  The results of STM and RHEED studies of a thin Ge film grown on the
Si/Si(001) epitaxial layers with different surface relief are presented.
Process of the partial stress relaxation was accompanied by changes in the
surface structure of the Ge wetting layer. Besides the well-known sequence of
surface reconstructions ($2 \times 1 \rightarrow 2 \times N \rightarrow M
\times N$ patches) and hut clusters faceted with {105} planes, the formation of
isolated {105} planes, which faceted the edges of $M \times N$ patches, has
been observed owing to the deposition of Ge on a rough Si/Si (001) surface. A
model of the isolated {105} facet formation has been proposed based on the
assumption that the mutual arrangement of the monoatomic steps on the initial
Si surface promotes the wetting layer formation with the inhomogeneously
distributed thickness that results in the appearance of $M \times N$ patches
partially surrounded by deeper trenches than those observed in the usual Ge
wetting layer grown on the smooth Si(001) surface. Isolated {105} facets are an
inherent part of the Ge wetting layer structure and their formation decreases
the surface energy of the Ge wetting layer.
