The effect of temperature on the structure of iron-implanted sapphire

The defect structures of sapphire (α-Al2O3) implanted with iron at room temperature and 1000 deg. C were determined by Rutherford backscattering spectroscopy/ion channelling and transmission electron microscopy. Crystals with the c-axis normal to the surface were implanted with 1 x 1017 Fe/cm2 (150 keV). Samples implanted at RT were then annealed at 1000 deg. C in a reducing atmosphere. Implantation at RT produced precipitates, identified as α-Fe, 1-3 nm in size and the typical 'black spot' damage. Implantation at 1000 deg. C produced little residual disorder and a microstructure containing faceted iron precipitates ranging in size to 100 nm. Voids were associated with many of the precipitates. A second population of voids in the size range of 5-15 nm was also present. Annealing produced a microstructure containing 1-60 nm faceted precipitates but fewer voids