EFFECT OF DEPOSITION CONDITIONS ON THE MICROSTRUCTURE AND THE THERMOELECTRIC PROPERTIES OF GALVANOSTATICALLY ELECTRODEPOSITED Bi2Te3 FILM

Abstract

Bismuth Telluride ( Bi2Te3 ) films were deposited by a simple and cost-effective galvanostatic electrodeposition process from a solution containing bismuth tri-nitrate penta-hydrate and tellurium dioxide of different concentration ratios in 1 M nitric acid onto gold sputtered silicon substrate at various current densities. The effect of distinct current densities, electrolyte concentrations and electrodes distances on the microstructure and the thermoelectric properties of Bi2Te3 films were investigated. X-Ray diffraction (XRD) and field emission scanning electron microscope (FESEM) analysis ensured a high density, homogenous and near stoichiometric film. The surface morphology, crystalline structure and grain size were correlated with the applied current density. A prominent orientation (110) was observed for all the films and the grain size was acquired from 21 to 45 nm. The Seebeck measurement affirmed n-type semiconductor behavior of the deposited films. Enhancement in carrier mobility without significant change of the carrier concentration and Seebeck coefficient was achieved by tuning the electrodes distance. The thermoelectric film has a maximum measured Seebeck coefficient of –61.215 μV/K and a very high electrical conductivity of 2.13 × 103 Ω-1 ⋅ cm n-1. The maximum calculated power factor was 8.2 μ W ⋅ K -2 ⋅ cm -1.