X-ray Absorption Studies on Cu-doped ZnO Nanoparticles Synthesized by Coprecipitation Method

Copper-doped ZnO (CZO) nanoparticles have successfully been synthesized by coprecipitation method with Cu concentrations ranging from 0 to 5 wt%. The effect of Cu concentration on electrical properties and the oxidation state of ZnO were investigated. The x-ray diffraction (XRD) pattern analysis shows CZO phase formed with calcination at 400°C for 3 h. The crystal size of CZO nanoparticles, evaluated using MAUD software, is in the range of 56 - 90 nm. It was obtained that the Cu doping has reduced the optical band gap from 2.85 eV to 3.06 eV, while the electrical conductivity increased from 1.03 x 10^-8 to 24.25 x 10^-8 S/cm. The highest conductivity of CZO is achieved by the sample doped with 4 wt% Cu. This result has been further studied by the x-ray absorption near edge spectroscopy (XANES) measurement at Cu K-edge related to the oxidation state of the Cu ions substituting Zn sites.