Atomic steps on a single-crystal surface studied with in situ UHV reflection-electron microscopy

Ultra-high vacuum reflection electron microscopy and atomic force microscopy were used to study atomic steps on the Si(111) surface, with the focus on the structural and morphological transitions during gold adsorption and oxygen treatments. Subsequent stages of gold three-dimensional island nucleation with different morphologies in a wide temperature range of the substrate were imaged. The influence of the monatomic step density on the redistribution of the three-dimensional islands was revealed during thermal annealing of the substrate. Investigations of the structural transformations of the silicon surface during oxygen treatments were performed in the temperature range 500-900degreesC. Monatomic step movements in the step-up direction and negative island formation due to vacancy nucleation were imaged. The dependence of the step velocity on the width of neighbouring terraces was measured. The intensity oscillations of the high-energy electron beam reflected from the silicon surface was found to be caused by a periodic change of the surface morphology due to formation of two-dimensional negative islands.