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1.
The microwave absorption dielectric-spectrum technique was used to study the decay kinetics of photoelectrons in sulfur-sensitized
silver halide crystals. The time-resolution spectrum of free electrons and shallow-trapped electrons generated in sulfur-sensitized
AgBrl crystals has been obtained. The relationship of the trapping effect of sensitization centers Ag2S and sensitization time or temperature in emulsions has been duscussed. With the increase in the sensitization time and temperature,
the trap effect of sulfur sensitization centers varies from hole trap to shallow electron trap, and deep electron trap. 相似文献
2.
利用微波吸收相敏检测技术,对AgBrI-T颗粒乳剂中光电子时间行为进行了检测,并获得了自由光电子与浅束缚光电子的时间分辨谱。实验结果表明,在加入Na2S2O3相同的条件下S与S+Au增感中心所起的电子陷阱作用不同,S增感中心所起的作用为深电子陷阱,增感中心由于增加了对光电子的深束缚,从而造成自由光电子与浅束缚光电子的衰减加剧;S+Au增感中心所起的作用为浅电子陷阱,增感中心通过暂时束缚光电子有效降低了光电子与光空穴的复合,减缓了自由光电子与浅束缚光电子的衰减,可见加入KAuCl4后形成的S+Au增感中心陷阱深度要比S增感中心的陷阱深度浅。从光电子时间分辨谱的变化可以看出S与S+Au增感中心在衰减曲线的不同时域中对光电子衰减的作用表现不同。 相似文献
3.
利用微波吸收介电谱技术研究了K4Fe(CN)6浅电子陷阱掺杂剂和S+Au增感剂对立方体AgCl微晶光生电子衰减时间分辨特性的影响。结果表明,掺杂浓度为10-8~10-7 mol·mol-1Ag时,在增感之前,掺杂位置越接近表面时,光电子衰减过程会变慢,即衰减时间增加;S+Au增感后的掺杂乳剂中光电子衰减变快,说明了增感中心起深电子陷阱作用,当掺杂位置接近表面90%Ag时,光电子衰减时间突然减小,说明表面掺杂中心和增感中心可能发生了某些反应。 相似文献
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借助微波吸收介电谱检测技术,对AgCl立方体乳剂中光电子的时间行为进行了检测,同时获得了自由光电子与浅束缚光电子在不同增感条件下的时间分辨谱。实验结果表明:化学增感时由于硫加金增感中心的浅电子陷阱作用有效地抑制了空穴与光电子之间的复合,化学增感使得光电子的衰减相对未增感的减缓、衰减时间得到延长;光谱增感时由于染料J聚集体增加了卤化银晶体中添隙银离子的浓度、促进了光电子与添隙银离子之间的结合,光谱增感使得光电子的衰减相对未增感的加剧、衰减时间变短;化学与光谱共同增感使光电子的衰减时间在光谱增感的基础上得到了延长,且硫加金化学增感中心的浅电子陷阱效应在光谱增感的基础上更明显。 相似文献
6.
Experimental investigation of the time and temperature dependences of the process of relaxation of excited silver chloride has been carried out by the method of a photostimulated burst of luminescence. It is found that the relaxation process can be divided into two components, the rates of which differ by an order of magnitude. The activation energies of these processes of 0.03 and 0.06 eV correspond to the thermal ionization energies of electrons from shallow traps. Thermally activated relocalization of charges from shallow to deep traps in the process of relaxation has been revealed. The depth of a corresponding trap appeared equal to 0.17 eV. A model of a crystal phosphor has been suggested that contains five levels in the forbidden band: a hole center of recombination (luminescence), a deep electron trap, two shallow electron traps located at a depth of 0.03 and 0.06 eV from the bottom of the conductivity band, and a hole trap located at a height of 0.17 eV from the valence band top. Within the framework of this model, we can qualitatively explain the time and temperature dependences of stored light sums. We have shown the possibility of applying the method of a photostimulated burst of luminescence to investigation of the processes of relaxation of electron excitations in crystals to establish the relaxation mechanisms. 相似文献
7.
Temperature dependences of the intensity of Gudden-Pohl flashes in zinc sulfide crystals in various electric fields were measured in order to study trap ionization by electric fields. The decrease in the flash intensity from trap levels of a given depth in a certain temperature range is due to a decrease in the probability for the liberation of an electron from a trap as the temperature decreases. The temperature dependences of the flash intensity found in various electric fields are compared with the theoretical temperature dependence of the probability for electron liberation from a trap. The agreement between experimental and theoretical curves indicates that electrons are liberated from the deeper levels through ionization by an electric field involving many phonons.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 53–58, October, 1969. 相似文献
8.
