Electrical properties of underformed and plastically deformed bismuth-thallium and bismuth-lead systems in the temperature range 4.2 to 300 K

Abstract

Measurements of electrical conductivity and Hall coefficient have been made on undeformed and plastically deformed states of Bi-Tl (Bi + 3.92 at % Tl) and Bi-Pb (Bi + 4.00 at % Pb) single-crystal specimens, from 4.2 to 300 K. The carrier concentrationn and the Hall mobilityμ obtained from these measurements show strong dependence on temperature. From the variation ofn with temperature, there is evidence for bend gaps of 40 meV obtained from observations between 100 and 300 K for Bi-Tl, and 18 meV between 70 and 300 K for Bi-Pb, in the undeformed states of the specimens. Theme band gaps increase due to plastic deformation. In the low-temperature region, the increase and the subsequent decrease inn have been explained on the basis of a thermal activation process and a phonon-induced electron-hole recombination process. The activation energies thus observed in the undeformed state of the specimens have been greatly reduced due to plastic deformation. These results show that the band structure of bismuth is greatly affected by doping, end that of the doped specimens of bismuth is further affected by plastic deformation. There is a correspondence between the increase inn and the decrease inμ and vice versa, over the entire range of temperature. The dependence ofμ onT has been utilized to identify the scattering mechanisms.