Contact Metal–MoS2 Interfacial Reactions and Potential Implications on MoS2-Based Device Performance

Thin films of contact metals, specifically Au, Ir, Cr, and Sc, are deposited on exfoliated, bulk MoS2 using electron beam deposition under two different reactor base pressures to determine the contact metal–MoS2 interface chemistry and its dependence on the reactor ambient. The high work function metal Au does not react with MoS2 regardless of reactor ambient. In contrast, interfacial reactions between MoS2 and another high work function metal, Ir, are observed when it is deposited under both high vacuum (HV, ∼ 1 × 10–6 mbar) and ultrahigh vacuum (UHV, ∼ 1 × 10–9 mbar). Interfacial reactions occur between metals with low work functions (Cr, Sc) near the electron affinity of MoS2 when the contact metal is deposited under UHV conditions. In addition, Sc is rapidly oxidized on the MoS2 surface, whereas Cr is only partially oxidized when deposited under HV conditions. This indicates that deposition chamber ambient can affect the contact metal chemistry in addition to the chemistry present at the contact metal–MoS2 interface. These results elucidate the true chemistry of some contact metal–MoS2 interfaces and its dependence on the deposition ambient, and highlight the need to consider the chemical states present at the interface and their impact on contact resistance with MoS2.