Tuning optical band gap of vertically aligned ZnO nanowire arrays grown by homoepitaxial electrodeposition

Vertically aligned ZnO nanowire arrays are grown homoepitaxially on the ZnO seeded indium tin oxide substrate by electrochemical deposition from aqueous solution at low temperature $(70°\mathrm{C})$ without using any template. ZnO nanowires exhibit single crystalline, wurtzite crystal structure determined by transmission electron microscopy and powder x-ray diffraction. The ZnO nanowire arrays show high transmittance in the visible wavelengths. Interestingly, the optical band gap of the ZnO nanowire arrays has been tuned by simply changing zinc salts in the electrodeposition from aqueous solution.