Energy-filtered chemical mapping: Current applications to materials science

Abstract

Elemental mapping is a powerful technique for elucidating the distribution of elements on the nanometer scale in materials with complex morphologies. In electron microscopy, mapping is usually performed on a scanning transmission electron microscope (STEM) fitted with a field emission gun (FEG) using the techniques of energy-dispersive x-ray spectroscopy (EDX) or electron energy-loss spectroscopy (EELS). However, recent advances in spectrometer design and digital image recording have stimulated renewed interest in energy-filtered imaging and elemental mapping with a conventional transmission electron microscope. Here, some applications of energy-filtered chemical mapping in materials science are described.Experiments were conducted on a Zeiss 912 operating at 120 kV with a thermal source and equipped with an omega filter spectrometer. A variable width slit in the spectrometer image plane allows energy-filtered images to be formed on the microscope viewing screen. These images are digitally recorded using a Gatan 679 slow-scan CCD camera with 1024 pixels.