Titania (TiO2) is employed as a host for the Eu3+ activator ion. Thin films were produced by the sol-gel method on silicon and corning glass substrates and, depending on the nature of the substrate, they present different crystalline structure. The films show an intense red photoluminescence associated with the D05→7F2 transition of the electronic structure of Eu3+. The photoluminescence presents better characteristics for the films deposited on silicon wafers. For above band gap excitation the emission from the TiO2 matrix is obscured by the luminescence of the Eu3+ ions. The peak energy position, the spectral shape, and the width are insensitive to changes of temperature in the 12–300 K range, making the TiO2:Eu3+ a very attractive system for technological applications.

Spectral photoconductivity, photoconductive quenching, photoluminescence, and thermally stimulated current measurements, have been carried out in order to study the evolution of defect energy levels in CdS thin films, grown in cubic phase by chemical bath deposition, as a function of thermal annealing temperatures in Ar+S2 atmosphere. The results are influenced by a cubic-to-hexagonal phase transition. From those measurements, a number of trap levels and deep levels in the forbidden band are determined. The results can be explained in terms of the evolution of native and phase transition generated defects in the sample structure.

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Articles you may be interested inEffect of donor-acceptor concentration ratios on nonradiative energy transfer in closely packed CdTe quantum dots Appl. Phys. Lett. 95, 133123 (2009); Photoluminescence ͑PL͒ spectra of CdTe single crystals and films, undoped and Ag-doped, were studied in the range of the photon energy (h): 1.5-1.6 eV, at 10 K. Films were doped during the growth process. Thin layers of Ag were vacuum evaporated onto the surface of undoped CdTe crystals, then were submitted to thermal annealing in a N 2 ϩ2% H 2 ambient at 400°C for 3 h. PL spectra of crystals exhibit a donor-acceptor pair ͑DAP͒ emission at hϭ1.491 eV ͑named here DAP Ag 2 ) with the highest intensity with respect to other signals. The PL of films is characterized by a peak at 1.5 eV followed by several phonon replicas. In both cases, the DAP emissions are due to the Ag-impurity presence and are accompanied by phonon replicas. Unannealed intrinsic crystals exhibit a unique broad DAP Ag 1 peak at hϭ1.501 eV, and one month aged at room temperature Ag-doped crystals only display a wide DAP Ag 2 peak at hϭ1.491 eV with 65% of its initial intensity, that reflects a reduced density of Ag diffused-doping levels. The origin of DAP lines in a PL spectra of CdTe:Ag has not been completely well defined until now, and we have introduced some explanatory conclusions about and a simple model for electronic transitions. This issue is important because Ag is an everpresent residual impurity in CdTe.

In this work, Fluorine + Antimony doped Tin oxide thin films (SnO2:Sb + F), were deposited on heated glass substrates using the ultrasonic spray pyrolysis technique. Tin(IV)-bis(acetylacetonate) dichloride ((C5H8O2)2SnCl2), was used as source of Tin. The use of the latter reagent was considered important, since its usage had scarcely been reported. Antimony chloride (SbCl3) and Ammonium fluoride (NH4F) were used as sources of the dopants of Antimony and Fluorine, respectively. The properties of the films resulted dependent on the relative amount of these dopants. The films as deposited were polycrystalline, with a low roughness, and showed excellent optical transparency, close to 90%, in the visible region of the electromagnetic spectrum. Fluorine in the films was only detected by Secondary Ion Mass Spectroscopy (SIMS) measurements, and films deposited with 5% of NH4F and 5% of SbCl3 in solution, showed the best electrical properties. An electronic conductivity up to 400 S/cm, and mobility, close to 10 cm2/V sec, were found in the best SnO2 film. An ionized impurity scattering mechanism seems to be responsible for the electronic transport in these films. In addition, the electronic conduction by bulk (or grains), was verified by impedance spectroscopy.