Heteroepitaxial growth and superstructure of Ge on Si(111)-7×7 and (100)-2×1 surfaces

The initial stage of the heteroepitaxy, and the superstructure of Ge on Si surfaces, have been investigated by LEED and AES. Germanium was evaporated on to a clean Si(111–7×7 surface and also on to an Si(100)–2×1 surface. The layer-by-layer growth of Ge films on the Si surfaces was confirmed from the decrease in intensity of the Si(LVV)-AES signal with increase in Ge coverage. It was found that the (7×7) superstructure of the Si (111) surface is replaced by a (5×5) superstructure at about 2 monolayers coverage of Ge. The phase diagram of the superstructure of Ge on the Si(111) system was constructed for Ge coverage in monolayers evaporated at room temperature, versus annealing temperature. A similar study was also extended to Ge on an Si(100)–2×1 surface, where the original LEED pattern is not strongly distrubed at about 1–2 monolayers of Ge.