Papers by Keyword: Green Emission

Abstract: Phosphate glasses, characterized by their high thermal expansion coefficients, low melting temperatures, and excellent transparency across a wide spectral range are ideal for optical applications. In particular, phosphate-based glasses are effective hosts for rare earth ions due to their ability to incorporate heavy metal oxides while retaining an amorphous structure. Building on these properties, a series of (50-x)P₂O₅-20ZnO-15SrO-15Li₂O-xSm₂O₃ where x = 0, 0.5, 1.0, 1.5 and 2.0 mol% were prepared by using melt-quenching technique to explore the effects of Sm₂O₃ concentration on structural and optical properties. This study addresses the challenge of optimizing Sm₂O₃ concentration in phosphate glasses to enhance properties such as density, structural stability and emission intensity for efficient green-orange-red luminescence. XRD spectra confirmed the amorphous nature and indicate that samples are glass. The physical measurements indicated that density and molar volume of increased with Sm₂O₃ concentration from 0 to 1.5 mol% and decreased when Sm₂O₃ further increase to 2.0 mol%. FTIR spectra revealed seven spectra bands within range 650 to 1500 nm. The emission spectra were recorded under 402 nm excitation, emits strong emission band at 562, 593, 644 and 705 nm which correspond to excitation from ⁶H_5/2 ground state. The optimal emission intensity was observed at 1.0 mol% Sm₂O₃, highlighting the potential of these glasses for applications in green-orange-red emitting materials.

Abstract: Abstract. In an effort to successfully fabricate InGaN-based for green emitting devices on patterned sapphire substrate, the indium composition in In_xGa_1-xN/GaN multi-quantum well structure is crucial because lower indium composition will shift the wavelength towards ultraviolet region. In this study, 5 micrometre of undoped GaN epilayer was deposited as a buffer layer prior to the growth structure. 6 pairs of InGaN/GaN multi-quantum well structure grown by metal organic chemical vapour deposition (MOCVD). In this research, the indium to gallium composition ratio was 9:1. The crystal and optical properties of the samples were characterized using field effect atomic force microscopy, high resolution x-ray diffraction, and photoluminescence spectroscopy.

Abstract: Ti-doped SrLaAlO₄ green-emitting phosphor was synthesized via solid-state reactions in air and N₂ atmosphere. Sample heated in air showed no emission, however, sample heated in N₂ showed broad green emission around 492 nm and broad near-infrared emission around 950 nm by 321 nm near-ultraviolet excitation. XPS measurement and UV-Vis diffuse reflectance spectra suggest that Ti in the sample was reduced to Ti³⁺ state when the sample was heated in N₂. Possible emission mechanism of the sample can be explained as O^2-–Ti³⁺ charge-transfer transition.

Abstract: Zinc oxide (ZnO) films are grown by two methods-pulse laser deposition (PLD) and radio-frequency magnetron sputtering at various oxygen ambiences. Based on x-ray diffraction spectra and photoluminescence (PL) spectra, effects of the oxygen ambient on the grain size and emission properties of the ZnO films are investigated. For the samples grown by PLD, the PL spectrum consists of a single ultraviolet (UV) peak except one sample deposited at a low O₂ pressure of 7 Pa. All the samples grown by sputtering have both a UV peak and a green emission. The disappearance of the green emission of the PLD samples is ascribed to deficiency of oxygen vacancies (O_v), and the green emission of the sample grown by sputtering is due to abundant O_v. The intensity change of the UV emission is due to the variation of exciton emission, which is related to grain size and stoichiometry. The position shifting of the UV peak of the PLD samples originates from the Zn interstitial-related degradation of stoichiometry.

Abstract: Undoped and Cr doped ZnS nanoparticles with Cr concentrations of 3.0 at.% were prepared by a chemical co-precipitation method for the fist time, using 2-Mercaptoethanol as the capping agent and annealed the synthesized particles at 600°C for 3h in air. The effect of annealing on morphological, structural and optical properties of ZnS and ZnS:Cr have been studied and compared with as prepared samples. EDAX measurements confirmed the presence of Cr in the ZnS lattice and it also confirms the conversion of ZnS into ZnO after annealed at 600 0C/3h. Surface morphologies of all samples were characterized using scanning electron microscopy (SEM). XRD spectra of as synthesized nanoparticles of ZnS and ZnS:Cr exhibited cubic phase. After annealing, the cubic phase is transformed into hexagonal phase. The particle sizes of the ZnS:Cr powders were increased from 5 to 30 nm when the powders were annealed at 600°C. A stable blue emission peak at 445 nm is observed from the as prepared samples (pure ZnS and Cr doped ZnS) but annealed at 600 0C the PL peaked at 500 nm for pure ZnS and Cr doped ZnS nanoparticles exhibited PL peak at 500 nm as well as 654 nm. The emission intensity decreased in annealed particles compared to as synthesized samples.