Application of electron optical techniques to the study of amorphous materials

摘要

Despite the sub-angstrom resolution capability of modern transmission electron microscopes, elucidation of the structure of amorphous materials by direct-imaging methods is still challenged by problems of projection and data presentation identified over 20 years ago. Classical diffraction analysis, leading to the radial distribution function not only retains its essential importance but has been extended to deal with small scattering volumes in inhomogeneous samples by the use of focused electron probe illumination but retaining orientation averaging. Fluctuation microscopy provides a significant advance in the detection and statistical representation of medium-scale spatial variations in amorphous structure. Issues of scattering coherence are crucial in both these approaches. Further opportunities for use of focused probes include the study of angular correlations in nanodiffraction patterns as well as fine structure in energy loss spectra. Finally, there may be a return to the direct imaging approach thanks to recent advances in electron tomography and in aberration-corrected depth sectioning.