Layer-dependent Schottky contact at van der Waals interfaces: V-doped WSe₂ on graphene

Contacting two-dimensional (2D) semiconductors with van der Waals semimetals significantly reduces the contact resistance and Fermi level pinning due to defect-free interfaces. However, a Schottky barrier remains depending on the band alignment. This study investigates the valence and conduction band edges in pristine and heavily vanadium (0.44%), i.e., p-type, doped epitaxial WSe₂ on quasi-freestanding graphene (QFEG) on silicon carbide as a function of thickness. With increasing layers, the Fermi level of doped WSe₂ gets pinned at the highest dopant level for three or more monolayers, implying a charge depletion region of about 1.6 nm. V dopants in the first and second WSe₂ layer are ionized (negatively charged), while they are charge neutral beyond the second layer.

Samuel Stolz, Azimkhan Kozhakhmetov, Chengye Dong, Oliver Gröning, Joshua A. Robinson, Bruno Schuler