Perovskite-structured Ba1-xLaxSnO3 (x=0.04, 0.06, 0.08) (BLSO) films were epitaxially grown on SrTiO3 (001) substrates by a sol-gel method. The microstructure and surface of the films were analyzed by X-ray diffraction and atomic force microscopy, respectively. The results show that the films exhibit preferred orientation along the c-axis without cracks or voids. Optical properties were studied in a wide photon energy range between 1.1 and 5.9 eV by spectroscopic ellipsometry. It was found that the optical band gap of the BLSO films increases gradually from 3.42 to 3.73 eV with increasing La concentration.
La-doped BiFe0.92Mn0.08O3 films with the composition from 0 to 20% (BLFMx) have been deposited on Si(100) substrates by a sol-gel route. X-ray diffraction analysis shows that the films are polycrystalline and exhibit the pure perovskite phase structure (R3c). The La dopant effects on the surface morphology, dielectric function, and optical transition of the films have been investigated by atomic force microscopy and spectroscopic ellipsometry at room temperature. The dielectric functions of the films have been uniquely extracted by fitting the measured ellipsometric spectra with a three phase layered model (air/film/Si) and the Tauc-Lorentz dielectric function model in the photon energy range of 0.5-3.5 eV. It is found that the optical transitions decrease with increasing La composition, which is crucial for future photoelectric device.
Transparent p-type conductive CuGaO2 films have been fabricated on sapphire substrates by sol–gel method. The stable sol solution for CuGaO2 were formed by copper(II) acetate monohydrate and gallium(III) nitrate hydrate, and the c-axis orientation of CuGaO2 films were strengthened with increasing annealing temperature. The pure phase CuGaO2 film was obtained at 900°C for 30 min in N2 atmosphere, and its microstructure, compositions, optical and electrical properties were analyzed. It was found that the sol-gel derived CuGaO2 films show a high optical transparency (60-80%) in the visible region, the direct and indirect band gaps were approximately 3.56 and 3.24 eV, respectively. It shows a crossover from the thermal activation behavior to that of three-dimensional variable range hopping from the temperature-dependent electrical conductivity at about 160 K.