Formation of hierarchical ZnO nanostructures “nanocombs”: Growth mechanism, structural and optical properties

ZnO nanocombs have been fabricated in high yield via a thermal evaporation process on Si(1 1 1) substrate by using metallic zinc powder and oxygen as source materials for zinc and oxygen, respectively, without the use of catalyst or additives at low-temperature. Morphological investigations revealed that the nanocombs were grown in high density over the whole substrate surface. The branches (teeth) of the nanocombs are uniform and nicely attached along one side of the ribbon-like stem and are arranged in a proper manner. X-ray diffraction patterns confirmed that the grown nanostructures were single-crystalline and possessed a wurtzite hexagonal phase. Room-temperature photoluminescence (PL) spectrum of the grown nanostructures is exhibit a dominant, sharp and strong UV emission with a suppressed deep-level emission indicating good crystallinity and optical properties for the as-grown ZnO nanocombs.