Effect of Substrate on the Structure and Thermoelectric Properties of n-Type Bi2Te3−ySey Thin Films Prepared by Electrodeposition

n-Type Bi2Te3−ySey thin films were prepared by potentiodynamic electrodeposition onto Au, Bi, and Bi2Te3−ySey substrates at room temperature. The electrochemical behaviors of Bi3+, HTeO2+, and H2SeO3 on different substrates were investigated by cyclic voltammetry. The morphology, composition, and structure of the films were studied by using environmental scanning electron microscopy (ESEM), energy-dispersive spectroscopy (EDS), and x-ray diffraction (XRD), respectively. The thermoelectric properties of n-type Bi2Te3−ySey films were determined by measuring the Seebeck coefficient (α) and electrical resistivity (ρ). The results showed that the composition and morphology of the films were sensitive to the substrate material. X-ray diffraction (XRD) analysis indicated that the preferred orientation of annealed films was affected by the substrate and that the film prepared on the Bi2Te3−ySey substrate exhibited the strongest (015) orientation, with rhombohedral structure. It was proved that the properties of the annealed films could be affected by the substrate and that the film with the highest power factor (P = α2/ρ) was obtained on the Bi2Te3−ySey substrate.