An epitaxially aligned ZnO nano-seed layer was used to improve the microstructure and crystal alignment in metalorganic chemical vapor deposited ZnO films on Al2O3 (0 0 0 1) substrates. Comparative investigations were performed on the properties of the ZnO films grown with and without the seed layer. The ZnO film grown directly on the substrate without applying the seed layer shows an irregular, leaf-like surface morphology with a large surface roughness. Moreover, its crystal alignment is random. In sharp contrast, a fairly smooth surface is observed for the ZnO film grown with the seed layer. In addition, the film shows an epitaxially aligned nature. Our results suggest that the insertion of the nano-seed layer be an effective way to grow well-oriented, smooth ZnO films. (c) 2004 Elsevier B.V. All rights reserved.