Overcoming Contamination‐Induced Barriers: Ohmic Vertical Transport in Atomically Clean MoS 2 /Au Junctions

ABSTRACT The application of two‐dimensional (2D) semiconductors, such as monolayer MoS 2 , is limited by high contact resistance commonly attributed to interfacial barriers at metal contacts. Furthermore, the dependence of electrical conductivity on MoS 2 thickness remains unsettled, as both increasing and decreasing trends with layer number have been reported. Using conductive atomic force microscopy (CAFM), we measure local electrical transport in MoS 2 /Au junctions with contrasting interface cleanliness: pristine interfaces prepared under ultra‐high vacuum (UHV) and contaminated interfaces prepared by the widely used PDMS‐assisted transfer under ambient conditions. By comparing monolayer MoS 2 /Au junctions prepared under these contrasting conditions, we demonstrate that an atomically clean interface enables highly conductive, ohmic transport in the vertical CAFM geometry. Measurements on mono‐ and multilayer regions further show that interfacial contamination introduces a substantial transport barrier and can reverse the thickness dependence of electrical transport. We rationalize these findings using electrical transport simulations based on Kirchhoff's laws, identifying the interplay between MoS 2 /Au interfacial resistance and lateral current spreading within MoS 2 layers as the origin of the opposite thickness trends. Lastly, we show that local force‐mediated lamination on lightly contaminated contacts can recover pristine, ohmic contacts, offering a route toward nanoscale patterning.