Atomic force microscopy study of the growth and annealing of Ge islands on Si(100)

Atomic force microscopy is used to study the growth and annealing of Ge islands on Si(100) by molecular beam epitaxy. The Ge island shape, size distribution, number density, and spatial distribution under various growth conditions, such as different substrate temperatures, Ge beam fluxes, and annealing times, are investigated. By limiting the growth to a low coverage of 6 ML of Ge, we find that either a low growth temperature (⩽875 K) or a high beam flux can produce films dominated by pyramids of {105} facets. Domes of higher aspect ratios only appear at high growth temperatures or after a long time of annealing at low temperatures. This indicates that in the competition between the different kinetic processes responsible for the pyramid and dome formation, the domes require a higher activation energy and grow slower. We also demonstrate that appropriate annealing at low temperature can form locally ordered arrays of pyramids with a narrow size distribution.