Phosphor Thin Films Research Articles

Crystal Structures and Photoluminescence Properties of Gd2O3:Eu3+ Phosphor Thin Films Prepared by Laser Ablation

We prepared red-light-emitting europium-doped gadolinium oxide (Gd2O3:Eu3+) phosphor thin films by laser ablation using a KrF excimer laser, and characterized the correlation between the crystal structures and the photoluminescence properties of the ablated targets and the prepared thin films. The crystal structures of the Gd2O3:Eu3+ targets were changed from a cubic type to a monoclinic one by evaporation for the laser ablation. The prepared Gd2O3:Eu3+ thin films exhibited not only the cubic phase but also the monoclinic one on the quartz substrate heated at 500°C for the thin-film deposition. The thin films also showed photoluminescence spectra that were superpositions of the individual cubic and monoclinic spectra. By increasing the laser fluence during the deposition of thin films, the monoclinic phase was more efficiently formed in the prepared Gd2O3:Eu3+ thin films.

Enhanced Light Extraction Efficiency in Pulse Laser Deposited Gd2O3 : Eu3 + Thin-Film Phosphors on 2-D PCLs

Enhanced Light Extraction Efficiency in Pulse Laser Deposited Gd2O3 : Eu3 + Thin-Film Phosphors on 2-D PCLs

Luminescence of Pulsed Laser Deposited Y2SiO5:Tb3+ Thin Film Phosphors on Flat and Corrugated Quartz Glass Substrates

Y2SiO5:Tb3+ thin film phosphors were deposited on flat and corrugated quartz glass plates by pulsed laser deposition (PLD) techniques in an attempt to use them in field emission displays (FED). As a preliminary step, cathodoluminescence and photoluminescence was monitored as a function of several processing parameters such as the oxygen partial pressure, the deposition time and the annealing conditions for films deposited on flat quartz glass plates. By adopting optimum processing conditions taken from the preliminary optimization process based on flat quartz glass substrates, Y2SiO5:Tb3+ thin films were also deposited on substrates on which a two-dimensional photonic crystal layer (2-D PCL) was developed, i.e., corrugated substrates. It was found that the Y2SiO5:Tb3+ thin film phosphor developed by PLD represents a promising candidate for use in field emission displays, and that the use of corrugated substrates enhanced the light extraction efficiency by a factor of 1.72.

Photoluminescence of wet chemical process-derived (Y, Gd) BO 3: Eu 3+/Tb 3+ thin film phosphors

Using metal nitrates and boric acid as starting materials and glycerol as additives, we prepared (Y, Gd)BO 3: Eu 3+/Tb 3+ thin film phosphors by a wet chemical process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy, photoluminescence (PL) spectra as well as lifetimes were employed to characterize the resulting samples. The results of the XRD and FT-IR indicated the films began to crystallize at 700 °C and the crystallinity increased with elevation of the annealing temperature. Eu 3+ and Tb 3+ showed their characteristic emissions in (Y, Gd) BO 3 films, i.e., 5D 0– 7F J ( J=0, 1, 2, 3, 4) for Eu 3+ and 5D 4– 7F J ( J=6, 5, 4, 3) for Tb 3+, respectively. Both the lifetimes and PL intensity of Eu 3+ and Tb 3+ ions increased with increasing the annealing temperature. The optimum concentrations for Eu 3+ and Tb 3+ were determined to be 10 and 12 at% of Y 3+ in YBO 3 films. Partial introduction of Gd 3+ in YBO 3:Eu 3+/Tb 3+ films is good for enhancing the PL intensity of Eu 3+ and Tb 3+, and the best concentration of Gd 3+ is 50 at% of Y 3+ in the films.

