Surface morphology of silicon grown on CaF2/Si by electron-beam-assisted molecular-beam epitaxy

Abstract
The surface morphology of silicon, grown on epitaxial CaF2/Si by electron‐beam‐assisted molecular‐beam‐epitaxy was studied using atomic force microscopy, x‐ray photoelectron spectroscopy, and low‐energy electron diffraction. It was found that the roughness of the silicon overlayer was minimized by exposing the CaF2 to an electron dose of 1.0 mC/cm2 before growing the epitaxial silicon overlayer. The observed hexagonally shaped microcrystals formed by the silicon were explained by a model based on geometrical thermodynamics. Contact angle measurements yielded a Si—Ca interface bond strength of 2.5±0.3 eV and a free energy of 520±95 erg/cm2 for the irradiated CaF2 surface.