Tunable electrical properties of multilayer HfSe 2 field effect transistors by oxygen plasma treatment.

HfSe2 field effect transistors are systematically studied in order to selectively tune their electrical properties by optimizing layer thickness and oxygen plasma treatment. The optimized plasma-treated HfSe2 field effect transistors showed a high on/off ratio improvement of four orders of magnitude, from 27 to 105 , a field effect mobility increase from 2.16 to 3.04 cm2 V-1 s-1 , a subthreshold swing improvement from 30.6 to 4.8 V dec-1 , and a positive threshold voltage shift between depletion mode and enhancement mode, from -7.02 to 11.5 V. The plasma-treated HfSe2 photodetector also demonstrates a reasonable photoresponsivity from the visible to the near-infrared region of light.