Electric-field-induced metal-insulator transition and quantum transport in large-area polycrystalline MoS2 monolayers

Abstract

Monolayer ${\mathrm{MoS}}_{2}$ is an attractive candidate for developing future electronics and exploring fundamental physics because of its unique quantum properties. High-performance ${\mathrm{MoS}}_{2}$ transistors with superior transport originating from spin-valley coupling have been reported. However, these transistors have used single-crystalline flakes. In most large-area polycrystalline ${\mathrm{MoS}}_{2}$, these excellent transport properties have not been realized because of the effects of grain boundaries, and their fundamental low-temperature transport has not been studied in detail. Here, we apply electrolyte-gating methods using chemically grown centimeter-scale polycrystalline monolayers. Owing to the high carrier density, the resistance is systematically tuned from insulating to metallic conduction. Importantly, we observed metallic transport at temperatures down to 1.9 K and a high mobility of $>100\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}\mathrm{n}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Moreover, the magnetotransport exhibits an electric-field-induced crossover from weak localization to weak antilocalization, indicating that high carrier density dramatically suppresses the grain boundary effects to enable intrinsic quantum transport. The results reveal that polycrystalline ${\mathrm{MoS}}_{2}$ monolayers have significant potential for use in large-area nanoelectronics.