Optimization of chemical and electrochemical parameters for the preparation of n-type Bi2Te2.7Se0.3 thin films by electrodeposition

A 2(3) (1) fractional factorial design comprising four runs and three centre points was applied in order to optimize the electrodeposition process to find a compound with the best stoichiometry leading to a Bi2Te2.7Se0.3 thin film suitable for thermoelectric applications. The key factors considered were the deposition potential, the percentage of bismuth and the percentage of selenium in the solution. The Bi-III, Se-IV, Te-IV electrolyte mixtures in 1 M HNO3 (pH 0), allowed deposition of ternary alloys to be achieved at room temperature on stainless steel substrates. The deposition mechanism was investigated by linear voltammetry. The films were characterized by micropobe analysis, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The XRD patterns of the film show that the as-deposited are polycrystalline and isostructural to Bi2Te3. The SEM study shows that the film is covered by crystallites while the AFM image reveals a low level of roughness.