Showing papers by "S. A. Tomás published in 2012"
TL;DR: In this paper, Cadmium sulfide (CdS) thin films were synthesized by chemical bath deposition on glass substrates at 80°C and X-ray diffraction patterns displayed the zincblende crystalline structure for all the CdS:Er samples, with a remarked preferred orientation along the (111) direction.
Abstract: Cadmium sulfide (CdS) thin films were synthesized by chemical bath deposition on glass substrates at 80 °C. The CdS thin films were doped with erbium (Er3+) during the growth process by adding aqueous solutions of Er(NO3)3·3H2O to the CdS chemical bath. The relative volume (V
r) of the doping-solution was varied to obtain ten different doping levels. X-ray diffraction patterns displayed the zincblende crystalline structure for all the CdS:Er samples, with a remarked preferred orientation along the (111) direction. The (111) interplanar distance (ID) first decreased, reaching a minimum value at V
r = 3%, after which point it increased up to saturation for largest values of V
r. The dependence of the band-gap energy (E
g) on V
r followed an opposite behavior to that described by the ID. The photoluminescence (PL) spectra showed essentially two main bands: the green emission (GE) band of CdS and a red emission (RE) band. The increasing of the PL signal, for V
r ≤ 4% has been associated with the presence of Er3+ into the CdS lattice. For V
r > 4%, Er degrades the lattice. In addition, the crystalline quality (CQ) and PL of the material improved for low V
r values, which was in agreement with measurements of the mobility.
19 citations
TL;DR: Er 3 þ ions were introduced into a new type of oxide matrixes prepared with different proportions of CdO and V2O5, which yielded an Er 3 þ concentration of 1 at%. Depending on the reactants proportions, the samples resulted in crystalline or amorphous structures as discussed by the authors.
17 citations
TL;DR: In this paper, the effect of a ZnSe layer on the thermochromic properties of MoO3 thin films was investigated and it was shown that the effect was more accentuated with respect to the MoO 3 sample, for temperature treatments above 150 °C.
Abstract: The effect of a ZnSe layer on the thermochromic properties of MoO3 thin films was investigated. ZnSe/MoO3 and MoO3 thin films were deposited by thermal evaporation in vacuum of MoO3 and ZnSe powders. Photoacoustic spectra of the films indicated that the thermochromic response for the ZnSe/MoO3 bilayer system was more accentuated, with respect to the MoO3 sample, for temperature treatments above 150 °C. This result is explained in terms of the injection of electrons from the II–VI semiconductor to the oxide film.
8 citations
08 Feb 2012
TL;DR: In this article, the photochromic and thermochromic properties of molybdenum oxide (MoO3) thin films doped with zinc selenide (ZnSe) were studied.
Abstract: The photochromic and thermochromic properties of molybdenum oxide (MoO3) thin films doped with zinc selenide (ZnSe) were studied. The films were deposited on glass substrates by thermal evaporation of MoO3-ZnSe powder mixtures. EDS measurements confirmed the incorporation of ZnSe in the MoO3 matrix while MicroRaman spectra of the samples showed structural changes by increasing ZnSe. MoO3 films doped with 5 mol% ZnSe presented an enhancement in the photochromic effect compared to the undoped MoO3 samples. The thermochromic effect was most pronounced for 5 mol% ZnSe samples annealed at 23-125 °C, and for undoped samples annealed at 125-225 °C. The MoO3 films doped with 10 mol% showed neither photochromic nor thermochromic effect.
5 citations