Influence of potential barriers on the thermoelectric properties of PbTe thin films

Abstract

The PbTe films, 0.4-3 /spl mu/m thick, were formed on different substrates by the method of flash evaporation. The samples had a single crystal structure with blocks and the angle of misorientation was /spl les/1/spl deg/. The dimensions of the blocks were /spl sim/1 /spl mu/m for the films on mica. Block boundaries were a system of edge dislocations. On one side of each dislocation there was a region of compression and on the other a region of dilatation. Regardless of the sign of the deformation potential, potential energy relief is formed near a block boundary. Estimates obtained using parameters of bulk PbTe have shown that the energy barrier can reach 0.1 eV. The electrical conductivity /spl sigma/, Seebeck coefficient S, Hall coefficient R, and Nernst-Ettingshausen coefficient Q were measured in the 80-500 K range. A comparison with bulk PbTe single crystals with the same charge concentration indicates that the films were characterized by a higher parameter S/sup 2//spl sigma/. This difference was attributed to energy-selective carrier scattering by potential barriers. The potential relief in PbTe thin films was obtained using an electron-beam induced current. Doping of PbTe films with certain impurities can be used to control their barrier properties.