2, University of Maryland, Adelphi, Maryland, United States
3, University of California, Riverside, Riverside, California, United States
The performance of transistors utilizing 2D materials as the channel is typically limited by the contact resistance. Here, we investigate the efficiency of electron injection into monolayer MoS2 from a variety of potential contact metals. To keep the MoS2 channel properties consistent, a single CVD-grown sample of MoS2 on SiO2 was broken into four pieces. On each piece, multiple identically-sized transfer length method (TLM) devices for two different contact metals were fabricated and tested in a back-gated configuration. A total of eight metals were investigated including Ag, Au, Cr, Cu, In, Mo, Ni, and Ti. All contact metals were capped with a top layer of Au and samples were kept in a nitrogen environment until testing to limit oxidation of the contact and channel material. Devices were electrically tested in vacuum before and after a 45-hour anneal at 400 °K. Device metrics including contact resistance and maximum current were extracted to compare contact metal performance. Agreeing with metal-semiconductor work function theory, metals with a low work function (Ti, In, and Ag) demonstrated the best prospects as a contact metal to monolayer MoS2.