Coarsening of Self-Assembled Ge Quantum Dots on Si(001)

Abstract

The size distribution of self-assembled heteroepitaxial islands is critical to their application as quantum dots in novel devices. In situ, real time UHV transmission electron microscopy studies of Ge island growth on Si(001) show that island coarsening occurs even during growth. With increasing volume, a shape transition from pyramids to domes gives rise to an abrupt change in chemical potential. This leads to a bifurcation in the size distribution and ultimately to a narrow size range. Simulations of coarsening in the presence of a shape transition are in good agreement with experimental results.