Preparation of Sr2CeO4:Eu3+,Dy3+ White Luminescence Phosphor Particles and Thin Films by Using an Emulsion Liquid Membrane System

Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) phosphor particles and thin films were prepared by using an emulsion liquid membrane (ELM, water-in-oil-in-water (W/O/W) emulsion) system, containing VA-10 (2-methyl-2-ethylheptanoic acid) as extractant (cation carrier). A two-step extraction enabled efficient extraction for Sr(3+) and rare earth ions, and the resulting precursor metal oxalate particles produced in the internal water phase of the ELM system were about 60 nm in diameter. Calcination of the oxalate particles in air gave submicrometer-sized Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) particles, which showed blue and white luminescence, respectively, by UV excitation. Blue and white luminescence phosphor thin films were also prepared by soaking alumina substrates into the W/O emulsion containing precursor oxalate particles, followed by calcination in air.

Luminescent properties of CaTiO 3:Pr thin-film phosphor deposited on ZnO/ITO/glass substrate

Red-emitting CaTiO 3:Pr phosphor thin films were deposited on glass, ZnO/ITO/glass, and ITO/glass substrates by RF magnetron sputtering. The effects of various substrates and heat treatment on the structural and luminous properties were investigated. The films deposited on ZnO/ITO/glass exhibited superior crystallinity and more enhanced PL and CL properties compared with those on ITO/glass. The intermediate ZnO layer between phosphor film and ITO contributed to the growing behaviors and the roughening of CaTiO 3:Pr phosphor thin films, and consequently, to the excellent luminescence. The luminescent properties of the films were improved by following heat-treatment due to a combination of factors, namely the transformation from amorphous to poly crystalline phases, the activation of the activators, and the elimination of microdefects.

Crystallinity of Li-doped Gd2O3:Eu3+ thin-film phosphors grown on Si (100) substrate

Gd 2 O 3 : Eu 3 + and Li-doped Gd2O3:Eu3+ luminescent thin films have been grown on Si (100) substrates using pulsed-laser deposition. The films grown at different deposition conditions show different microstructural and luminescent characteristics. Both cubic and monoclinic crystalline structures were observed in both Gd2O3:Eu3+ and Li-doped Gd2O3:Eu3+ films, but the cubic phase becomes more dominant and the ratio of peak values IC(222)∕IM(−402) increases rapidly for Li-doped Gd2O3:Eu3+ films. The photoluminescence brightness data obtained from Li-doped Gd2O3:Eu3+ films indicate that Si (100) is a promising substrate for growth of high-quality Li-doped Gd2O3:Eu3+ thin-film red phosphor. In particular, the incorporation of Li+ ions into the Gd2O3 lattice induced changes of crystallinity, surface roughness, and photoluminescence. The highest emission intensity was observed with Gd1.84Li0.08Eu0.08O3, whose brightness was a factor of 2.1 larger than that from Gd2O3:Eu3+ films. This phosphor is promising for applications in flat-panel displays.

Effects of 2D SiO2 Nanorod-Modified Substrates on the Morphology and CL Properties of ZnS:Mn Particle-like Thin-Film Phosphors

To improve light extraction from ZnS:Mn thin-film phosphors, we have studied the effects of introducing various two-dimensional (2D) nanorod arrays onto glass substrates. We determined the effects of 2D nanorods on the morphology and cathodoluminescence (CL) emissions of ZnS:Mn thin films with a view to optimizing the lattice constant of the array and the diameters of the nanorods. Particle-like thin-film phosphors were obtained from the sputtering growth of ZnS:Mn thin films on the nanorod-modified glass substrates, particularly for nanorods with higher aspect ratios and lower nanorod array density. We obtained a significant enhancement (a factor of ) of the CL extraction efficiency at the interface between ZnS and air, for low voltage electron beam excitation of ZnS:Mn thin-film phosphors deposited on 2D nanorod-modified substrates. This improvement in the extraction efficiency is due to the uniform and nanoscale particle-like morphology of these thin-film phosphors, as well as to the diffraction scattering produced by the 2D periodic nanorod array.

