Layer Thickness Influenced Irradiation Effects of Proton Beam on MoS2 Field Effect Transistors.

We investigated the influence of flake thickness of molybdenum disulfide (MoS2) field effect transistors (FET) on the effect of a 150 keV high-energy proton beam applied on these devices. The electrical characteristics of the devices with channel thicknesses ranging from monolayer to bulk were measured before and after proton irradiation with a proton fluence of 5×1014 cm-2. The subthreshold swing (SS), threshold voltage shift, and electron mobility extracted with Y-function method degraded significantly after proton irradiation were observed. It is found that, with the increase of layer thickness, mobility degradation and threshold voltage shift were both eased, but the SS degradation was insensitive to the MoS2 flake thickness increase. We also demonstrate that the V_TH shift is dominated by oxide charges, however, the mobility and SS degradations are mainly affected by the interface traps. Our study will enhance the understanding of the influence of high-energy particles on MoS2-based nano-electronic devices. By increasing the MoS2 flake thickness to a certain extent, one can hopefully find a balance between effectively resisting V_TH shift and achieving high mobility and small SS degradation.