The determination of the ionicity of sapphire using energy-filtered high resolution electron microscopy

The sensitivity of high resolution images to the degree of ionicity of sapphire is assessed through a comparison of experimental [2<(11)over bar>0] images with simulations. It is shown that, while the degree of ionicity does indeed affect image contrast, its quantification requires the determination of microscope imaging parameters to an unfortunately high degree of accuracy. Significantly, in contrast to previous results, the contrast of the experimental high resolution images Is found to be comparable to that of the simulations. The reasons for this unusual lack of discrepancy are discussed, as are the potential advantages of electron holography rather than high resolution electron microscopy for determining the ionicities of such materials.