Thickness-dependent electron mobility of single and few-layer MoS₂ thin-film transistors

We investigated the dependence of electron mobility on the thickness of MoS₂ nanosheets by fabricating bottom-gate single and few-layer MoS₂ thin-film transistors with SiO₂ gate dielectrics and Au electrodes. All the fabricated MoS₂ transistors showed on/off-current ratio of ∼10⁷ and saturated output characteristics without high-k capping layers. As the MoS₂ thickness increased from 1 to 6 layers, the field-effect mobility of the fabricated MoS₂ transistors increased from ∼10 to ∼18 cm²V⁻¹s⁻¹. The increased subthreshold swing of the fabricated transistors with MoS₂ thickness suggests that the increase of MoS₂ mobility with thickness may be related to the dependence of the contact resistance and the dielectric constant of MoS₂ layer on its thickness.