A theoretical and experimental analysis of the heat conductivity in metal-dielectric point contacts is given. The contribution of the phonon diffraction effects to the heat conductivity is investigated. The phonon heat transport through the point contacts is measured from 0.1 K to 100 K using the anvil-needle technique. In KBr-KBr and KBr-Cu point contacts, substituting a Cu needle for the dielectric cold edge does not disturb the heat conductivity pattern. Measurements for Si-Cu point contacts reveal well-defined diffraction maxima of reduced heat conductivity at temperatures in the range 0.5 K-1 K.

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New types of thermoelectric effects occurring in semiconducting point contacts whose dimensions are smaller than the inelastic electron and phonon relaxation lengths are analysed. Among them are the reduction of thermoelectric electromotive iorce in the point contact relative to the bulkmaterial, making possible the determination ofthe phonon-drag contribution to the Seebeck coefficient. the heat release asymmetry in the banks of the contact, and hot-spot formation in the area of current concentration. These effects are of interest in an investigation ofrelaxation mechanisms insemiconductors aswell as instudying possible new phenomena omrring in high-level integration electronic microcircuits.

This review is devoted to describing nonequilibrium carrier systems and relaxational and kinetic phenomena in three-dimensional point-contacts. Attention is focused on describing a phonon system which becomes substantially modified under conditions of ballistic transport. In such systems the energy fluxes are limited by the presence of weakly coupled layers of impurity atoms, planar defects, or microscopic-size contacts. The small size of point-contacts, ranging from several to 1000 nm, makes it possible to investigate low-temperature heat and charge transfer on scales less than the characteristic inelastic scattering lengths. A mechanism of phonon transport in the presence of an interface is analyzed, and various models of a planar defect are examined. The special features of interfacial phonon transport, where the transport coefficients are determined not by scattering processes in the volume of a bulk crystal but rather by the properties of the intercrystalline boundary, are studied. The quantum phonon thermal conductivity of point-contacts is studied in detail.