Substrates for enhancing contrast in optical microscope images of layered materials

Abstract

Optical observation of ultrathin films on substrates is important in layered materials research. Ultrathin films have been visualized using the optical interference effect of thermally-grown silicon substrates. We propose a visualization technique that focuses on the optical properties of the substrate. The method allows recognition of monolayer and reliable identification of the number of layers of hexagonal boron nitride films. Furthermore, the monolayer thickness difference in a thick film is visualized, which can be applied to the selection of mechanically exfoliated films.