This study reports on the synthesis of ternary semiconductor (BixSb1-x)(2)Te-3 thin films on Au(1 1 1) using a practical electrochemical method, based on the simultaneous underpotential deposition (UPD) of Bi, Sb and Te from the same solution containing Bi3+, SbO+, and HTeO2+ at a constant potential. The thin films are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and reflection absorption-FTIR (RA-FTIR) to determine structural, morphological, compositional and optic properties. The ternary thin films of (BixSb1-x)(2)Te-3 with various compositions (0.0 <= x <= 1.0) are highly crystalline and have a kinetically preferred orientation at (0 1 5) for hexagonal crystal structure. AFM images show uniform morphology with hexagonal-shaped crystals deposited over the entire gold substrate. The structure and composition analyses reveal that the thin films are pure phase with corresponding atomic ratios. The optical studies show that the band gap of (BixSb1-x)(2)Te-3 thin films could be tuned from 0.17 eV to 0.29 eV as a function of composition. (C) 2010 Elsevier Ltd. All rights reserved.