Electronic structure and morphology of dark oxides on zinc generated by electrochemical treatment
By Chen, Ying; Schneider, Paul; Liu, Bi-Ju; Borodin, Sergiy; Ren, Bin & Erbe, Andreas
Published in Phys. Chem. Chem. Phys.
The Royal Society of Chemistry
2013
Abstract
Oxides formed by electrochemical treatment of metals frequently have properties and structures very different from the respective bulk oxides. Here, electronic structure and chemical composition were investigated for the oxide formed on polycrystalline zinc after electrochemical oxidation, and after subsequent reduction, in a Na2CO3 electrolyte. Photoluminescence and spectroscopic ellipsometry show the presence of states deep in the ZnO band gap in the oxidized sample, which consists of a highly disordered oxide. These states determine the absorption of light in the visible spectral range. After reduction, the characteristics of the ZnO electronic structure have disappeared, leaving a defect-dominated material with a band gap of [similar]1.8 eV. Complementary detailed analysis of the morphology of the resulting surfaces shows hexagon-shaped metallic Zn- nanoplates " to be formed in the reduction step. The optical appearance of the surfaces is dark