Coating process of ZnO thin film on macroporous silica periodic array

ZnO was deposited onto a 3D ordered macroporous SiO2 structure using sol-gel method with reverse dip-coating. It was observed that a very thin layer of ZnO film formed on the surface of the macroporous SiO2 using field emission scanning electron microscopy (FESEM). This thin layer was approximately 70 nm thick. The layer was near transparent, clearly revealing the macroporous SiO2 structure underneath. The formation of this ZnO thin film suggests that miniscule air spheres trapped within the pores of the SiO2 structure prevent the ZnO precursor sol from entering into these preoccupied positions. This unique structure can probably serve as an embedded planar defect for photonic crystals in the future and is believed to exhibit unusual photonic and luminescence properties which hold novel future applications.