Theoretical analysis of thin film epitaxial growth monitored by differential reflectance

Abstract

The thin film growth at the level of a single molecular layer can be achieved via laser molecular beam epitaxy approach. Such a growth can be monitored not only via the reflection high-energy electron diffraction technique, but also with the use of relative reflectivity change between s- and p-polarized light. The epitaxy growth of thin film is modeled as a microscopic two-dimensional (2D) gratings on the surface of the substrate with a period over two orders of magnitude less than the wavelength of probe light. The solution of Maxwell’s equations for such a 2D gratings leads to an effective multilayer medium model, from which the reflectance-difference (RD) signal in the process of epitaxy growth can be calculated in the framework of general optics. The simulation results demonstrate that the growth of thin film at the atomic level can be detected by such an optical RD technique. The theoretical calculations of RD signal are in agreement with the experimental measurements both in the order of magnitude and variation character of RD signal curve.