Fresnel fringe contrast of faceted voids within gem‐quality diamond

Abstract
SUMMARY: The topology of faceted void‐like defects (‘voidites’) in gem‐quality type la diamonds has been revealed by high resolution phase‐contrast electron microscopy. Interpretation of the images in terms of a Fresnel contrast mechanism allows the defects to be identified as octahedral in shape. Image contrast is sensitive to defocus and other parameters, and Fresnel fringe interference effects may generate ‘superlattice’‐like contrast.