Observation of high carrier density, ohmic contact, and metallic conductivity down to 5 K in aluminum-contacted multilayer MoS2 flakes

Abstract

Molybdenum disulfide (MoS2) has attracted considerable attention, because the monolayers or multilayers of MoS2 may become building blocks of electronic/optoelectronic devices in post-silicon technology. The contact metals have significant effects on the transport properties of MoS2 devices. We previously reported that unconventional transport properties of back-gated MoS2 flakes with Al contact may be attributed to a contact-induced doping effect. However, measurements of carrier density, which can confirm the doping effect, were not performed. In this paper, we present the experimental results of carrier density estimated via Hall effect measurements. The observed carrier densities of the Al-contacted MoS2 flakes ((3–8) × 1013 cm−2) are ∼10 times greater than those reported for Au-contacted MoS2 flakes, indicating the doping effect due to the Al contact. We also observe ohmic contact and metallic conductivity down to 5 K for the Al-contacted flakes, which are distinct from the properties of Au-contacted MoS2 flakes.