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Silicon-rich hydrogenated amorphous silicon nitride (a-SiNx:H) films were grown by plasma enhanced chemical vapor deposition (PECVD) with different r=NH3/SiH4 gas flow ratios. The optical absorption characteristics were analyzed by Fourier transform infrared (FTIR) and UV-visible transmittance spectroscopies. The recombination properties were investigated via photoluminescence (PL) measurements. As r was increased from 2 to 9, the PL emission color could be adjusted from red to blue with the emission intensity high enough to be perceived by naked eye at room temperature. The behaviors of the PL peak energy and the PL band broadness with respect to the optical constants were discussed in the frame of electron-phonon coupling and band tail recombination models. A semiquantitative analysis supported the band tail recombination model, where the recombination was found to be favored when the carriers thermalize to an energy level at which the band tail density of states (DOS) reduces to some fraction of the relevant band edge DOS. For the PL efficiency comparison of the samples with different nitrogen contents, the PL intensity was corrected for the absorbed intensity fraction of the incident PL excitation source. The resulted correlation between the PL efficiency and the subgap absorption tail width further supported the band tail recombination model. 相似文献
54.
O. Aissaoui L. Bechiri M. Benabdeslem A. Amara K. Djessas 《Journal of luminescence》2011,131(1):109-113
Polycrystalline CuIn1−xGaxTe2 bulk films were synthesized by reacting, in stoichiometric proportions, high purity Cu, In, Ga and Te in a vacuum sealed quartz ampoule. The phase structure and composition of the bulk films were analysed by X-ray diffraction and energy-dispersive X-ray analysis, respectively. The bulk samples, of p-type conductivity, are found to be near-stoichiometric, polycrystalline, with tetragonal chalcopyrite structure, predominantly oriented along a direction perpendicular to the (1 1 2) plane. Photoluminescence spectra were recorded at 7 K and 700 mW to characterize the defects and the structural quality. The main peak as a function of composition has been studied. 相似文献
55.
The optical properties of a silver-doped phosphate glass have been monitored during thermal processing at several fixed temperatures by in situ optical microspectroscopy. Silver nanoparticle (NP) formation and growth processes were assessed by analysis of surface plasmon resonance spectral features. Nucleation and growth processes were distinguished, which appeared temperature and time dependent. While nucleation was favored at low temperatures, relatively high temperatures promoted NP growth by silver diffusion. Photoluminescence spectra acquired along with optical absorption data indicated a continuous reduction of Ag+-Ag0 pairs concomitant with NP precipitation, suggesting their role as nucleation centers. The work of Ag NP formation and the activation energy for silver diffusion were estimated. 相似文献
56.
The optical properties of ZnO grown on (1 0 0) GaAs substrate using metalorganic chemical vapor deposition are investigated by photoluminescence (PL) spectroscopy. Postgrowth annealing in nitrogen and oxygen was performed for different times and temperatures in order to incorporate As from the substrate into the ZnO thin films. The PL spectra of the samples annealed in different ambients reveal that the effect of As diffusion into the ZnO thin films is more pronounced when the annealing is performed in oxygen at 550 °C. The 11 K PL spectra show the appearance of a transition at ∼3.35 eV after annealing in oxygen at 550 °C for 1 h. A further increase in the annealing temperature leads to the disappearance of this line, while for annealing times longer than 2 h at 550 °C, it is no longer prominent. The increase in intensity of this new transition is also accompanied by the enhancement of radiative centers related to structural defects, such as the stacking fault-related transition at 3.31 eV and the Y-line. Temperature dependent PL illustrates the excitonic nature of the new transition at ∼3.35 eV, which is therefore assigned to (A0, X) transition, where the acceptor is possibly the 2VZn-AsZn complex, with an activation energy EA in the range of 160-240 meV. Furthermore, the enhancement of the radiative centers related to structural defects is regarded as evidence that As atoms tend to segregate in the vicinity of structural defects to relieve local strain. 相似文献
57.
