Impact of grain boundaries on the electronic properties and Schottky barrier height in 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 an edge dislocation–double S vacancy complex (S4|6), and a dislocation–double S interstitial complex (S6|8), respectively, on the electronic properties of MoS₂ and the Schottky barrier height (SBH) in MoS₂@Au heterojunctions. Our findings demonstrate that GBs formed by edge dislocations can significantly reduce the SBH in 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 in 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.