Search

Room temperature cathodoluminescence and photoluminescence were used to study silicon rich oxide (SRO) films with 5.5% silicon excess. Intense blue and red luminescence emissions were found. A SRO film was deposited by low-pressure chemical vapor deposition and was annealed at 1100 °C by 3 h in a nitrogen ambient. The emission from the SRO films was modeled as being due to donor-acceptor-pair decay. Calculations have been made to obtain the first estimates of the donor and acceptor energy distributions in SRO films. [ABSTRACT FROM AUTHOR]

The objective of this work is to investigate the origin of the emission bands of Photo and Cathodo — luminescence (PL, CL) in thermal silicon dioxide films implanted with Silicon. The films were obtained by 150 KeV Si implantation into thermal oxide, with doses of 1×10[sup 16] cm[sup -2] and 1×10[sup 17] cm[sup -2]. Thermal treatments of 0, 30, 60 and 180 minutes in nitrogen at 1100 °C were applied. We found light emission in the visible range, the bands change with the ion implantation conditions and thermal treatments. The as implanted samples present photoluminescence bands around 1.95 eV and 2.4 eV for both doses, and they disappear with thermal treatments. After annealing, the low dose samples has a photoluminescence band at 2.6 eV, while those of dose of 1 x 10[sup 17] cm[sup -2] has a band centered at 1.7 eV. The intensity of the bands changes with thermal treatment. The cathodoluminescence bands are at 2.7 eV for both implantation doses in samples with and without thermal treatments. A discussion of the results and conclusions that contribute to better understand this nowadays controversial subject is presented. [ABSTRACT FROM AUTHOR]

Hafnium oxide nanoparticles doped with trivalent samarium (HfO 2 :Sm3+) were synthesized by hydrothermal route from chloride reagents. Different samarium doping concentrations (0, 0.5, 1, 3, 5 and 10 at% with respect to Hf) and different post-annealing temperatures (200, 400, 600, 800 and 1000 °C) were evaluated. The resulting nanoparticles showed an oval morphology with average sizes below 30 nm. A sensitive relationship between the samarium concentration and the resulting crystal structure of the material was observed by X-Ray diffraction and further evidenced by the cathodoluminescence and photoluminescence spectra. Low concentrations of samarium (0, 0.5 and 1 at%) generated a monoclinic phase, whereas higher concentrations of samarium (5 and 10 at%) generated a metastable cubic phase. The average crystallite sizes calculated by the Scherrer's equation were close to 8 nm and 12 nm for cubic and monoclinic phases, respectively. The luminescent emission corresponded to the characteristic 4f-4f transitions of the samarium ion with a principal peak centered at 610 nm. The best luminescent properties were obtained with the sample doped with samarium at 0.5 at%, annealed at 600 °C. [ABSTRACT FROM AUTHOR]

In this work we investigate the luminescent properties of HfO 2 films doped with Eu 3+ , Tb 3+ and Eu 3+ + Tb 3+ ions excited through photoluminescence and cathodoluminescence. These films were synthesized by the pulsed laser ablation technique and structurally studied by X-ray diffraction and Raman spectroscopy; the surface morphology was observed by scanning electron and atomic force microscopies. The optical transmittance was measured as well. The crystalline phase observed was the monoclinic of the HfO 2 . The surface morphology of the films exhibited a low roughness, as measured by atomic force microscopy. These films show a high transparency in the visible region. The emission spectra show bands centered at 598, 614 (strongest emission), and 631 nm for the HfO 2 :Eu 3+ films under excitation of 267 nm. HfO 2 :Tb 3+ films when excited at 277 nm exhibit emission bands centered at 491, 543 (dominant emission), 551 and 586 nm. In the case of co-doping with Eu 3+ and Tb 3+ ions white emission was observed under excitation with 320 nm, as indicated by the CIE chromaticity diagram. [ABSTRACT FROM AUTHOR]

The luminescent properties of Al 2 O 3 :Tb 3+ powders embedded in polyethylene terephthalate (PET) films have been studied. Luminescent Al 2 O 3 :Tb 3+ polycrystalline powders were synthesized by a simple evaporation method. The powder embedded films were obtained by the spray pyrolysis technique. The photoluminescence and cathodoluminescence emission spectra from these samples show, in both cases, luminescence peaks associated with transitions within the electronic energy levels of Tb 3+ ions. The dominant peak is at 544 nm corresponding to the 5 D 4 to 7 F 5 transition. In the case of the powder embedded films, the CIE coordinates depend on the excitation wavelength because there is a blue emission contribution from the PET host. UV–Vis% transmission measurements on these films show that they are transparent (∼80% and 95% T). [ABSTRACT FROM AUTHOR]

ZrO 2 , ZrO 2 :Dy 3+ and ZrO 2 :Dy 3+ , Gd 3+ films were synthesized using the Pyrosol technique. These films have a ZrO 2 -metastable tetragonal crystalline structure, which is better defined as the deposition temperature increases. Photoluminescence and cathodoluminescence properties of these films were studied as a function of deposition parameters such as substrate temperature and Dy 3+ and Gd 3+ relative concentrations. All luminescent emission spectra showed the typical electronic transitions 4f → 4f of the Dy 3+ ions at 480, 574 and 655 nm. The luminescent intensity is observed to increase with the Dy 3+ ion concentration up to 7 at.% in the spraying solution (1.8 at.% inside films), higher concentration result in an inhibition of the luminescence. Incorporation of Gd 3+ ions in ZrO 2 :Dy 3+ films produced a marked increase in the luminescent emission intensity (approximately 15 times). The elemental composition and surface morphology of these films are also reported. [ABSTRACT FROM AUTHOR]

