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Maria LOSURDO NIM_NIL Laurea cum laude in Chemistry from University of Bari, Italy
Joint PhD from Ecole Polytechnique (Palaiseau-France) and University of Bari,
Italy in Materials Science.
Senior Scientist in the Institute of Inorganic Methodologies and of Plasmas at
National Council of Reserach (CNR), and an Adjunct Professor at the
Department of Electrical and Computer Engineering of the Duke University at
Durham, NC-US.
Co-editor of 2 Journals: “EP-JAP” and "ISRN Materials Science"
Specialist in CVD growth of materials and ellipsometry
She approached graphene by her expertise in CVD growth and plasma processing of SiC.; she is co-author of a US patent on “Metal-aided graphenization of SiC”
Location, 09/09/2009 Page 1N.N. (Speaker), Name of the Partner Brussels, March 21-22, 2011
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Graphenein
Maria Losurdo and Giovanni Bruno
Large Area Fabrication of 3D Negative Index Materials by
NanoImprint Lithography
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Outline
NIMNIL Consortium
NIMNIL Objective
Graphene for Metamaterials in the NIMNIL context
Processing/Structuring of Graphene
Synthesis of Grapheneexfoliation
SiC “graphenization”
CVD
Real-Time Monitoring and Controlling Graphene growth
Summary/Outlook
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Consortium
Duration: 3 years
Starting date: 01.09.09Coordinator: Profactor GmbH; Iris Bergmair
Consortium Structuring Graphene
Synthesis of Graphene Real Time Monitoring Conclusions
Objectives Graphene for Metamaterials
Characterisation
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Project Objectives
Design of NIMs
• New structure designs for NIMs
• New material Graphene
Fabrication of NIMs
• NIL as fabrication method
• Deposition & Structuring of Graphene
• Large area NIMs
• 3D NIMs
Characterisation of NIMs
• Optical properties of Graphene and its structures
• Ellipsometry, Raman, AFM/SEM
• Transmission, reflection, phase measurements
Demonstration of NIMs
• 3D NIM prism
NIM= Negative Index Materials
Objectives Structuring Graphene
Synthesis of Graphene Real Time Monitoring Conclusions
Consortium Graphene for Metamaterials
Characterisation
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Graphene for Metamaterials
Original concepts for using graphene
Structuring graphene
Fabrication of graphene
Characterisation of graphene
Main activities relate to:
Consortium Structuring Graphene
Synthesis of Graphene Real Time Monitoring Conclusions
Objectives
Characterisation
Graphene for Metamaterials
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Graphene for Metamaterials
[Science, 328, (2010) p.582]
2 In the Infrared and Terahertz:Electroptical Modulation
1Medium composite consisting of
single- or few-layer graphene on
nanostructured metal films
grapheneSilver metamaterial
structure
In the Visible:
Graphene has potential to cover the range
Visible-infrared-terahertz by 2 approaches
Consortium Structuring Graphene
Synthesis of Graphene Real Time Monitoring Conclusions
Objectives
Characterisation
Graphene for Metamaterials
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Graphene in a Photonic Metamaterial: Approach-1
[N. Papasimakis et al. OPTICS EXPRESS 18, 8353 (2010)]
IR: Graphene on Gold
Graphene modifies the transmission
spectrum of such a metamaterial leading to
an increase of transmission exceeding 250%.
graphene
Change o
f T
ransm
issio
n w
ith G
raphene
Wavelength (nm)
oxidized cleaned 1h 1day 3day 5day12.5
13.0
13.5
14.0
14.5
15.0
P
SI
@ A
g p
lasm
on
pe
ak
TIME of AIR EXPOSURE
Visible: Graphene on Silver
2
mx2
m
Silver fishnet
5
mx5
m
Silver gratings
Plasma Passivation of Ag + Transfer of graphene ontop 1 2
Graphene limits/inhibits silver oxidation
370 368 366
As deposited gratings
After processing
Ag
AgO
AgGraphene enhances resonance
2 3 4
20
25
30
35
40
PS
I°
Photon Energy (eV)
Ag as-grown
after passivation
enhancem
ent
Consortium Structuring Graphene
Synthesis of Graphene Real Time Monitoring Conclusions
Objectives
Characterisation
Graphene for Metamaterials
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Graphene in Metamaterials: Approach-2
The height of structures is 2 nm
Graphene Swiss Cross structures.
Linewidth is 20 nm. Layer height is 500 pm
Graphene Fishnet
structures.
