title: Decisive factors for realizing atomic-column resolution using STEM and EELS .
abstract: We demonstrate atomic-column imaging by scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). The silicon atomic-columns of a beta-Si3N4 (0 0 1) specimen are clearly resolved. The atomic-site dependence and the energy-loss dependence of the spatial resolution are elucidated on the basis of the experimental results and multislice calculations. We describe two decisive factors for realizing atomic-column imaging in terms of localization in elastic and inelastic scattering. One is the channeling of the incident probe due to dynamical diffraction, which has atomic-site dependence. The other is the localization in inelastic scattering; in addition to the energy-loss dependence of delocalization, we point out its dependence on the offset energy from the ionization energy, i.e., an additional localization factor concerning the Bethe surface. The present atomic-column observation of the Si-L core-loss image indicates that the local approximation, which can be interpreted intuitively, is achievable under appropriate experimental conditions, such as high-energy-loss, a small convergence angle and a large collection angle (e.g., 400 eV, 15 and 30 mrad, respectively).
authors.affiliation: National Institute for Materials Science, Ibaraki, Japan. kimoto.koji@nims.go.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Kimoto
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ishizuka
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Matsui