Structural and optical properties of electrodeposited ZnO thin films on conductive RuO2 oxides

Abstract

ZnO thin films were grown on the 150nm-thick RuO2-coated SiO2/Si substrates by electrochemical deposition in zinc nitrate aqueous solution with various electrolyte concentrations and deposition currents. Crystal orientation and surface structure of the electrodeposited ZnO thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy, respectively. The XRD results show the as-electrodeposited ZnO thin films on the RuO2/SiO2/Si substrates have mixed crystallographic orientations. The higher electrolyte concentration results in the ZnO thin films with a higher degree of c-axis orientation. Moreover, the use of an ultra-thin 5nm-thick ZnO buffer layer on the RuO2/SiO2/Si substrate markedly improves the degree of preferential c-axis orientation of the electrodeposited ZnO crystalline. The subsequent annealing in vacuum at a low temperature of 300°C reduces the possible hydrate species in the electrodeposited films. The electrodeposited ZnO thin films on the 5nm-thick ZnO buffered RuO2/SiO2/Si substrates grown in 0.02M electrolyte at −1.5mA with a subsequent annealing in vacuum at 300°C had the best structural and optical properties. The UV to visible emission intensity ratio of the film can reach 7.62.