Line width is 70 nm
100 µm
100m
a) exfoliated graphene is placed on the substrate.
b) resist is patterned on the graphene by nanoimprint lithography
c) an O2 plasma etching of graphene takes place on the area
without mask
d) a graphene pattern is obtained after removing the resist
(b)
(c)
(d)
(a)
GrapheneResist
Mold
Graphene
Graphene
Graphene
Graphene is nanostructured to achieve Controlled Size and Shape layers
using NIL and an O2 plasma
Consortium Graphene for Metamaterials
Synthesis of Graphene Real Time Monitoring Conclusions
Objectives
Characterisation
Structuring Graphene
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CVD-G on Cu
Controlled Etching of Graphene
Magnification 20.000x. Line width is 1.5 µm
CVD-G on Ni
Graphene Gratings on Nickel and Copper by CVD structured using NIL and an O2 plasma
1000 1500 2000 2500 3000 3500
Wavenumber (cm-1)
G
2D
G2D
1500 2000 2500
Wavenumber (cm-1)
Consortium Graphene for Metamaterials
Synthesis of Graphene Real Time Monitoring Conclusions
Objectives
Characterisation
Structuring Graphene
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Synthesis Routes to Graphene in NIMNIL
2719
TIMET
EM
PE
RA
TU
RE
( C
)
Cle
an
ing &
An
ne
alin
g o
f su
bstr
ate
H2
flo
w
Gra
ph
ene
gro
wth
CH4 inCH4 out
Co
olin
g d
ow
n
H2
flo
w
CH4 + H2/Ar graphene
T900 C, P<4 Torr1
2
3
1200 1400 1600 1800 2000 2200 2400 2600 2800
2D
G
Wavenumber (cm-1)
1587cm-1
2705cm-1
FWHM=39cm-1
FWHM=31cm-1
I2D/IG=2.8
CVD on Polycrystalline&foils Nickel and Copper3
Structuring Graphene
Synthesis of Graphene
Exfoliation of Graphite
100 µm
100m
1
SiC Decomposition
1594
24cm-1
1200 1400 1600 1800 2000 2200 2400 2600 2800
Wavenumber (cm-1)
2719
2
G
D
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Graphene CVD: Implementation of Growth Process
Peculiarities of our CVD growth processes:Integration of a Remote Plasma Source
Integration of in-situ Real Time Monitoring by Ellipsometry
Challenging goal:
To growth graphene of large scale with uniform thickness
How to achieve this?
We have uniquely developed a Real-Time Graphene Metrology
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Graphene on Copper Foil by CVD
Since the growth was first demonstrated on Copper foil, there is a tendency to use the same foil:
Impurities affect not only quality but also the catalytic decomposition of CH4 and
therefore the thickness (Single or bi-layer)
[Z. Luo et al. Adv. Funct. Mater. 2011, 21, 911–917]
Kinetic factors, such as the surface reaction rate, play a critical role on the uniformity of thickness of CVD
graphene layers by limiting the deposition of carbon atoms on Cu surface.
The higher the impurities (e.g. Cu 99.8%), the faster surface reaction rate, the lower the thickness uniformity.
The dopants or impurities could effectively enhance the catalytic activity of the Cu surface
No growth of bilayer even after 120min
1500 2000 2500
Wavenumber (cm-1)
D
G 2D
Bi-L G grown on 99.5%Cu
(800°C 50min)
Impact of Copper foil impurities
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Graphene by CVD on Copper Films
Graphene on Cu/SiO2/Si
0
100
200
300
400
500
600
700
800
900
1 000
1 100
1 200
1 300
1 400
Inte
nsi
ty (
cn
t/sec
)
1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000
Raman Shift (cm-1)
500
1 000
1 500
2 000
2 500
3 000
3 500
4 000
4 500
5 000
5 500
6 000
6 500
7 000
7 500
Inte
nsi
ty (
cn
t/sec
)
1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000
Raman Shift (cm-1)
FWHM=
33cm-1
FWHM=
60cm-1
IG/I2D=0.6
1581 26981595 2699
G
2D
T=1200°CT=1100°C
0
50
100
150
200
250
300
350
400
450
500
550
Inte
nsi
ty (cnt/
sec
)
1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000
Raman Shift (cm-1)
FWHM=
50cm-1
T=1000°C
Single Loretnzian peak mark of monolayer graphene
Impact of Growth temperature
D
G 2D
D
G2D
1593 2700
Three regimes of temperature have been identified that can be exploited for improving processes
grapheneResidual Cu
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Graphene by CVD on Copper Films @ T>1200 C
Taking benefit of Cu dewetting (Tmelting =1084 C), graphene can be obtained on any
substrate avoiding the tedious etching/transferring/PMMA steps
Substrate engineering
30
0
mx3
00
m
Graphene directly on SiO2 and Al2O3
(residual copper-white strips can be removed by 5min HCl etching)
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Graphene on Polycrystalline Nickel
2D FWHM=50cm-1
[A.J. Pollard et al. J. Phys. Chem. C,
113, 2009, 16565]
[A.Reina et al , Nanotechnology 21
(2010) 015601]
State-of-the-art[A. Reina et al. Nano Lett., 9,1, 2009]
Typically growth on polycrystalline Ni results in a
non-homogeneous mixture of few-layers graphene
