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 (PAr) of 80Pa by pulsed laser deposition (PLD). The effects of film morphologies, structures, and compositions on the thermoelectric properties were investigated. At a substrate temperature (Ts) of 220–340°C, stoichiometric films with highly (00l)-oriented and layered structures showed the best properties, with a carrier mobility μ of 83.9–122.3cm2/Vs, an absolute Seebeck coefficient |α| of 172.8–189.7μV/K, and a remarkably high power factor (PF) of 18.2–24.3μWcm−1K−2. By contrast, the Te-rich films deposited at Ts⩽120°C with (015)-preferred orientations and columnar-small grain structures or the Te-deficient film deposited at 380°C with Bi4Te5 polyhedron structure possessed poor properties, with μ<10.0cm2/Vs, |α|<54μV/K, and PFs⩽0.44μWcm−1K−2. The morphology of highly (00l) oriented-layered structures and the stoichiometry predominantly contribute to the substantial enhancement of μ and |α|, respectively, resulting in remarkable enhancement in PF.