Overcoming contact resistance at metal-2D semiconductor interfaces: atomically clean MoS2/Au ohmic junctions

Abstract

The application of two-dimensional (2D) semiconductors, such as monolayer MoS2, is limited by the high contact resistance commonly attributed to interfacial barriers at metal contacts. Furthermore, the dependence of electrical conductivity on MoS2 thickness is still unsettled, as both increasing and decreasing trends with layer number have been reported. By showing the contrast between electrical transport of mono- and multilayer MoS2 exfoliated on Au under ultra-high vacuum (UHV) and ambient conditions, we experimentally prove that, contrary to the prevailing view in the literature, the intrinsic MoS2/Au junction is highly conductive and exhibits ohmic behaviour. Our results indicate that interfacial contamination is responsible for the high contact resistances reported to date and affects the thickness dependence of electrical transport, explaining the discrepancies observed in the literature. We rationalize those findings using electrical transport simulations. Lastly, we show that local force-mediated lamination on lightly contaminated contacts can recover pristine, ohmic contacts, offering a route towards nanoscale patterning.