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

摘要

Nanostructured n-type bismuth telluride (Bi_2Te_3) thin films were grown on SiO_2/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 temper ature (T_s) of 220-340℃ , stoichiometric films with highly (001)-oriented and layered structures showed the best properties, with a carrier mobility μ of 83.9-122.3 cm~2/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 μWcm~(-1) K~(-2). By contrast, the Te-rich films deposited at T_s< 120℃ with (015)-preferred orientations and columnar-small grain structures or the Te-defkient film deposited at 380℃ with Bi_4Te_5 polyhedron structure possessed poor properties, with μ< 10.0 cm~2/Vs, |α| < 54 μV/K, and PFs < 0.44 μW cm~(-1) K~(-2). The morphology of highly (001) oriented-layered structures and the stoichiometry predominantly contribute to the substantial enhancement of μ and |α|, respectively, resulting in remarkable enhancement in PF.