Insights into the Electrodeposition of Bi[sub 2]Te[sub 3]

In this paper, the processes associated with the electrodeposition of bismuth telluride ( Bi 2 Te 3 ) , a thermoelectric material, are reported along with an analysis of the composition and crystallinity of the resulting films. The electrodeposition can be described by the general reaction 3 HTeO 2 + + 2 Bi 3 + + 18 e − + 9 H + → Bi 2 Te 3 + 6 H 2 O . Cyclic voltammetry studies of Bi, Te, and Bi/Te dissolved in 1 M HNO 3 reveal two different underlying processes depending on the deposition potential. One process involves the reduction of HTeO 2 + to Te 0 and a subsequent interaction between reduced Te 0 and Bi 3 + to form Bi 2 Te 3 . A second process at more negative reduction potentials involves reduction of HTeO 2 + to H 2 Te followed by the chemical interaction with Bi 3 + . Both processes result in the production of crystalline Bi 2 Te 3 films in the potential range − 0.1 < E < − 0.52 V vs. Ag/AgCl (3 M NaCl) on Pt substrates as determined by powder X-ray diffraction (XRD). Electron probe microanalyses and XRD reveal that the films are bismuth-rich and less oriented for more negative deposition potentials.