A novel method to synthesize large-scale ZnO nanoflower arrays using a protrusion patterned ZnO seed layer was investigated. Different thicknesses of aluminum (Al) film were deposited on the concave patterned sapphire substrate as a sacrificial layer. ZnO gel was layered onto the Al film as a seed layer and OE-6370HF AB optical glue was used as the adhesive material. A lift-off technique was used to transfer the protrusion patterned ZnO/AB glue seed layer to a P-type Si <100> wafer. The hydrothermal method using Zn(CH3COO)2 and C6H12N4 solutions as liquid precursors was used to synthesize ZnO nanoflower arrays on the patterned seed layer. X-ray diffraction spectra, field-effect scanning electron microscopy, focused ion beam milling (for obtaining cross-sectional views), and photoluminescence (PL) spectrometry were used to analyze the effects that different synthesis times and different thicknesses of Al sacrificial layer had on the properties of ZnO nanoflower arrays. These effects included an increased diameter, and a decreased height, density (i.e., number of nanorods in μm−2), total surface area, total volume, and maximum emission intensity of PL spectrum. We showed that when the synthesis time and the thickness of the Al sacrificial layer were increased, the emission intensities of the ultraviolet light and visible light had different variations.

In this study, the hydrothermal method was used to synthesize ZnO nanorods and ZnO nanoflower arrays. Two different substrates were used to prepare the ZnO seed layer. For the p-type silicon <100> wafer, a prepared ZnO gel was deposited as the seed layer using the spin coating method. When a patterned sapphire recess-type substrate was used as a template, Al film, with a thickness of 120 nm, and OE-6370HF AB glue were used as a sacrificial layer and an imprinting lithography carrier for the ZnO seed layer, respectively. To prepare the array-patterned ZnO seed layers with a protrusion structure, a lift-off technique was used. A 0.2 M solution of zinc acetate dihydrate (Zn(CH3COO)2-2H2O) was used at a synthesis temperature of 90°C and a synthesis time of 10–60 min. Because the ZnO seed layer had a protrusion and matrix structure, the ZnO nanorods grew in the vertical bottom direction to form ZnO nanoflower arrays. X-ray diffraction patterns, scanning electron microscopy, and a focused ion beam system were used to analyze and compare the crystal characteristics and the heights and widths of the ZnO nanorods and ZnO nanoflower arrays. We found that the photoluminescence properties were enhanced in the ZnO nanoflower arrays compared with the ZnO nanorods.