Specific features of self-compensation in Er x Sn1 − x Se solid solutions

The effect of doping and degree of compensation on the conductivity activation energy ΔE _i in Er _x Sn_{1 ? x} Se has been investigated. The carrier concentration decreases at a low doping level in the case of low and moderate compensations. It is found that, beginning with x ≥ 0.005 at % Er, carriers in the solid solutions under study change sign, depending on the amount of substituted erbium in the SnSe samples that is in equilibrium with the selenium phase. This phenomenon can be explained in terms of the concepts of the self-compensation of donors in the Sn sublattice.     

Effects of Neutron Irradiation on the Current–Voltage Characteristics of SiO<Subscript>2</Subscript> Nanoparticles

Current–voltage characteristics of SiO₂ nanoparticles have been studied before and after neutron irradiation within 5 V steps in the voltage range of ??100 V to +?100 V at room temperature (RT). The angle of the current–voltage curve is changed appropriately for neutron irradiation periods. Simultaneously, it is seen that the amount of the current flowing through the environment increases proportionally to the irradiation period. Moreover, the mechanism of electrical conductivity appropriate to the obtained results is given in this work.     

Effect of Neutron Flux on the Frequency Dependence of Permittivity of Nano Silicon Particles

In the present work, nano silicon is irradiated with a neutron flux (2x10 ¹³ n ?cm ^?2 s ^?1) up to 20 hours at different times. In the first stage frequency dependencies of real and imaginary parts of the permittivity of nanomaterials affected by neutron flux was analysed comparatively. As a result of this analysis it is known that the permittivity of nano silicon increases under the influence of neutron flux. The dependence of real and imaginary parts of permittivity of nano silicon particles is also reviewed. Moreover, the mechanism of the observed peaks and other effects is given in the work.     

On the thermopower and thermomagnetic properties of Er<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Se solid solutions

The Er _x Sn_1–x Se system is characterized by a significant deviation of the temperature dependence of the differential thermopower from linearity at temperatures below room temperature and a change in the sign of the thermomagnetic coefficient. The deviation of the thermopower of Er _x Sn_1–x Se samples in the nonequilibrium state from linearity is found to be caused mainly by the entrainment of charge carriers by phonons α_ph. The statistical forces of electronic entrainment, A _ph(ε), are estimated.     

Effects of Neutron Flux on the Temperature Dependency of Permittivity of 3C-SiC Nanoparticles

In the present work, the real and imaginary parts of permittivity of cubic modification silicon carbide (3C-SiC) nanoparticles are investigated before and after neutron irradiation. The real and imaginary parts of permittivity for the samples were studied in 0.1 Hz–2.5 MHz frequency and 100 K–400 K temperature ranges. The samples were continuously irradiated by neutron flux (2x10 ¹³ n ?cm ^?2 s ^?1) up to 20 hours. The real and imaginary parts of permittivity were comparatively studied before and after irradiation. Neutron irradiation effects were studied with comparative analysis of non-irradiated samples. The increase in polarization was observed as a result of the increase in the impact period of neutron flux. All the mechanisms of the observed effects are given in the work.     

Methods of constructing suboptimal solutions of integer programming problems and successive improvement of these solutions

Two-stage methods of constructing an improved suboptimal solution of problems of integer linear programs with nonnegative coefficients are developed. A solution is constructed on the first stage on the basis of newly introduced criteria, and the indices of the intervals of the variables determined, where the coordinates of the optimal solution may differ from the suboptimal solutions already constructed. On the second stage, new solutions are constructed by varying the values of the variations only within these intervals and the best of these new solutions are selected. Computational experiments for high-dimension problems confirm the high degree of efficiency of the newly developed methods.     

Phase relations and properties of alloys in the SnSe-DySe system

Phase relations in the SnSe-DySe system have been studied using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and its T-x phase diagram has been mapped out. The SnSe-DySe system contains a new ternary compound with the composition DySnSe₂, which crystallizes in orthorhombic symmetry with unit-cell parameters a = 5.74 ± 0.02 Å, b = 10.49 ± 0.03 Å, and c = 11.66 ± 0.05 Å (Z = 7, V = 702 ų, measured density ρ_meas = 7.02 g/cm³, X-ray density ρ_x = 7.26 g/cm³). In addition, the system contains SnSe-based solid solutions, Sn_{1 ? x} Dy _x Se (up to 4 mol % DySe). Their electrical conductivity and thermoelectric power have been measured as functions of temperature.     

Thermal conductivity of Er<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Se (<Emphasis Type="Italic">x</Emphasis> ≤ 0.025) solid solutions

The thermal conductivity of Er _x Sn_{1 ? x} Se solid solutions has been measured at temperatures from 80 to 360 K. The results have been used to evaluate the electronic and lattice components of thermal conductivity for elastic carrier scattering, parabolic bands, and arbitrary degeneracy. With increasing erbium content and temperature, both the electronic and lattice components decrease considerably. Long-term annealing increases both components. It follows from the present experimental data that heat conduction in Er _x Sn_{1 ? x} Se is mainly due to phonons and that the observed rise in thermal resistance with Er content is due to phonon-phonon and paramagnetic-ion scattering.     

Transverse Nernst–Ettingshausen Effect in Superlattices Upon Electron-Phonon Scattering

The Nernst–Ettingshausen coefficient is calculated in superlattices with the cosine dispersion law in the case of the scattering of charge carriers at acoustic and polar optical phonons in a magnetic field in the layer plane. A significant increase in the Nernst–Ettingshausen coefficient of a degenerate quasi-three-dimensional electron gas in a weak magnetic field is shown. For polar optical-phonon scattering, the Nernst–Ettingshausen coefficient changes sign in a strong magnetic field.