We are able to achieve on polycrystalline Ni results similar to what obrained on single crystalline Ni
On Single crystal Ni(111)
CNR-IMIP
On poly-Ni
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Graphene by CVD on Nickel
30
40
50
60
70
80
90
100
110
120
130
Inte
nsi
ty (
cn
t/se
c)
1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800
Raman Shift (cm-1)
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
Inte
nsi
ty (cnt/
sec)
1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800
Raman Shift (cm-1)
•Non homogeneity mainly depends on pre-treatment of Ni, CH4/H2 ratio and deposition time
•Noteworthy, absence of the D peak indicative of defects
(we started from here-heterogeneous) We can get this-more homogeneous
G
2D
I2D/IG0.9
I2D/IG2.1
1200 1400 1600 1800 2000 2200 2400 2600 2800
2D
G
Wavenumber (cm-1)
1587cm-1
2705cm-1
39cm-1
31cm-1
I2D/IG=2.8
G2D
59cm-1
48cm-1
Progress Beyond the State-of-the-art
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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1200 1400 1600 1800 2000 2200 2400 2600 2800
Wavenumber (cm-1)
Graphene transferred from Ni to SiO2Progress Beyond the State-of-the-art
700mx700m
Starting from typical non-homogeneous
43cm-1
I2D/IG=0.92695cm-1
1593cm-1
D
G
2D
D
G
2D
1200 1400 1600 1800 2000 2200 2400 2600 2800
Wavenumber (cm-1)
1587cm-1
30cm-1
I2D/IG=2.1 2696cm-1
39cm-1
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
Improvement is achieved by enhancement of catalysts substrate treatments
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Real Time Monitoring of CVD process
0 500 1000 1500 2000 2500 3000 3500
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0G21
G19
G15
< 1
>
Time (s)
0 500 1000 1500 2000 2500 3000 3500
1.0
1.5
2.0
<K
>
Time (s)
A
BB’
C’
B’’
C”
5mx5m
0 500 1000-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
< 1
>
Time (s)
0 500 1000
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
<k>
Time (s)
CH4 off
CH4 off
Ni ref
Ni ref
D
Ni substrate crystallization Graphene deposition
D
A
C’
C
CH4 in
CH4 offCH4 in
CH4 offCH4 in
C
D
C’
A
C
A
C’
D
CH4 in
G15
cooling
G19
G21
G21
G19
G15
G19
G21
G15
G19
1200 1400 1600 1800 2000 2200 2400 2600 2800
Wavenumber (cm-1)
1200 1400 1600 1800 2000 2200 2400 2600 2800
1200 1400 1600 1800 2000 2200 2400 2600 2800
Wavenumber (cm-1)
DG
2D
I2D/IG3
39cm-1
I2D/IG0.9
51cm-1
I2D/IG0.78
80cm-1
Real Time Monitoring
Growth
kinetics
100mx100m
Ex-situ Raman mapping In-situ Real-Time Ellipsometry and We have set a correlation between that allows us to monitor and control the whole CVD process from substrate preparation to
graphene thickness and quality
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Conclusions
Objectives
Characterisation
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Hydrogen in CVD Graphene
When the angle of incidence is increased the C-H stretching band increases.
This suggests that the C-H bonds are out-of-plane
IR Reflection spectra run at BESSY Synchrotron
Intrinsic Hydrogen is the main difference between CVD and exfoliated graphene
Structuring Graphene
Synthesis of Graphene
Consortium Graphene for Metamaterials
Real Time Monitoring Conclusions
Objectives
Characterisation
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Roadmap for Progress in Graphene Synthesis
The electron mobility within the graphene is effected by the substrate.
finding better substrates for future graphene devices in order to reduce the
effects of charged impurity scattering and remote interfacial phonon
scattering
There are still many chemical routes to synthesis of graphene and a lot of
room for improving the exploited ones.
Challenging the growth of large area graphene with controlled thickness
Substrate Engineering
Conclusions
Real Time Monitoring vs Parametric Trials
Finding technological solution to optimize processes
Structuring GrapheneConsortium Graphene for Metamaterials
Real Time Monitoring
Objectives
CharacterisationSynthesis of Graphene
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We will be pleased to take any question/curiosityCoordinator: Iris Bergmair
Nanoimprint Lithography of NIMs
Maria Losurdo, Giovanni Bruno
Synthesis and Characterisation of Large area Graphene
Rados Gajic
Exfoliation and characterisation of graphene
Costas Soukoulis
Simulation of Different Design of NIMs
Markus Oppel, C. Helgert,
Nanoimprint Litography stamps
Kurt Hingerl
Modelling Optical properties in the IR and UV-VIS
Karsten Hinrichs, Tom Oates
Ellipsometry measurements in the IR and UV-VIS
Lars Reissmann, Michael Arens
Ellipsometry, Plasma Etching
Hakan Atasoy, S. Herrndorf
Resists for Nanoimprint Litography
Ingolf Reischel, Lars Dick
Master Fabrication