Leed studies of Si molecular beam epitaxy onto Si(111)

Abstract

The nucleation and annealing of submonolayer silicon films evaporated in UHV onto Si(111) has been investigated in situ by spot profile analysis of low energy electron diffraction (SPA-LEED). It will be shown, that an evaluation within the kinematic approximation is quantitatively correct as long as ratios of intensities are used. The broad shoulder of each diffraction spot - caused by the island structure - yields the island size or terrace width distribution, the energy dependence of the spot profile yields the vertical distribution of the evaporated amount over different layers. After annealing all evaporated atoms (θ<1) are arranged in one layer without appreciable nucleation in a third layer (θ 3<0.5%). The resulting terrace width distributions include always all sizes from narrow to wide terraces. With increasing annealing temperature the distribution is centered around larger distances due to increased size and decreased number of islands. The island density is measured in the range of 10 11 to some 10 13 cm -2, where no other technique provides quantitative data.