A quantitative roughness and microstructural analysis of ZnO grown on sapphire by atmospheric metalorganic chemical vapor deposition (MOCVD) is presented. In order to investigate the influence of the substrate on the morphology, different sapphire orientations have been employed. Scanning force microscopy data have been analyzed for a variety of thicknesses to elucidate, if possible, the growth mechanisms involved in the growth process. Our study reveals significant differences between morphologies depending on whether the substrate surface exhibits steps (misoriented a-, c- and r-planes) or not (m-plane); however, no major differences on the calculated roughness coefficients have been found. (C) 2004 Elsevier B.V. All rights reserved.