Structural and optical properties of thin TiO2:C films – influence of the substrate-erosion zone radial distance

Abstract

The structural and optical properties were studied of thin TiO2:C films deposited on glass substrates by r.f. magnetron co-sputtering of a TiO2 target and carbon plates placed on its erosion zone in an atmosphere of Ar (0.5 Pa) + air(0.6 Pa). The total area of the carbon plates was 830 mm2, and the radial distance between the center of the glass substrates (15×25×1 mm) and the circle of the erosion zone with a maximum sputtering rate was 2 cm and 4 cm. The as-deposited and annealed (air, 400 °C, 1 h) thin films with a thickness of about 150 nm were studied via reflectance and transmittance measurements, X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffractometry (GI XRD) and Raman spectroscopy. The optical spectra of the thin films deposited at the higher radial distance from the erosion zone maximum demonstrated absorption in the visible range. The XRD patterns revealed a mix of amorphous and nano-crystalline anatase and rutile TiO2 phases in all thin films. The reflections of the experimental XRD patterns indicated the presence of tensile stress in the grains. The Raman spectra confirmed the nano-crystalline structure of the anatase and rutile phases of the films. The incorporation is discussed of C atoms in the TiO2 films.