Spontaneous and stimulated-radiation of impurity molecular crystals with optical and electron pumping

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 6, pp. 966–972, June, 1989.     

Electrical conductivity studies of cobalt-precipitation in RbCl crystals

The results of electrical conductivity measurements in heavily doped RbCl:CoCl₂ crystals with 2500 and 6000 ppm of cobalt are being reported in this paper. The different regions of the conductivity plots for the crystals with the two concentrations of cobalt have been explained and relevant energy parameters determined. The crystals with 6000 ppm of cobalt have been found to contain two types of precipitates one of these being of the same type as that existing in RbCl crystals with 2500 ppm of cobalt while the other being of a different composition. Further, it has been found that the crystals appear blackened after heating during measurements. The blackening has been attributed to the expulsion of cobalt from the bulk of the crystal which forms an oxide at the surface.     

Image contrast of impurity regions of semiconductor crystals in scanning electron microscopy

A critical survey of the current state of the problem of visualizing local impurity regions of semiconductor crystals in a scanning electron microscope (SEM) is presented. A new physicotechnical solution for monitoring impurity distributions in doped regions that allows us to increase the contrast between images of impurity sectors in a wide range of concentrations is proposed.     

Luminescence and ESR detected hydrogen related electron traps in yellow-colored CaO crystals

Abstract

Electron spin resonance of the off-center H^2- ions replacing oxygen in additively colored CaO crystals has been investigated. Electron tunneling in F… H^? pairs is essential in photoconversion and thermoluminescence of CaO at low temperatures.     

Local modes due to U-centers in RbCl containing potassium additive impurity

The frequencies of the localised modes of vibrations of hydride ions in rubidium chloride containing cation impurity have been computed by Green function technique and compared with the experimental measurements. There is found to be a satisfactory agreement between the theoretical and the experimental values.     

Thermoactivated spectroscopy of heterovalent impurity traps in CdWO4

Abstract

Recombination luminescence emission spectra, TSL and trap spectra estimated by fractional glow technique (FGT), in nominally pure and Li-, Bi- and Ho-doped CdWO₄, crystals are reported. According to the investigations by FGT heterovalent impurities Li, Bi and Ho causes localized electronic states which act as traps for charge carriers. It is shown that TSL results in emission of known blue-green luminescence band by emptying of the Li⁺-related traps in CdWO₄-Li and yellow luminescence band by emptying of the Bi³⁺-related traps in CdWO₄-Bi. It is proposed that blue-green and yellow luminescence occur by recombination correspondingly of free holes and free electrons at different intrinsic tungstate group related luminescence centers.     

ELectron traps in silver chloride crystals

The photoelectret state has been examined for AgCl crystals after treatment with heat and light; it is found that there are shallow electron trapping levels, whose ionization energy ₁ is about 0.2 eV and whose concentration n₁ is about 10¹⁷ cm^–3. These appear to be due to inherent defects in the lattice of AgCl.     

Positron traps in radiation-colored KCl crystals

We studied the effect of thermal and radiation annealing of defects and optical deexcitation with Flight on the angular distribution of annihilation radiation of KCl crystals irradiated with electrons and protons. The results show that divacancies are the main type of positron traps in irradiated KCl crystals.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 55–61, November, 1978.     

The effects of magnetic field and hydrogen-like impurity on RbCl quantum pseudodot qubit

By using a variational method of Pekar type, we investigate the effects of the hydrogen-like impurity and magnetic field on the electron’s probability density (PD) and oscillating frequency (OF) of a RbCl quantum pseudodot qubit. Numerical results indicate that (1) the PD oscillates periodically; (2) the crest of the PD will decrease with increasing the cyclotron frequencies and the Coulombic impurity potential strength; (3) as the cyclotron frequency of the magnetic field and the strength of the Coulombic impurity potential increases, PD’s peaks will occur more frequently; (4) besides, Figs. 1b and 2b clearly show that in a single period the PD will decrease with increasing the cyclotron frequency and the Coulombic impurity potential strength when \( t > 1.8\;\text{fs} \); whereas the changing law is just the opposite when \( t < 1.8\;\text{fs} \); (5) the OF is an aggrandizing function of the strength of the Coulombic impurity potential, whereas it is a decaying one of the cyclotron frequencies of the magnetic field. The coherence of qubit is crucial to the investigations of quantum information and quantum computation, where the electron’s PD, the OF and the coherence time are the physical quantities representing the properties of coherence. Our research results fine that by changing the cyclotron frequency of the magnetic field and the strength of the Coulombic impurity potential one can adjust the electron’s PD and the OF.

