Electrodeposition and thermoelectric characterization of Bi2Te3

Bismuth and tellurium were electrodeposited from acidic aqueous solutions of Bi-2(SO4)(3) and K2TeO3 at constant potentials in order to produce a Bi2Te3 film for miniaturized thermoelectric devices. Electrodeposition behavior was examined using cathodic polarization and electrochemical quartz crystal microbalance techniques. The solution composition and the cathodic potential affected the chemical composition, preferred crystal orientation, and thermoelectric characteristics of the deposits. Films electrodeposited at potentials more positive than -100 mV vs Ag/AgCl had a dense, smooth surface and high crystallinity. The film composition depended more strongly on the solution composition than on the applied potential. A stoichiometric Bi2Te3 film could be obtained from a solution containing 2 mM Bi(III) and 2.6 mM Te(IV). The Seebeck coefficient increased with Te content of the film and was inversely proportional to the electrical conductivity. The highest power factor (7.4x10(-4) Wm(-1) K-2) was obtained in the case of the Bi2Te3 film electrodeposited at 0 V, 293 K, pH 0.5, in a sulfuric acid solution containing 2 mM Bi(III) and 2 mM Te(IV); the film contained 57 mol % Te, corresponding to Bi-rich and a carrier concentration of 6.6x10(20) cm(-3).