First-principles calculations and bias-dependent STM measurements at the alpha-Sn/Ge(111) surface: a clear indication for the 1U2D configuration

TL;DR

This study combines first-principles calculations and bias-dependent STM measurements to determine that the stable configuration of the alpha-Sn/Ge(111) surface is the 1U2D arrangement, clarifying previous debates.

Contribution

The paper provides a definitive identification of the alpha-Sn/Ge(111) surface configuration using combined computational and experimental STM analysis.

Findings

STM simulations match experimental images at 78K

The 1U2D configuration is confirmed as the stable surface structure

Analysis of adatom inequivalence is discussed

Abstract

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 3x3 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). By means of first-principles quasiparticle calculations we could simulate STM images as a function of bias voltage and compare them with STM experimental results at 78K, obtaining an unambiguous indication 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.