Strain induced stabilization of stepped Si and Ge surfaces near (001)

TL;DR

This paper investigates how biaxial strain influences the stability of various step structures on Si and Ge (001) surfaces, revealing a new stable step type under compression that explains experimental observations of quantum dot side walls.

Contribution

It introduces a novel rebonded [100] step structure stabilized by compressive strain and links it to the formation of quantum dot side walls and mound growth.

Findings

Rebonded [100] step is strongly stabilized by compressive strain.

Explains nucleationless growth of shallow mounds.

Accounts for stability of (105) facets under strain.

Abstract

We report on calculations of the formation energies of several [100] and [110] oriented step structures on biaxially stressed Si and Ge (001) surfaces. It is shown that a novel rebonded [100] oriented single-height step is strongly stabilized by compressive strain compared to most well-known step structures. We propose that the side walls of ``hut''-shaped quantum dots observed in recent experiments on SiGe/Si films are made up of these steps. Our calculations provide an explanation for the nucleationless growth of shallow mounds, with steps along the [100] and [110] directions in low- and high-misfit films, respectively, and for the stability of the (105) facets under compressive strain.