Volume 85, Number 6, March 2009
Article Number 66001
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 07 April 2009
EPL, 85 (2009) 66001
DOI: 10.1209/0295-5075/85/66001

First-principles calculations and bias-dependent STM measurements at the $\chem{\alpha}$-Sn/Ge(111) surface

P. Gori1, 2, F. Ronci1, S. Colonna1, A. Cricenti1, 2, 3, O. Pulci2, 4 and G. Le Lay5, 6

1   ISM CNR - Via del Fosso del Cavaliere 100, I-00133 Roma, Italy, EU
2   NAST Centre - Via della Ricerca Scientifica 1, I-00133 Roma, Italy, EU
3   Department of Physics and Astronomy, Vanderbilt University - Nashville, TN 37235-1807, USA
4   ETSF, INFM-CNR Dipartimento di Fisica, Università di Roma “Tor Vergata" Via della Ricerca Scientifica 1, I-00133 Roma, Italy, EU
5   CINaM-CNRS, Campus de Luminy - Case 913, F-13288 Marseille Cedex 09, France, EU
6   UFR Sciences de la Matière, Université de Provence - Marseille, France, EU

received 15 October 2008; accepted in final form 25 February 2009; published March 2009
published online 7 April 2009

The nature of the $\alpha $-Sn/Ge(111) surface is still a matter of debate. In particular, two possible configurations have been proposed for the 3$\times$3 ground state of this surface: one with two Sn adatoms in a lower position with respect to the third one (1U2D) and the other with opposite configuration (2U1D). We report ab initio GW calculations for the $\alpha $-Sn/Ge(111) system, simulating STM images as a function of bias voltage and comparing them with STM experimental results at 78 K. The concurrent application of theory and experiments and the very good match between their results provide unambiguous indications that the stable configuration for the $\alpha $-Sn/Ge(111) surface is the 1U2D. The possible inequivalence of the two down Sn adatoms is also discussed.

68.37.Ef - Scanning tunneling microscopy (including chemistry induced with STM).
73.20.-r - Electron states at surfaces and interfaces.
68.35.-p - Solid surfaces and solid-solid interfaces: structure and energetics.

© EPLA 2009