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Fig. 1 The PD \( \text{Q}\left( {r,t} \right) \) versus the time \( t \) and the cyclotron frequency of the magnetic field \( \omega_{c} \) with \( \text{V}_{0} = 10.0\,\text{meV, r}_{0} = 1.0\,\text{nm, }\beta \text{ = 1.0}\,\text{meV} \cdot \text{nm} \) and \( x = y = z = 1.0\,\text{nm} \)

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Fig. 2 The PD \( \text{Q}\left( {r,t} \right) \) versus the time \( t \) and strength of the Coulombic impurity potential \( \beta \) with \( \text{V}_{0} = 10.0\,\text{meV, r}_{0} = 1.0\,\text{nm,} \, \omega_{c} \text{ = 2.0}\, \times \text{10}^{13}\,\text{Hz} \) and \( x = y = z = 1.0\,\text{nm} \)

     

The annihilation probability for the components of a primary F-H pair in thermally activated motion

Annihilation probabilities P _a have been calculated for the components of a primary F-H pair for various interaction functions E (r). It is shown that P _a is small for E (r)=0 but increases for E(r) < 0, being also a function of temperature, with a negative temperature coefficient for E(r) < 0.Translated from Izvestiya Vysskikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 41–44, October, 1977.     

Aggregation of impurity centers in ionic crystals

Results of modeling of the aggregation process in complex centers of ionic crystals are presented. Concentration dependences of the number of paired centers are obtained. A nature of the paired luminescence centers is discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 62–65, February, 2007.     

Recombination luminescence of KI crystals with a sodium impurity

It is shown in this paper that both electron-hole and hole -electron recombination luminescence are excited effectively in KI Na crystals at low temperatures. In addition to the radiation of self-localized excitons and of excitons localized at the sodium ions, the luminescence of excitons localized at dual sodium centers is detected.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 63–66, February, 1975.     

Quantum theory of impurity migration in crystals

A quantum theory of impurity migration in crystals is proposed. The impurity state is taken in the form of a wave packet constructed out of its Bloch states in the host lattice. Its time evolution is studied including its interaction with the host lattice phonons. A correspondence is established between the classical diffusion equation and the time evolution of the probability density arising out of the impurity wave packet. The diffusion coefficient D_T and trapping rate γ_T are related to the imaginary part of the energy shift of the impurity caused by its interaction with phonons. The detailed calculations are carried out using second order perturbation theory for the energy shift. The Debye model for the host lattice and effective mass approximation for the impurity band are used. At low temperature D_T is found to be proportional to_T3/2, and at high temperature the Arrhenius formula of Vineyard is obtained. The estimated migration energy for μ⁺ migration in bcc metals agrees reasonably with the experimental values.     

Diffusion in crystals with traps: A simple phenomenological model

We present a phenomenological model describing the trapping and release of mobile defects at random inhomogeneities. The traps are characterized by two parameters, the capture radiusR _t, describing the range of the interaction and the binding energyE _b describing the escape. We give an integral representation of the correlation function of the mobile particles in the presence of traps. For large distances the correlation function can be described by a simple diffusional process with an effective diffusion constant. Finally we discuss the neutron scattering by mobile defects resulting from this trapping model.     

High-frequency conductivity of a two-dimensional electron gas with impurity electron states

The high-frequency conductivity tensor for a two-dimensional electron gas with short-range-acting impurity atoms has been computed. Spatial dispersion of the conductivity was taken into account. The threshold and maxima of the dissipative part of the conductivity arising from ionization of the impurity atoms by the field of electromagnetic waves were found. Numerical calculations of the conductivity were carried out for semiconductor structures with a two-dimensional electron gas. Khar’kov State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 91–94, July, 1997.     

Shallow traps in pure KTaO 3 crystals

We made Thermally Stimulated Conductivity (TSC), Thermoluminescence (TL) and Electron Spin Resonance (ESR) measurements on single crystals of potassium tantalate in the temperature range 4.2-290 v K. We revealed two sorts of O m shallow hole centers which are responsible for Photoconductivity (PC) and Photoluminescence (PL) enhancement. Both O m centers were identified by their ESR spectra. We show that these centers serve as radiative electron-hole recombination centers. The measurements of TSC and TL after UV irradiation revealed several glow peaks at temperatures 18-30 v K and 65-70 v K. Both TSC and TL are attributed to the thermal ionization of the same shallow donor centers related with oxygen vacancies. Experimental data were treated in a simple one-trap/one-recombination center model, which takes into account the presence of "thermally disconnected" deep electron traps.