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

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

2. MOTIVATION Self-organized low dimensional structures of metal on Si(111) surface Quasi-one dimensional chain formation of ~ 1ML In on Si(111)-77 Phase transition from 41 to 42 or 82 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

3. (top) empty state image at – 0.12 V (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.

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

5. Ball-and-stick model of the Si(111)-(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.

6. INTRODUCTION 4. RT & LT STM + PES LT RT RT Phys. Rev. Lett. 82, 4898 (1999)H. W. Yeom et al.

7. INTRODUCTION 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.

8. INTRODUCTION 6. LT Theoretical Calculation 41 42 RT 41 Filled LT 42 Filled LT 42 Empty RT 41 Empty 82 Phys. Rev. B 64, 235302 (2001)Jun-Hyung Cho et al.

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)

10. RESULTS 1. Clean Si(111) 7  7 Surface RT LEED : E = 35.3 eV RT STM : V = -2.0V, I = 0.1nA

11. RESULTS 2. RT Si(111)-In 4 1 Surface RT LEED : E = 26.3 eV RT STM : V = -1.8V, I = 0.08nA

12. RESULTS 3. LT In 4  2 Surface LT STM : V = -1.4V, I = 0.3nA LT STM : V = +1.4V, I = 0.3nA

13. RESULTS 4. LT In 4  2 Surface LT STM : V = -1.0V, I = 0.3nA LT STM : V = +1.0V, I = 0.3nA

14. RESULTS 5. Bias Dependent LT-In 4  2 +1.4V +1.6V +1.0V +1.2V -1.4V -1.6V -1.0V -1.2V

15. RESULTS 6. ‘8’ 2 Periodicity Observed Tip Changed LT STM : V = -1.0V, I = 0.1nA LT STM : V = +0.4V, I = 0.2nA

16. RESULTS 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

17. RESULTS 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

18. Experiments – 5. LT STS Observation of In/Si(111)-82 dI/dV Curve I/V Curve

19. Experiments – 5. LT STS Observation of In/Si(111)-82 NdI/dV Curve

20. RESULTS 9. Additional Depo. of In +1.6 V -1.6 V

21. CONCLUSION (to be modified) 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)