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 2000.3em0exK. 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 0.100.3em0exeV, is considerably smaller than the activation energy of the electrical conductivity, about 0.280.3em0exeV. 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 0.10.3em0excm²∕V0.2em0exs at room temperature), anomalously signed (n-type), and increases with rising temperature with an activation energy of about 0.050.3em0exeV. These results are consistent with the charge carriers being holelike small polarons that move by thermally assisted hopping.