Nucleation of Two-Dimensional Si Islands Near a Monatomic Step on an Atomically Clean Si(111)-(7 × 7) Surface

摘要

The process of nucleation of 2D islands near a monatomic step at the initial stage of growing of a silicon film on the Si(111)-(7 × 7) surface is studied by means of in situ ultrahighvacuum reflection electron microscopy. The dependence of the depletion region width W near the step, where no islands are formed, on the deposition rate R is described by the expression W~2 ∝ R~(-x) with the exponent X = 1.18 and X = 0.63 at temperatures of 650 and 680℃, respectively. It is demonstrated that the change in X is associated with the step structure, which provides the transformation from the growth kinetics limited by attachment of adatoms to the step to that limited by diffusion of adatoms. A competition of the processes of nucleation and attachment to the step leads to an increase in the critical size of the island nucleus from i = 1 far from the step to i = 3-5 near the step and to i = 6-8 on the terrace of critical width for 2D nucleation.