ZnO Nanowire-Based Antireflective Coatings with Double-Nanotextured Surfaces

High-aspect-ratio nanotextured surfaces with different morphologies (straight, core-shell type, and core-branch type nanowires) are prepared by a hydrothermal method of ZnO nanowires, followed by means of RF sputtering for core-shell type nanowires and e-beam evaporation for branch-type nanowires. The structural analysis showed that the MgO has highly preferred orientation along the ⟨111⟩ and ⟨200⟩ direction, respectively, and the crystalline continuity between the ZnO and MgO layers were also showed. Compared with ZnO nanowires, the MgO/ZnO samples drastically suppress broad and omnidirection reflection, which ascribes to the refractive-index modulation along the lateral direction of nanowires growth as well as the vertical direction. It was also shown that morphology could have a substantial influence on the antireflection property. These results suggest that double-nanotextured surface is one of the promising structures for antireflective surfaces without fine control in nanowire morphology.