The microstructural changes which occurred during the initial stages of Ge islanding on vicinal (100) Si were studied to nanometre resolution in an ultra-high vacuum scanning transmission electron microscope. The Ge was deposited, using molecular beam epitaxy techniques, onto vicinal (100) Si surfaces which were misoriented by 1 or 5º towards [110]-type directions. It was found that metastable growth of the Ge occurred up to thicknesses which were much greater than the equilibrium critical thickness. The layer could grow to some 7 monolayers in thickness before islanding in the Stranski-Krastanov fashion. The presence of strong adatom sinks markedly altered the growth and size distribution of the islands when the spacing of these sinks was less than one adatom diffusion distance. Studies of the initial stages of islanding in solid-phase molecular beam epitaxial material indicated that there was no long-range adatom diffusion. There was an initial fast transformation from disordered layer growth, followed by the sluggish growth of islands. The coarsening of the islands in the earliest stages was studied. It appeared that a novel coarsening mechanism occurred which was affected by the presence of an unstable intermediate layer and by dislocation-free islands. In all cases, the dislocation-free islands grew more slowly than those which had been relaxed by the introduction of misfit dislocations.

M.Krishnamurthy, J.S.Drucker, J.A.Venables: Journal of Applied Physics, 1991, 69[91, 6461-71