Induced by Au Hybridization

The interaction between bulk metal contacts and two-dimensional (2D) transition metal dichalcogenides (TMDs) has a critical influence on overall device performance in a variety of potential applications. This interaction has been studied extensively in the past, especially in the case of moldybdenum disulfide (MoS₂), with seemingly contradictory results. In this work, we directly exfoliate monolayer MoS₂ onto bulk Au and anneal the resulting heterostructure under ultra-high vacuum (10^-10 Torr, UHV) to 450 °C. After annealing, the MoS₂ monolayer is observed under scanning tunneling microscopy/spectroscopy (STM/STS) to remain in its 2H lattice configuration, yet with regions ranging from fully gapped to metallic. This observation is corroborated by ex situ Raman and photoemission spectroscopies, which show no signs of the otherwise expected 1T or 1T' structural phase transitions. Theoretical calculations suggest the previous band-gap tuning observed in MoS₂-Au heterostructures is due to hybridization and chemical bonding at the S-Au interface, which can completely close the band-gap of 2H-MoS₂ at sufficiently short S-Au distances.