Three-Dimensional STEM for Observing Nano-Structures

Abstract Three-dimensional (3D) observation is one of the important trials of future TEM and STEM methods. in the field of biological science, 3D-observation has already become general because the biological materials are usually amorphous and computed tomography (CT) routines can be effectively used. The CT assumes that the image intensity is linearly proportional to the projection of material density. in a crystalline specimen, however, this linearity does not hold due to the dynamical diffraction effect depending on spepimen thickness and incident directions of electron beam. High-angle annular-darkfield STEM (HAADF-STEM) and EDX mapping images could meet this requirement of the linearity because their image intensity are little affected by the dynamical diffraction effect. Our 3D-STEM is based on a 300 kV FE-TEM/STEM(Hitachi HF-3000) equipped with a specially designed eucentric specimen stage with double spherical fulcra, a newly developed dark/bright field STEM detectors, a 3D-sampling system and a 3D-imaging processor for 3D topography and tomography.