The device level modulation of carrier transport in a 2D WSe₂ field effect transistor via a plasma treatment

Tungsten diselenide (WSe₂) has received significant attention because it shows the pristine ambipolar property arising from the Fermi level located near the midgap and can be converted to uni-polar form. In this study, we observe the formation of tungsten oxide (WO_x) on the WSe₂ surface after oxygen plasma treatment and show that the p-type WO_x dopes WSe₂. In our devices that underwent plasma treatment, it was interesting to find a strong correlation between the changes in the work function of WSe₂ and a gold electrode, and the channel and contact resistances. The channel resistance changes very sensitively at a rate of 64 meV per dec with the increase in the WSe₂ channel work function, which is close to the thermal limit; this indicates the defect-free oxidized WSe₂ channel. The carrier transport in the oxidized WSe₂ FET is shown to change to a high performance p-type device with greatly reduced channel and contact resistances with the increase in the plasma oxidation time.