Probing bonding and electronic structure at atomic resolution with spectroscopic imaging

By measuring the energy losses of high-energy electrons transmitted through a thin sample, electron energy-loss spectroscopy provides information on the local electronic structure in materials. Using electron beams smaller than 0.1 nm, the technique provides exquisite sensitivity to changes in valence and coordination of the excited atoms such that local changes in the bonding environment are probed with a resolution approaching the Ångstrøm level, with an energy resolution competitive with complementary techniques such as x-ray absorption spectroscopy. With the development of spectroscopic imaging in the scanning transmission electron microscope, this technique can be used to map, at the atomic level, the composition of atomic columns and the valence of atoms at defects, interfaces, and surfaces. Recent applications of this technique are provided as examples showing the potential of the method for materials research.