Effect of prefiring condition on the in-plane orientation of epitaxial oxide films in coating-pyrolysis process

Epitaxial alpha -Fe2O3 films were obtained by using iron 2-ethylhexanoate a s a starting material. A coating solution was spun on alpha -Al2O3 single-c rystal substrates, and prefiring and final heat-treatment at various temper atures in air or low oxygen partial pressure were carried out. The degree o f in-plane orientation was estimated in terms of full width at half maximum of X-ray diffraction (XRD) phi -scans. The results of TG-DTA, IR, and XRD suggested that the optimum prefiring condition for obtaining highly epitaxi al films is in the range 200-300 degreesC which corresponds to removal of m ost of the organic component from the precursor, prior to crystallite forma tion of metal oxide. When the films were prefired at higher temperatures, d ifferent atmospheres in prefiring and final heat-treatment lowered the in-p lane orientation of the films.