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.
