In this work an epitaxial Mg-Al spinel layer was successfully grown on a C- and A-plane sapphire single crystal surface by solid-state reactions. When observed by a scanning electron microscope, it can be seen that the morphology of an epitaxial spinel layer surface has a three-fold symmetrical structure. The results of X-ray diffraction analysis indicate that the surface morphology of the epitaxial spinel layer has particular crystallographic directions and the crystallographic directions will be influenced by the orientation of the sapphire substrates. (c) 2006 Elsevier B.V. All rights reserved.