Mn Phosphor Thin Films Research Articles

Luminescent properties and structural characteristics of sputter-deposited ZnGa2O4:Mn phosphor thin films

The correlation between the luminescent properties and structural characteristics of ZnGa2O4:Mn phosphor thin films has been investigated. The ZnGa2O4:Mn films have been prepared by radio frequency planar magnetron sputter deposition from a 2 mol. % Mn-doped ZnGa2O4 target in an Ar-O2 gas mixture whose pressure ranged between 2 and 20 mTorr. Films deposited at gas pressures above 10 mTorr showed a random crystallographic orientation, while the films deposited ≤10 mTorr exhibited a preferential orientation of the [110] direction perpendicular to the film surface. Internal stress in the ZnGa2O4:Mn films became increasingly compressive upon decreasing the gas pressure, reaching a value of ∼1.7 × 1010 dyne/cm2 at 2 mTorr. The observed change in internal stress correlated with the changes in the crystalline structure of the films. After a post-deposition anneal at 800 °C, the crystallinity of the films was improved. The rms surface roughness of the annealed ZnGa2O4:Mn films did not systematically depend on the gas pressure. Both photoluminescence (PL) and cathodoluminescence (CL) resulted in green light, and the emission peaked at ∼505 nm. This was attributed to the Mn2+ 3d-3d intrashell 4T1 → 6A1 transition. The intensities of both PL and CL emission increased as the gas pressure decreased, presumably due to the better crystalline quality with a highly [110]-textured structure and a more densely-packed microstructure in the ZnGa2O4:Mn films deposited at lower pressures.

Study of pulsed laser deposited ZnGa2O4 : Mn phosphor thin films in an oxygen controlled environment

Photoluminescent properties of ZnGa2O4 : Mn phosphor thin films grown on Si and quartz substrate using the pulsed laser deposition technique under different deposition conditions (i.e. oxygen partial pressure and substrate temperature) are reported. The charge transfer band (283 nm) excitation of the phosphor exhibited green emission (504 nm) due to electronic transition from 4G(4T1)–6S(6A1) of 3d5 Mn2+ ions. The SEM image with elemental composition analysis shows a change in the film porosity and the Ga/Zn ratio with respect to variation in the oxygen partial pressure during the growth of the thin films at a constant temperature (650 °C). The changes in the emission intensity of the films are attributed to the variation in oxygen and Zn content (low vapour pressure) with respect to the change in O2 partial pressure.

Near‐field measurement of ZnS:Mn nanocrystal and bulk thin‐film electroluminescent devices

A near-field study of the electro-optical phenomena and aging characteristics of nanostructured and bulk ZnS:Mn alternating-current thin-film electro-optical devices is presented. ZnS:Mn nanocrystals embedded in the glass matrices as well as ZnS:Mn thin-film phosphors contain four different concentrations of Mn (from 0.05 to 1.0 mol%). The activator impurity in the phosphor influences the spectral properties and, to a large extent, the temporal properties of optical emission and an aging process of the devices. Therefore, a local photoluminescence and electroluminescence investigation using a scanning near-field optical microscope technique is provided and the aging characteristics of ZnS:Mn nanocrystal structure also presented.

Structural and luminescence properties of pulsed laser deposited green-emitting Zn 2SiO 4:Mn phosphor thin films

The structural and photoluminescent (PL) properties of Zn 2(1− x ) Mn x SiO 4 (1 ⩽ x ⩽ 5) thin film phosphors grown using a pulsed laser deposition technique have been investigated. The effect of systematic variation of oxygen partial pressures (O 2 pp) (100, 300, 500 and 700 mTorr) during the growth of these thin films has been studied. Thin film grown on silicon substrate at 750 °C and in situ annealed in 300 mTorr of O 2 pp exhibits superior PL property; ex situ annealing at higher temperatures improves the PL intensity.

