STRUCTURAL STUDY OF SI GROWTH ON A SI(111) 7X7 SURFACE

Intensity oscillations and rocking curves of reflection high energy electron diffraction (RHEED) during silicon deposition on a Si(111)7 x 7 surface at several temperatures are measured and analyzed by RHEED dynamical calculations. For silicon deposition on a Si(111) substrate at room temperature, it is concluded that backbonds of adatoms of Takayanagi's dimer-adatom-stacking-fault (DAS) structure are broken at an initial stage of the deposition. For the further deposition, dimers and stacking-faults remain at the interface of the substrate and the amorphous layer is formed subsequently on the substrate. For molecular beam epitaxial (MBE) growth at about 300-degrees-C, rocking curves from the surface during growth are very different from that before the growth. This suggests that the structure of the surface during growth is not the usual DAS structure. From 380 to 600-degrees-C, a mixed phase of 5 x 5 and 7 x 7 structures, which have the DAS structure, is observed. From the intensity oscillations of the fractional order spots, it is concluded that the 5 x 5 structure grows at terraces and the 7 x 7 one from step edges. At higher temperatures like 700-degrees-C, RHEED intensity oscillation is scarcely observed. The surface structure is the 7 x 7 structure which is almost the same as that of the clean surface.