ABSTRACT Nanostructured TiO2 and TiO2/W thin films were deposited on Corning glass substrates by RF and DC magnetron co-sputtering at room temperature, using three targets of TiO, Ti and W. After deposition, samples were subjected to an annealing treatment in air at 500 °C for 3 hrs. The effect of the annealing treatment and tungsten addition to the TiO2 matrix were studied by Raman spectroscopy and X-ray diffraction. Morphology and composition was studied with field emission scanning electron microscopy and optical characterization was made with UV-Vis spectroscopy. All the obtained samples presented an amorphous TiO2 phase; however, after the annealing treatment, a crystallization process from amorphous to anatase phase occurred with gain sizes between 15.6 and 18.3 nm, additionally, a small amount of rutile was also observable. The SEM images corroborated the XRD behavior, besides it was possible to calculate the thickness of the films which was greater for the W-doped films owing the extra power of the sputtering growth, and after the samples had the thermal treatment the thickness decreased due to a more organized structure. Finally, the UV-vis transmittance analysis revealed that the transmittance is higher in heat-treated films as compared to those without any thermal treatment; also, the TiO2 thin films showed a greater transmittance than the W doped TiO2 films, reaching 91%. The lack of transmittance in the non-thermal-treated films made it impossible to compute the band gap of the films; nevertheless, for the thermal-treated films the band gap had a minimal change to the classic TiO2 bang gap value, even for the W doped sample, providing them with the benefits of the tungsten within the same TiO2 structure due to a great homogenization on the structure.

ABSTRACT The effect of annealing temperature on the structural properties of Al-N codoped ZnO films were studied by X-ray diffraction, photoluminescence and Raman spectroscopy. ZnO films were deposited by sputtering technique on silicon substrates at 20 ºC, Al-concentration was kept constant and N-flow was changed to 6, 12 and 15 sccm. A thermal treatment was performed by annealing the sample during 30 minutes at 300, 400, 500, 600 and 700 °C. Before annealing, Raman spectra shows two vibration modes located at 275 and 580 cm-1 associated to the nitrogen incorporation and the presence of point defects. Both Raman intensities of modes I275 and I580 decreases when the nitrogen flow increases from 6 to 12 and 15 sccm, which is originated by a decreasing interstitial defects density. The improving of the crystal quality was confirmed by x-ray diffraction and room temperature photoluminescence measurements. After annealing, in the Raman spectra it was observed that I275 increases as the temperature increase, reaches a maximum intensity between 500 and 600 °C, and decreases for higher temperatures. X-ray diffraction measurements show that after annealing the compressive stress decrease progressively as the annealing temperature increase. This study suggests that 275 Raman mode could be used to estimate the optimal thermal treatment in order to achieve p-doping ZnO.