Preparation And Characterisiation Of ZnO/ZnAl₂O₄, Co₃O₄-ZnO/ZnAl₂O₄ Films

ZnO thin films, especially ZnO composite films, have attracted considerable attention because the composite semiconductors could generate new synergetic properties. Development of a simple, economical and environmentally friendly fabrication process for ZnO composite films is essential if their potential applications are to be realized in practice.In this work, we report a precursor route to fabricate ZnO/ZnAl₂O₄, and ZnO-Co₃O₄/ZnAl₂O₄ composite films by thermal decomposition of layered double hydroxides (LDHs). The crystallographic structure, microstructure, chemical composition and optical property of the samples are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photo-electron spectroscopy (XPS) and UV-Vis spectroscopy. The results show that ZnO single crystals are embedded in a matrix of nanoparticles Co₃O₄/ZnAl₂O₄, forming porous Co₃O₄-ZnO/ZnAl₂O₄ composite films. In addition, the shape and sizes of ZnO are controlled by changing the initial molar ratio of [Co²⁺+ Zn²⁺] / Al³⁺. The details are as follows:1. The well dispersed and stable suspension precursors of ZnAl-CO₃-LDHs and CoZnAl-CO₃-LDHs were synthesized by separate nucleation and aging steps. The resulting slurries were cast on theα-Al₂O₃ and quartz substrate, followed by drying and sintering at 900℃, forming composite films, ZnO/ZnAl₂O₄ and Co₃O₄-ZnO/ZnAl₂O₄.2. The effect of Co₃O₄ on the control of crystal size for ZnO and ZnAl₂O₄ is discussed in the paper. CO₃O₄ doping were found to increase the crystallization interfacial energy of ZnO, then the crystal nucleus formation is inhibited, crystal growth is promoted, meanwhile, ZnAl₂O₄ particle growth can be controlled by the Co₃O₄, which will segregate and contribute toward its inhibition.