Local Electronic Structure and Control of Nanoscale Heterogeneity in Transition Metal Dichalcogenide-Au Interfaces

Two-dimensional transition metal dichalcogenides (TMDs) have recently garnered much attention owing to their extraordinary physical, chemical, electrical, and optical properties. Initial applications in functional electronic and optoelectronic devices have revealed that these properties are particularly sensitive to extrinsic factors like substrate interactions, strain, and charge transfer which have limited performance. Thus, unlocking the intrinsic nature of TMD-metal interfaces is critical for studies of native TMD properties and optimal device development. Here, we find that the electronic structure of mechanically exfoliated TMD-Au interfaces exhibit pronounced heterogeneity arising from local variations in the strength of the interface interaction and provide a means to engineer these interfaces. To examine these nuanced interactions, we employ a direct probe of the electronic structures of WS₂ and WSe₂ with the spatial resolution to delineate the influences of nanoscale heterogeneities at TMD-Au interfaces. Spectroscopic analysis reveals key differences in work function, electron binding energy of the occupied states, and intensity near the Fermi level owing to distinct μm sized regions of strong and weak TMD-Au interface interactions. Regions of stronger TMD-Au interactions are found to experience a larger degree of charge transfer resulting in greater hole doping as opposed to the more weakly interacting regions. We then fabricate uniformly strong and weak TMD-Au interfaces via Au processing thereby selectively dictating the electronic properties of the TMDs. Our findings illustrate that the electronic properties of TMDs are greatly impacted by metal interface interaction strength and provide a means to engineer these important junctions via simple processing methods.<br/><br/>We acknowledge insightful discussions with G. Copeland, N. Bartelt, C. D. Spataru, K. Thürmer, C. Smyth, T. M. Lu, and S. Chou at Sandia National Laboratories. The work at Sandia National Laboratories was supported by Sandia’s LDRD program. The work at the US Naval Research Laboratory was funded by the Office of Naval Research. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly-owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. The views expressed in the article do not necessarily represent the views of the U.S. Department of Energy or the United States Government.