Effect of a magnetic field on the starting stress and mobility of individual dislocations in silicon

The strong effect of a magnetic field on the starting stress and mobility of individual dislocations is discovered in silicon grown by the Czochralski method with a high concentration of dissolved oxygen. It is shown that exposure of dislocations preliminarily introduced into the sample to a magnetic field considerably reduces the starting stresses for the motion of these dislocations. The effect is not observed in samples with a low oxygen concentration. It is assumed that the magnetic field induces singlet-triplet transitions in thermally excited states of silicon-oxygen complexes in the dislocation core, thus stimulating a change in the state (atomic configuration) of oxygen already located at dislocations. As a result, the mean binding energy of oxygen with a dislocation decreases.     

Generation of dislocations introduced by bending stress in a Si wafer

Distribution and morphology for dislocations introduced in (001) Si wafers subjected to bending stress at 800°, 900°, and 1100°C were investigated. For wafers bent around a [110] axis at 900° and 1100°C, straight dislocations appeared along the [110] direction only near the neutral plane, and were absent at the surfaces where bending stress is greatest. However, for wafers bent at 800 °C, such straight dislocations were not formed. Dependence of the dislocation distribution and morphology on heat treatment temperature is explained on the basis of interaction between bending stress and SiO₂ precipitates introduced in bulk. Also, it was found that the straight [110] dislocations remained still near the neutral plane, even when additional reverse bending stress was applied around an axis parallel to the dislocations, but were transfered toward the tensile surface by bending around an axis normal to the dislocation direction.     

Redistribution of dislocations in silicon near stress concentrators

The distribution of defects in dislocation tracks in silicon plates was studied for various indentation angles. The regularities of variations in the linear density and maximum path of dislocations in slip bands are established. A model is proposed to describe the distribution of dislocations in the dislocation tracks. By fitting the theory to the experimental data, the dependence of this distribution on the energy relaxation time is determined.     

Elastic stress of moving dislocations in finite crystals

The elastic stress of a single crystal with finite dimensions is investigated by means of the linear continuum theory; external forces and dislocation motion are assumed to be known. A formal solution is derived with a Green's dyadic. The dyadic is expanded in a series, the first term of which delivers the well-known solution for infinite crystals, the following terms describe successive reflections of sound at the surface of the finite crystal. They can be computed by iteration. This expansion corresponds to the physical situation of pulse-echo-experiments. Fourier transforms lead to analogous expressions describing the influence of the surface on time-periodic dislocation experiments.     

Solitons in a ring superlattice

We consider the propagation of electromagnetic solitons in a ring superlattice formed by the successive deposition of coaxial ring-shaped layers lying in parallel planes. In contrast to a rectilinear (infinite) superlattice, in which either one soliton (a single solution) or an infinite number of solitons (fluxon solution), any finite number of equidistant solitons is possible in a ring superlattice. We calculate the constant component of the electric field along the axis of the superlattice and the density of the current of electron drag by solitons (solitonelectric current).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 79–81, November, 1990.     

Mixed state in a superlattice

Presented in this paper is a theoretical calculation of the vortex solution in a chosen superlattice (Nb/NbZr) using the Gibbs free energy of an inhomogeneous superconductor. The eigenvalue obtained in this geometry from de Gennes-Werthamer proximity coupling theory is first examined according to a set of experimental data, while the correspondent eigenfunctions are then used to construct vortex solutions with either square lattice or triangle lattice symmetry. The Gibbs free energy is calculated in terms of the vortex solutions of both symmetries. The effective Ginzburg-Landau parameter,K _NS , for this superlattice is determined asK _NS =0.218 by requiring a consistency between the microscopic and macroscopic theoretical calculations. Of particular importance is a new mechanism revealed by this calculation that a highly localized state of superconducting condensate in its hosting layer, despite the spatially rapid varying characteristic of its correspondent nucleating order parameter, provides a lower eigenvalue state, which results in a dimensional crossover. A further examination of this mechanism is carried out in the mixed state calculation. Finally, a generalization of the present theoretical results to a large class of superlatices is discussed.     

Effect of electric current on starting characteristics and activation parameters of short dislocations in Si crystals

It is shown that the passage of an electric current through crystalline silicon may lead to the so-called galvanoplasticization, as well as the galvanostrengthening, effect. It is found that the effect is sensitive to the temperature regime of deforming and to the preliminary high-temperature treatment of the samples. The motion delay time for short dislocations and starting stresses are significantly affected by the current. The relation of these effects to the change in the electric state of the Cottrell atmosphere as a result of the passage of the current through the crystal is considered.     

Plasmons in a planar graphene superlattice

Plasmon collective excitations are studied in a planar graphene superlattice formed by periodically alternating regions of gapless graphene and of its gapped modification. The plasmon dispersion law is determined both for the quasi-one-dimensional case (the Fermi level is located within the minigap) and for the quasi-two-dimensional case (the Fermi level is located within the miniband). The problem concerning the absorption of modulated electromagnetic radiation at the excitation of plasmons is also considered.     

The intermediate glassy phase in a ferroelectric with dislocations

This paper examines, in the mean-field approximation, the phase transitions in an elasto-isotropic cubic ferroelectric crystal with randomly distributed ring dislocations. It is found that a transition to the dipole-glass phase with chaotic, spontaneous unit-cell dipole moments, characterized by the Edwards-Anderson nonlocal parameter, precedes the transition to the ferroelectric phase. Also determined are the features of the thermodynamic parameters of the crystal at the phase-transition points. Zh. éksp. Teor. Fiz. 116, 986–1000 (September 1999)     

A Disorder Solution for a superlattice GMS Model

A closed form expression for the free energy per site of the triangular superlattice in generalized mixed-spin (GMS) case is obtained by means of the exact decimation approach. A criterion determining the validity of the solution is also given.