Selective Electrodeposition and Growth Mechanism of Thermoelectric Bismuth-Based Binary and Ternary Thin Films

Abstract

Different morphologies of thermoelectric Bi(1-x)Sb(x) and Bi(2-x)Sb(x)Te(3) thin films, including rods, dendrites, thin sheets, and spherical particles, were selectively obtained by an electrodeposition method at room temperature (25 degrees C). Cyclic voltammetry was used for determination of the deposition potentials of thin films. The influences of the deposition potential and the electrolyte composition on the films were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were employed to characterize the thin films. It was found that the different shaped Bi-rich Bi(1-x)Sb(x) films can be obtained by tuning the electrolyte composition. However, the Bi(2-x)Sb(x)Te(3) films can be fabricated by changing the deposition potential. In underpotentials (UPD), the reduction reactions of Bi(3+), Te(4+), and Sb(3+) take place to form (Bi(0.5)Sb(0.5))(2)Te(3). When the potential shifts into overpotentials (OPD), Bi(0.5)Sb(1.5)Te(3) is formed on the electrode surface. The EDS data indicates that the composition of the films is consistent with XRD results. The SEM investigations show that the growth mechanism of deposited Bi(1-x)Sb(x) and Bi(2-x)Sb(x)Te(3) films depends on the electrolyte composition and the deposition potential, respectively.