Correlation between structural changes and luminescent properties of ZnMgS:Mn thin film phosphor with annealing temperature

With varying rapid thermal annealing temperature, luminescent properties of Zn 0.75 Mg 0.25 S :Mn thin film deposited by RF-magnetron sputtering technique were investigated. Although all samples were deposited from identical source composition, it was found that a main peak wavelength of photoluminescence of Zn 0.75 Mg 0.25 S :Mn depended on RTA temperatures and it shifted toward shorter wavelength upon the increase of RTA temperature. The same dependence of wavelength on RTA temperature was also observed in cathodoluminescence as well as electroluminescence measurements. It is noticeable that Zn 0.75 Mg 0.25 S :Mn thin film phosphor in this study showed more reddish emission than those of the previous studies. It was revealed that changes of the luminescent properties were originated from structural changes in Zn 0.75 Mg 0.25 S :Mn thin film phosphor from cubic to hexagonal phases using X-ray pole figure mapping, and the growing up of hexagonal phase mainly caused cracks and porous morphology on the surface of thin films. It is suggested that the phase transition would be the origin of luminescent property changes with respect to rapid thermal annealing temperature.

Characterization of AlN:Mn thin film phosphors prepared by metalorganic chemical vapor deposition

The structural and luminescent properties of AlN:Mn films, which showed red-orange luminescence originated from the transition of 3d-electrons in a Mn ion, were investigated. The samples were grown on sapphire (0 0 0 1) wafers by an atmospheric-pressure metalorganic chemical vapor deposition at 1050 °C. The grown films were polycrystal oriented preferentially towards the 〈 0 0 0 1 〉 direction of wurtzite structure. It is suggested from the dependence of Mn concentration ( C Mn ) on the lattice constant and the low-temperature photoluminescence spectrum that most of the Mn atoms occupy the lattice sites for C Mn up to about 1 × 10 20 cm - 3 . The samples exhibited bright cathodoluminescence reflecting the improved crystalline quality compared to that of the low-temperature-grown samples. The highest luminance, 245 cd/m 2, has been obtained from the layer with C Mn of 3 × 10 19 cm - 3 under the excitation conditions of 5 kV and 0.1 mA/cm 2 as an accelerating voltage and a current density, respectively.

Pulsed Laser Deposited Oxide Green Emitting Thin Film Phosphors : Optimization of Growth Conditions

AbstractStructural and photoluminescence (PL) properties of Zn2(1-x)MnxSiO4 (1 ≤ x ≤ 5) and diffuse reflectance spectroscopy (DRS) and morphological studies of ZnGa2O4:Mn thin film green emitting phosphors grown using pulsed laser deposition (PLD) technique have been investigated. Zn2(1-x)MnxSiO4 thin films grown on Si substrate at 700°C in 300 mTorr of oxygen partial pressure, upon ex-situ annealing at higher temperatures exhibit superior PL intensity. ZnGa2O4:Mn phosphor thin films grown on quartz substrate at 650oC and in-situ annealed in 300mTorr of oxygen partial pressure show better emission intensity. For both Zn2SiO4:Mn and ZnGa2O4:Mn phosphors, luminescence can be assigned to 4T1 – 6A1 transition of Mn2+ within the 3d orbital giving rise to emission at 525 and 503 nm, respectively.

High-Luminance EL Devices Using Zn2Si1-XGeXO4:Mn Thin Films Prepared by Combinatorial Deposition by r.f. Magnetron Sputtering with Subdivided Powder Targets

A new technique incorporating combinatorial deposition to develop thin-film phosphors by r.f. magnetron sputtering is demonstrated using subdivided powder targets. In comparison with development using conventional r.f. magnetron sputtering, the atomic ratios of Si and Ge as well as the Mn content in Zn 2 Si 1-X Ge X O 4 :Mn thin film phosphors could be more efficiently optimized in order to obtain the highest intensity in electroluminescent and photoluminescent emissions. High luminances of 11800 and 1536 cd/m 2 were obtained in Zn 2 Si 0.6 Ge 0.4 O 4 :Mn thin-film electroluminescent devices fabricated under optimized conditions and driven at 1 kHz and 60 Hz, respectively.

Effect of the extinction coefficient on the extraction efficiency of ZnS:Mn thin-film phosphors grown on two-dimensional nanorod substrates

We have studied the effects of varying the extinction coefficient of two-dimensional (2D) nanorod-assisted ZnS:Mn thin-film phosphors on their photoluminescence extraction efficiency. The finite-difference time-domain method was employed for the design and analysis of 2D nanorod-assisted thin-film phosphors. Using a nanorod pattern with a depth of 200 nm, a lattice constant of 600 nm, and a radius of 180 nm, the extraction efficiency of a transparent ZnS:Mn thin-film phosphor is predicted theoretically to increase by a factor of more than ∼9.1. Experiments have shown that incorporation of the 2D SiO2 nanorod layer only improves the light extraction efficiency over that of a conventional ZnS:Mn thin-film phosphor by a factor of ∼4.0. We discuss the reasons for this mismatch between the theoretical and experimental extraction efficiencies, in order to further improve the extraction efficiency of ZnS-based thin-film phosphors.

