Controlled surface oxidation of HfSe2 via oxygen-plasma treatment

Growing uniform surface oxides is vital for fabricating 2D materials based electronic and optoelectronic devices. However, the surface transition metal oxides (TMOs) of air-exposure transitional metal dichalcogenides (TMDs), such as HfOx on HfSe2, are island-type, with poor TMOs/TMDs interface quality. Here, we report a controlled surface oxidation of atomically thin HfSe2 flakes via oxygen-plasma treatment, where a dense atomically flat HfOx film is produced. This HfOx film is found to be a good surface passivation layer to prevent the inner part from further oxidation in air, which is also promising as a high-K dielectric in HfSe2-based devices.