Influence of hydrogen addition to an Ar plasma on the structural properties of TiO2-x thin films deposited by RF sputtering

The influence of hydrogen addition to an Ar plasma on the structural properties of TiO2-x films produced by RF sputtering of a TiO2 target at room temperature was studied. The structural properties of the films were characterized by x-ray photoelectron spectroscopy while the surface morphology was analysed using scanning electron microscopy (SEM). The valence band analysis showed the crystal field splitting of d states into doubly and triply degenerate states. H-2 addition to the Ar plasma created additional d-state splitting due to distortions in the TiO2 structure by the Jahn-Teller mechanism. The occurrence of the Jahn-Teller split is well-correlated with oxygen vacancies in the TiO2-x films. Water adsorption at the TiO2-x surface and film hydroxylation were also addressed. The as-grown films were amorphous and SEM analysis showed a columnar structure for all the films but with a lower packing density of the columns after H-2 introduction in the Ar plasma.