The present study aims at investigating the effect of co-doping on the photoluminescence(PL) property of Zn2SiO4:Mn phosphor. Experimental data were interpreted by the first principles embedded-cluster discrete variational (DV)-Xα method.

Europium doped zinc silicate (Eu:Zn2SiO4) phosphors in the forms of nanoscale powder and film has been prepared by sol-gel method. XRD analysis indicz: ed that the powders have willemite structure with a small amount of triclinic structure and the filn has, pure willemite structure. Photoluminescence measurement showed that strong red emission of Eu3+5D0→7 F2transition could be obtained under excitation at both 256 and 393 nm. Luminescence decay of the emission under 393 nm excitation can be fitted by a single exponential, yielding a decay time τ =1.43 ms; and the luminescence under 256 nm excitation shows double exponential decay with a slow decay time τs,=2.13 ms and a fast decay time τf =2.05 ms.

This investigation studied the effects of Ho3+ and Er3+ on the luminescence of the blue emitting phosphor yttrium silicate, (Y1-mCem)2SiO5. Yttrium silicate has a large emission tail that extends into the red portion of the visual spectrum. To improve the chromaticity of this phosphor to give it a more saturated blue color, the emission intensity of the tail needs to be decreased. Photoluminscence and low-voltage cathodoluminescence measurements were performed on yttrium silicate phosphors with varying concentrations of Gd3+, Ho3+ and Er3+. It was found that when co-doping with Ho3+ and Er3+, the relative intensity of the emission tail was decreased, but so to was the overall luminescence intensity of this phosphor.

Thin films of zinc sulfide (ZnS) doped with Mn, were deposited using magnetron sputter source. The electroluminescent properties of the as-deposited films were relatively poor. Post- deposition rapid thermal annealing (RTA) with and without co-dopants was studied. Significant changes in microstructure and EL performance were observed on the samples after post-sputter processing. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the microstructure. Both inter-grain and intra-grain distributions of the co-dopants were measured using energy dispersive X-ray spectra (EDX) and the distribution versus thickness was determined by dynamic secondary ion mass spectrometry (SIMS). A correlation between electroluminescent properties and the microstructure is obtained.

The possibility of further improving the sensitivity of the widely used BaFBr:Eu X-ray storage phosphor is investigated. The influence of CsF- and EuF3-doping on the stimulation spectrum is identical to the one of other ways to vary F/Br-ratio of this mixed crystal. The effect of CsF-doping turns out to be not primarily due to a replacement of Ba2+ by Cs1+ and subsequent charge comensation, but rather to the change in the F/Br ratio. Sr doping not only gives rise to FA(Br; Sr2+)-center formation but, at the same time increases the PSL-response in the bands ascribed to F(Br -)-centers.

Nanoparticles of CdS (5.0 nm diameter) are prepared in aqueous solution, and copper or silver ions are incorporated into the nanoparticle lattice (doped) or adsorbed to the nanoparticle surface (activated). The materials are characterized by ultraviolet-visible spectroscopy, photoluminescence spectroscopy, transmission electron microscopy and electron diffraction. The photoluminescence efficiency of the materials is affected by the concentration of the foreign ion. The effect of spatial location (doped vs. activated) on the spectral distribution of the emission are modest. Photodecomposition of copper-doped CdS is suppressed compared to CdS alone.

Ambient temperature blue luminescence was observed under both UV and X-ray excitation during our investigation of the chemisorption of small molecules into both α- and β CuAIC14. The optical properties of the CuAIX4 (X=CI, Br) indicate a copper centered phosphorescence mechanism. The thermal history of the sample influences both which polymorph is formed and the color of the luminescence. The sorption of small molecules into the framework quenches the blue photoluminescence, which provides a useful probe of the interaction between the metal-halide framework and sorbed gases.

In this paper, we introduce rare earth- or transition metal-activated oxide phosphor thin films prepared by magnetron sputtering and dip-coated solution deposition. Thin-film electroluminescent (TFEL) devices using these oxide phosphor thin films as the emitting layer were investigated with a single insulating layer device structure using a thick ceramic sheet insulating layer. High-luminance multicolor emissions and high luminous efficiencies were obtained in TFEL devices using various oxide phosphors: binary compound, Ga2O3; ternary compound, Zn2SiO4, CaGa2O4 and ZnGa2O4; and multicomponent oxide, Zn2SiO4- Zn2GeO4 system. Luminances above 2000 cd/m2 were obtained in CaGa2O4:Mn and Zn2Si1−XGeXO4:Mn TFEL devices driven at 1 kHz. Maximum luminous efficiencies of 2.53, 1.7 and 1.2 lm/W were obtained in Zn2Si0.7Ge0.3O4:Mn, Ga2O3:Mn and ZnGa2O4:Mn TFEL devices, respectively. Stable long-term operation was obtained in dip-coated and sputtered Ga2O3:Mn phosphor TFEL devices even when driven at 10 kHz. Various thin-film oxide phosphors activated with transition metals are suitable for the emitting layer of full-color electroluminescent displays (ELD) without the use of color filters. In particular, Ga2O3 is very promising as a phosphor host material for ELDs.

