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STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 4 1 PowerPoint Presentation

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 4 1

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STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 4 1

Park Sejun, Min Suk-wha, and Lyo In-whan

Institute of Physics and Applied Physics

MOTIVATION Si(111)-In 4

Self-organized low dimensional structures of metal on Si(111) surface

Quasi-one dimensional chain formation of ~ 1ML In on Si(111)-77

Phase transition from 41 to 42 or 82 structures at ~ 100 K

Reversible phase transition accompanied by a 1D CDW

Atomic structures at Low Temperature are not exactly known

Different chain to chain correlations upon transverse or longitudinal

(top) empty state image at – 0.12 V Si(111)-In 4 (mid) filled state image at +1.9 V

INTRODUCTION

1. Room Temperature STM

- 2.0 V

+ 2.0 V

Phys. Rev. B 36, 6221 (1987)J. Nogami et al.

Phys. Rev. B 56, 1017 (1997)A. A. Saranin et al., and K. Oura et al.

INTRODUCTION Si(111)-In 4

2. RT ARPES & IPES

Surf. Sci. 325, 33-44 (1995)T. Abukawa et al.

Phys. Rev. B 56, 15725 (1997)I. G. Hill and A. B. McLean

Ball-and-stick model of the Si(111)-(4 Si(111)-In 4 1)-In reconstruction

INTRODUCTION

3. RT XRD & Cal. Model

‘4’ 1

4 ‘1’

Phys. Rev. B 59, 12228 (1999)O. Bunk et al.

Phys. Rev. B , 63, 193307 (2001)Jun Nakamura et al.

INTRODUCTION Si(111)-In 4

4. RT & LT STM + PES

LT

RT

RT

Phys. Rev. Lett. 82, 4898 (1999)H. W. Yeom et al.

INTRODUCTION Si(111)-In 4

5. LT RHEED & XRD

100K

RT

Phys. Rev. Lett. 82, 4898 (1999)H. W. Yeom et al.

Phys. Rev. Lett. 85, 4916 (2000)C. Kumpf et al.

INTRODUCTION Si(111)-In 4

6. LT Theoretical Calculation

41

42

RT 41 Filled

LT 42 Filled

LT 42 Empty

RT 41 Empty

82

Phys. Rev. B 64, 235302 (2001)Jun-Hyung Cho et al.

EXPERIMENT Si(111)-In 4

Apparatus

: RT/LT-STM/STS, LEED, In-evaporator

Sample Preparation

: N-type Si(111) substrate ( 0.7~1.3 Ω·㎝, P-doping )

: Conventional annealing & 1200 C flashing

: ~ 1 ML In-deposition on sample at ~ 400 C

: No subsequent annealing after deposition

: LN2 used for low temperature (~77K)

RESULTS Si(111)-In 4

1. Clean Si(111) 7 7 Surface

RT LEED : E = 35.3 eV

RT STM : V = -2.0V, I = 0.1nA

RESULTS Si(111)-In 4

2. RT Si(111)-In 4 1 Surface

RT LEED : E = 26.3 eV

RT STM : V = -1.8V, I = 0.08nA

RESULTS Si(111)-In 4

3. LT In 4 2 Surface

LT STM : V = -1.4V, I = 0.3nA

LT STM : V = +1.4V, I = 0.3nA

RESULTS Si(111)-In 4

4. LT In 4 2 Surface

LT STM : V = -1.0V, I = 0.3nA

LT STM : V = +1.0V, I = 0.3nA

RESULTS Si(111)-In 4

6. ‘8’ 2 Periodicity Observed

Tip Changed

LT STM : V = -1.0V, I = 0.1nA

LT STM : V = +0.4V, I = 0.2nA

RESULTS Si(111)-In 4

7. Comparison with Model

A

B

A

B

A

B

DFT Cal. (Blue : +1.0V, Red : -1.0V)

LT STM : V = +1.0V, I = 0.3nA

RESULTS Si(111)-In 4

8. Comparison with Model

A

B

A

B

A

B

DFT Cal. (Blue : +1.0V, Red : -1.0V)

LT STM : V = -1.0V, I = 0.3nA

Experiments – 5. LT STS Observation of In/Si(111)-8 Si(111)-In 4 2

NdI/dV Curve

CONCLUSION (to be modified) Si(111)-In 4

4 2 unit cells are out of phase across the row upon the polarity reversal(consistent with the previous 1st principle DFT calculation)

No zig-zag patterns are observed at filled states(inconsistent with previous 1st principle DFT calculations)

Weak longitudinal interchain correlation of 4X2 unit cells between the rows is found (consistent with previous RHEED results)

Easily delocalized one dimensional empty states of 4X2 unit cells alongthe row is found (extended empty states)

‘8’ 2 unit cells are clearly visible at filled states Thus ‘8 ’ periodicity may not be originated from the out of phase of 4X2 units across the rows (consistent with previous RHEED results)

There are some long-range interactions across the rows

Additional In deposition at LT shows no change of 4X2 periodicity(contrast to the previous STM Results)

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