기판온도 및 Annealing에 따른 ZnGa2O4형광체 박막의 특성

A ZnGa<TEX>$_2$</TEX>O<TEX>$_4$</TEX> phosphor target was synthesized through solid-state reactions at a calcine temperature of 700 <TEX>$^{\circ}C$</TEX> and sintering temperature of 1300 <TEX>$^{\circ}C$</TEX> in order to deposit ZnGa<TEX>$_2$</TEX>O<TEX>$_4$</TEX> phosphor thin film at various temperature using rf magnetron sputtering system. A ZnGa<TEX>$_2$</TEX>O<TEX>$_4$</TEX> phosphor thin film was deposited on Si(100) substrate and annealed by a rapid thermal processor(RTP) at 700 <TEX>$^{\circ}C$</TEX>, for 15 sec. The x-ray diffraction patterns of ZnGa<TEX>$_2$</TEX>O<TEX>$_4$</TEX> phosphor target and thin film showed the main peak (311) direction. ZnGa<TEX>$_2$</TEX>O<TEX>$_4$</TEX> thin film has better crystalization due to as function of increasing substrate and annealing temperature. The cathodoluminescence(CL) spectrums of ZnGa<TEX>$_2$</TEX>O<TEX>$_4$</TEX> phosphor thin film showed the main peak 420 nm wavelength and the maximum intensity at the substrate temperature of 500 <TEX>$^{\circ}C$</TEX> and annealing temperature of 700 <TEX>$^{\circ}C$</TEX>, for 15 sec.

Effects of x and R3+ on the luminescent properties of Eu3+ in nanocrystalline YVxP1-xO4:Eu3+ and RVO4:Eu3+ thin-film phosphors

Using inorganic oxides and salts instead of alkoxides as the main starting materials, we prepared nanocrystalline YVxP1-xO4:Eu3+ and RVO4:Eu3+ (0≤x≤1; R=Y,La,Gd) thin-film phosphors by the Pechini sol–gel dip-coating process. The resulting films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and photoluminescence excitation and emission spectra as well as luminescence decay. The results of XRD showed that a solid solution formed in the YVxP1-xO4:Eu3+ film series from x=0 to x=1 with zircon structure. The same structure also held for the GdVO4:Eu3+ film, but the LaVO4:Eu3+ film crystallized with a different structure, monazite. AFM and SEM studies revealed that the phosphor films consisted of spherical particles ranging from 90 to 400 nm depending on the film compositions. With the increase of x values in YVxP1-xO4:Eu3+ films, the integrated emission intensity and the red (5D0–7F2)-to-orange (5D0–7F1) intensity ratio of Eu3+ increase due to the increased energy-transfer probability from VO43- to Eu3+ and the increased polarizability of the surrounding oxygen ions, respectively. The x values also have an influence on the decay behavior of Eu3+. The YVO4:Eu3+ and GdVO4:Eu3+ films showed very similar luminescence properties due to their same crystal structures. However, the LaVO4:Eu3+ film exhibited a much different emission property from those of the YVO4:Eu3+ and GdVO4:Eu3+ films due to the structural effects.

Morphology and crystalline-phase-dependent luminescence of Li-doped Gd2O3:Eu3+ thin films grown by pulsed laser deposition

Gd2O3:Eu3+ and Li-doped Gd2O3:Eu3+ luminescent thin films have been grown on Si(100) substrates using pulsed laser deposition. The films grown at different deposition conditions show different crystalline and morphology structures and luminescent characteristics. Although both cubic and monoclinic crystalline structures were observed in both Gd2O3:Eu3+ and Li-doped Gd2O3:Eu3+ films, the cubic structure becomes more dominant for Li-doped Gd2O3:Eu3+ films. The photoluminescence brightness data obtained from Li-doped Gd2O3:Eu3+ films indicate that Si(100) is a promising substrate for growth of high-quality Li-doped Gd2O3:Eu3+ thin-film red phosphor. In particular, the incorporation of Li+ ions into the Gd2O3 lattice induced a change of crystallinity and enhanced surface roughness. Two major factors to determine photoluminescence brightness for Li-doped Gd2O3:Eu3+ films were crystalline phase and surface roughness. The highest emission intensity was observed with Gd1.84Li0.08Eu0.08O3, whose brightness was a factor of 2.1 larger than that of Gd2O3:Eu3+ films. This phosphor is promising for applications in flat-panel displays.

