The influence of surface stress on the equilibrium shape of strained quantum dots

TL;DR

This paper investigates how surface stress affects the equilibrium shape of strained InAs quantum dots on GaAs substrates using a hybrid approach combining DFT calculations and elasticity theory.

Contribution

It introduces DFT-based calculations of surface stresses and analyzes their impact on quantum dot shapes, a factor previously neglected in studies.

Findings

Surface stresses significantly influence quantum dot equilibrium shapes.

The study provides insights into whether observed quantum dots are at thermal equilibrium.

Edge energies also play a role in determining island shapes.

Abstract

The equilibrium shapes of InAs quantum dots (i.e., dislocation-free, strained islands with sizes >= 10,000 atoms) grown on a GaAs (001) substrate are studied using a hybrid approach which combines density functional theory (DFT) calculations of microscopic parameters, surface energies, and surface stresses with elasticity theory for the long-range strain fields and strain relaxations. In particular we report DFT calculations of the surface stresses and analyze the influence of the strain on the surface energies of the various facets of the quantum dot. The surface stresses have been neglected in previous studies. Furthermore, the influence of edge energies on the island shapes is briefly discussed. From the knowledge of the equilibrium shape of these islands, we address the question whether experimentally observed quantum dots correspond to thermal equilibrium structures or if they are a result of the growth kinetics.