Tunable Schottky Barrier at MoSe2/Metal Interfaces with a Buffer Layer

Transition-metal dichalcogenide monolayers have gained significant attention because of their excellent physical properties and promising applications as a channel material in the next-generation transistors. In this work, we focus on contacts at the surface of various metals and single-layer MoSe2. Partial Fermi level pinning is demonstrated by the first-principle calculations, which indicates modulation of the electron Schottky barrier. Upon inserting a VS2 layer between MoSe2 layer and metal electrodes, all the n-type contacts at MoSe2/metal interfaces turn into p-type, and the hole Schottky barrier can be tuned effectively by varying metal electrodes. The high work function of the VS2 layer exerts significant influence on the band realignment of MoSe2, making all the n-type contacts at MoSe2/metal interfaces become p-type contacts at MoSe2/VS2–metal interfaces. Variation of the Schottky barriers and band alignments with the work function of metal electrodes demonstrated a partial Fermi level pinning at the interfaces of MoSe2/metal and MoSe2/VS2–metal. The partial Fermi level pinning results from the low density of interfacial states, which can be reflected partly by the interaction between MoSe2 layer and metal electrodes. Our results would provide guidelines for designing novel 2D nanoelectronic devices with good performance.