Structural, optical, and electrical properties of laser deposited FeTiO3 films on C- and A-cut sapphire substrates

FeTiO3 (FTO) thin films were epitaxially grown on two kinds of alpha-Al2O3 substrates [(0001) and (11 (2) over bar 0)] through pulsed laser deposition under a mixtured gas ambient of 5% oxygen with argon used as the balance. The x-ray diffraction (XRD) and XRD pole figure measurements show parallel growth relationships of the films on these two kinds of substrates, (0006) parallel to (0006), (11 (2) over bar 0) parallel to (11 (2) over bar 0), respectively. The interplane XRD pole texture measurement also shows that a parallel relationship exists. Rutherford backscattering spectrometry and Auger electron spectrometry analyses show that the films are stoichiometric and without distinguishable impurities. The optical properties were characterized in the ultraviolet-visible region, and 3.55 eV was obtained for the first time as the band gap of these epitaxial and stoichiometric FTO films. This value in the present high quality films is higher than the band gap reported for bulk material, 2.58 eV. The measurement of the electrical resistance in a quite wide temperature range shows typical semiconductor properties. (C) 1999 American Institute of Physics. [S0021-8979(99)00710-0].