ZnO nanorods were epitaxially grown by metalorganic chemical vapour deposition (MOCVD) on sapphire (0001) and (112-bar 0) substrates. The nanorods were elongated along the ZnO c-axis which was parallel to the substrate normal. Good alignment among the rods was achieved both in the length direction and in the in-plane orientations. The line width of bound exciton emissions was <= 1 meV at low temperatures. Emissions due to free excitons were observed from low to room temperature. Biexciton emissions were observed up to approx 200 K. The band edge emission at room temperature was found to be a mixture of emissions due to free excitons and other impurity-related emissions, indicating that care must be taken when assigning the emission peak at higher temperatures.
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