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Reduction of threading dislocations in ZnO/(0001) sapphire film heterostructure by epitaxial lateral overgrowth of nanorods J. Appl. Phys.Growth mechanism and properties of ZnO nanorods synthesized by plasma-enhanced chemical vapor deposition Highly arrayed ZnO nanorods were fabricated on the Si substrate buffered with patterned ZnO film ͑ZnO f /Si͒ via wet-chemical process. The growth behavior and morphology of single-crystal ZnO nanorods ͑ZNs͒ were investigated in terms of the annealing temperatures of the sputtered ZnO film. We found that the growth morphology of ZnO nanorods is strongly dominated by the grain size of the ZnO film on the Si substrate. The ZnO f / Si substrate was annealed at above a critical temperature to promote the crystallization of ZnO phase, and high-resolution transmission electron microscopy demonstrated that both ZNs and ZnO f on Si substrate are coherent. Furthermore, the ZNs seem to nucleate from the concave tip near the grain boundary between two ZnO grains in the ZnO film because of higher surface energy. However, a higher annealing temperature may lead to the formation of a larger ZnO crystal due to the coplanar coalescence behavior of several individual ZnO nanorods.

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The undoped ZnO films were grown on silicon ͑001͒ substrates by radio frequency magnetron sputtering. The dependence of defect formation and photoluminescence ͑PL͒ of ZnO films on the annealing temperature and oxygen mole ratio ͑OMR͒ were investigated using X-ray diffraction and PL spectra. A sharp ZnO ͑002͒ peak with a strong UV emission peak around 3.28 eV can be obtained for the films annealed in O 2 and N 2 atmospheres. However, the films annealed in nitrogen show strong deep-level emission peaks that vary with the annealing temperature. Below 850°C, Zn interstitials become the dominant point defects, but for the ZnO films annealed at higher temperatures such as 1000°C, oxygen vacancies become the predominant point defects. In contrast, in an oxygen atmosphere, a strong UV emission along with invisible deep-level peaks can be detected for ZnO films sputtered at an OMR of 5% and annealed at 850°C. This result is attributed to the enhanced crystallization and a reduced defect concentration.