XPS investigations of the interactions of hydrogen with thin films of zirconium oxide II. Effects of heating a 26 Å thick film after treatment with a hydrogen plasma

In order to help establish the role hydrogen plays in the oxidation and reduction of zirconium oxide thin films, XPS was used to study the effects of heating a 26 Å thick ZrO2 film after a hydrogen-plasma treatment. The latter treatment produced a uniform hydrogen-trapped ZrO2 film. Heating to 425°C yielded a reduced suboxide, ZrOx, particularly in the deeper regions of the film, but near the surface this heating produced a zirconium state with Zr3d52 binding energy at 183.4 eV, which is higher than that of ZrO2 by about 0.5 eV. This new chemical state of zirconium appears especially related to ZrOH bonding. This result, with the observed inhomogeneity of the film, strongly suggests that either H2O or OH− species migrate to the surface region of the hydrogen-trapped ZrO2 film during the heating process.