Thickness characterization of atomically-thin WSe${}_2$ on epitaxial graphene by low-energy electron reflectivity oscillations

Abstract

In this work, low-energy electron microscopy is employed to probe structural as well as electronic information in few-layer WSe${}_2$ on epitaxial graphene on SiC. The emergence of unoccupied states in the WSe${}_2$--graphene heterostructures are studied using spectroscopic low-energy electron reflectivity. Reflectivity minima corresponding to specific WSe${}_2$ states that are localized between the monolayers of each vertical heterostructure are shown to reveal the number of layers for each point on the surface. A theory for the origin of these states is developed and utilized to explain the experimentally observed featured in the WSe${}_2$ electron reflectivity.

15 pages, 7 figures