Kinetically Self-Limiting Growth of Ge Islands on Si(001)

The evolution of the size and shape of individual $\{\}\left(105\right)$ faceted Ge islands on Si(001) is measured with a high temperature scanning tunneling microscope during growth. A slower growth rate is observed when an island grows to larger sizes. This behavior can be explained by kinetically self-limiting growth. A kinetic growth model involving a nucleation barrier for each repeated growth of a new atomic layer on the $\{\}\left(105\right)$ facets agrees with the experimental results for the evolution of the island volume. The experimentally observed shape transition from nearly square shaped islands to elongated islands is described by the kinetic growth model.