ELECTROTRANSPORT IN SINGLE-CRYSTAL BISMUTH TELLURIDE

Abstract

The movement of silver, gold, and copper in single-crystal bismuth telluride has been measured, parallel to the cleavage planes, as a function of temperature for two current densities. At the lower current density (150 A/cm2) movement occurred always to the cathode. At the higher current density (250 A/cm2) a transition occurred from cathodic movement below about 300 °C to bipolar movement—to both the anode and the cathode. This effect remained in evidence up to about 400 °C with an increasing tendency to anodic migration with increase of temperature. By about 400 °C essentially all transport occurred to the anode.The bipolar movement is considered to be due to the metal ions occupying two types of sites in the bismuth telluride lattice where different electrical forces are present.Similar experiments with iodine-doped bismuth telluride indicated negligible movement of iodine under comparable conditions.