Gorsky P. Theory of the layered semiconductors diagnostic for the instrument engineering

In the thesis the theoretical undergrounds of the layered semiconductors described by the Fivaz model using possibilities estimation are developed. For this purpose general formulae of longitudinal conductivity and themoEMF have been derived that are valid in a wide range of magnetic fields, charge carrier concentrations and temperatures, for the case when the magnetic and electric fields, as well as temperature gradient are normal to layers. On the basic of these formulae the influence of nonparabolicity describing by Fivaz model on the frequency, phase and amplitude of the de Haas-Shubnikov-oscillations and the temperature and field dependencies of electrical conductivity, thermoEMF and power factor are considered. These calculations are performed for different relaxation time models and degeneration rates in strong and weak magnetic field. The condensation of current carriers on the lowest Landau subband at the conditions of strong magnetic field and strong degeneracy is taken into account. Moreover, the influence of interlayer charge ordering on the temperature and field dependencies of the longitudinal conductivity, thermoEMF and power factor are considered and diagnostic properties of the charge ordered materials are established. The new class of the functionally graded materials on the basic of the powders with variable granulometric composition is proposed. The possibilities of thermoelectric figure of merit improvement for the materials with parabolic band structure and materials described by Fivaz model during the nonparabolicity increase and transition from single crystals to powders are considered. Key words: Fivaz model, nonparabolicity, electric conductivity, ther-moEMF, power factor, oscillations, negative magnetoresistance, charge order-ing, powders of variable granulometric composition, Debye model, thermoelec-tric figure of merit.