INITIAL-STAGES OF SIGE EPITAXY ON SI(001) STUDIED BY SCANNING-TUNNELING-MICROSCOPY

We have studied the initial stages of strained SiGe alloy growth on the Si(001)(.)(2 X 1) surface by scanning tunneling microscopy. The Si0.36Ge0.64 alloy was grown on the silicon substrate at various coverages (0.13-3.6 ML) and at different temperatures (similar to 310-470 degrees C). The growth was one dimensional, preferring the direction perpendicular to the underlying silicon dimer rows at low coverages and low temperatures. Anti-phase boundaries were observed to lead multi-layer growth. Strong interaction between the overlayer and the substrate was found to buckle the substrate as well as SiGe dimers. Different growth mechanisms, island formation and step flow, were identified at low and high substrate temperatures. (2 X n) ordering of the strained overlayer was only observed at an intermediate growth temperature(similar to 390 degrees C).