Electron trapping properties at HfO_2/SiO_2 interface,studied by Kelvin probe force microscopy and theoretical analysis 下载免费PDF全文
Electron trapping properties at the HfO_2/SiO_2 interface have been measured through Kelvin Probe force microscopy,between room temperature and 90 ℃.The electron diffusion in HfO_2 shows a multiple-step process.After injection,electrons diffuse quickly toward the HfO_2/SiO_2 interface and then diffuse laterally near the interface in two sub-steps:The first is a fast diffusion through shallow trap centers and the second is a slow diffusion through deep trap centers.Evolution of contact potential difference profile in the fast lateral diffusion sub-step was simulated by solving a diffusion equation with a term describing the charge loss.In this way,the diffusion coefficient and the average life time at different temperatures were extracted.A value of 0.57 eV was calculated for the activation energy of the shallow trap centers in HfO_2. 相似文献
9.
Electrons were trapped in an electrostatic quadrupole trap with superimposed homogeneous magnetic field. The electrons were polarized by spin exchange with a polarized atomic beam. The free trapped electron polarization was converted to a change in the electron translational energy via spin-dependent inelastic collisions with the atomic beam, and the electron translational temperature was monitored. Discussed are the development of this variation of the measurement technique, characteristics of electron storage, and the electron-polarized atom inelastic interaction as a function of electron temperature and time. The method has been applied to the detection of the (g-2) resonance of free, stored electrons. 相似文献
10.
Properties of the color and emission centers induced with an electron pulse beam at temperature within 80-300 K have been studied in CsI(Tl) crystals. It has been established by optical spectrometry with time resolution that initial color centers in this crystal are only Tl0 and Vk centers, which spontaneously recombine emitting visible light at 2.25 and 2.55 eV. It has been shown that the emission decay kinetics at 80 K include two fast exponential components with decay constants 3 and 14 μs as well as slow hyperbolic component with the power index depending on the wavelength of the emitting light. The temperature effect on the emission kinetics has been studied and it has been directly proved that the emission rise stage at the temperature above 170 K is caused by the recombination of electrons, which are thermally released from single Tl0 centers, with VkA centers. The origin of scintillations in CsI(Tl) crystal is discussed in terms of the tunnel electron transitions from ground state of Tl0 centers to ground state of Vk centers at different distances from each other. 相似文献
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V. K. Kalevich E. L. Ivchenko M. M. Afanasiev A. Yu. Shiryaev A. Yu. Egorov V. M. Ustinov B. Pal Y. Masumoto 《JETP Letters》2005,82(7):455-458
Room-temperature spin-dependent recombination in a series of GaAs1?xNx solid solutions (x = 2.1, 2.7, 3.4%) has been observed as manifested by a more than threefold decrease in intensity of the edge photoluminescence upon switching from circular to linear polarization of the exciting light or upon the application of a transverse magnetic field (~300 G). The interband absorption of the circularly polarized light is accompanied by the spin polarization of conduction electrons, which reaches 35% with an increase in the pumping level. The observed effects are explained in terms of the dynamic polarization of deep paramagnetic centers and the spin-dependent trapping of conduction electrons on these centers. The electron spin relaxation time, as estimated from the dependence of the edge photoluminescence depolarization in the transverse magnetic field (the Hanle effect) on the pumping intensity, is on the order of 1 ns. According to the adopted theory, the electron spin relaxation time in the presence of spin-dependent recombination is determined by a slow spin relaxation of localized electrons. The sign (positive) of the g factor of localized electrons has been experimentally determined from the direction of the magnetic-field-induced rotation of their average spin observed in the three GaAsN crystals studied. 相似文献
13.
C. Ortiz R. M. Macfarlane R. M. Shelby W. Lenth G. C. Bjorklund 《Applied Physics A: Materials Science & Processing》1981,25(2):87-90
Thin films of aggregate color centers have been produced by electron and ion irradiation of bulk alkali halide crystals. The transverse spatial distribution of the centers was controlled on a submicron scale using electron lithography. Photochemical hole burning has been accomplished for the first time in a thin film of color centers, using the 6070 Å zero-phononN 1 line produced by ion and electron irradiation of NaF crystals. 相似文献
14.
E. V. Korovkin 《Physics of the Solid State》2017,59(3):490-494
The assumption has been made that defects binding free polarons in colored alkali halide crystals are F'-center, i.e., defects that slow down the motion of dislocations (photoplastic effect). This assumption has been confirmed by the experiments performed in this study. Thus, the anion vacancy in alkali halide crystals at a low temperature can capture three electrons: two electrons at a deep level (F'-center) and one electron in a bound polaron state. This electron is retained due to the energy gain in the interaction of a local deformation of the polaron and a local deformation surrounding the F'-center, despite the presence of the Coulomb repulsion. 相似文献
15.
