The surface morphology of epitaxial (001) Si1-xGex films, subject to b
iaxial strain, is studied by atomic force microscopy (AFM). Distinct f
acets are observed, oriented on {105}, {311}, and {518} crystal faces.
The tiled arrangement of facets resembles a mosaic. We find that the
growth sequence begins with the shallow {105} facets, followed by the
appearance of steeper facets. After strain relaxation, the morphology
coarsens and facets become less distinct. The existence of discrete fa
cets produces a kinetic barrier to strain-induced roughening; and we s
how that increasing this barrier (by growing at reduced strain or redu
ced temperature) leads to a flatter surface morphology.