Optimization of Electrodeposited p-Doped Sb2Te3 Thermoelectric Films by Millisecond Potentiostatic Pulses

• Published in: Advanced energy materials 2012-03, Vol.2 (3), p.345-352
• Main Authors: Schumacher, Christian, Reinsberg, Klaus G., Akinsinde, Lewis, Zastrow, Sebastian, Heiderich, Sonja, Toellner, William, Rampelberg, Geert, Detavernier, Christophe, Broekaert, José A. C., Nielsch, Kornelius, Bachmann, Julien
• Format: Article
• Language: English
• Subjects: antimony; pulsed electrochemical deposition; Seebeck coefficient; telluride; thermoelectrics
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201100585

A systematic optimization of p‐type Sb2Te3 thermoelectric films made by potentiostatic electrodeposition on Au and stainless steel substrates is presented. The influence of the preparative parameters of deposition voltage, concentration, and the deposition method are investigated in a nitric acid solution. As a postdeposition step, the influence of annealing the films is investigated. The use of a potential‐controlled millisecond‐pulsed deposition method could improve both the morphology and the composition of the films. The samples are characterized in terms of composition, crystallinity, Seebeck coefficient, and electrical resistivity. Pulsed‐deposited films exhibit Seebeck coefficients of up to 160 μV K−1 and an electrical conductivity of 280 S cm−1 at room temperature, resulting in power factors of about 700 μW m−1 K−2. After annealing, power factors of maximum 852 μW m−1 K−2 are achieved. Although the annealing of DC‐deposited films significantly increased the power factor, they do not reach the values of the pulsed‐deposited films in the preannealing state. Structural analysis is performed with X‐ray diffraction and shows the crystalline structure of Sb2Te3 films. The performance is tuned by annealing of deposited films up to 300 °C under He atmosphere while performing in‐situ X‐ray diffraction and resistivity measurements. The chemical analysis of the films is performed by inductively coupled plasma optical emission spectroscopy (ICP‐OES) as well as scanning electron microscope energy dispersive X‐ray analysis (SEM‐EDX). Electrodeposited thermoelectric films are fabricated from aqueous electrolytes using potentiostatically (DC) as well as potentiodynamically (pulsed) deposition methods. Pulsed‐deposited films show higher crystallinity and Seebeck coefficients than DC‐deposited films. Annealing improves the power factor of both the DC‐ and the pulsed‐deposited films. Structural improvements during annealing are detected by in‐situ X‐ray diffraction.