STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 1

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

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 2

MOTIVATION

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

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

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

4. Reversible phase transition accompanied by a 1D CDW

5. Atomic structures at Low Temperature are not exactly known

6. Different chain to chain correlations upon transverse or longitudinal

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 3

INTRODUCTION

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

+ 2.0 V

- 2.0 V

1. Room Temperature STM

(top) empty state image at – 0.12 V (mid) filled state image at +1.9 V

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

l.

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 4

INTRODUCTION 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

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 5

INTRODUCTION 3. RT XRD & Cal. Model

Ball-and-stick model of the

Si(111)-(41)-In reconstruction

Phys. Rev. B , 63, 193307 (2001)

Jun Nakamura et al.

Phys. Rev. B 59, 12228 (1999)

O. Bunk et al.

4 ‘1’

‘4’ 1

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 6

INTRODUCTION 4. RT & LT STM + PES

Phys. Rev. Lett. 82, 4898 (1999)

H. W. Yeom et al.

RT LT

RT

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 7

INTRODUCTION 5. LT RHEED & XRD

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

Phys. Rev. Lett. 82, 4898 (1999)

H. W. Yeom et al.

RT 100K

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 8

INTRODUCTION 6. LT Theoretical Calculation

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

41

42

82

RT 41 Filled

RT 41 Empty

LT 42 Filled

LT 42 Empty

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 9

EXPERIMENT

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)

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 10

RESULTS 1. Clean Si(111) 7 7 Surface

RT LEED : E = 35.3 eV RT STM : V = -2.0V, I = 0.1nA

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 11

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

RT LEED : E = 26.3 eV RT STM : V = -1.8V, I = 0.08nA

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 12

RESULTS 3. LT In 4 2 Surface

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

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 13

RESULTS 4. LT In 4 2 Surface

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

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 14

RESULTS

-1.2V

+1.2V

5. Bias Dependent LT-In 4 2

+1.4V

-1.6V

+1.6V

-1.4V

+1.0V

-1.0V

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 15

RESULTS 6. ‘8’ 2 Periodicity Observed

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

Tip Changed

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

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 16

RESULTS 7. Comparison with Model

A B

A B A B

LT STM : V = +1.0V, I = 0.3nADFT Cal. (Blue : +1.0V, Red : -1.0V)

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 17

A B

A B A B

RESULTS 8. Comparison with Model

LT STM : V = -1.0V, I = 0.3nADFT Cal. (Blue : +1.0V, Red : -1.0V)

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 18

Experiments – 5. LT STS Observation of In/Si(111)-82

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Cu

rren

t (A

)

Energy (eV)

-1.0 V Tranch +1.0 V Tranch -1.0 V Top +1.0 V Bright Top

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

dI/d

V (

Arb

.)

Energy (eV)

-1.0 V Tranch +1.0 V Tranch -1.0 V Top +1.0 V Bright Top

I/V Curve dI/dV Curve

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 19

Experiments – 5. LT STS Observation of In/Si(111)-82

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

0

5

10

15

20

25

(dI/d

V)/

(I/V

)

Energy (eV)

-1.0 V Tranch +1.0 V Tranch -1.0 V Top +1.0 V Bright Top

NdI/dV Curve

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 20

+1.6 V -1.6 V

RESULTS 9. Additional Depo. of In

STM Study of Low Temperature 1-D Quantum Structures of Si(111)-In 41 21

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

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

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

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

5. ‘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)

6. There are some long-range interactions across the rows

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

CONCLUSION (to be modified)