“nanostructure characterization techniques”shih/imaging quantum phenomena.pdf ·...

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

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

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)

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)

Eigler, Nature 344, 524 (1990)

Xe on Ni(110)

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)

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.

Science 254, 1319 (1991)

• Transfer on/near contact• Field evaporation• Electromigration

Parallel Processes• Field-assisted diffusion• Sliding process (lateral)

Perpendicular Processes

1 V Å-1 = 108 V/cm

Vt-s = 3V

R = 100 Å

s = 5 Å

Cs on p-GaAs(110) Imaging at -2V sample biasManipulation pulse: +1V

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

Sliding process

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

“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

Band Structure of Copper

Free electron band

here is for surface band structure(at k|| = 0)

It coincides with the L point of the bulk BZ

n ~ cos(2kF x)

Friedel Oscillations

Solid line (Photoemission result)

STM data (cicles)Dashed line (k = (kF + k||)/2)

Step edge

Point defects

Step edge

,

Point defects

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

The Making of the Circular Corral

A quantum corral made of 48 Fe atoms(average diameter 142.6 Å)

V = 0.01 V, I = 1 nA.

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.

Peak at center approximated by l = 0

9 Å off-center approximated by l = 1

Stadium

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

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)

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

When a Co atom is placed at one of the foci.

c, d: dI/dV maps

e, f: simulations