Abstract
ZnO flower‐like nanostructures were grown on Ge (100) substrate, by a modified chemical vapor condensation technique of zinc acetate dihydrate at 300 °C, without using any catalyst. These self‐organized three‐dimensional nanostructures were composed of hierarchical arrangement of ZnO nanorods of diameter ∼50 nm around a common nucleus and were distributed uniformly over the entire substrate surface. Evolution study of these structures indicates that the growth begins with a two‐dimensional planar arrangement of 〈0001〉‐oriented ZnO nanorods. With increasing growth time, the expanding adjacent two‐dimensional growth fronts approach each other, followed by which, the formation of three‐dimensional flower‐like structures evolve. Surface diffusion mechanism seems to play an important role in forming these nanostructures, which has been discussed in detail. Elaborate electron microscopic (SEM, TEM) techniques have been used to investigate the growth characteristics of the flower structures. The photoluminescence measurements showed pure free excitonic transition centered at about 3.249 eV with full width at half‐maximum of about 141 meV at 300 K, which blue shifted to 3.361 eV at 10 K with corresponding half width of 7 meV with no defect‐related bandgap peak due to relatively low growth temperature. The optical emission area was imaged through a cathodoluminescence technique.
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Scanning electron micrograph of a typical ZnO nanorod flower structure grown at 300 °C on Ge (100).