Effect of W–Ti target composition on the surface chemistry and electronic structure of WO3–TiO2 films made by reactive sputtering

Abstract

A c c e p t e d M a n u s c r i p t 2 Highlights  An approach to fabricate WO 3 -TiO 2 thin films using W-Ti alloy target is presented. The effect of W-Ti ratio on the surface chemistry of W-Ti-O oxide films is evaluated. Increasing Ti decreases W-Ti-O film thickness drastically due to sputtering kinetics. Optimum conditions to deposit stoichiometric WO 3 -TiO 2 films are reported. ABSTRACTTungsten-titanium (W-Ti) mixed oxide thin films were fabricated using reactive sputtering of W-Ti alloy targets with Ti content ranging from 0 to 30 wt.%. The effect of target composition on film structure, surface/interface chemistry and chemical valence state of the W and Ti cations was investigated in detail. All films were amorphous in nature as confirmed by X-ray diffraction analyses. For growth times of 1 hour, the thicknesses of the W-Ti-O films decreased significantly from 150 nm to 35 nm with increasing Ti content in the target, confirming that the oxide film growth behavior is dependent on the sputter-target composition.The chemistry and composition of the films probed using X-ray photoelectron spectroscopy (XPS) confirms the existence of W and Ti in their highest oxidation states of 6+ and 4+, respectively. Quantification of binding energy shifts for W and Ti core-level transitions confirms the formation of WO 3 -TiO 2 composite oxide films. Depth profiles confirm and validate film uniformity, as well as film thickness differences and variable oxidation behavior of W and Ti in the films.

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