Improvement of dielectric properties of ZnO nanoparticles by Cu doping for tunable microwave devices

We report a facile chemical polyol method to synthesize Cu-doped ZnO nanoparticles with various levels of Cu. X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV–Visible diffuse reflectance spectroscopy techniques were used to analyze the structural and optical properties of Zn 1− x Cu x O nanoparticles. The crystallite size varies between 9.8 and 18.9 nm and decreased with the increase of Cu doping. The band energy gaps of pure and Cu-doped ZnO samples are in the range 2.5–3.1 eV. The dielectric properties, ac conductivity and impedance analysis of Zn 1− x Cu x O nanoparticles were systematically investigated. It was revealed that the doping of ZnO by Cu (with low Cu molar content) leads to obtain high dielectric constant and low tangent loss, which are very encouraging for microwave semiconductor devices.