Thermally induced transformations at an ion implanted alpha-Fe2O3/alpha-Al2O3 interface: A Mossbauer spectroscopy study

Thermally induced chemical transformations at the interface between a 100 nm alpha-Fe2O3 and a polycrystalline alpha-Al2O3 substrate are studied and compared for the cases of the as-formed and ion bombarded interfaces. The thermal annealings are carried out under vacuum at 450 degrees C for different time durations and the transformations are examined by conversion electron Mossbauer spectroscopy. It is shown that in the sample prebombarded with 110 keV Ar+ ions, the formation of Fe3-xAlxO4, FeAl2O4, and FeO phases is favored at variance with a nonbombarded sample in which primarily a defective Fe3O4-y phase is produced with some amount of FeO. This difference is explained in terms of the annealing process of the oxygen vacancies produced during Ar implantation near the interfacial region. (C) 1996 American Institute of Physics.