Date of Award

1980

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

An investigation of the roles of carrier diffusion and carrier-phonon drag in the thermoelectric power, the Ettingshuasen and Nernst-Ettingshausen effects was carried out on single crystals of antimony at low temperatures. Previous investigations have shown that the ideal resistivity and the high field resistivity are characterized by strong mutual drag. Here the Ettingshausen and Nernst-Ettingshausen effects were characterized by a strong simple drag. In contrast to these two extreme cases the thermoelectric power exhibited a clear admixture of the two drag conditions. Interpretation of Ettingshausen and Nernst-Ettingshausen data indicates that these two measurements are less reliable for the determination of the density of states than had been previously assumed because of the presence of surface conduction and size effects. The transport properties of an antimony single crystal in a Corbino geometry at low temperature (1.1-4.2(DEGREES) K) and high magnetic field (4-20 KG) was studied. In this geometry the sample is in the form of a circular disk in which the current entered along the axis, flowed radially to the circumference where it left the sample. In this situation the circular symmetry does not permit the existences of either azimuthal temperature gradients or electric field. Therefore, the geometry could be used for the isothermal magnetoconductivity and isopotential thermal magnetoconductivity measurements. The effect of surface current on the magnetoresistance, (rho)(,11), in the Corbino geometry was investigated. This effect can be observed by studying the magnetic field and thickness dependence of the magnetoresistance of the sample. The experimental results did not reveal a quadratic field dependence of magnetoresistance, (rho)(,11), as predicted by Lifshitz, Azbel, Kaganou theory. In general (rho)(,11) (PROPORTIONAL)H('(alpha)), where (alpha) is always smaller than two and depends on the surface treatment of the sample. The largest values for (alpha) and (rho) were obtained with the electropolished sample. These results are consistent with those obtained in a rod geometry. The results of the thickness effect study in a Corbino geometry revealed that the effect was smaller than in a rod geometry, and apparently, for thickness greater than about 3 mm, the measured magnetoresistivity was almost independent of the thickness of the sample. An experimental investigation of the lattice thermal conductivity in the rod and Corbino geometries indicates that the boundary scattering in the Corbino geometry is much smaller than in the rod geometry. This parameter is responsible for a large difference between the measured lattice thermal conductivity in these geometries. Theoretical study of the phonon fan effect, which is a result of phonon drag in the Corbino geometry, showed that the radial temperature gradient due to this effect is not only much smaller than that caused by the selfheating, but also it had the same current dependence (quadratic) as the selfheating does.

Pages

139

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