The surface morphology of ZnO grown on p-GaN templates and p-Si ( 1 1 1) substrates at various temperatures by metal organic chemical vapor deposition (MOCVD) in a vertical reactor at atmospheric pressure is reported. A low temperature ZnO buffer was deposited initially at 200 degrees C for 15 min as a nucleation layer. Epitaxial ZnO was grown at 500 degrees C, 550 degrees C, 600 degrees C for 40 min, respectively. Uniformly distributed and well-aligned ZnO nanorods with diameter in the range 80-120 nm and length similar to 0.7 mu m were observed for deposition on p-GaN template. By contrast, themorphology of ZnO epilayers grown on p-Si (1 1 1) transitioned from 2D to 3D with increasing growth temperature. X-ray diffraction (XRD) spectra showed all the ZnO epilayers had the hexagonal wurtzite structure but different preferred orientation. PL spectra showed only free-exciton emission at 378 nm (similar to 3.28 eV) with a full width at half maximum of 13 nm without defect-related green emission in the epitaxial ZnO grown at 550 degrees C and 600 degrees C. The epitaxial ZnO layers grown on p-GaN and p-Si at the same temperature have similar PL spectra. The PL measurement also exhibits strong exciton-related emission without defect peak, which showed that the ZnO nanostructures grown at 550 degrees C and 600 degrees C have good optical properties with excellent crystal quality. (C) 2008 Elsevier B.V. All rights reserved.