“nanostructure characterization techniques”shih/imaging quantum phenomena.pdf ·...
TRANSCRIPT
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Subject:
“Nanostructure characterization techniques”
UT-AustinPHYS 392 T, unique # 59770
ME 397 unique # 19079CHE 384, unique # 15100
Instructor:Professor C.K. Shih
• Atomic and Molecular Manipulation• Quantum Phenomena (Quantum Corrals and etc)
Lecture note on Sept 15, 2009
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Xe atoms on Ni(110) are arranged into the letters “IBM” A quantum corral made of 48 Fe atoms
Also, see the IBM Almaden website:
http://www.almaden.ibm.com/vis/stm/gallery.html
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Reference Literatures
• On Atomic Manipulations– Eigler and Schweizer, Nature 344, 524 (1990)– Eigler, Lutz and Rudge, Nature 352, 600 (1991)– Stroscio and Eigler, Science 254, 1319 (1991)
• On Quantum Corrals– Hasegawa and Avouris, PRL 72, 1071 (1993)– Crommie, Lutz and Eigler, Nature 363, 324 (1993)– Crommie, Lutz and Eigler, Science 262, 5131 (1993)– Manoharan, Lutz and Eigler, Nature 403, 512 (2000)
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Atomic ManipulationThree main parameters : • the electric field, • the tunneling current• van der Waals or chemical forces (tip-to-sample distance).
Lateral Manipulation
(a) tip above the adsorbate (atom or molecule) (b) approach to the surface (~ 0.2 - 0.4 nm), a bond is formed between tip and adsorbate. (c) lateral movement (drag, slide, or push) of the tip parallel to the surface. (d) tip moved to the final point (e) the tip is retracted start imaging
Eigler, Nature 344, 524 (1990)
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Eigler, Nature 344, 524 (1990)
Xe on Ni(110)
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An Atomic Switch (Eigler, Nature 352, 600)
A: low conductance state (-0.02 V tip-bias)B: voltage pulse (0.8 V, 64 ms)
C: high conductance state (-0.02 V)D: voltage pulse (-0.8 V, 64 ms)
Xe on Ni(110) (surface kink site)
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Transfer rate: 2.09.4 I At a junction resistance of 906 KI: current during the manipulation pulse
Suggesting a thermally activated process caused by the Joule heating
However, electron wind-force induced electromigration is also possible.
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Science 254, 1319 (1991)
• Transfer on/near contact• Field evaporation• Electromigration
Parallel Processes• Field-assisted diffusion• Sliding process (lateral)
Perpendicular Processes
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1 V Å-1 = 108 V/cm
Vt-s = 3V
R = 100 Å
s = 5 Å
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Cs on p-GaAs(110) Imaging at -2V sample biasManipulation pulse: +1V
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Surface potential landscape for a polarizable atom
-3V
+3V
Dipole moment: 1.6 x 10-27C-cm; polarizabilty: 50Å3
Static dipole term
induced dipole term
Sum
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Sliding process
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CO on Pt(111)
Threshold resistance for sliding
Xe on Ni(110): 5 MCO on Pt(111): 200 KPt on Pt(111): 20 K
Pt on Pt(111)
http://users.physik.fu-berlin.de/~ag-rieder/pr4eo/manipulation/atmansite.html
atomic manipulation site
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“CONFINEMENT OF ELECTRONS TO QUANTUM CORRALS ON A METAL-SURFACE”Author(s): CROMMIE MF, LUTZ CP, EIGLER DMSource: SCIENCE Volume: 262 Issue: 5131 Pages: 218-220 Published: OCT 8 1993
Quantum Corrals
Also, see the IBM Almaden website:
http://www.almaden.ibm.com/vis/stm/corral.html
Original Papers on Standing Waves
DIRECT OBSERVATION OF STANDING-WAVE FORMATION AT SURFACE STEPS USING SCANNING TUNNELING SPECTROSCOPY Author(s): HASEGAWA Y, AVOURIS P Source: PHYSICAL REVIEW LETTERS Volume: 71 Issue: 7 Pages: 1071- 1074 Published: AUG 16 1993
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Band Structure of Copper
Free electron band
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here is for surface band structure(at k|| = 0)
It coincides with the L point of the bulk BZ
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n ~ cos(2kF x)
Friedel Oscillations
Solid line (Photoemission result)
STM data (cicles)Dashed line (k = (kF + k||)/2)
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Step edge
Point defects
Step edge
,
Point defects
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Single Fe atom on Cu(111) surface(Vt = 0.02 V, I = 1 nA)
13 nm x 13 nm
Topographic height 0.9 Å
Concentric Fringes: Standing Waves
Model as a cylindrical scattering potential
At low energy
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The Making of the Circular Corral
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A quantum corral made of 48 Fe atoms(average diameter 142.6 Å)
V = 0.01 V, I = 1 nA.
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Spectroscopic mapping
Adatoms are easily moved when voltage is ramped; even with tip at center, within 1 minute, ~20% of the ring atoms are moved with 1-2 lattice sites.
However, during imaging at low bias, adatoms are stable.
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Peak at center approximated by l = 0
9 Å off-center approximated by l = 1
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Stadium
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Quantum mirages formed by coherent projection of electronic structure
Manoharan HC, Lutz CP, Eigler DM
NATURE Volume: 403 Issue: 6769 Pages: 512-515
By positioning a Co atom at one focus of the ellipse, a strong Kondo signature is detected not only at the atom, but also at the empty focus. This behavior contrasts with the usual spatially-decreasing response of an electron gas to a localized perturbation
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Kondo resonance localized around a single Co atom on Cu(111)
STM topography (V = 5 mV, I = 1 nA)
35 Å by 35 Å
dI/dV map of the same area(average of ±5mV)
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e = 1/2 e = 0.786
Corrals formed by Co atoms on Cu(111)
c, d, topographs (150 Å and 154 Å)
e, f, dI/dV maps
c: 10 mV, 1 nA; d: 8 mV, 1 nA
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When a Co atom is placed at one of the foci.
c, d: dI/dV maps
e, f: simulations