Abstract
Nanostructured n-type bismuth telluride (Bi <sub>2</sub> Te <sub>3</sub> ) thin films were grown on SiO <sub>2</sub> /Si (1 0 0) substrates at argon ambient pressure (P <sub>Ar</sub> ) of 80 Pa by pulsed laser deposition (PLD). The effects of film morphologies, structures, and compositions on the thermoelectric properties were investigated. At a substrate temperature (T <sub>s</sub> ) of 220-340 °C, stoichiometric films with highly (0 0 l)-oriented and layered structures showed the best properties, with a carrier mobility μ of 83.9-122.3 cm <sup>2</sup> /Vs, an absolute Seebeck coefficient |α| of 172.8-189.7 μV/K, and a remarkably high power factor (PF) of 18.2-24.3 μW cm <sup>-1</sup> K <sup>-2</sup> . By contrast, the Te-rich films deposited at T <sub>s</sub> ≤ 120 °C with (0 1 5)-preferred orientations and columnar-small grain structures or the Te-deficient film deposited at 380 °C with Bi <sub>4</sub> Te <sub>5</sub> polyhedron structure possessed poor properties, with μ < 10.0 cm <sup>2</sup> /Vs, |α| < 54 μV/K, and PFs ≤ 0.44 μW cm <sup>-1</sup> K <sup>-2</sup> . The morphology of highly (0 0 l) oriented-layered structures and the stoichiometry predominantly contribute to the substantial enhancement of μ and |α|, respectively, resulting in remarkable enhancement in PF. © 2014 Published by Elsevier B.V.