Thermodynamic driving force of formation of coherent three-dimensional islands in Stranski-Krastanov growth

TL;DR

This paper analyzes the thermodynamic factors influencing the formation of coherent 3D islands during Stranski-Krastanov growth, emphasizing the role of adhesion and phase differences in highly mismatched epitaxy.

Contribution

It introduces a thermodynamic explanation for 3D island formation, highlighting the non-equilibrium nature of wetting layers and the discrete height of islands.

Findings

Critical misfit explains 3D islanding onset.

Discrete island heights are due to thermodynamic stability.

Reduced adhesion drives 3D island formation.

Abstract

The formation of coherent three-dimensional islands in highly mismatched epitaxy is discussed in terms of the traditional concept of wetting. It is shown that the wetting layer and the 3D islands represent different phases which cannot be in equilibrium with each other, and the transfer of matter from the stable wetting layer to the 3D islands is thermodynamically unfavored. The experimentally observed critical misfit for coherent 3D islanding to occur and the coexistence of pyramids with discrete heights of two, three, four... monolayers can be explained assuming that the thermodynamic driving force of formation of coherent 3D islands on the surface of the wetting layer of the same material is the reduced average adhesion of the islands to that layer and that the islands height is a discrete variable.