The effect of deformation and forest dislocations density on the activation volume in zinc single crystals

The obstacle density calculated from the experimental values of the activation volume is compared with the density of forest dislocations. The density of obstacles is about two or three order higher than that of the forest dislocations. It is assumed that nonconservative jog motion is the rate-controlling mechanisms in stage A, while in stage B the activation volume is more directly determined by interaction with the forest dislocations.     

The photodamping of dislocations in KCl single crystals

The effect of F-light (λ = 550 nm) on the dislocation amplitude-dependent internal friction (dislocation photodamping) and dislocation charge in KCl crystals of different purity containing F-centers has been investigated. The photodamping process in all the crystals under study has been found to be due to the optical generation of new pinning points. The conditions of photopinner formation are found to depend on the magnitude of dislocation charge, the manner of the F-center introduction (γ-irradiation, additive coloration), and crystal purity. A model of photopinner formation has been proposed. The results obtained are used to analyse the binary systems in which the effect of dislocation photodamping is likely to occur.     

Dynamics of kinks on dislocations in SiGe single crystals

The method of intermittent pulse loading is used for obtaining the dependences of the mean free path of individual dislocations in SiGe single crystals with various concentration of Ge (0–5.5 at. %) on the duration of loading pulses and time intervals between them. It is found that these dependences change qualitatively upon an increase in the Ge concentration. It is shown that the motion of dislocations in SiGe crystals under small shear stresses is characterized by a nonlinear drift of kinks and the formation of superkinks. A theory of the motion of dislocations under the action of intermittent pulse loading under the conditions of heterogeneous kink dynamics is developed. Extended quasi-one-dimensional defects repeating the shape of a part of a segment of a moving dislocation are discovered in SiGe crystals containing 0.96 at. % Ge. The mechanism of formation of such defects as the result of the shedding of a part of the impurity atmosphere by a dislocation segment during overcoming of a local obstacle is proposed.     

Specific features in the generation and motion of dislocations in silicon single crystals doped with nitrogen

The specific features in the generation and motion of dislocations are investigated in Si: N single crystals grown by the Czochralski method. The motion of dislocation loops is analyzed by the four-point bending technique in the temperature range 500–800°C. The dislocation loops are preliminarily introduced into the samples with the use of a Knoopp indenter at room temperature. It is found that doping with nitrogen leads to a considerable increase in the critical stress of the onset of dislocation motion from surface sources (indentations) and in the stress of the generation of dislocations from internal sources. The velocity of dislocation motion in Si: N crystals is less than that in undoped crystals (under comparable loads). The hardening effect of nitrogen is explained by the fact that nitrogen promotes the decomposition of a solid solution of oxygen in silicon during postcrystallization cooling.     

Effects of size on the dynamics of dislocations in ice single crystals

Single crystals of ice subjected to primary creep in torsion exhibit a softening behavior: the plastic strain rate increases with time. In a cylindrical sample, the size of the radius affects this response. The smaller the radius of the sample becomes while keeping constant the average shear stress across a section, the softer the response. The size-dependent behavior is interpreted by using a field dislocation theory, in terms of the coupled dynamics of excess screw dislocations gliding in basal planes and statistical dislocations developed through cross slip occurring in prismatic planes. The differences in the results caused by sample height effects and variations in the initial dislocation microstructure are discussed.     

The influence of pressure on the luminescence of zinc sulphide single crystals

Experiments were made which show that luminescence originated under the application of pressure on the single crystals of zinc sulphide. The calculated formula gives the same dependence of luminescence on the change of pressure dP/dt as in [1], [2].     

On the effect of impurities on the critical resolved shear stress of zinc single crystals

The dependence of the critical resolved shear stress of zinc single crystals on the impurity content and the dislocation density is observed. It is shown that the effect of impurities on the critical resolved shear stress is indirect.

---

. , .

     

Kerr-like nonlinearity induced via terahertz generation and the electro-optical effect in zinc blende crystals

A model is proposed to account for Kerr-like nonlinearity induced by femtosecond pulses via terahertz generation and electro-optical effect. This phenomenon, so far overlooked, is evidenced in a zinc blende single crystal with a heterodyne optical Kerr effect setup. The spectral evolution of this phenomenon as well as its noninstantaneous response character are reported. Its competition with a third-order optical Kerr effect is demonstrated.     

X-ray topography study of microsegregation in crystals

Concentration microinhomogeneities in crystals were characterized using x-ray topography, digital image processing, and spectral analysis of signals. Based on the features in lattice strains in such layered inhomogeneous crystals, methods for optimizing the conditions of x-ray topography detection of growth striations were proposed to obtain quantitative information on the composition fluctuation amplitude and spatial characteristics.     

