Stabilization of semiconductor surface reconstructions by configurational entropy

Abstract

Surface unit cells with a larger area and a reduced symmetry have a larger configurational entropy. The entropy may even stabilize reconstructions with higher energy at finite temperatures. We study the entropy contribution to surface reconstructions on the basis of ground-state calculations employing density-functional theory. Specifically, the ground-state $\text{GaSb}(111)A$ surface reconstruction has a $(2\ifmmode\times\else\texttimes\fi{}2)$ symmetry, but at elevated temperatures, we experimentally observe the $(2\sqrt{3}\ifmmode\times\else\texttimes\fi{}2\sqrt{3})\text{\ensuremath{-}}R30\ifmmode^\circ\else\textdegree\fi{}$ symmetry in agreement with the theoretical results. The findings based on the general expressions are consistent with experimental data from other semiconductor surfaces.