Effects of MoS2 thickness and air humidity on transport characteristics of plasma-doped MoS2 field-effect transistors

The authors present a study on transfer characteristics of plasma-doped MoS2 transistors with various MoS2 thicknesses and those acquired under different air humidity conditions. The MoS2 thickness-dependent characterization implies that plasma-assisted doping processes induce p-doping to multilayer MoS2 channels through a surface-charge-transferlike mechanism and the effective space-charge layer thickness is estimated to be similar to 22 nm. The humidity-dependent characterization shows that plasma-doped MoS2 transistors exhibit a much more prominent dependence of the transfer characteristics on humidity in comparison with pristine MoS2-based transistors. This is attributed to the plasma-induced dangling bonds or absorbate centers on MoS2 surfaces, which can enhance the absorption of water molecules and result in additional p-doping to MoS2 transistors. This work advances the understanding of the effects of plasma doping processes on the electronic properties of MoS2 and provides important technical insights for making MoS2-based gas and chemical sensors. (C) 2014 American Vacuum Society.