In ScF3 single crystals (pure and doped) as well as in Rb2KScF6 and Rb2KDyF6 crystals with a perovskite-like structure, point nanodefects (vacancy in place of trivalent cations) have been found and studied. Electron paramagnetic resonance has been used to investigate local paramagnetic centers that are not detected using X-ray diffraction. The angular dependence of the spectra indicates a local distortion of the cubic symmetry of the crystals. An additional hyperfine structure in the observed spectra is due to the delocalization of electrons over six F? ions forming the first coordination polyhedron around the vacancy. The crystals studied are characterized by a high electron mobility and a high electron velocity, which depends on the impurity. The high mobility of electrons of the cation center can be indirectly responsible for the structural phase transition occurring in the ScF3 crystal under uniaxial pressure. 相似文献
16.
The optical absorption (OA) and thermoluminescence of oriented -Al2O3 crystals colored in aluminum vapor have been studied. Optical absorption measurements of an X-irradiated sample at the orientation EC3 during isochronal annealing revealed mutual transformations of F- and F+-centers within the dosimetric peak from 380 to 500 K. The transformations occurred simultaneously with emptying of the electron trap whose OA is at 2.8 eV. The predominant F→F+ conversion, which could be explained by delocalization of holes, was observed in the low-temperature part of the peak near 380–440 K. From the available experimental data it was inferred that the simultaneous release of electrons and holes in the low-temperature part of the peak facilitated formation of excitons bound on F-type centers. The excitons transferred part of the energy stored in the irradiated crystal to F+- and F−-centers during thermal stimulation, leading to luminescence of these centers. 相似文献
17.
C. Basu K. Goswami S. Chaudhuri A. Choudhury 《Journal of Physics and Chemistry of Solids》1981,42(6):527-528
Lattice imperfections were produced in KCl crystals by a thermal process. The heat treated specimen was irradiated with 50 KeV electrons and the corresponding range of electrons in the crystal has been estimated. It was found that the electron range in the crystal depends upon the temperature of heat treatment, being a decreasing function of this temperature up to about 625 K, above which it becomes an increasing function. This anomaly has been explained in terms of dissolution of vacancies through dislocation loops. 相似文献
18.
B. Marí A. Segura A. Casanovas A. Chevy 《Applied Physics A: Materials Science & Processing》1991,52(6):373-379
Deep level transient spectroscopy measurements in indium selenide samples doped with different amounts of tin are reported. Three tin-related electron traps have been detected with activation energies for emission of 56, 74, and 110 meV. The capture cross-section has also been measured and it is very low and weakly dependent on temperature for the 74 and 110 meV deep levels that are attributed to electron trap states related to ionized acceptor centers. For the 56 meV level the apparent capture cross-section shows an activated temperature dependence with an activation energy of 35 meV, which yields an ionization energy of 21 meV for the related level, which corresponds to the tin-related shallow donor. That behaviour is interpreted through the presence in InSe of stacking-fault-related barriers. When one of these barriers is swept by the depletion zone edge during the emptying or filling pulses, electrons must overcome that barrier in order to be emitted or captured, which results in a reduction of the effective capture and emission rates of shallow donors which thus become observable through capacitance transients. 相似文献
19.
R. C. Bhuniya 《Czechoslovak Journal of Physics》1978,28(7):798-806
The electrical conductivity and optical absorption of potassium chloride crystals, pure and doped with divalent cation impurities, have been measured before and after X-irradiation at room temperature. The concentration of free positive ion vacancies at room temperature has been calculated from conductivity for each crystal before irradiation and is found to be much less than the first stage F centre concentration. This shows that both free and associated positive ion vacancies are the latent source of F centres in the first stage colouration. Pb+ + ions trap electrons producing Pb+ + and Pb0 centres and making free the associated cation vacancies. Such centres are not produced in Ca-doped crystals where impurity-vacancy complexes trap F centres producing Z centres. The higher ratio of F centres to positive ion vacancies in Pb-doped crystals indicates that free cation vacancies are more effective in producing F centres. However, the concentration of divalent cations is found to decrease in both the crystals after irradiation, the decrease being more in Ca-doped crystals.The author is indebted to Prof. H. N. Bose for helpful discussions. Thanks are also due to Dr. M. L. Mukherjee for providing the crystals. 相似文献
20.
M. A. Krivov E. V. Malisova É. N. Mel'chenko V. S. Morozov M. P. Nikiforova S. S. Khludkov Yu. A. Grigor'ev O. L. Egorova V. B. Osvenskii 《Russian Physics Journal》1983,26(11):1047-1050
The temperature dependences of the density, mobility, and lifetime of electrons, and the photoconductivity and cathodoluminescence spectra of gallium arsenide with different electron densities doped with germanium when single crystals are grown by the Czochralski method are investigated. An analysis of the scattering mechanism is given, and the acceptor and donor densities are determined. The acceptor-type capture levels are found from the temperature dependence of the electron lifetime. The results of a study of the cathodoluminescence spectra indicate the presence in the specimens of complex radiational recombination centers similar to germanium-atom complexes with inherent lattice defects. 相似文献