Thin films of TiO2/SnO2:F multilayers were prepared by spray pyrolysis technique on glass substrate. The samples were prepared using titanium (IV) isopropoxide 98%, ammonium fluoride and tin(II) chloride dehydrate extra pure as precursor materials. Thus, a TiO2 thickness dependence optical study of TiO2/SnO2:F/glass system is presented. The optical property was characterized by UV-Visible transmittance spectroscopy. For all the samples, the average transmissions in the visible wavelength region (400-800 nm) were between 69 and 84%. The optical parameters, such as the real part dielectric function ε1 and the imaginary part dielectric function ε2, of TiO2 and SnO2:F in the TiO2/SnO2:F thin films structure, determined by fitting the measured optical transmittance spectra, are presented and analyzed. Among the various classical dispersion relations for the dielectric function, the Drude model combined with the Lorentzian oscillators was used to get a good fit of transmittance in the measured spectral range. Results on related parameters such as high frequency dielectric constant, plasma frequency, film thickness and band gap are presented.

Tin oxide is of great interest due to their potential technological applications, such as: gas sensors, energy conversion, catalysts and others. Appropriate doping can further enhance the conductivity of the SnO2 material with little loss of transparency. Isolated tin iron oxide fibers (Sn1-xFexO2-δ) with x (molar %) = 0, 2, 4, 6, 8 and 10 were prepared by the electrospinning technique. Anhydrous SnCl4, FeCl3·6H2O, different alcohols, chloroform and a polymer (PEO) were used as precursor materials. Appropriate mixture of these reagents defines the deposition solution. The samples were deposited on glass substrates and annealed at 500o C. The fibers are characterized by scanning electron microscopy (SEM), impedance spectroscopy and temperature dependence current-voltage measurements. The fibers with diameters between 2 to 12 microns were used for sensorial purpose. Thus, water vapor sensor responses were also measured and the experimental results are tested using the Freundlich isotherms model.

The effect of time and voltage on the fabrication of self ordered nano porous aluminum oxide structure is studied. A two-step anodization process in 0.4M sulphuric acid and at low temperature was used to prepare structure with pore diameter between 20 to 29 nm. The surface morphology, including porous structure mainly, is characterized using scanning electron microscopy. Pore density 10 10 to 10 11 cm -2 is found. Thickness and electrical response are performed to these films. Capacitive sensor measurements for different water concentration are presented and discussed. The gas sensibility dependences with pore diameter and thickness layer are also reported.

Tin oxide thin films were prepared by spray pyrolysis method using SnCl 2 .2H 2 O as starting precursor and deposited on glass substrate. Three groups of samples with different preparation conditions (temperature, time and thickness) were synthetized. The samples were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), UVVisible Spectroscopy and Van der Pauw four-point electrical measurements. The grain size in the samples changes from 80 to 500 nm. Optical and electrical parameters were measured or calculated, such as: band gap, refractive index, sheet resistance, transmittance spectrum and figure of merit. Film thicknesses were obtained from fringes features in the transmittance spectra with a variation from 76 to 761 nm. A mechanism of transformation from tin dichloride to tin oxide is proposed and discussed; additionally the visual yellow color of some samples, related with a low transparency, is associated to the amount of abhurite or tin hydroxide complex coexisting with tin oxide. The figure of merit showed that 500 ºC, 42 sprays and 1 hour of annealing time were the best conditions in the preparation of SnO 2 with TCO properties.

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