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.

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).

Characterization of compositional variation and luminescence of ZnGa 2O 4:Mn thin film phosphor

ZnGa 2O 4:Mn thin film phosphors were prepared on ITO/glass by rf magnetron reactive sputtering. The effects of the oxygen partial pressure in sputtering and annealing atmospheres on crystallinity, compositional variations, and luminescent properties of thin films were investigated. Atomic ratio of Ga/Zn in films strongly depended on the postannealing conditions, as well as the oxygen partial pressure in sputtering gas during sputtering, and accordingly affected the luminous properties.

Luminescent characteristics of Se-doped ZnGa2O4:Mn thin film phosphors grown by pulsed laser ablation

Mn-doped ZnGa2O4−xSex (x=0.00, 0.025, 0.05, 0.075 and 0.10) thin film phosphors have been grown using pulsed laser ablation under various growth conditions. Structural characterization was carried out on a series of ZnGa2O4−xSex:Mn2+ films grown on MgO(100) substrates using Zn-rich ceramic targets. Zn-rich ceramic targets were prepared to compensate for loss of vaporization of Zn during deposition. The oxygen pressure was fixed at 100 mTorr and the substrate temperatures were varied from 500 to 700 °C. Luminescence results indicated that MgO (100) is a promising substrate for the growth of high-quality of ZnGa2O4−xSex:Mn2+ films. The crystallinity and surface roughness of the ZnGa2O4−xSex:Mn2+ films are highly dependent on the growth conditions, in particular on the substrate temperature and composition ratio of targets. The crystallinity of the films improved with Se doping. Incorporation of Se into the ZnGa2O4 lattice led to a remarkable increase of photoluminescence. The highest green emission intensity was observed with ZnGa2O3.925Se0.075:Mn2+ films whose brightness was increased by a factor of 3.1 in comparison with that of ZnGa2O4:Mn2+ films. This phosphor is promising for application in flat panel displays.

Enhancement of cathodoluminescence of ZnGa2O4:Mn thin-film phosphor by energetic particle bombardment

Enhancement of cathodoluminescence of manganese-activated zinc gallate (ZnGa2O4:Mn) thin-film phosphor by energetic particle bombardment is reported. The ZnGa2O4:Mn thin-film phosphor was grown at room temperature on silicon (100) substrates by rf magnetron sputter deposition from a 2 mol % Mn-doped ZnGa2O4 target in an oxygen–argon mixture. After the deposition, the films were annealed at 800 °C for 3 h in air. The influence of energetic particle bombardment on cathodoluminescent (CL) properties of ZnGa2O4:Mn films was investigated by varying a gas pressure during the sputter growth. Our results have shown that CL brightness from ZnGa2O4:Mn films grown at 2 mTorr was more than eight times higher than that of films grown at 20 mTorr. The remarkable improvement in CL brightness from ZnGa2O4:Mn films grown at a low pressure is presumably due to the energetic particle bombardment of the growing film surface yielding a densely packed microstructure and a better crystalline quality with a highly [110]-textured structure.

Effects of substrates and heat treatment on growing behavior and luminescent characteristics of ZnGa2O4:Mn thin film

ZnGa2O4:Mn phosphor thin films were deposited on ZnO:Ga/glass, ZnO:Al/glass, ZnO/ITO/glass, and ITO/glass by rf magnetron sputtering. Effects of substrates and heat treatment on the structural and luminescent properties were investigated. The surface morphology, growing behavior, and luminescent properties of thin films depend on the crystallinity of the substrates. Thin film phosphors were heat-treated in a N2+vacuum, vacuum (∼10−3 Torr), and air atmosphere, respectively. The annealing conditions did not affect the surface morphology and crystallinity of the films. However, the Ga/Zn atomic ratios and luminescent characteristics were dependent on these conditions.

