Single-step electrodeposition of polycrystalline CdSe microwire arrays: structural and optical properties

In this work we report on the single-step synthesis of CdSe microwires with good crystalline characteristics by template-assisted electrochemical deposition from an electrolytic solution containing CdSO4+SeO2 and sulfuric acid. Deposition was conducted at three different temperatures (25 C, 60 C and 80 C) under potentiostatic control using a commercial nanoporous alumina membrane as the working electrode. The best results were obtained when the electrodeposition was carried out at E=-0.610 V vs. Ag/AgCl and T=80 C. Under these experimental conditions, the microwires are uniform, well aligned, have a high packing density, and present a good crystalline character according to XRD analysis. TEM observations revealed that they are dense and continuous, with a mean diameter ranging from 360-380 nm, greater than the channel diameters of the alumina template used. A detailed study of the reflectance in the region close to CdSe bandgap energy allows the determination of a weak direct absorption edge at 1.65 eV, close to the bulk bandgap energy. The Raman spectra consist of a strong mode centered at 208 cm-1 arising from the LO phonon and a somewhat weak, but still strong, mode arising from the second order LO(2LO) appearing at 415 cm-1. (orig.)