Thermoelectric properties of nanostructured bismuth-telluride thin films grown using pulsed laser deposition

Abstract

Nanostructured n-type bismuth telluride (Bi2Te3) thin films were grown on SiO2/Si (100) substrates at argon ambient pressure (P-Ar) 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-s) of 220-340 degrees C, stoichiometric films with highly (001)-oriented and layered structures showed the best properties, with a carrier mobility mu of 83.9-122.3 cm(2)/Vs, an absolute Seebeck coefficient vertical bar alpha vertical bar of 172.8-189.7 mu V/K, and a remarkably high power factor (PF) of 18.2-24.3 mu W cm(-1) K-2. By contrast, the Te-rich films deposited at T-s <= 120 degrees C with (015)-preferred orientations and columnar-small grain structures or the Te-deficient film deposited at 380 degrees C with Bi4Te5 polyhedron structure possessed poor properties, with mu < 10.0 cm(2)/Vs, vertical bar alpha vertical bar < 54 mu V/K, and PFs <= 0.44 mu W cm(-1) K-2. The morphology of highly (001) oriented-layered structures and the stoichiometry predominantly contribute to the substantial enhancement of mu and alpha vertical bar, respectively, resulting in remarkable enhancement in PF. (C) 2014 Elsevier B.V. All rights reserved.