Papers by Keyword: Photoluminescence Spectra

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Authors: Ya Fen Wu, Jiunn Chyi Lee
Abstract: We investigate the effect of carrier dynamics on the temperature dependence of photoluminescence spectra from InAs/GaAs quantum dot heterostructures with different dot size uniformity. Intersublevel relaxation lifetimes and carrier transferring mechanisms are simulated using a model based on carriers relaxing and thermal emission of each discrete energy level in the quantum dot system. Calculated relaxation lifetimes are decreasing with temperature and have larger values for sample with lower dot size uniformity. In the quantitative discussion of carrier dynamics, the influence of thermal redistribution on carriers relaxing process of quantum dot system is demonstrated by our model.
Authors: N. Bošnjaković, S. Uskoković-Marković, U.B. Mioč
Authors: Kevin Alvin Eswar, F.S. Husairi, Azlinda Ab Aziz, M. Rusop, Saifollah Abdullah
Abstract: Zinc acetate as starting material along with diethanolamine as a stabilizer and isopropyl as a solvent were used in ZnO precursor preparation while p-type silicon was used as a substrate in this work. ZnO thin films were deposited on silicon wafer by spin coating deposition method. Samples were annealed at different temperature in range 500°C to 800°C. In other to study the surface morphology of thin film, Field Emission Scanning Microscopic (FESEM) was employed for every sample. It was found that, the thin films are composed by ZnO nanoparticles with size of about 18.3 nm to 32.95 nm. Topology of ZnO thin films was characterized by atomic force microscopy (AFM). In other to study the photoluminescence properties, 325 nm of xenon lamp was used as sources within range of 350 nm and 600 nm. It is found that two peaks are appears for the entire sample with the high intensity peak at 373 nm originated from the contribution of near band edge recombination from ZnO and low intensity at 573 nm was corresponding to ZnO defects.
Authors: Karim Zare, Nasibeh Molahasani, Nazanin Farhadyar, M.S. Sadjadi
Abstract: In this paper, we report enhanced blue green emission of hexagonal shaped ZnO nanorods (NRS) grown via a simple hydrothermal method and silica coated then by using tetraethoxysilane (TEOS). The composition and structural characteristic of the prepared samples were studied by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy and Energy Dispersive X-ray analysis (FESEM-EDAX). The results revealed well crystallized hexagonal structure possessing a perfect and ideal growth habits of wurtzite zinc oxide grown along the [00 direction in preference in both the cases. Optical properties and quality of the prepared ZnO and silica coated ZnO nanorods were examined by UV-visible and FTIR spectroscopy. Photoluminescence (PL) spectra were used to study ZnO and silica coated ZnO nanorod electronic structure, which resulted in an obvious enhanced blue-green emission for ZnO nanorod and an intense red emission with a very low UV intensity for the silica coated nanorods. Appearance of intense red emission seems to be very promising since and it could favor more reliable fluorescence sensing in drug delivery fluorescent detection with a minor UV emission.
Authors: Andriy P. Luchechko, Igor I. Syvorotka, Yaroslav Zakharko, I.M. Syvorotka
Abstract: Abstract. Excitation and emission spectra under UV and X-ray excitations, as well as the luminescence decay kinetics of Gd3Ga5O12: Bi single crystalline films were studied. The emission spectra observed in the spectral region 350-700 nm at room temperature consist two elementary bands peaked at 446 and 521 nm. The influence of growth conditions on the luminescent properties of Gd3Ga5O12: Bi3+ garnet have been revealed. The integral and relative intensities of the luminescence bands depend on the excitation wavelength. The Bi3+ decay curves of all investigated films show non-single exponential behavior at room temperature.
Authors: Arthur Medvid, Y. Hatanaka, V.G. Litovchenko, L. Fedorenko, D. Korbutjak, S. Krylyuk
Authors: Dmytro Gnatyuk, Tetsu Ito, Toru Aoki
Abstract: Low temperature photoluminescence (PL) of high-resistivity detector-grade Cl-compensated CdTe semiconductor crystals subjected to irradiation with nanosecond (τ = 7 ns) laser pulses of the second harmonic (λ = 532 nm) of a YAG:Nd laser is studied. Irradiation of CdTe crystals within the certain range of laser pulse energy densities results in a relative decrease in the emission intensity in both the deep energy level and edge regions and an increase in the exciton band intensity in the PL spectra. The evolution of the PL spectra depending on laser energy density, excitation level and temperature under excitation are analyzed. Laser-stimulated transformation of the point defect structure of the CdTe surface region and mechanisms of laser-induced defect formation are discussed. The optimal regimes of laser processing have been obtained which result in the minimum ratio of the defect and exciton bands that is an evidence of an increase in the structural perfection of the irradiated crystals.
Authors: Xiao Lan Sun, Yan Hua Dong, Chao Li, Xiao Hong Liu
Abstract: The size of quantum dots (QDs), their shape, and ordered arrays have significant impact on electrical and optical properties of the QDs. We synthesized near-infrared-emitting PbSe QDs via an oil phase method in a noncoordinating solvent. Transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the samples. Sizes of the QDs were accurately controlled from 4.2 nm to 10.2 nm through control of the reaction time as well as the growth temperature. The PL spectra showed strong size dependence, which is large red shift with increasing size of the QDs.
Authors: Kevin Alvin Eswar, F.S. Husairi, Azlinda Ab Aziz, Mohamad Rusop, Saifollah Abdullah
Abstract: ZnO thin film was successfully deposited on different substrate by sol-gel spin coating. Zinc acetate dihydrates, diethanolamine and isopropyl were used as starting material, stabilizer and solvent respectively. Two different substrate used in this work are p-type silicon wafer and porous silicon. Porous silicon was prepared by electrochemical etching. In order to study the surface morphology, field emission scanning electron microscopy (FESEM) was employed. It is found that, ZnO thin film was composed by ZnO nanoparticles. The averages size ZnO nanoparticle is 23.5 nm on silicon and 17.76 nm on porous silicon. Based on Atomic Force Microscopy (AFM) topology analysis, surface of ZnO thin films on porous silicon was rougher compared to ZnO thin films on silicon due to substrate surface effect. Photoluminescence spectra shows two peaks are appear for ZnO thin film on silicon and three peaks are appear for ZnO thin film on porous silicon. PL spectra peaks of ZnO thin film on silicon are correspond to ZnO and ZnO native defects while peaks of PL spectra on porous silicon are corresponds to ZnO, ZnO native defects and porous silicon.
Authors: Jing Liu, Ming Ying, Yu Ling Tan, Bo Xi
Abstract: ZnS quantum dots (ZnS QDs) synthesized in aqueous solution is easy to gather a mass, which always results in low quantum yield. So, in this study benzene was used as reaction medium in which ZnS QDs with different hues were synthesized, and the hues of ZnS QDs were depend on the molar ratio of Zn (CH3COO)2 and Na2S·9H2O. The results show the emission spectra of ZnS QDs shifts with the change of the precursor molar ratio but the absorption peak at 310nm is not. The emission peaks centered at 430nm and 580nm at higher molar ratio [Zn2+]/[S2-] with blue-violet emitting phosphors; but, ZnS QDs synthesized at higher molar ratio [S2-]/[Zn2+] have orange-red emission at 580nm only. The X-ray diffraction analysis shows the crystallinity of ZnS QDs is better at [Zn2+]/[S2-]=1:10, which are typical zinc blend with nanorod structure.
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