 77Salomon, 62Sanchez-Barriga, 53, 61Sanchez-Portal, 52Sanchez-Sanchez, 28Santos, 25Savoyant, 50Schnadt, 5Schröder, 78Schulte, 5, 78Schumacher, 64Schumann, 35Seyller, 20Shen, 15Sheverdyaeva, 26, 80Shi, 15Shikin, 19Shinde, 74Siber, 77Sicot, 22Simon, 37Simonov, 47Sipahi, 27, 60Sokcevic, 64Solja£ic, 42Spadafora, 43Springate, 6, 20Srut Rakic, 64, 67Stöhr, 6Standop, 24Starke, 6Stauber, 18Stierle, 17Stratmann, 5Struzzi, 54Sutter, 4Svec, 29, 43, 68, 72

Talirz, 28, 44Telychko, 43Tesch, 48Themlin, 50, 62, 65Thissen, 23Troeppner, 71

INDEX 84

Uder, 71Ugeda, 15Ulstrup, 20Usachov, 54, 63

Vázquez de Parga, 49Valla, 64van Gastel, 69van Loosdrecht, 56Varykhalov, 53, 61Vasseur, 22Verbitskiy, 54Vilkov, 54, 63Vinogradov, A., 47Vinogradov, N., 47Vita, 23Vlaic, 25Vlieg, 17Voloshina, 23, 48, 56Vonk, 17Vyalikh, 63

Wang, 12, 15, 44Wehling, 14, 40, 64Winter, 56Wirtz, 58Wo�ord, 35

Zacchigna, 20Zacharias, 56Zagrebina, 47Zandvliet, 69Zeppenfeld, 44Zhang, 15Zielke, 26, 48Zimmermann, 70Zutic, 27, 60

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