Trace of interface reconstruction in Ge solid-phase epitaxy on Si(111)

We describe the mechanism of solid-phase epitaxy (SPE) of Ge on a Si(111)-7×{}7 surface using reflection high-energy electron diffraction and scanning tunneling microscopy. Amorphouslike Ge layers crystallize in the registry of the 7×{}7 reconstruction preserved at the Ge/Si interface. The preferred basic unit of epitaxy is a triangular domain corresponding to four half-units of the 7×{}7 reconstruction. Faultedly stacked (twinned) domains cover almost half of the surface at the initial stage of SPE because Ge grows epitaxially on both the unfaulted and faulted halves of the 7×{}7 reconstruction. These twinned Ge layers are transformed into normally stacked Ge layers above 400 ^∘{}C.