Electron transport and device physics in monolayer transition-metal dichalcogenides

Two-dimensional transition-metal dichalcogenides (TMDs) represent a promising class of materials for electronic and photonic devices, benefiting from their sizable bandgap of 1-2eV and ultrathin body. However, one of the major issues is that the experimental mobility is much lower than the theoretical phonon limit. We carry out systematic investigations on the electron transport and field-effect transistors of monolayer TMDs, including MoS2 and WS2. We find that the major extrinsic mobility limiting factors are charged impurities, traps and point defects. We develop a facile low-temperature thiol chemistry to repair the sulfur vacancies and improve the interface quality, resulting in significant reduction of the charged impurities and traps. In combination with high-k dielectrics, we are able to achieve room-temperature mobility of similar to 150cm(2)/Vs and 83cm(2)/Vs for monolayer MoS2 and WS2, respectively. We further develop a theoretical model to quantitatively correlate these extrinsic scattering sources to measured electrical data. Our study shows that interface engineering is critical for high-performance transistors based on 2D semiconductors.