OM-II-3Challenge to atomic-scale characterization of electron-beam-sensitive microporous materials

Electron beam irradiation causes damage in varying degree on any material during electron microscopy observation. Ordered microporous material zeolite is one of the most challenging target to reveal the fine structure on the atomic scale by electron microscopy although the spatial resolution has reached sub-angstrom scale with spherical aberration (Cs) correctors. Zeolite is a crystalline aluminosilicate and composed of covalently bonded framework and ordered nano-spaces. The most serious irradiation damage of zeolites under electron beam is radiolysis, which is associated with ionization of the constituent elements. Cs-corrected scanning transmission electron microscopy (STEM) has been an essential technique for the atomic scale characterization in the fields of materials science, physics and chemistry. There are some advantages for atomic-scale characterization of electron-beam-sensitive materials compared with conventional TEM, such as serial acquisition of the image and selective imaging of high-atomic-number elements [1]. We have applied high resolution STEM to zeolites and imaged their framework structures on the atomic scale. Fig. 1 shows annular dark-field (ADF) STEM image of CON-type zeolite, which is one of the most important catalysts and consists of a three-dimensional pore system with 12-, 12-, and 10-membered ring pores. The ADF-STEM image reveals the single atomic columns of T-atoms (Si and Al), which are clearly distinguished each other. !!...!!