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71.
Characteristics of charge traps in TlInS2 single crystals are investigated by the use of thermally stimulated current (TSC) technique. The TSC spectra of the sample from 80 K to 300 K are recorded at a constant heating rate. The spectra reveal that there are several trapping levels associated with the complex structure of overlapping peaks. The experimental results indicate that the traps in TlInS2 associated with the spectra in the measuring range of temperature obey the monomolecular (first order) kinetics. Thus, the spectra are resolved into first order shaped peaks by the use of computerized best fit procedure. The trapping parameters; such as the energy depth, temperature dependent frequency factor and capture cross section, together with concentrations of the corresponding six discrete levels are computed. These centers all having low capture cross sections with strong temperature dependence are found to be at the energies of 0.11 eV, 0.22 eV, 0.25 eV, 0.26 eV, 0.29 eV and 0.30 eV with high concentrations of 6.6 × 1016, 2.0 × 1017, 3.3 × 1017, 9.6 × 1016, 2.3 × 1017 and 4.0 × 1017 cm?3, respectively. 相似文献
72.
B. P. Chandra R. K. Goutam V. K. Chandra D. S. Raghuwanshi A. K. Luka R. N. Baghel 《辐射效应与固体损伤》2013,168(12):907-919
Mechanoluminescence (ML) emission from coloured alkali halide crystals takes place during their elastic and plastic deformation. The ML emission during the elastic deformation occurs due to the mechanical interaction between dislocation segments and F-centres, and the ML emission during the plastic deformation takes place due to the mechanical interaction between the moving dislocations and F-centres. In the elastic region, the ML intensity increases linearly with the strain or deformation time, and in this case, the saturation region could not be observed because of the beginning of the plastic deformation before the start of the saturation in the ML intensity. In the plastic region, initially the ML intensity also increases linearly with the strain or deformation time, and later on, it attains a saturation value for large deformation. When the deformation is stopped, initially the ML intensity decreases at a fast rate; later on, it decreases at a slow rate. The decay time for the fast decrease of the ML intensity gives the relaxation time of dislocation segments or pinning time of the dislocations, and the decay time of the slow decrease of the ML intensity gives the diffusion time of holes in the crystals. The saturation value of the ML intensity increases linearly with the strain rate and also with the density of F-centres in the crystals. Initially, the saturation value of the ML intensity increases with increasing temperature, and for higher temperatures the ML intensity decreases with increasing temperature. Therefore, the ML intensity is optimum for a particular temperature of the crystals. From the ML measurements, the relaxation time of dislocation segments, pinning time of dislocations, diffusion time of holes and the energy gap between the bottom of the acceptor dislocation band and interacting F-centre level can be determined. Expressions derived for the ML induced by elastic and plastic deformation of coloured alkali halide crystals at fixed strain rates indicates that the ML intensity depends on the strain, strain rate, density of colour centres, size of crystals, temperature, luminescence efficiency, etc. A good agreement is found between the theoretical and experimental results. 相似文献
73.
Abstract Raman and XPS measurements have been performed on KI crystals irradiated near 200 K. The Raman studies show I3 ? and In ? (n = 5, 7,—) clusters which anneal together with F- and V- centres at 338 K. A small development of (I2)n aggregates occurs during the anneal; these decay near 378 K and are responsible for a broad and weak residual V-band. The I 3d 5/2 XPS peak has been fitted to reveal the presence of 3 components after low energy argon- ion bombardment. These are identified as due to normal lattice iodine, I3 ? and 15 ? whose behaviour is consistent with the Raman work. 相似文献
74.
Thermoluminescence (TL) and deformation luminescence (DL) studies in KC1 γ-irradiated at room temperature are reported. The roles that F-centres and their higher conglomerates on the one hand, and V2- and V3-centres as recombination centres on the other hand, play in these processes are specified. Two peaks at 2.5 eV and 3 eV are observed in the emission spectra of both TL and DL. The close relationship between TL and DL is confirmed. 相似文献
75.
This work is devoted to an analysis of thermal decay processes of the stable colour centres (CC) created in gadolinium gallium garnet (GGG) Gd3Ga5O12, crystals under irradiation by gamma-quanta (E=1.25 MeV, D=106 Gy). An analysis of the model of CC accumulation under irradiation as well as an isochronous heating model is presented. The decay activation energy (Δ E) for O? and F centres in GGG crystals is calculated in accordance with this model. 相似文献
76.
The optical absorption (OA) of F and Fz, centres in beta-and UV-irradiated KCl: Eu2? have been studied. The spectra measured at room temperature and during the subsequent heatings up to 600 K, were analyzed by a deconvolution procedure. The OA bands of the F and Fz centres are well described respectively by asymmetric and symmetric gaussiane with parameters that are linearly dependent on the temperature. The thermal stability of the Fz centres correlates with the low-temperature thermostimulated luminescence (TL) peaks. The stability of the F centres is determined at least by two processes. Part of the F centres is destroyed together with the Fz centres. The remaining ones are destroyed during further heating up to 470 K, correlating with the TL peak at 425 K (at heating rate of 0.1 K/s). 相似文献
77.
Abstract Mn+ ions in off-centre position along [100] have been produced in BaF2:Mn by X-irradiation at LNT. Their EPR spectra are characterized by g-2. 0107. D = 265.8·10?4cm?1. A = 122.9·10?4cm?11 and a superhyperfine structure arising from 8 surrounding F? nuclei. In the optical absorption spectrum they show up by a band at 411 nm. This behaviour is compared with the results found for SrF2:Mn. After X-irradiation at room temperature beside a different Mn+ centre two species of Mn0 appear in non-cubic position. Both interact dominantly with two F? neighbours. Possible models for these species are discussed. 相似文献
78.
V. Mussi A. Cricenti B. Jacquier T. Marolo R. M. Montereali P. Moretti 《辐射效应与固体损伤》2013,168(1-6):181-184
The measured room-temperature absorption spectra of LiF crystals implanted with 1.5 MeV He? ions at different ion doses are presented. The application of a theoretical model allowed us to give an estimation of the band intensities associated with various kinds of electronic defects and to study their dependence on the ion dose. The model also considers the contribution due to nanometric lithium colloids, whose formation starts in the dose range at which the production of colour centres saturates. 相似文献
79.
80.
We report an exact analytical solution of so-called positron diffusion trapping model. This model have been widely used for the treatment of the experimental data for defect profiling of the adjoin surface layer using the variable energy positron (VEP) beam technique. However, up to now this model could be treated only numerically with so-called VEPFIT program. The explicit form of the solutions is obtained for the realistic cases when defect profile is described by a discreet step-like function and continuous exponential-like function. Our solutions allow to derive the analytical expressions for typical positron annihilation characteristics including the positron lifetime spectrum. Latter quantity could be measured using the pulsed, slow positron beam. Our analytical results are in good coincidence with both the VEPFIT numerics and experimental data. The presented solutions are easily generalizable for defect profiles of other shapes and can be well used for much more precise treatment of above experimental data. 相似文献