Photoluminescence characteristics of pulsed laser-ablated Y 2− xGd xO 3/Eu 3+ thin film phosphors grown on Si (100) substrate

Y 2− x Gd x O 3/Eu 3+ thin films have been grown on Si (100) substrates using pulsed laser deposition. The films deposited at the different conditions show different microstructural and luminescent characteristics. The crystallinity, surface morphology, and photoluminescence (PL) of the films are highly dependent on the amount of Gd. The PL results obtained from Y 2− x Gd x O 3/Eu 3+ films grown under optimized conditions have indicated that Si (100) is a promising substrate for the growth of high-quality Y 2− x Gd x O 3/Eu 3+ thin film phosphor. In particular, incorporation of Gd into the Y 2O 3 lattice can induce a remarkable increase of PL. The highest emission intensity was observed with Y 1.35Gd 0.60O 3/Eu 3+, whose brightness was a factor of 1.9 larger than that from Y 2O 3/Eu 3+ films. This phosphor is promising for applications in flat panel displays.

Luminescent properties of SrGa 2S 4:Eu thin film phosphors deposited by two electron beam evaporation

SrGa 2S 4:Eu thin film phosphors have been deposited on quartz glass substrates at substrate temperatures of 350–450 °C by multi-source deposition method in which two electron beam (2EB) evaporation sources were used. The films were annealed between 750 and 850 °C for 30 min in H 2S atmosphere after the deposition. It was shown by XRD measurement that SrGa 2S 4 phase was not formed but crystalline GaS was included in an as-deposited film, therefore, PL and CL due to SrGa 2S 4:Eu were not observed. The SrGa 2S 4 phase was formed by the annealing. Photoluminescence (PL) and cathodoluminescence (CL) spectra of all annealed films showed green emission peaked at about 530 nm. CL luminance of all the films increased as the substrate temperature was increased. But the dependence on annealing temperature was not observed. So CL luminance depended only on substrate temperature during deposition. However, the CL luminance did not depend clearly on the annealing temperature between 750 and 850 °C. The SrGa 2S 4:Eu film deposited at 450 °C and annealed at 850 °C for 30 min showed a CL luminance and CIE coordinates of 1700 cd/m 2 and (0.27, 0.67), respectively under excitation with 3 kV and 60 μA/cm 2.

Extraction Efficiency in Pulsed Laser Deposited Y&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;:Eu&lt;sup&gt;3+&lt;/sup&gt; Thin Film Phosphors on Corrugated Substrates

The luminance level of thin film Y2O3:Eu3+ phosphors deposited by a pulsed laser deposition (PLD) technique are not acceptable for field emission display (FED) because of so-called wave guiding effect. Corrugated glass plates were employed as a substrate in order to relieve the wave guiding effect and in turn improve light extraction efficiency of Y2O3:Eu3+ thin film phosphors. Integrated photoluminescent efficiency, film surface roughness and crystallinity were monitored as function of the pitch of corrugation. The integrated photoluminescence efficiency of Y2O3:Eu3+ thin film phosphor deposited on the corrugated substrate was promoted significantly. The corrugated substrate makes it possible not only to enhance the roughness of phosphor film surface but also to facilitate the film growth in a specific orientation if the pitch size condition was met.

8.1: Invited Paper: TDEL: Technology Evolution in Inorganic Electroluminescence

In 1991, iFire Technology Corp. invented a new solid state display technology based on a combination of thick film screen printing and thin film phosphors, called Thick Dielectric Electroluminescent, or TDEL. Since that time, the technology has been under continuous development to improve brightness, contrast, colour, image quality, lifetime, and manufacturability (cost). Now the company is in transition from R&D to commercialization, with the construction of a pilot manufacturing facility underway, and plans for volume production in discussion. This paper will review TDEL's development stages and current status.

