Controlling the Schottky barrier at MoS 2/metal contacts by inserting a BN monolayer

Making a metal contact to the two-dimensional semiconductor MoS 2 without creating a Schottky barrier is a challenge. Using density functional calculations we show that, although the Schottky barrier for electrons obeys the Schottky-Mott rule for high work function (≳4.7 eV) metals, the Fermi level is pinned at 0.1–0.3 eV below the conduction band edge of MoS 2 for low work function metals, due to the metal-MoS 2 interaction. Inserting a boron nitride (BN) monolayer between the metal and the MoS 2 disrupts this interaction, and restores the MoS 2 electronic structure. Moreover, a BN layer decreases the metal work function of Co and Ni by ∼2 eV, and enables a lineup of the Fermi level with the MoS 2 conduction band. Surface modification by adsorbing a single BN layer is a practical method to attain vanishing Schottky barrier heights.