Selective growth of ZnO nanorods on pre-coated ZnO buffer layer

Hexagonal ZnO nanorods have been selectively synthesized via vapor-solid process without gold catalysis on a pre-coated ZnO buffer layer. The presence of nanometer-sized pits or hills on the surface of ZnO buffer layer provides nucleation sites to which the zinc vapor is transferred and condensed. Followed by immediate oxidation the ZnO nanorods were grown on the buffer layer. Contrarily, the SEM images hardly show growth of irregular ZnO nanometer-sized products on the bare sapphire substrate. Besides a strong ultra-violet emission at 3.26 eV observed at room temperature, the coupling strength of the radiative transition to LO-phonon polarization field was deduced in use of the Huang-Rhys factor from low temperature photoluminescence spectra to show that single crystalline ZnO nanorods.