Z-CONTRAST STEM FOR MATERIALS SCIENCE

The use of a high-angle annular detector on a scanning transmission electron microscope (STEM) for imaging crystalline materials with strong chemical sensitivity is described. The image can be used to form an elemental map with high efficiency which can be quantified irectly in terms of atomic concentrations. Examples of ion-implanted silicon recrystallized by solid-or liquid-phase epitaxial growth will be shown, illustrating the usefulness of the image in studies of phase transformations and grain boundary segregation. At high resolution it is possible to resolve a crystal attice, while preserving the strong chemical sensitivity of the image. A simply interpretable image results, with a minimum dependence on objective lens defocus and specimen thickness, and examples of high-temperature superconductors will be shown. 1