Thickness characterization of atomically-thin WSe$_2$ on epitaxial   graphene by low-energy electron reflectivity oscillations
  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. 
Sergio C. de la Barrera, Yu-Chuan Lin, Sarah M. Eichfeld, Joshua A.   Robinson, Qin Gao, Michael Widom, Randall M. Feenstra
cond-mat.mes-hall