High field-effect performance and intrinsic scattering in the two-dimensional MoS2 semiconductors

Abstract

The mobility of MoS2 nanosheets plays an important role in the application of nanoelectronics. The two-dimensional (2D) MoS2 semiconductors have been investigated while the reported mobility varies enormously. We adopt a standard four-terminal electrical measurement and eliminate any contact contributions. We fabricated several tens of field-effect transistors (FETs) with MoS2 nanosheets exfoliated from the same MoS2 bulk. The MoS2 FETs can be grouped into either high- or low-mobility devices according to their temperature behaviors of mobilities. With an RT mobility higher than ~ 25 or ~ 30 cm2V-1s−1, the MoS2 FETs exhibit an increasing mobility with decreasing temperature, implying phonon scattering in these high-mobility (HM) devices. The HM devices are accompanied with metallic states and their conductivities close to ~ 1 e2/h. A low specific contact resistivity of ~ 450 Ω·μm is observed in these HM devices. In contrast, the MoS2 FETs with an RT mobility lower than ~ 30 or ~ 35 cm2V-1s−1, categorized as low-mobility (LM) devices, reveal a decreasing mobility with decreasing temperature. These LM devices show an insulating state, carriers suffering from impurity scattering, and a high contact resistance. Their temperature dependent resistances are highly concordant with the 2D Mott’s variable range hopping. These observations corroborate a large variation of intrinsic disorders in MoS2 nanosheets.