MICROSTRUCTURAL AND CHEMICAL EFFECTS IN AL2O3 IMPLANTED WITH IRON AT ROOM-TEMPERATURE AND ANNEALED IN OXIDIZING OR REDUCING ATMOSPHERES

Rutherford backscattering (RBS)-ion channeling, transmission electron microscopy (TEM), and conversion electron Mossbauer spectroscopy (CEMS) have been used to determine the structure of alpha-Al2O3 implanted with iron at room temperature. Changes produced by post-implantation annealing in oxidizing and reducing atmospheres were followed using the same techniques. Implantation of 160 keV Fe at room temperature produces a damaged but crystalline microstructure for fluences as high as 1 x 10(17) Fe/cm2. The iron resides in a variety of local environments: three Fe2+ components, one Fe0 component, and two Fe4+ components. The relative amount of each component varies with implantation fluence. Only the Fe0 component seems to be associated with second-phase formation. In this case, 2 nm diameter alpha-iron particles were detected by TEM studies. Recovery of implantation-induced disorder in the Al- and oxygen-sublattices occurs in two stages for annealing in oxygen and in one continuous stage for hydrogen-annealing. The end state for iron is Fe3+ for oxygen anneals and Fe0 for hydrogen anneals. The precipitated phases observed are those to be expected from the equilibrium phase diagrams.