Using x-ray Rietveld analysis the fcc (fluorite-type) structure of a Na-containing nanocrystalline zirconia powder (9.5 nm estimated crystallite size) obtained by precipitation and calcination has been confirmed. The result shows that conventional x-ray diffraction techniques can distinguish the cubic crystallographic form of ZrO2 from the tetragonal one in nanosized powders. These conclusions are supported by independent Raman scattering experiments.

A zinc borate glass, 4ZnO·3B2O3, activated by different concentrations of Pr3+ was investigated by Brillouin, Raman and luminescence spectroscopies. Energy levels and optical transitions of Pr3+ in zinc borate glass are assigned. At low Pr3+ concentration the luminescence is dominated by emission from the 1D2 state which is populated by fast multiphonon relaxation from the 3P0 state. At Pr3+ concentrations higher than 2% mol energy transfer processes become efficient in the relaxation of the 3P0 state. Cross relaxation dominates the 1D2 depopulation in the full range of Pr3+ concentrations. Self-absorption of the 3P0 → 3H4 luminescence was observed for glassed doped with 4% and 8% mol Pr3+. Refractive index and sound velocities were measured for all the samples. Raman spectra show vibrational modes due to Pr3+ bonded to oxygen ligands.

Amorphous hydrogenated carbon (a-C:H) films, with thickness up to 2 μm, were deposited onto polymeric substrates [poly(tetrafluorethylene) (PTFE), poly(ethylene) (PE), poly(ethylene terephtalate) (PET) and poly(dimethylsiloxane) (PDMS)] by 13.56 MHz r.f. self-bias glow discharge in a pure methane atmosphere. The film depositions were performed at 8 Pa with self-bias voltages ranging from −200 to −700 V. The film structure was analysed by Raman spectroscopy and the spectra taken from films deposited on all substrates had as the main feature the D and G bands typical of amorphous carbon films. The position, width and intensity ratio of these two bands are quite similar to those obtained from films deposited onto Si substrates. To verify the homogeneity of the films, samples deposited onto PTFE substrates were also analysed by RBS. Room temperature conventional gas permeation measurements were performed on covered and uncovered PDMS substrates. Gas permeation results reveal that a-C:H films work as barriers against CO2, reducing the permeation coefficient by at least 50%. The reduction of the permeation coefficient does not depend on the self-bias voltage and film thickness for coatings thicker than 0.5 μm. The surface topography of the samples was analysed by optical microscopy.

The Na+ ions in the solid electrolyte β″alumina (Na+-β″-Al2O3) have been exchanged with Pr3+ ions. The Pr3+ ion has been used as an optical and magnetic probe to investigate the local structure within the conduction planes of this oxide. With this aim, optical spectra and susceptibility measurements have been carried out. Both fluorescence and excitation spectra, related to the 3Po→3F2, 3H4 transitions, have been recorded on single crystals. The magnetic susceptibility shows temperature-independent paramagnetism at low temperatures. The physical properties have been interpreted with the help of ligand-field calculations by applying the angular overlap model. It has been deduced that the Pr3+ ions occupy mostly the eightfold-coordinated mid-oxygen (mO) sites.

Room-temperature Stokes and anti-Stokes Raman scattering spectra have been measured in the low-energy acoustic and high-energy optical phonon region for Cd(S, Se)-doped glasses. The peaks observed in the low-frequency region were assigned to the confined acoustic eigenmodes of II-VI semiconductor nanoparticles embedded in an amorphous matrix. The size dependence of the acoustic peak positions and the relation between the size distribution and bandwidth of these peaks was derived. The size-dependent changes in the region of CdS longitudinal-optical modes were attributed to the confinement of phonons in a small nanocrystal volume.

Light-emitting porous silicon films have been obtained by anodic etching p-type Si samples in a HF-ethanol solution. Porous Si samples efficiently luminesce at room temperature in the visible region. A degradation of the luminescence intensity with time is observed. Micro-Raman spectroscopy of free-standing porous silicon layers indicates phonon confinements as well as a strong laser heating effects. The surface chemical composition and the effect of electron-beam irradiation has been investigated through Auger spectroscopy. The Si LVV Auger transition dominates the spectrum, even in aged samples. The Si line shape gives evidence of a covalent bond between the porous Si surface atoms and some adsorbed species. A prolonged electron irradiation results in a strong variation of the surface chemical composition, with an anomalous carbon accumulation. Gold thin films have been deposited on the porous Si surface to form metal-semiconductor junctions. Schottky diodes with large rectifying ratio, ideality factor, and series resistance are obtained. When the junction is forward biased, electroluminescence is observed. Electroluminescence degrades with time while the current does not. When the junction is reverse biased a significant photocurrent is obtained. The results are discussed in the framework of the surface state emission model for the luminescence.

Crystals of Na+/Pr3+ β-Al2O3 with different amounts of lanthanide ions have been investigated by optical spectroscopy methods between 4.2 K and 300 K. Optical absorption spectra in the visible region show three main features which are related to the 3H4→3P0, 3H4→3P1(1I6) and 3H4å3P2 transitions. Polarized luminescence spectra have been recorded under cw excitation of various Ar+ ion laser lines. Complex emission spectra consisting of several, not fully resolved, components even at very low temperature, are observed for the 3P0→3H4 transition between 20000 and 210000 cm−1. Excitation spectra and resonant fluourescence line narrowing (FLN) spectra of different components of this transition recorded at low temperature indicate the presence of, at least, two distinct sets of centers, in agreement with recent structural refinement results. Finally, we have evaluated the energy levels and crystal-field splittings by ligand-field calculations based on the angular overlap model (AOM). Our calculations reproduce the ground state splitting of Pr3+ ions in the β-Al2O3 structure with different site symmetrics.

An optical spectroscopy study of differently Pr+-doped sodium β-Al2O3 crystals has been carried out to probe the optical properties of Pr3+ ions in this host material. Therefore the3P0 →3H4 luminescence has been investigated in more detail by recording low-temperature absorption, excitation and fluorescence decay time spectra. Site-selective spectra of the same transition indicate the presence of, at least, two sets of centres for Pr3+ in the conduction planes of β-Al2O3.

We report on the results of a low-temperature optical spectroscopy study of Pr3+-exchanged sodium beta-alumina single crystals (Na+/Pr3+ beta-Al2O3), containing different amounts of luminescent ions, in which excitation and fluorescence spectra have been carried out in sigma and pi polarization.The P-3(0)--> H-3(4) emission spectra, obtained under broad band excitation, show an intriguing structure consisting of several components even with crystals containing low Pr3+ concentrations. The excitation spectra indicate the presence of at least two sets of different sites, available to Pr3+ in the conduction plane of beta-alumina. Independently of the crystal composition, a quite satisfactory site-selective emission from each sets of centres has been achieved under cw excitation of the 465.8 nm and 476.5 nm lines of an Ar+ ion laser.

Polarized Raman spectra from single crystals of sodium β″-alumina, Li-stabilized, have been measured for the first time at several temperatures between 4.2 and 300 K. The spectra show significant, although minor, differences with respect to those obtained from Mg-stabilized composition. In fact, an accurate analysis of the low-frequency spectra reveals an unlike distribution of mobile cations in two isomorphs, with no evidence of any superlattice arrangement in Li-stabilized one. On the other hand, the vibrational dynamics of spinel blocks is sensitive to the nature of stabilizing cations, which locally produce different charge compensating defects in the two compounds. Surprisingly some Raman features of Li-stabilized β″-alumina recall the behaviour of Na β-alumina, in quite sharp agreement with the results obtained by a recent optical spectroscopy study of Cr3+ ions in the same crystals.