Optical and electrical properties of Ti(Cr)O2:N thin films deposited by magnetron co-sputtering

Abstract

The paper deals with TiO2-based thin films, doped with Cr and N, obtained by magnetron co-sputtering from titanium dioxide ceramic and chromium targets in Ar+N2 atmosphere. Co-doped samples of Ti(Cr)O2:N are investigated from the point of view of morphological, crystallographic, optical, and electrical properties. Characterization techniques such as: X-ray diffraction, XRD, scanning electron microscopy, SEM, atomic force microscopy, AFM, Energy Dispersive X-ray spectroscopy, EDX, X-ray photoelectron spectroscopy, XPS, optical spectrophotometry as well as impedance spectroscopy are applied. XRD reveals TiO2 and TiO2:N thin films are well crystallized as opposed to those of TiO2:Cr and Ti(Cr)O2:N. XPS spectra confirm that co-doping has been successfully performed with the biggest contribution from the lower binding energy component of N 1s peak at 396eV. SEM analysis indicates uniform and dense morphology without columnar growth. Comparison between the band gaps indicates a significant shift of the absorption edge towards visible range from 3.69eV in the case of non-stoichiometric Ti(Cr)O2−x:N to 2.78eV in the case of stoichiometric Ti(Cr)O2:N which should be attributed to the incorporation of both dopants at substitutional positions in TiO2 lattice. Electrical conductivity of stoichiometric Ti(Cr)O2:N increases in comparison to co-doped nonstoichiometric TiO2−x thin film and reaches almost the same value as that of TiO2 stoichiometric film.