SEM images. Schematic illustration of the strategy for fabricating patterned quasi-1D ZnO nanowire arrays. Bottom of (a) shows low-magnification SEM image of the self-assembled monolayer polystyrene spheres. Inset is the high-magnification SEM image. Bottom of (b) reveals top-view SEM image of sol–gel-derived ZnO thin film patterned by periodic nanospheres. Bottom of (c) shows tilt-view SEM image of quasi-1D ZnO nanowire arrays grown on ZnO buffer layer, where the hexagonal pattern is apparent.