Manipulation of nucleation by growth rate modulation

Abstract

We report on manipulation of nucleation by means of periodic modulation of the growth rate R, both during molecular beam epitaxial growth of Si on Si(111) and using a simulated bilayer structure. We have found that the bilayer-by-bilayer growth can be improved and that the surface roughness can be reduced by applying the R modulation synchronized with the deposition of a multiple of full bilayers. For nonsynchronized growth the phase of reflection high-energy electron diffraction (RHEED) intensity oscillations could be shifted relative to the bilayer deposition period and a beating phenomenon of the RHEED oscillations was observed, which can be attributed to the superimposed effects of the R modulation and the regular bilayer-by-bilayer growth. We have used the phenomenological correspondence between the surface step density and the RHEED oscillations as a basis to discuss the growth. By employing a kinetic solid-on-solid Monte Carlo model without vacancies and overhangs all significant experimental features could be simulated.