Growth of ZnO Nanoflower Arrays on a Patterned Sapphire Substrate

In this study, we investigated a novel technology to grow the ZnO nanoflower arrays on a patterned sapphire substrate using hydrothermal method. The process to prepare the substrate and grow ZnO nanoflower arrays were that the patterned concave sapphire substrates were cleaned using acetone, isopropyl alcohol, and D.I. water in an ultrasonic cleaner. Al sacrificial layer with the thickness of 600 nm was deposited using a thermal evaporation technology. The sol-gel process was used to deposit the ZnO seed layer on the patterned concave sapphire substrates, and then the ZnO seed layer was annealed at 500°C in Ar ambient for 1 h. The optical grade silicone A-B glue was coated on the ZnO seed layer and then the mixed solution of K₃Fe(CN)₆ : KOH : H₂O = 10 g : 1 g : 100 ml was used to etch the sacrificial Al layer. (f) A lift-off technology was used to move the ZnO seed layer/silicone A-B glue to silicon substrate. Finally, a hydrothermal method was used to grow the ZnO nanorods on the ZnO seed layer/silicone A-B glue/silicon substrate at 90°C with the different durations of 10 to 60 min. Focused ion beam system (FIB) was used to observe the cross sectional morphology of patterned ZnO seed layer. The crystal structural of the flower-like ZnO nanostructures was analyzed using X-ray diffraction (XRD) pattern, the morphological of the flower-like ZnO nanostructures was observed using FIB and field emission scanning electron microscope (FESEM). Also, the optical properties of the flower-like ZnO nanostructures were investigated.