We investigate the nature of electron transport through monolayer molybdenum dichalcogenides (MoX2, X=S, Se) suspended between Au and Ti metallic contacts. The monolayer is placed ontop of the close-packed surfaces of the metal electrodes and we focus on the role of the metal-MoX2 binding distance and the contact area. Based on \emph{ab initio} transport calculations we identify two different scattering mechanisms which depend differently on the metal-MoX2 binding distance: (i) An interface resistance between the metal and the supported part of MoX2 which decreases with decreasing binding distance and increasing contact area. (ii) An edge resistance across the 1D interface between metal-supported and free-standing MoX2 which increases with decreasing binding distance and is independent on contact area. The origin of the edge resistance is a metal-induced potential shift within the MoX2 layer. The optimal metal thus depends on the junction geometry. In the case of MoS2, we find that for short contacts, L<6 nm, Ti electrodes (with short binding distance) gives the lowest resistance, while for longer contacts, Au (large binding distance) is a better electrode metal.
@article{arxiv.1311.2393,
title = {Electron transport across a metal/MoS$_2$ interface: dependence on contact area and binding distance},
author = {Zhaoqiang Bai and Troels Markussen and Kristian S. Thygesen},
journal= {arXiv preprint arXiv:1311.2393},
year = {2013}
}