The growth and properties of undoped and Mn-doped ZnGa2O4 thin-film phosphors on (100) MgO and glass substrates using pulsed laser ablation were investigated. Blue-white and green emission were observed for as-deposited undoped and Mn-doped films, respectively. Luminescent properties as well as crystallinity were considerably affected by processing conditions and film stoichiometry. Films with enhanced luminescent characteristics were obtained on single crystal substrates without post-annealing.

An area of considerable research interest is the development of visible light, down- conversion phosphors for application in white light emitting diodes (LEDs). In such devices, a blue LED can act as the primary light source, exciting photoluminescence in a phosphor with subsequent broad band emission occurring at visible wavelengths of lower energy. A combinatorial approach to synthesize and screen potential inorganic phosphors for such an application has been developed. Using solution chemistry techniques, solid state thin film arrays of (Y1−xGdx)3-z(Al1−yGay)5O12:Ce3+Z, where x and y range from 0 to 1.0 and z is equal to 0.03 were synthesized. Subsequent characterization demonstrates that the combinatorial approach can be used to rapidly screen potential phosphors for use as luminescence down-converters in white LEDs. Emission and excitation trends match those reported in the literature for traditionally prepared powder samples. The optimal Ce3+ concentration in Y3Al5O12 (YAG) was identified as approximately 1.5 mol%, and within the YAG-substituted host specific compositions were identified as promising blue to yellow phosphor candidates.

Organic molecular beam deposition (OMBD) has been used to deposit thin films of free base phthalocyanine (H2Pc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). The structural, optical and morphological properties of the films have been measured as a function of annealing temperature using x-ray diffraction (XRD), electronic absorption spectroscopy and atomic force microscopy (AFM). A phase transition, (α-β), is observed for H2Pc films which is accompanied by changes in the bulk film properties and surface morphology. In the case of PTCDA increasing temperature does not affect the structural and optical properties of the film, but different surface morphologies are observed.

Thin films have been deposited by rf magnetron sputtering from a stoichiometric Ta2Zn3O8 ceramic target (3ZnO + 1Ta2O5). Negative ion re-sputtering effects have been observed in the stoichiometric Ta2Zn3O8 target and have been attributed to O ion formation from primarily Ta-O bonds. Zinc deficient thin films were deposited as a result of the preferential re- sputtering of Zn versus Ta. The negative ion re-sputtering effects are exacerbated at higher powers and lower pressure. This observation is correlated to the oxygen ion transport through the dark space and the plasma, which ultimately controls the energy distribution of the oxygen particles that arrive at the substrate. To circumvent the negative ion re-sputtering, a mosaic ZnO-Ta target was sputtered, which resulted in stoichiometric and luminescent thin films.

Europium-activated yttrium oxide (Eu:Y2O3) thin films were deposited on (100) silicon and (0001) sapphire substrates using 248 nm KrF pulsed laser. To investigate the effect of the Eu:Y2O3 film roughness on cathodoluminescence (CL) and photoluminescence (PL) properties, the substrate surfaces with various roughnesses were used. The roughness was found to play an important role in determining CL and PL brightness of the Eu:Y2O3 films. The improvement in brightness by increasing the film roughness is due to increase in total portion of light that escapes from the surface of the phosphor film. A model has been proposed which supports strongly this explanation. Our results show that depositions with slower growth rate and lower laser energy are more important parameters than increasing the roughness to improve CL brightness of the Eu:Y2O3 thin film phosphors.

Need for efficient blue light emitting source for optoelectronic device applications such as flat panel displays has made the research in luminescent material ever so important. Tungsten doped zinc oxide (ZnO:W) has been identified as a blue light emitting phosphor exhibiting cathodoluminescence near 490 tim. This paper details work done on ZnO:W phosphor preparation conditions for efficient light emission from the phosphor. Material characterization to identify the possible source of blue light emission will also be discussed.

This study has used secondary ion mass spectrometry (SIMS) as a technique for thin film EL material characterization. It has shown that the Cu dopant concentration in the SrS films directly correlates with the luminescent brightness of the EL devices. A series of SrS:Cu,Y were grown using MBE to study the Y co-doping effects. It has been found that Y peak concentration and areal density in the SrS increased as the Y evaporation cell temperature was increased. The maximum PL intensity was found in the sample grown in the middle of the Y cell temperature range used. The Y co-doping has shown to reduce the thermal quenching effects in SrS EL devices. Therefore, in this series of samples, a good correlation has been found between Y and Cu concentration and the EL device performance characteristics.

The effects of high temperature annealing on the microstructure and optical properties of luminescent SiOx:H films have been investigated. Micro-Raman scattering and IR absorption, in combination with atomic force microscopy (AFM), provide evidence for the existence of both a-Si clusters in the as-grown a-SiOx:H and Si nanocrystals in the 1170°C annealed films. The dependence of optical coefficients (μ) on photon energy (hv) near the absorption edge (Eg) is found to follow the square root law: (μhv)½ μ (Eg – hv), indicating that nano-Si embedded in Si02 is still an indirect material. A comparison of the deduced absorption edge with the PL spectra shows an obvious Stokes shift, suggesting that phonons should be involved in the optical transition process.

