Annealing of Ge nanocrystals on Si(001) at550°C: Metastability of huts and the stability of pyramids and domes

We performed a series of annealing experiments for Ge nanocrystals on Si(001) at $550°\mathrm{C}$ in order to clarify some issues related to island stability and coarsening. We determined the nanocrystal shape and size distributions for 8 Ge equivalent monolayers as a function of annealing time for up to 80 min after terminating the depositions. Elongated islands or “huts” disappear within 30 s, leaving only equiaxial islands, the “pyramids” and “domes.” During the first 10 min of annealing, the nanocrystals grow further by drawing additional Ge from the wetting layer. Thereafter, the pyramid and dome size distributions are stable.