Electrical Contacts to MoS ₂ with Covellite (CuS): The Contact Type and Schottky Barrier Modulation

Electrical contacts between conventional metals and two-dimensional (2D) semiconductors often exhibit Fermi-level pinning (FLP), which limits the tunability of the Schottky barrier height (SBH). The use of covellite (CuS), a semimetallic binary compound electrode, shows the potential for mitigating FLP and advancing contact engineering. While experimental studies have reported n-type contact for the interface of CuS and MoS2, theoretical predictions suggest p-type contact for CuS interfaced with pristine MoS2. The current study demonstrates that the above discrepancy can be attributed to dopants such as hydrogen─commonly present during material growth─which induces n-type doping in MoS2. Furthermore, surface doping of CuS with iodine is shown to reduce the SBH by modifying the surface work function. Additionally, we introduce a more general computational approach to address asymmetric surface configurations in the SBH simulation, which arise from surface doping. By investigating CuS/MoS2 junctions with doped MoS2 and doped CuS surfaces, this study elucidates the origin of experimentally observed n-type contacts, proposes a strategy for FLP suppression in 2D electronic devices through semimetallic compound electrodes with tunable work functions, and hence provides guidance for the design of low-power nanoelectronic devices.