Nucleation of Ge dots on the C-alloyed Si(001) surface

Abstract
The growth of Ge on Si(001) surfaces precovered with 0.1 ML carbon has been investigated by ultrahigh vacuum scanning-tunneling microscopy. Unlike the Stranski-Krastanov growth of Ge on bare Si(001), three-dimensional islands start to nucleate already at submonolayer Ge coverage. This Volmer-Weber growth mode is forced by the surface strain pattern related to the C incorporation into the Si surface. Ge dots nucleate between the c(4×4) reconstructed C-rich areas, where the lattice mismatch is higher with respect to Ge. Based on this observation and the evolution of islands towards higher Ge coverage, which give insight into the spatial dot composition, a modified model for the photoluminescence mechanism of C-induced Ge dots is proposed.