MANIPULATION OF NUCLEATION BY GROWTH-RATE MODULATION

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 acid 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. (C) 1995 American Institute of Physics.