Effect of the electric fields of immobile dislocations on photoluminescence and EPR in deformed ZnS crystals

The influence of the electric fields of immobile growth dislocations on the luminescence properties of deformed zinc sulfide crystals is considered. Variations in the photoluminescence and EPR spectra with plastic deformation of ZnS crystals are shown to be caused by an increase in the radius of Read cylinders during the breakaway of growth dislocations from Cottrell atmospheres.     

Mechanism of self-trapping of electron excitation in alkali-halide crystals

A dynamic method is used to calculate the equilibrium positions of ions near heavy and light homologous impurities for KCl:J and KJ:Cl crystals. The most probable sites of self-traps are shown.Lattice ralaxation near an excited anion is modeled. The localization of electron excitations (EE) in alkali-halide crystals is examined from the viewpointof the formation of a covalent bond between anions as a relust of their approach toward each other. The EE localization time is determined by the lifetime of local vibrations in the crystal near the excited anions (5-10^–13–10^–11 sec).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 35–38, January, 1986.     

On the mechanism of the electric field effect on dislocation mobility in alkali-halide crystals

The dependence is investigated of the velocity of motion of edge and screw dislocations on the applied shear stress in annealed and quenched NaCl and KC1 crystals with various impurity content under the action of an electric field of up to 50 kV/cm. It is shown that in impure crystals the action of the field is determined by its effect on damping centers, while in pure crystals, by its effect on charged dislocations. The interaction force of an edge dislocation with impurity-vacancy dipoles of various orientation is calculated. The charge density and sign of a dislocation is estimated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 16–21, May, 1975.     

Amplitude dependence of the internal friction of alkali-halide crystals in an electric field

The influence of an electrical field on the internal friction of an alkali-halide crystal (AHC) was investigated for relative deformation amplitudes corresponding to separation of dislocations from fastening centers, and for higher amplitudes when plastic deformation of the specimen occurs in an ultrasonic wave field. The influence of the electrical field in the deformation domain under consideration reduces to direct action on charged dislocations, re-orientation of dipole fastening centers, and activation of sources in block boundaries.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 5–11, August, 1989.The author is grateful to Dr. N. A. Tyapunina for valuable comments, remarks, and unchanging interest in the research.     

Electroelastic fields of moving dislocations and disclinations in piezoelectric crystals

Integral representations for the electroelastic fields of moving dislocations and disclinations in piezoelectric crystals have been obtained in terms of a four-dimensional formalism of dynamic Green’s functions. The cases of continuously distributed and single linear defects are considered. The correctness of the results is confirmed by the fact that they meet the necessary requirements as one goes to the purely elastic solution. Fiz. Tverd. Tela (St. Petersburg) 41, 1210–1213 (July 1999)     

Hopping motion of nonisolated dislocations in KC1 crystals

An investigation was made of hopping of nonisolated dislocations in KC1 crystals. It was found that hopping of dislocations in bands was characterized by a correlation between the lengths of successive jumps, rest periods, and numbers of jumps. Irradiation with rays and quenching did not change these results, which was explained by the motion of dislocations together with their atmospheres.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 60–64, July, 1980.The authors are grateful to Prof. A. A. Predvoditelev for his valuable advice and help.     

Effect of ultrasonic treatment on the mobility of short dislocations in Si crystals

The effect of ultrasonic treatment on the mobility of short surface dislocations in Si crystals is investigated. It is found that ultrasonic treatment of Si crystals changes the velocity of dislocations under a permanent mechanical load. The nature of variation of dislocation velocity is determined by the sign of external stresses acting on the sample: compressive forces decrease while tensile forces increase the velocity of dislocations. After ultrasonic treatment of the samples, a decrease in the activation energy for dislocation motion and the enhancement of the electroplastic effect are observed. A possible mechanism of the observed effects is considered.     

