Structure of AlSb(001) and GaSb(001) Surfaces Under Extreme Sb-rich Conditions

TL;DR

This study uses density-functional theory to analyze AlSb(001) and GaSb(001) surface structures, proposing new models and explaining experimental reconstructions under various growth conditions.

Contribution

The paper introduces a new surface reconstruction model for GaSb(001) that better matches experimental STM images and discusses the kinetic limitations of observed structures.

Findings

AlSb(001) predictions match experiments

New GaSb(001) model improves STM agreement

Observed GaSb structures are kinetically limited

Abstract

We use density-functional theory to study the structure of AlSb(001) and GaSb(001) surfaces. Based on a variety of reconstruction models, we construct surface stability diagrams for AlSb and GaSb under different growth conditions. For AlSb(001), the predictions are in excellent agreement with experimentally observed reconstructions. For GaSb(001), we show that previously proposed model accounts for the experimentally observed reconstructions under Ga-rich growth conditions, but fails to explain the experimental observations under Sb-rich conditions. We propose a new model that has a substantially lower surface energy than all (nx5)-like reconstructions proposed previously and that, in addition, leads to a simulated STM image in better agreement with experiment than existing models. However, this new model has higher surface energy than some of (4x3)-like reconstructions, models with periodicity that has not been observed. Hence we conclude that the experimentally observed (1x5) and (2x5) structures on GaSb(001) are kinetically limited rather than at the ground state.