Influence of electrical pulses on the distance traveled by dislocations in NaCl single crystals

A study was made of the influence of rectangular electrical pulses, applied either before or simultaneously with mechanical loads, on the distance traveled by edge and screw dislocations. A considerable increase in this distance was observed. The effect was a function of the type of dislocation, impurity composition of crystals, and electric field orientation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 10–14, October, 1980.     

Interstitial oxygen in zinc oxide single crystals

Irradiation of zinc oxide single crystals with 2.5 MeV electrons produces both interstitial ions and vacancies. By means of ESR measurements oxygen ions on interstitial sites with tetrahedral and octahedral symmetry have been identified. Furthermore the behaviour of the oxygen vacancyV _o ⁺ is discussed.     

Effect of a dislocation forest on the bauschinger effect during the twinning of zinc single crystals

A study was made of the effect of a dislocation in the {{11¯22}} 11¯23 system (pyramidal slip) on the characteristics of the Bauschinger effect during the twinning of single crystals of zinc and of the alloy Zn + 0.6% Cu. The dislocation forest retards the backward motion of the twinning dislocations, leading to the effect.Translated from Izvestiya VUZ. Fizika, No. 5, pp. 101–104, May, 1971.In conclusion the authors thank candidates of physicomathematical sciences F. F. Lavrent'yev for useful discussion.     

The effect of channelling on the fast-electron radiation in single crystals

Summary The interaction of fast electrons, moving along the crystallographic axis, with the periodical field of the single-crystal lattice is treated. It is shown that this interaction, accompanied by a discrete change of the transversal electron energy in channelling and of the longitudinal momentum, leads to a quasi-monochromatic electromagnetic radiation. The angular and frequency radiation distributions are studied. The maxima of the frequency distribution occur in a frequency range which exceeds sufficiently that of the spontaneous transition radiation, emitted by the channelling particle.

---

Riassunto Si tratta l'interazione degli elettroni veloci, che si muovono lungo l'asse cristallografico, con il campo periodico del reticolo del cristallo singolo. Si mostra che questa interazione, accompagnata dal cambiamento discreto dell'energia trasversale dell'elettrone in canalizzazione e dell'impulso longitudinale, porta alla radiazione elettromagnetica quasi monocromatica. Si studiano le distribuzioni angolare e di frequenza della radiazione. I massimi della distribuzione di frequenza si verificano in un intervallo di frequenze che eccede a sufficienza quello della radiazione di transizione spontanea, emessa dalla particella di canalizzazione.

---

Резюме Рассматривается взаимодействие быстрого каналированного электрона с продольными периодическими неоднородностями потенциала кристалла. Показано, что это взаимодействие, сопровождающееся дискретными передачами продольного импульса решётке кристалла и дискретными изменениями поперечной энергии электрона, приводит к появлению специфического, монохроматического электромагнитного излучения с частотами, существенно превосходящими частоты квазихарактеристического излучения при каналировании. Исследуются спектральные и угловые распределения этого излучения.

---

---

To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Internal friction of deformed zinc single crystals

Zinc single crystals with the side in a (0001) basal plane were elongated and the internal friction measurements were carried out as a function of temperature in the mode of a flexural vibration. Two relaxation peaks were observed to appear: one at around 500°K and the other at about 570°K. Each activation energy was obtained 0.70±0.08eV and 1.01±0.06eV, respectively, by the peak shift method. The experimental results were discussed in terms of dislocations in pyramidal slip system {$\text{11}$22} 〈11$\text{2}$3〉 and twinning dislocations in the planes {$\text{1}$012} 〈10$\text{1}$1〉, respectively.     

Infrared radiation of zinc selenide single crystals

Long-wave photoluminescence (PL) spectra of both as-grown and Au-doped n-ZnSe single crystals are studied in the temperature range from 81 to 300 K. A narrow band of infrared (IR) radiation centered at 878 nm (1.411 eV) manifests itself in the low-temperature PL spectrum. It is established that this band intensity first increases and then decreases with increasing concentration of doping impurity. With increasing excitation radiation intensity, spectral position of the IR PL band is unchanged and its intensity increases under the linear law. With increasing excitation radiation wavelength, the IR PL band intensity increases, it becomes narrower and shifts towards long wavelengths. It is shown that the observed IR radiation is caused by recombination of free electrons with holes localized on associative acceptors in the ZnSe:Zn:Au crystals or in the undoped crystals.     

The effect of the orientation of zinc single crystals and of the rate of growth on the direction of cell substructure

The effect of the orientation of zinc single crystals and the rate of growth on the direction of the formation of cellular substructure is observed. A model accounting for the observed dependences is proposed.

---

. .