Sol–gel preparation and luminescent properties of CeO 2:Ln (Ln = Eu 3+ and Sm 3+) thin films

New transparent CeO 2:Ln (Ln = Eu 3+ or Sm 3+) thin-film phosphors have been fabricated by a sol–gel method. The CeO 2:Ln films with the Ln concentrations of 1 at.% showed the strongest photoluminescence (PL) upon ultraviolet (UV) light excitation. At higher Ln concentrations, the PL intensity decreased because of the nonradiative energy transfer. For Eu 3+ ions doped in the CeO 2 lattice with inversion symmetry, an orangey red emission due to a magnetic-dipole 5 D 0 → 7 F 1 transition (591 nm) was dominant when excited at a wavelength of 340 nm. In contrast, much stronger orange emissions (573 nm) due to 4 G 5/2 → 6 H 5/2 were observed for Sm 3+ ions. Apparently, the Eu 3+ and the Sm 3+ ions had different efficiencies of the excitation through the energy transfer from the “Ce 4+–O 2−” charge transfer state induced by the UV irradiation.

Preparation of SrAl2O4:Eu,Dy Phosphor Thin Films on Organic Substrates by Pulsed Ion-Beam Evaporation

Thin films of SrAl2O4:Eu,Dy were successfully deposited on polyethylene substrates at room temperature by pulsed ion-beam evaporation. From X-ray diffraction analysis results, the thin films were found to consist of a crystallized SrAl2O4:Eu,Dy phase. In the measurements of the photoluminescence properties of the thin films, broad peaks at 520 nm, which were characteristic of SrAl2O4:Eu,Dy phosphor, were observed. From the observation by scanning electron microscopy, the thin films were prepared on polyethylene substrates. From various observations, crystallized SrAl2O4:Eu,Dy phosphor thin films on polyethylene substrates were successfully obtained by IBE without damaging the substrates. These results suggest the possibility of IBE to deposit crystallized oxide thin films on various low-melting point substrates.

Ternary compound phosphor thin films for electroluminescent displays

Ternary compound phosphor thin films for electroluminescent displays

Cathodoluminescent characteristics of green-emitting ZnAl2O4:Mn thin-film phosphors

Green electroluminescence was obtained from thin films of ZnAl2O4: Mn prepared by rf magnetron sputtering onto thick insulating ceramic sheets. Photoluminescence and stress-stimulated luminescence was obtained for Mn-doped ZnAl2O4 powder synthesized by the solid phase reaction. Since it is extremely stable chemically and thermally, ZnAl2O4 may emerge as an alternative choice to sulphide-based phosphors. In the present paper, thin films of ZnAl2O4: Mn were grown on aluminosilicate ceramic plates using spray pyrolysis of aqueous solutions. The cathodoluminescence (CL) properties of the films under low to medium excitation voltage (<5 kV) were investigated. The films exhibited green CL after being annealed at temperatures above 550 degrees C, which corresponds to the transition between 4 T1 and (6)A1 of Mn2+ ions located in the tetra coordination of the Zn2+ site in the spinel structure. The chromaticity coordinates were x = 0.150 and y = 0.734 with a dominant wavelength of 525 nm and an 82% color purity. The CL luminance and efficiency depended on the excitation voltage and current density. Saturation effects were observed as the current density increased. A luminance of 540 cd x m(-2) and an efficiency of 4.5 lm x W(-1) were obtained at an excitation voltage of 4 kV with a current density of 38 microA x cm(-2).

Sphere-supported thin-film electroluminescence: A new platform technology for displays and lighting

— Currently, powder electroluminescence is used for low-brightness flexible lamps offering durable plastic-based lighting solutions principally for low-ambient light conditions where lighting or backlighting is required. Sphere-supported thin-film electroluminescence (SSTFEL) promises dramatic new capability in both flexible lamps and displays owing to its high brightness and long-life capability. SSTFEL is based on robust thin-film phosphors deposited on spherical ceramic dielectric particles which are embedded in a thin plastic sheet. A printing approach permits versatile, low-cost manufacturing of patterned SSTFEL devices and eliminates the need for high-temperature substrates.