SiOx films with oxygen concentrations ranging 13–46 at.% were deposited by plasma enhanced chemical vapor deposition (PECVD) technique using pure SiH4 and N2O mixture. Erbium was then implanted at an energy of 500 KeV with dose of 2×1015 ions/cm2. The samples were subsequently annealed in N2 for 20 sec at temperatures of (300–950°C). Room temperature (RT) photo-luminescence (PL) data were collected by Fourier Transform Infrared Spectroscopy (FTIS) with an argon laser at a wavelength of 514.5 nm and an output power from 5 to 2500 mw. The intense room-temperature luminescence was observed around 1.54 μm. The luminescence intensity increases by 2 orders of magnitude as compared with that of Er-doped Czochralski (CZ) Si. We found that the Er.- luminescence depends strongly on the SiOx microstructure. Our experiment also showed that the silicon grain radius decreased with increasing oxygen content and finally formed micro-crystalline silicon or nano-crystalline silicon. As a result, these silicon small particles could facilitate the energy transfer to Er3+ and thus enhanced the photoluminescence intensity.

The intense UV-visible-IR adjustable light emissions from silicon-rich oxynitride thin films without any thermal annealing were observed at room temperature under a 325 nm He-Cd laser excitation. The silicon-rich oxynitride thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) with the mixture of 5% Ar diluted silane and nitrous oxide gases. The strong naked-eye recognizable photoluminescence (blue-white-red) could be adjusted by changing the process gas flow ratio τ =([SiH4]/[N20]). To the best of our knowledge, intense and adjustable UV-blue light emissions in the as-deposited thin films are first reported in this work. The Fourier Transform infrared (FTIR) spectroscopy was applied to investigate the microstructure-bonding configurations, in which silicon polysilane related bonding at 830-890 cm' present that silicon complex, exists along with the Si-O-Si bonding. X-ray photoelectron spectroscopy was used to investigate the binding configuration, the binding energy of Si 2p appearing at 99.3 eV was indicative of formation of the silicon clusters. As a consequence, we suppose that the visible-IR lights emissions might possible be strongly related to silicon clusters formation in the films and the intense UV emissions might come from the oxygen-related defects.

ZnO thin films were epitaxially grown on A12O3 (0001) single crystalline substrate by RF magnetron sputtering. The films were grown at the substrate temperature of 550°C and 600°C for 1 h and at a power of 60–120 W. The crystalline structure of the ZnO films was analyzed by 4-circle X-ray diffraction and backscattering (BS)/channeling. The FWHM of XRD ø -rocking curve increase from 9.45 to 18 arc-min. as the RF power increased from 80 to 120 W at 550°C. In-plane ZnO growth on sapphire.(0001) substrate at 550°C and at 80 W was found to be ZnO [1010] |: A12O3[1120], indicating a 30° rotation of ZnO unit cell about the sapphire (0001) substrate. For a specimen that was grown at an RF power of 120 W, 550°C, 1 h, the FWHM of XRD ø -rocking curve was 7.79 arc-min. In BS/channeling studies, the films deposited at 120 W, 600°C showed good crystallinity with the channeling yield minimum (Xmin) of only 5%, but for films deposited at 550°C the yield was as high as 50-60%, was of lower crystalline qualilty. From the results of the AFM measurement, the grain size gradually increased as the growing temperature and power increased. In case of the film deposited at 120 W and 600°C. the hexagonal shape of the grains were clearly observed. In PL measurement, only the sharp near band edge (NBE) emission were observed at room temperature for the film deposited at 80-120 W and 550°C, but the emission from deep level were also detected in the films deposited at 60 W, 550°C and 120 W, 600°C. The FWFM was decreased from 133 meV to 89 meV as RF power increased from 80 to 120 W at 550°C, and that of film deposited at 120 W and 600°C showed 98 meV respectively. The results were somewhat opposite to those of XRD. In the present study, the relationship between optical properties and crystal structure is discussed in terms of the quality of grains and the defects.

In the field of display phosphors, the efficiency of the cathodoluminescence process is a characteristic that is often used to assess the potential of a phosphor for use in flat-panel display applications such as field emission displays (FEDs). Cathodoluminescence characterization in a demountable vacuum chamber is important for preliminary evaluation and lifetesting of phosphor powders and screens prior to incorporation into an actual display device. There are many experimental factors that influence accurate measurement and calculation of the cathodoluminescence efficiency. These include electron beam profile (uniform, Gaussian), current density, electron accelerating voltage, secondary electron collection, and optical detection system. This paper will present some methods for achieving improved accuracy of cathodoluminescence measurements in systems at Sandia National Laboratories, using Y2O3:Eu as a representative phosphor.