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

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.