Synthèse de films TiO2 et étude structurale et optique.

Abstract

TiO2 thin films were prepared on glass and Si polycrystalline substrates (1-TiO2/glass, 5-TiO2/glass, and 1-TiO2/SP) by Sol-Gel method. The structural, optical and electrical properties of the samples were analyzed at various annealing temperatures, varying from 100 until 500°C for 5-TiO2/glass samples and by varying the rate of cobalt doping (0%, 3% and 7%) for the samples 1-TiO2/glass and 1-TiO2/SP. The samples were characterized by mean of: x-ray diffraction (XRD), retrodiffusion Rutherford spectroscopy (RBS), atomic force microscopy (AFM), ellipsometric spectroscopy and UV-VISIBLE spectroscopy. For the series of samples 5-TiO2/glass, the XRD patterns show that the as deposited sample is amorphous and it crystallizes to anatase phase starting from 300°C. The mean grains size and the roughness of the samples increase with increasing in annealing temperatures. For the series 1-TiO2/glass the un-doped sample is amorphous and it crystallizes to anatase phase starting from a doping of 3% Co. AFM study shows that the surface morphology of the samples doped with 0% and 7% Co is porous with pyramidal grains, while the sample doped with 3% Co, surface is more compact with such pyramidal grains and a considerably high roughness value. For the samples 1-TiO2/SP we note the appearance of the anatase phase at 0% and 7% Co and also, the appearance of an anatase-rutile mixture at 3% Co. 5-TiO2/glass thin films are transparent in the visible and opaque in UV, as well as the transmission and the calculated optical band gap decrease with increasing in temperature. The values of refractive index and packing density increase with increasing in temperature, in parallel the porosity decreases. The values of dielectric constants dielectric (ε (Re), ε (Im)), increase with increasing in annealing temperatures.