Transport properties of amorphous antimony telluride

The electrical conductivity, Seebeck coefficient, and Hall coefficient of micron thick films of amorphous Sb2Te3 have been measured as functions of temperature from room temperature down to as low as 200 K. The electrical conductivity manifests an Arrhenius behavior with a pre-exponential factor that is larger than that of a conventional semiconductor. The Seebeck coefficient is p type. Unlike a conventional semiconductor, the energy characterizing the Seebeck coefficient's temperature dependence, about 0.10 eV, is considerably smaller than the activation energy of the electrical conductivity, about 0.28 eV. In addition, the heat-of-transport constant of the Seebeck coefficient is much larger than that of conventional semiconductors. The Hall mobility is low (near 0.1 cm(2)/V s at room temperature), anomalously signed (n-type), and increases with rising temperature with an activation energy of about 0.05 eV. These results are consistent with the charge carriers being holelike small polarons that move by thermally assisted hopping.