ANNEALING EFFECT ON AN AMORPHOUS SI FILM DEPOSITED ON A 7X7 SUPERLATTICE SURFACE OF SI(111) STUDIED WITH LOW-ENERGY-ELECTRON DIFFRACTION

The intensity profile of low-energy electron diffraction (LEED) was observed for a Si film grown on a Si(111)-7x7 substrate under low-temperature epitaxial growth conditions. The epitaxial relation for Si(111) holds for each film with its thickness region below a certain value (d(C)) from the substrate, and an amorphous phase is formed above it. The values of d(C) were 0.5, 6.5, 17, and 100 nm at substrate temperatures (T(s)) of 35, 170, 200, and 250-degrees-C, respectively. The annealing effect on the films grown at T(s) = 35 and 170-degrees-C was studied. The LEED intensity (I(S)) is proportional to the surface area occupied by the 7 x 7 and 5 X 5 superlattices such that (1) I(S) depends sensitively on the film thickness (d) and T(S), and (2) the dependence of I(S) on the annealing temperature is independent of T(S) and d. This is discussed from the viewpoint of the change in structural hierarchy formed in the as-grown film due to the annealing.