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

In this paper we present an atomic force microscopy and X-rayphotoemission spectroscopy study of the composition and shape evolutionof self-assembled Ge/Si(001) islands upon capping with Si. We foundthat the islands undergo a reverse Straski-Krastanov shape evolution,with a progressive Si-enrichment of both the wetting layer and theislands. We demonstrate that the island shape evolves at constantvolume with silicon atom incorporation occurring in the absence oflateral diffusion of Ge and Si atoms from the wetting layer to theislands themselves. (C) 2008 Elsevier Ltd. All rights reserved