Utilizing microwave irradiation heating, 100-nm-diameter ZnO nanorods were grown from aqueous solution on sputtered ZnO films on glass substrates. Its out-of-plane X-ray diffraction (XRD) measurement indicated that the ZnO nanorods were grown with c-axis orientation, similar with the underlying ZnO films. In the in-plane XRD measurement, intensity of the (11 (2) over bar0) diffraction was comparable with that of the ( 10 (1) over bar0) one, suggesting their intensity ratio would contain useful information on nanorods density. (C) 2008 Elsevier B.V. All rights reserved.