Terbium, europium and yttrium β diketonates have been synthesized from acetylacetone and inorganic metal salts and used as precursors for the deposition of Tb 3+ or Eu 3+ doped Y 2 O 3 polycrystalline films by the ultrasonic spray pyrolysis technique. The films were deposited on c-Si substrates at temperatures in the 400–550 °C range. The optical and structural characterization of these films as a function of substrate temperature and Tb 3+ and Eu 3+ concentration was carried out by means of photoluminescence (PL), cathodoluminescence (CL), infrared (IR), ellipsometry, and UV–visible spectroscopy and atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and X ray diffraction (XRD) measurements respectively. The PL intensity from these films was found to depend on deposition temperature. Films deposited above 450 °C exhibited the characteristic PL peaks associated with either Tb 3+ or Eu 3+ intra electronic energy levels transitions. The most intense PL emission was found for dopant concentration of 10 at% for Tb 3+ and at 8 at% for Eu 3+ ions into precursor solution. In both cases concentration quenching of the PL emission was observed for concentrations above these values. The films had a refractive index (1.81), low average surface roughness (∼62 Å) and a UV–Vis. transmission of the order of 90 %T. [ABSTRACT FROM AUTHOR]

Trivalent erbium doped zirconium oxide films were deposited by the ultrasonic spray pyrolysis technique. Films were deposited using zirconium tetrachloride octahydrate (ZrCl4O·8H2O) and erbium nitrate hexahydrate ((NO3)3Er·6H2O) as precursors and deionized water as solvent. The dopant concentrations in the spray solution were 1, 3, 5, 10 and 15at% in ratio to zirconium content. The films were deposited on corning glass substrates at different temperatures from 400 up to 550°C. Films deposited at temperatures lower than 400°C were amorphous, however, as substrate temperatures are increased, the ZrO2 films presented a better crystallinity and showed a tetragonal phase. Cathodoluminescence (CL) emission spectra showed bands centred at 524, 544 and 655nm associated with the electronic transition of Er3+. [ABSTRACT FROM AUTHOR]

Abstract: The luminescent characteristics of Dy3+-doped Y2O3 nanopowders synthesized using the polyol method are reported. The Y2O3 nanoparticles presented a cubic phase crystalline structure of Y2O3 after an annealing treatment in oxygen ambient at temperatures above 600°C. The averaged crystallite size determined from the X-ray diffraction peaks width was in the 20–32nm range depending on the annealing temperature. Scanning and transmission electron microscopy studies indicate the formation of nanoparticle aggregates up to 175nm in diameter. Photoluminescence and cathodoluminescence measurements show a predominant emission at 573nm, which is attributed to the 4F9/2→6H13/2 of the Dy3+ ion. The luminescence emission dependence with the dopant concentration and post-annealing temperatures is discussed. [Copyright &y& Elsevier]

SrAl 2 O 4 : Tm3+, SrAl 2 O 4 : (Tb3+; Eu3+) and SrAl 2 O 4 : (Tb3+; Eu3+; Tm3+) films were deposited by ultrasonic spray pyrolysis (USP) method at 550 °C and subsequently heat-treated at 800 °C. XRD characterization showed a monoclinic/hexagonal polymorph phase of these films with orthorhombic Sr 4 Al 14 O 25 as secondary phase. The incorporation of Tm3+ ions in strontium aluminate host lattice generated emissions of blue color for photoluminescence and violet color for cathodoluminescence. The violet emission was associated to the electronic transition from 1I 6 energy level of Tm3+. Photoluminescence of the SrAl 2 O 4 : (Tb3+; Eu3+) films resulted in two different colors, white emission was observed when excited with 210 nm and bluish-white emission was achieved by exciting with 275, and 286 nm. When three dopant ions (Tm3+ ; Tb3+; Eu3+) were incorporated inside strontium aluminate host lattice, it was observed (exciting under 252 nm) white photoluminescence emission (x = 0.3377, y = 0.3294); for excitation wavelengths (λ exc) = 262, 315 and 375 nm, emissions in different shades of blue-green were achieved. Quantum efficiencies between 48 and 57% were obtained. [Display omitted] • High intensity cathodoluminescence emisión is due to transitions from 1I 6 energy level of Tm3+ in SrAl 2 O 4. • SrAl 2 O 4 : Tb3+; Eu3+; Tm3+ is a tunable and high intensity photoluminescent phosphor. • Persistent phosphor with high intensity luminescent emission is synthesized by scalable and low cost technique. [ABSTRACT FROM AUTHOR]

Manganese doped zirconia luminescent films have been deposited at temperatures ranging from 250 to 500 °C using the Pyrosol technique. The material obtained is in an amorphous state up 400 °C. For higher temperatures a polycrystalline material is obtained with a cubic and/or tetragonal crystalline zirconia phase. The photoluminescence and cathodoluminescence spectra show the bands associated with the electronic transitions 4T1(4G)→6A1(6S) of the Mn2+ ions. A decrease of the luminescence, as a function of the doping concentration, substrate temperature and electron accelerating voltage is observed. The presence of chlorine seems necessary for the red luminescence. The surface morphology of the films is also presented. [Copyright &y& Elsevier]