Structural and optical characteristics of filtered vacuum arc deposited N:TiOx thin films

Abstract

Nitrogen doped titanium oxide (N:TiOx) thin films were deposited using filtered vacuum arc deposition. The X-ray diffraction patterns of the TiO2 thin films deposited in a pure oxygen environment indicated that films were polycrystalline in the anatase phase, while films deposited in an atmosphere in which the N2 fraction was greater than 9% were amorphous, for substrate temperatures up to 500°C. Annealing at 400°C in N2 for 1h generated polycrystalline films with anatase phase, independent of %N2 during deposition. Film surface roughness increased from 0.5 up to 3.2nm when the substrate temperature was increased from room temperature to 500°C for films deposited in a 41%N2.X-ray photoelectron spectroscopy analysis indicated that all films deposited in pure oxygen were stoichiometric TiO2. N content in the films increased with %N2 in the deposition atmosphere, however the N-content in the film, 1-5at.%N, was much less than that in the gas mixture (9–69%N2). Annealing decreased the N-content in these films to <1at.%. In addition, the data revealed that all N:TiOx films had two main N 1s components, at 396–397eV and at 399–400eV, associated with substitutional and interstitial nitrogen, respectively.Transmission data indicated that the average transmission of films deposited at lower N2 partial pressures (<41%) was approximately 80%, and it decreased to ~50% for higher %N2. The absorption edge of the films shifted to longer wavelengths with increased substrate temperature and %N2, from ~380nm up to ~485nm for films deposited with 41%N2 and a substrate temperature of 500°C.