Mechanism for the creation of antisite defects,during combined climb-glide motion of dislocations in sphalerite-structure crystals

Processes are considered which lead to a formation of irregular jogs in a dislocation core, e.g., when in GaAs two As atoms are absorbed at an already existing jog. Then, after glide, the dislocation leaves an arsenic antisite defect behind. This mechanism can give an account of a correlation between the spatial distributions of EL2 donors (that are most likely related to the As_Ga defects) and dislocations in melt-grown GaAs crystals.     

Formation of near-defect excitons in alkali-halide crystals

Pulsed-spectrometric research shows that the presence of defects, including those that are electrically neutral with respect to the crystal lattice, has a significant influence on the distribution of the radiation-induced electron excitations. This is evident in the electron-excitation sink in the vicinity of defects and the formation of localized excitons around impurities in ionic crystals. This influence of defects on the electron-excitation distribution is probably due to deformation of the lattice in the region of the defect. It is shown that, in the region of the defect, there is oscillating potential relief, the presence of which leads to the capture of charge carriers and their localization in this region. Lattice distortion because of deformation in the region of the defect changes the mutual distribution of the ion pairs. This creates conditions for the effective conversion of electronic excitations to localized near-defect dihalide excitons, which are different from those created in an ideal lattice. Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 94–108, November, 1996.     

Influence of an electric field on the amplitude dependence of internal friction of alkali-halide crystals at low amplitudes

Application of an electric field of intensity 10⁵–10⁶V·m^–1 to alkali-halide crystal specimens results in the appearance of an amplitude dependence of the internal friction (IF) in the low amplitude domain of the relative deformation 10^–7–10^–6, where the amplitude dependence of the IF has a peak. A physical model is proposed that is based on the assumption of shifting of the dislocation under the action of the electric field into a new less secure equilibrium position. The growing and decreasing branches of the IF peak are described within the framework of this model. The question of the amplitude dependence of dynamic IF losses is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 47–50, December, 1989.In conclusion, the authors are grateful to Doctor of Physicomathematical Sciences N. A. Tyapunin for discussing the research, useful remarks, and comments.     

Electroluminescence in anthracene crystals under time-varying electric fields

Electroluminescence in anthracene crystals has been systematically measured under time varying electric fields at various temperatures using a sodium electrode as the electron-injecting contact and a silver electrode as the hole-injecting contact. The results show that the electroluminescent brightness decreases with increasing frequency over the temperature range from ? 20 to 60°C; and that for a given frequency the brightness increases with increasing temperature, reaches a peak at a critical temperature, and then decreases with increasing temperature. The electroluminescence under a half-wave rectified sinusoidal a.c. field is brighter than that under a sinusoidal a.c. field of the same peak amplitude. There is a delay time between the application of the field and the appearance of electroluminescence, and this delay time decreases with increasing frequency and saturates at a value which may be associated with the transit time of the injected electrons across the specimen. All these results can be explained on the basis of the model that electroluminescence occurs when an electron space charge built up near the anode is sufficient to enhance hole injection from the anode.     

超声振动对摩擦力的影响

超声振动的应用十分广泛,关于超声振动对摩擦力的影响这个问题,已引起国内外许多学者的注意。本文对其进行了实验和理论研究。在超声振动条件下,以理论计算为基础,通过摩擦实验,得到了几种材料的超声振动摩擦特性,并且对摩擦力在共振时减小的原因进行了初步的理论分析。此外,由实验证明,碳化钨与45#钢组成的摩擦副是用于超声马达的理想材料。     

Investigation of the motion kinetics of screw dislocations in sodium chloride and potassium chloride crystals

The kinetics of the motion and the surmounting of detents by dislocations in sodium chloride and potassium chloride crystals is investigated herein. Special attention is paid to a comparative study of the mean free paths of the screw and edge dislocations. It is established that the mean free paths of the screw dislocations is somewhat less than for edge dislocations under identical test conditions. The kinetic curves obtained were processed within the frame-work of theoretical representations about the motion of dislocations in crystals containing detents of two kinds.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 17–21, September, 1973.