Evolution of Ge islands on Si(001) during annealing

The evolution of the shape and size distributions of Ge islands on Si(001) during annealing after deposition has been studied at different temperature s and effective coverages. The initial distributions of square-based pyrami ds, elongated "hut'' structures, faceted "dome- shaped'' islands, and much larger "superdomes'' depends on the deposition conditions. During annealing after deposition, the islands coarsen over a limited range of times and te mperatures. Those pyramidal-shaped islands that grow transform to faceted, dome-shaped islands as they become larger. Initially dome-shaped islands th at dissolve transform to a pyramidal shape as they become smaller during th e process of dissolving. Outside of this coarsening regime, the islands can achieve a relatively stable, steady-state configuration, especially at low er temperatures. At higher temperatures, intermixing of Si into the Ge isla nds dominates, decreasing the strain energy and allowing larger islands to form. At lower and intermediate temperatures, the initial wetting layer is metastable, and some Ge transfers to the islands during the early stages of annealing. (C) 1999 American Institute of Physics. [S0021-8979(99)02702-4] .