Vertical Heterostructures between Transition-Metal Dichalcogenides--A Theoretical Analysis of the NbS2/WSe2 Junction

Low-dimensional metal-semiconductor vertical heterostructures (VH) are promising candidates in the search of electronic devices at the extreme limits of miniaturization. Within this line of research, here a theoretical/computational study of the NbS2/WSe2 metal-semiconductor vertical hetero-junction using density functional theory (DFT) and conductance simulations is presented. First atomistic models of the NbS2/WSe2 VH considering all the five possible stacking orientations at the interface are constructed, and DFT and quantum-mechanical (QM) scattering simulations are conducted to obtain information on band structure and transmission coefficients. Then an analysis of the QM results in terms of electrostatic potential, fragment decomposition, and band alignment is carried out. The behavior of transmission expected from this analysis is in excellent agreement with, and thus fully rationalizes, the DFT results, and the peculiar double-peak profile of transmission. Finally, maximally localized Wannier functions, projected density of states, and a simple analytic formula to predict and explain quantitatively the differences in transport in the case of epitaxial misorientation are used. Within the class of Transition-Metal Dichalcogenide systems, the NbS2/WSe2 VH exhibits a wide interval of finite transmission and a double-peak profile, features that can be exploited in applications.