Patterned zinc-oxide nanostructures are grown without using a metal catalyst by forming a seed layer of polycrystalline zinc oxide on a surface of a substrate. The seed layer can be formed by an atomic layer deposition technique. The seed layer is patterned, such as by etching, and growth of at least one zinc-oxide nanostructure is induced substantially over the patterned seed layer by, for example, exposing the patterned seed layer to zinc vapor in the presence of a trace amount of oxygen. The seed layer can alternatively be formed by using a spin-on technique, such as a metal organic deposition technique, a spray pyrolisis technique, an RF sputtering technique or by oxidation of a zinc thin film layer formed on the substrate.