Island and wetting-layer intermixing in the Ge/Si(001) system upon capping

In this paper we present an atomic force microscopy and X-ray photoemission spectroscopy study of the composition and shape evolution of self-assembled Ge/Si(001) islands upon capping with Si. We found that the islands undergo a reverse Straski–Krastanov shape evolution, with a progressive Si-enrichment of both the wetting layer and the islands. We demonstrate that the island shape evolves at constant volume with silicon atom incorporation occurring in the absence of lateral diffusion of Ge and Si atoms from the wetting layer to the islands themselves.