Target power influence on optical and electrical properties of amorphous titanium oxide deposited by reactive grid-assisted magnetron sputtering

•Sheet resistance of TiOx is lower than TiO2 but unstable.•Adsorption of hydroxyl radicals may stabilize the sheet resistance.•Redshift in the optical absorption of the suboxides.•Increase of the target power decreases the density of states in the material.•The optical gap entropy increases with target power increasing. Titanium oxide (TiOx) thin films were deposited by reactive grid-assisted magnetron sputtering on glass substrates as function of the target power. Films were characterized by mechanical profilometry, optical spectrophotometry, four-probe method, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in order to investigate the effect of the target power on electrical, structural and electronic properties. The electrical properties were measured after deposition and one year later to evaluate the stability of the sheet resistance. Data for suboxides show the decreasing of the optical gap, sheet resistance and density of electronic states in conduction and/or valence bands, and increasing of the optical gap entropy, optical absorption and film thickness as the target power increases. The absorption coefficient indicates the presence of mid-gap states in suboxides, inducing the redshift of the absorption onset. The TiO2 reference sample presents only a single transition in the ultraviolet part. XRD show amorphous structure for all samples. Ti2p and O1s spectra from XPS indicate an oxidized surface with a small contribution of Ti3+ states in either titanium suboxide or dioxide, where the surfaces with the highest concentrations of hydroxyl radicals presented the best stability of the sheet resistance after one year.