Effect of nitrogen doping on TiO_xN_y thin film formation at reactive high-power pulsed magnetron sputtering

The paper is focused on a study of formation of TiO_xN_y thin films prepared by pulsed magnetron sputtering of metallic Ti target. Oxygen and nitrogen were delivered into the discharge in the form of reactive gases O₂ and N₂. The films were deposited by high-power impulse magnetron sputtering working with discharge repetition frequency f = 250 Hz at low (p = 0.75 Pa) and high (p = 10 Pa) pressure. The substrates were on floating potential and thermally stabilized at room temperature during the deposition process. Post-deposition thermal annealing was not employed. The chemical composition from x-ray photoelectron spectroscopy diagnostic reveals formation of TiO_xN_y structure at low flow rate of oxygen in the discharge gas mixture. This result is confirmed by XRD investigation of N element's incorporation into the Ti–O lattice. Decrease in band-gap to values E_g ∼ 1.6 eV in TiO_xN_y thin film is attributed to formed Ti–N bonds. The discharge properties were investigated by time-resolved optical emission spectroscopy. Time evolution of particular spectral lines (Ar⁺, Ti⁺, Ti) is presented together with peak discharge current.