High-luminance thin-film electroluminescent devices using Y 2O 3:Mn phosphor

Mn-activated yttria (Y 2O 3:Mn) phosphor thin films, consisting of monoclinic Y 2O 3 host material, were prepared by r.f. magnetron sputtering. High-luminance yellow photoluminescence and electroluminescence emissions were obtained using Y 2O 3:Mn thin films prepared with a Mn content of 2 at.% at a substrate temperature of approximately 350 °C and postannealed at approximately 1020 °C in an Ar atmosphere. The obtainable electroluminescent (EL) characteristics of Y 2O 3:Mn thin-film EL (TFEL) devices were mainly related to the crystallinity of the thin-film emitting layers used in the devices. The obtained maximum luminance and luminous efficiency increased as the crystallinity of the monoclinic Y 2O 3:Mn thin-film emitting layers was improved. A luminance of 5110 cd/m 2 was obtained in a 1 kHz-driven TFEL device fabricated with monoclinic Y 2O 3:Mn phosphor thin film prepared under the optimized conditions.

Enhanced green emission in ZnGa2O4:Mn thin film phosphors by Se doping

Mn-doped ZnGa2O4−xSex thin film phosphors have been grown using pulsed-laser ablation under various growth conditions. The structural characterization was carried out on a series of ZnGa2O4−xSex:Mn2+ films grown on MgO(100) substrates using Zn-rich ceramic targets. Zn-rich ceramic targets have been prepared to compensate the vaporization loss of Zn. The oxygen pressure was fixed at 100 mTorr and substrate temperatures were varied from 500 to 700 °C. The luminescence results indicated that MgO (100) is one of the most promised substrates for the growth of high-quality ZnGa2O4−xSex:Mn2+ films. In particular, the incorporation of Se into the ZnGa2O4 lattice induced a remarkable increase of photoluminescence. The highest green emission intensity was observed with ZnGa2O3.925Se0.075:Mn2+ films whose brightness was increased by a factor of 3.1 in comparison with that of ZnGa2O4:Mn2+ films. This phosphor may promise for application to the flat panel displays.

Microstructural characterization of radio frequency magnetron sputter-deposited Ga2O3:Mn phosphor thin films

Ga 2 O 3 : Mn phosphor thin films have been prepared by radio frequency (rf) magnetron sputtering of a 2 mol % Mn-doped Ga2O3 target in an oxygen–argon mixture atmosphere. The deposition rate of the films decreased from 14 to 12 Å/min when the working gas pressure decreased from 30 to 2 mTorr, while the O/Ga ratio of ∼1.5 did not systematically depend on the pressure. Films deposited at higher working gas pressure had a porous columnar structure containing a large void, typical of zone 1 growth, while films produced at lower pressure had relatively smooth surfaces with a dense structure, typical of zone T growth. The results obtained are consistent with energetic particle bombardment of the depositing films promoting surface adatom mobility at lower working gas pressure. Films deposited at working gas pressures⩾15 mTorr showed a random orientation after a postdeposition anneal at 1000 °C. Below 15 mTorr, annealed films were strongly textured with the (111) and (020) planes parallel to the surface.

9.2: High‐Luminance Electroluminescence from {(Y2O3)1−x‐(Geo2)x} Phosphor Thin Film

AbstractHigh‐luminance yellow emissions were obtained in TFEL devices using newly developed {(Y2O3)1−X‐(GeO2)X}: Mn phosphor thin films prepared with a composition (X) of 0 to 0.92. Luminances of 7440 and 7700 cd/m2 were obtained in TFEL devices using a Y2O3: Mn and a {(Y2O3)0.6‐(GeO2)0.4}: Mn thin film, respectively: driving voltage at 1 kHz.

Electroluminescent Oxide Phosphor Thin Films Prepared by a Sol-gel Process

ABSTRACTGa2O3:Mn and (Ga2O3-SnO2):Eu thin films have been prepared by a sol-gel process. High luminance emissions were obtained in TFEL devices: green using a Ga2O3:Mn and red using a Ga2O3:Eu or a SnO2:Eu thin-film emitting layer. These sol-gel prepared devices were produced without using any vacuum processes and always exhibited higher luminances than equivalent devices prepared by r.f. magnetron sputtering: 40, 309 and above 1000 cd/m2 using SnO2:Eu, Ga2O3:Eu and Ga2O3:Mn phosphor thin films, respectively, in TFEL devices prepared by the sol-gel process and driven at 1kHz.