Impact of Grain Boundaries on the Electronic Properties and Schottky Barrier Height of MoS2@Au Heterojunctions

Abstract

Using density functional theory (DFT) calculations we thoroughly explored the influence of grain boundaries (GBs) in monolayer MoS2 composed of S-polar (S5|7), Mo-polar (Mo5|7), and (4|8) edge dislocation, as well as edge dislocation-double S vacancy complex (S4|6), and dislocation-double S interstitial complex (S6|8), respectively, on the electronic properties of MoS2 and the Schottky barrier height (SBH) at MoS2@Au heterojunctions. Our findings demonstrate that GBs formed by edge dislocations can significantly reduce the SBH compared to defect-free MoS2, with the strongest effect for zigzag (4|8) GBs (-20% reduction) and the weakest for armchair (5|7) GBs (-10% reduction). In addition, a larger tilt angle in the GBs leads to a more pronounced decrease in the SBH, suggesting that the modulation of SBH at the MoS₂@Au heterostructure and analogous systems can be accomplished by GB engineering. Our findings also suggest that planar defects with high mobility in MoS2 may contribute to the memory switching effect observed in MoS2-based memtransistors and the reduction caused by the presence of planar defects can partially contribute to the discrepancy observed between experimental measurements and theoretical SBH predictions at the MoS2@Au heterojunction.