The oxidation of tin layers deposited onto alumina substrates is investigated with the aim to identify the different steps of the process and obtain information on the sample homogeneity, phase segregation, and degree of oxidation. It is shown that at least three phases coexist at 450 °C, Sn, SnO, and SnO2, and remarkable inhomogeneities, already visible at an optical inspection, are found in the thin film. A micro-Raman mapping of the layer shows that these inhomogeneities are related to the presence of different Sn oxidation states, as evidenced by the inhomogeneous distribution of SnO and SnOx Raman bands. The thin film becomes homogeneous after annealing treatments above 550 °C, where only the SnO2 cassiterite phase is detected.

The influence of the niobium content on the anatase-to-rutile phase transition in nanopowders of Nb–Ti oxides was studied and the changes in the particle size and microstrain distribution obtained at different temperatures were analyzed. A correlation is found between the initial microstructure in the Ti1 – xNbxO2 (x = 0.03, 0.2) powder and the niobium content. The presence of Nb was found to inhibit the growth of both the anatase and the rutile phases.

We report on a microscopy and diffraction study of commercially available Cu-doped ZnS powders, along with an optical spectroscopy study of electroluminescent lamps fabricated with these powders. The results allowed us to identify a correlation between the microstructure and the optical properties (i.e. photoluminescence) of the ZnS powders. It is found that the best powders for EL lamps are those displaying a prevalent cubic, i.e. zincblend, structure, while the poor performances of the mixed phase (cubic + hexagonal) are tentatively ascribed to the quenching of luminescence due to defects (stacking faults) introduced into the cubic structure and resulting in a considerable amount of hexagonal phase, as detected by XRD. The mostly cubic powders have been selected to realize EL lamps. The optical properties of these lamps have been investigated by photoluminescence and electroluminescence spectroscopies with the aim to identify the degradation mechanisms leading to a decrease of brightness. The quenching of electroluminescence is primarily ascribed to a deterioration of the electrical contacts. However, the reduced brightness in photoluminescence spectra seems to indicate that additional quenching of luminescence is induced by transformations at the emitting layer of the lamps. This degradation is tentatively ascribed to the presence of voids in the emitting layer, which might induce, acting as traps for moisture, transformations in the optical and electrical properties of the transparent electrode (ITO).

Thin films of the Ti-W-O system grown by r.f. reactive sputtering from a Ti-W (10%–90% weight) target have been studied by Raman and microraman spectroscopy, X-ray diffraction and scanning electron microscopy with the aim to investigate their microstructural and morphological properties. To this purpose, the kinetics of structural transformations at different temperatures (600 °C, and 800 °C) have been studied, and the effect of Ti on the WO3 lattice has been singled out. The results show that annealing at different temperatures induces a microstructural evolution from the amorphous phase of the as-deposited thin film to WO3 crystalline phases via an intermediate cubic disordered phase of WO3. The effect of Ti on this cubic phase and on the thin film morphology is also investigated with the aid of microraman and scanning electron microscopy analysis. The results show that two distinct phases arise upon long annealing treatments; namely, small crystallites belonging to the WO3 monoclinic phase are dispersed on a layer composed of a disordered cubic WO3 phase with a high Ti content.

X-ray photoelectron spectroscopy of pure and K chemisorbed VxOy/TiO2 powders are reported. Core-line and valence band spectra suggest the presence of vanadium open shell ions on the pure VxOy/TiO2 interface, whereas potassium vanadate seems to form after K chemisorption. That results in the presence of a significant amount of gap states, with vanadium character, just above the O2p band edge, for the pure VxOy/TiO2 powder, while K chemisorption, reducing significantly the open shell vanadium ions, quenches the gap emission in the XPS valence band spectra.