Reactive sputter deposition of Al doped TiOx thin films using titanium targets with aluminium inserts

• Ti(Al)Ox thin films with varying Al fractions and increasing discharge current were deposited.
• The reactive sputtering behaviour of Ti targets with Al inserts was studied.
• XPS and EDX were used to check the stoichiometry of the films.
• Optical transmittance measurements were performed to determine the band gap.

Al doped TiOx thin films were deposited using Ti targets with Al inserts. Both the effect of the number of aluminium inserts and the discharge current on the discharge voltage, on the aluminium content in the thin films, and on the reactive sputtering behaviour was investigated. The aluminium content in the film was measured using X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) revealed that the as-deposited thin films were amorphous, independent of the aluminium content or the discharge current. The XPS results indicated that the oxide films were substoichiometric. The optical band gap of the Ti(Al)Ox thin films was investigated as a function of the aluminium concentration and the discharge current. The addition of aluminium results in a significant increase of the band gap at low discharge currents, while no significant influence on the band gap was found at higher currents.