Shitong Cui Yanfen Wu Yao Liu Qingwen Guan Yida Zhang Yilin Zhang Song Luo Meng Xu Juncheng Wang 《中国化学快报》2020,31(2):487-493
Carbon dots(CDs) with multi-color emissive properties and a high photoluminescent quantum yield(PLQY) have attracted great attention recently due to their potential applications in chemical,environmental,biological and photo-electronic fields.Solvent-dependent effect in photoluminescence provides a facial and effective approach to tune the emission of CDs.In this study,green emissive nitrogen-doped carbon dots(N-CDs) are synthesized from p-hydroquinone and ethylenediamine through a simple hydrothermal method.The as-prepared N-CDs possess a robust excitation-independent green luminescence and a high PLQY of up to 15.9%.Further spectroscopic characterization indicates that the high PLQY is achieved by the balance of nitrogen doping states and the surface passivation extent in CDs.The N-CDs also exhibit solvent-dependent multi-color emissive property and distinct PLQY in different solvents(the maximum can reach up to 25.3%).Furthermore,the as-prepared N-CDs are applied as fluorescence probes to detect acetone and H2O2 in water.This method has exhibited a low detection limit of acetone(less than 0.1 %) and a quick and linear response to the H_2O_2 with the concentration from 0 to 120 μmol/L.This work broadens the knowledge of applying CDs as probes in the bio and chemical sensing fields. 相似文献
58.
《Arabian Journal of Chemistry》2020,13(6):5750-5764
Herein, we describe the growth and morphology of well-defined dyed crystals of KH2PO4 (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping. 相似文献
59.
《Arabian Journal of Chemistry》2020,13(6):5593-5604
The present study aims to introduce three known and three new stable polycyclic aromatic compounds synthesized. With MALDI-Mass, 1H and 13C NMR spectroscopy, all new compounds were characterized. In the DMF solution were carried out the electrochemical and photophysical properties of the polyaromatic compounds. The compounds are highly fluorescent showing green-red emission when excited at one single wavelength. For the compound 3, it was shown that the highest Stokes Shift (191 nm) appeared which may be due to the excited state energy transfer. The compounds also indicated the blue-orange region of the electromagnetic spectrum strong emission bands. Additionally, compounds 1, 3, 4, and 5 were investigated for their in vitro cytotoxic activities against PC-3 prostate cancer cells, L-929 non-cancerous cells, and MDA-MB-231 breast cancer for 24 h, 48 h and 72 h. The results obtained from the experiment demonstrated that compounds had different cytotoxic activity against cell lines. Compound 3 was indicated to be inactive against L-929 cells and MDA-MB-231 cancer cells, whereas compounds 1, 4 and 5 indicated a dose and time-dependent cytotoxic activity against PC-3, MDA-MB-231, and L-929 cell lines. It was found that the most sensitive cells to compound 5 were MDA-MB-231 human breast cancer cells. Additionally, it became clear that compounds 1 and 3 had significant selectivity for human PC-3 prostate cancer cells, and compounds 1, 4 and 5 had considerable selectivity for human MDA-MB-231 breast cancer cells. Also, the quantum chemical examinations of six organic compounds were conducted at the B3LYP/6-31G level in the gas phase and water. According to calculated results, compound 5 was found to be the best candidate for NLO applications. 相似文献
60.
《Arabian Journal of Chemistry》2020,13(2):4126-4133
Three biscoumarin dyes bridged by polycyclic aromatic bridges (anthracen, pyrene and dibenzo[g,p]chrysene) were prepared as the emissive materials for the application of organic light-emitting devices. The relationship between their structures, photophysical properties, electrochemical properties and performances of organic light-emitting devices are described. The multilayered doped devices with a configuration of ITO/NPB (20 nm)/TBADN: biscoumarin compound (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method. All the devices showed green emission with high electroluminescent efficiencies. Especially, the device based on the compound containing pyrene as a bridge group at 7% doping concentration showed the best performance with a maximum brightness of 10552 cd/m2, maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency (EQE) of 2.35%. 相似文献