The microstructure of epitaxial delta-Bi2O3 thin films deposited by means of atmospheric pressure halide chemical vapour deposition on a c-sapphire substrate surface at 800 degrees C using BiI3 and O-2 as starting materials has been investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is shown that the delta-Bi2O3 films deposited on the c-sapphire substrate are epitaxially grown, keeping an orientation (111)delta-Bi2O3//(0001)sapphire and [110]delta-Bi2O3//[11-20]sapphire in spite of a large lattice mismatch of 17.8% between [110]delta-Bi2O3 and [11-20]sapphire. The mismatch is relaxed by misfit dislocations near their interface. Therefore, the deposited films have flat surface, a good crystal quality and contain low density of dislocation excluding the area near the interface. (c) 2004 Elsevier B.V. All rights reserved.