Substrates for enhancing contrast in optical microscope images of layered materials

Abstract

Optical observation of ultrathin crystals on substrates is important in research on layered materials. Ultrathin crystals are conventionally visualized using the optical interference effect in thermally-grown silicon substrates. Herein, a visualization technique that focuses on the optical properties of the substrate was developed. This method allows recognition of a monolayer and reliable identification of the number of layers in hexagonal boron nitride crystals. Furthermore, the difference in the thickness of the monolayer in a thick crystal was visualized, enabling the selection of mechanically exfoliated crystals.