Morphology and optical properties of Cu–Al co-doped ZnO nanostructures

Abstract

We have synthesized Cu–Al co-doped ZnO nanostructures with two steps processes i.e. seed deposition by ultrasonic nebulizer 1.7 MHz and ZnO nanorods were grown by chemical bath deposition (CBD) at 95 °C for two hours. According to scanning electron microscopy (SEM) images, the ZnO nanostructures change from nanorods to square nano-disks when Cu increased, and Al maintained constant. X-ray diffraction (XRD) pattern confirm that the Cu–Al co-doped ZnO nanostructures have a polycrystalline hexagonal wurtzite structure. Optically, the reflectance (R%), the transmittance (T%), and an absorbance of ZnO nanostructures influenced by the morphology. Further investigation, a proper content of Cu doping generates strong absorption in the range of ultraviolet (UV) and visible wavelength. Meanwhile, by increasing Cu content, the band gap energy of ZnO nanostructures tend to increase and photoluminescence (PL) energy in the visible range has a maximum peak of 1.75 eV. We believed the existence of Cu and Al compositions cause modification and the defects distribution change in ZnO nanostructures.