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

Nitrogen doped titanium oxide (N:TiO_x) 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 N ₂ for 1 h generated polycrystalline films with anatase phase, independent of %N₂ during deposition. Film surface roughness increased from 0.5 up to 3.2 nm 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, 1-5 at.% N, was much less than that in the gas mixture (9-69%N ₂). Annealing decreased the N-content in these films to < 1 at.%. In addition, the data revealed that all N:TiO_x films had two main N 1s components, at 396-397 eV and at 399-400 eV, 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 %N ₂. The absorption edge of the films shifted to longer wavelengths with increased substrate temperature and %N₂, from ~ 380 nm up to ~ 485 nm for films deposited with 41%N₂ and a substrate temperature of 500 C.