Tensile-strained Si0.6Ge0.4 alloys were deposited onto Ge(001), at 325 to 500C, by means of molecular beam epitaxy. The morphology and microstructure of as-deposited (6.5 to 130nm thick) and annealed (625 or 700C, 120s) epitaxial films were studied by means of  in situ  scanning tunnelling microscopy, ex situ  atomic force microscopy, and transmission electron microscopy. The 6.5nm-thick films which were deposited at 325 or 410C were atomically flat, with low densities of partial dislocations. Stress relaxation of 6.5nm-thick films was limited by dislocation blocking. The surface morphology of thicker films, grown at 410C, was strongly affected by the interaction of stacking faults and surface steps. The annealing of 13nm-thick films at 700C produced severe roughening, with the formation of a regular pattern of 50nm-deep surface pits that were bounded by {113} facets.

J.E.Van Nostrand, D.G.Cahill, I.Petrov, J.E.Greene: Journal of Applied Physics, 1998, 83[2], 1096-102