The effects of short-term air exposure of the monocrystal HfSe2 surface

We report the impact of short-term sequential exposure to air–atmosphere conditions on the mechanically exfoliated surface of HfSe₂ monocrystal. Our scanning electron microscopy studies show the early surface oxidation dynamics with a rapid increase of the Se-rich blister coverage. Further X-ray photoemission and energy dispersive spectroscopy measurements reveal a progressive diffusion of O atoms into the bulk and HfO₂ layer formation on the surface during the exposure time. Finally, Raman spectroscopy measurements confirm the coexistence of HfSe₂ and HfO₂ on the surface. However, the Raman spectroscopy technique does not allow quantitative determination of the degree of short-term surface oxidation. Additionally, we confirm the conclusions drawn from the experimental results with the results of the density functional theory calculations of the O/HfSe₂ adsorption system. The presented results hold substantial technological significance from the point of view of the application of HfSe₂ in electronics by filling the gap in the early oxidation dynamics under ambient conditions.