Microstructure characterization of δ-Bi2O3 thin film under atmospheric pressure by means of halide CVD on c-sapphire

The microstructure of epitaxial δ-Bi2O3 thin films deposited by means of atmospheric pressure halide chemical vapour deposition on a c-sapphire substrate surface at 800  °C using BiI3 and O2 as starting materials has been investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is shown that the δ-Bi2O3 films deposited on the c-sapphire substrate are epitaxially grown, keeping an orientation (1 1 1)δ-Bi2O3//(0 0 0 1)sapphire and [1 1 0]δ-Bi2O3//[1 1−2 0]sapphire in spite of a large lattice mismatch of 17.8% between [1 1 0]δ-Bi2O3 and [1 1−2 0]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.