Distribution Of Luminescence Centers Research Articles

Advanced Synthesis and Characterization of CdO/CdS/ZnO Heterostructures for Solar Energy Applications.

This study introduces an innovative method for synthesizing Cadmium Oxide /Cadmium Sulfide/Zinc Oxide heterostructures (CdO/CdS/ZnO), emphasizing their potential application in solar energy. Utilizing a combination of electrochemical deposition and oxygen annealing, the research provides a thorough analysis of the heterostructures through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. The findings reveal a complex surface morphology and a composite structure with significant contributions from hexagonal CdS and cubic CdO phases. The study highlights the uniformity in the distribution of luminescent centers and the crystalline quality of the heterostructures, which is evident from the PL analysis. The redshift observed in the emission peak and the additional peaks in the excitation spectrum indicate intricate optical properties influenced by various factors, including quantum confinement and lattice strain. The research demonstrates these heterostructures' potential in enhancing solar cells' efficiency and applicability in optoelectronic devices. This comprehensive characterization and analysis pave the way for future optimization and application in efficient and sustainable solar energy solutions.

Mapping the Origins of Luminescence in ZnO Nanowires by STEM-CL.

In semiconductor nanowires, understanding both the sources of luminescence (excitonic recombination, defects, etc.) and the distribution of luminescent centers (be they uniformly distributed, or concentrated at structural defects or at the surface) is important for synthesis and applications. We develop scanning transmission electron microscopy-cathodoluminescence (STEM-CL) measurements, allowing the structure and cathodoluminescence (CL) of single ZnO nanowires to be mapped at high resolution. Using a CL pixel resolution of 10 nm, variations of the CL spectra within such nanowires in the direction perpendicular to the nanowire growth axis are identified for the first time. By comparing the local CL spectra with the bulk photoluminescence spectra, the CL spectral features are assigned to internal and surface defect structures. Hyperspectral CL maps are deconvolved to enable characteristic spectral features to be spatially correlated with structural features within single nanowires. We have used these maps to show that the spatial distribution of these defects correlates well with regions that show an increased rate of nonradiative transitions.

Distribution of luminescence centers in the bulk of undoped, Fe-doped, and Cr-doped CVD ZnSe polycrystals studied by two-photon confocal microscopy

Edge and defective-impurity luminescence in polycrystalline CVD ZnSe has been studied in the range 0.46–0.73 μm by two-photon confocal microscopy. We have obtained luminescence intensity distribution maps for undoped, iron-doped, and chromium-doped ZnSe samples at depths of up to 1 mm with a spatial resolution of a few microns. It has been shown that crystal regions with low dopant concentrations contain centers that luminesce in the ranges 520–580 and >670 nm. The parts of the crystals with high iron and chromium concentrations contain centers that suppress the edge and defective-impurity (520–580 nm) luminescence. We discuss the nature of these centers and demonstrate the possibility of assessing the luminescence characteristics of grain boundaries in CVD ZnSe.

Distribution of luminescent centers in Ce3+-ion doped amorphous stoichiometric glass BaO–2SiO2 and dedicated glass ceramics

Distribution of luminescent centers in Ce3+-ion doped amorphous stoichiometric glass BaO–2SiO2 and dedicated glass ceramics

Distribution of luminescent centers in Ce3+-ion doped amorphous stoichiometric glass BaO–2SiO2 and dedicated glass ceramics

We investigated the influence of crystallization conditions on the luminescent properties of Ce3+-ions doped stoichiometric glass BaO–2SiO2 at the different stages of its transformation from amorphous phase to glass ceramics. The samples were investigated by confocal luminescence spectroscopy. It was found that the luminescent properties of the cerium-doped glass and the glassceramics composite consisting of BaSi2O5 crystallites and residual glass are quite similar, though the luminescence band in the composites are slightly redshifted and narrower.

Distribution of Luminescence Centers and Trapping Centers in Ba13Al22Si10O66: Eu2+, Tm3+

Distribution of Luminescence Centers and Trapping Centers in Ba13Al22Si10O66: Eu2+, Tm3+

Time-Resolved Spectroscopic Studies of the Photoluminescence of Nanoporous Silicon: Effects of Lewis Acid/Base Exposure

Visible light emission emanating from nanostructured porous silicon is sensitive to adsorption of a number of small molecules, suggesting its utility as a chemical sensor. In this work we investigate the mechanistic origin of the diminution of the luminescence by n-propyl amine adsorption and restoration by trifluoroacetic acid, most sensitively by an examination of the changes in observed lifetime of the porous Si luminescence. This is quantified in terms of a stretched exponential model that is consistent with a distribution of luminescent centers in this nanophase material.

Distribution of luminescent centers in electroluminescent SrS:Ce films prepared by post-annealing in H 2S

SrS:Ce films were investigated by secondary ion mass spectrometry (SIMS) in order to examine the luminescent center distribution in the phosphor before and after annealing. Cerium was accumulated near the interfaces between the phosphor and insulating layers, and this accumulation was most extensive in the phosphor annealed in H 2S. The Ce accumulation is found to shift the electroluminescent (EL) emission spectra to a longer wavelength. It is also found that crystallinity improvement of the SrS phosphor by annealing in H 2S causes Ce accumulation and the presence of oxygen enhances the Ce accumulation.

The galvanoluminescence spectra of porous oxide layers formed by aluminum anodization in oxalic acid

This paper presents the result of the most recent investigations of the galvanoluminescence (GL) spectra of porous oxide layers formed by aluminum anodization in oxalic acid. A new experimental procedure for GL spectra recording was established. This method can be easily applied to GL spectral measurements on porous anodic films. The spectra were recorded for different values of temperature and anodization current density. Two spectral peaks at 446 and 485 nm, respectively, were observed, indicating the probable existence of two kinds of luminescence centers incorporated in the oxide. In addition, it was discovered that the intensity ratio for the two peaks changes with the current density. Those GL measurements, with further photoluminescent (PL) measurements should lead to a definitive explanation of the GL phenomena, as well as of the nature and distribution of luminescent centers in both porous and barrier oxide films on aluminum.

Spatial Distribution of Luminescent Centers in Organometallic Vapor Phase Epitaxy Grown ZnxCdl−xSe/InP (001)

AbstractZincblende ZnxCdl−xSe alloys were grown on (001) InP by organometallic vapor phase epitaxy (OMVPE) using various VI / H precursor flow ratios, ranging from 0.95 to 12, at a temperature of 420°C. Spatial distribution of luminescent centers in the epilayer was characterized by cathodoluminescence (CL) spectroscopy and imaging. Both near band-gap (NBE) and deep level (DLE) emissions were observed in the spectra, with the width of the NBE peak increases with the VI / II flow ratio. Monochromatic CL images showed that the broadening of the NBE peak has its origin in the spatial inhomogeneity of the luminescent centers of the epilayer. Extended defects responsible for the DLE was only found in pyramidal hillocks seen in the CL images. The density of these defects was found to increase with the VI / I1 flow ratio.

Real color cathodoluminescence scanning electron microscopy—A new effective method for study of SiC materials and devices

AbstractColor cathodoluminescence scanning electron microscopy (CCL‐SEM) studies prove the correctness of available information concerning space distribution of luminescence centers in SiC layers. Established facts may be applied for investigation of the polytypism, space distribution of impurities, and native defects induced during growth by high‐energy particles radiation or by diffusion, as well as by the mechanisms of crystal formation. This paper presents a short survey of diagnostic availability of the CCL‐SEM technique for inspection of the SiC materials and devices.