Influence of MoS₂-metal interface on charge injection: a comparison between various metal contacts

Achieving good contacts is vital for harnessing the fascinating properties of two-dimensional (2D) materials. However, unsatisfactory 2D material-metal interfaces remain a problem that hinders the successful application of 2D materials for fabricating nanodevices. In this study, Kelvin probe force microscopy (KPFM) and other high-resolution microscopy techniques are utilized to characterize the surface morphology and contact interface between MoS₂ and common metals including Au, Ti, Pd, and Ni. Surface potential information, including the contact potential difference ([Formula: see text]) and surface potential difference ([Formula: see text]) of each MoS₂-metal contact, is obtained. By comparing the surface potential distribution mappings with and without illumination, non-zero surface photovoltage (SPV) values and evident shift with amplitudes of 32 mV and 44 mV are observed for MoS₂-Au and Ti, but not for MoS₂-Pd and Ni. The Schottky barrier heights of MoS₂-Au, Ti, Pd, and Ni are roughly evaluated from their I-V curves. Raman spectroscopy is also carried out to ensure more convincing results. All the results suggest that a smoother MoS₂-metal interface results in better charge transport behaviors. Our analysis of the underlying mechanism and experimental findings offer a new perspective to better understand MoS₂-metal contacts and underscore the fundamental importance of interface morphology for MoS₂-based devices.