Accurate crystal structure analysis by quantitative high-resolution electron microscopy

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We have tried to establish the process of crystal structure analysis with high-resolution electron microscopy and electron diffraction. High-resolution electron micrographs and electron diffraction patterns are measured as quantitative data by a slow-scan CCD (charge-coupled device) camera and IP (imaging-plate) attached to a 400 kV transmission electron microscope (JEM-4000EX) having a resolution of 0.17nm. The main purpose of this work has been to develop a procedure of crystal structure analysis with computer work of the quantitative data of high-resolution micrographs and electron diffraction patterns. Our results are summarized as the follows.1. In order to try accurate crystal structure analysis of a Tl_2Ba_2CuO_y superconducting oxide, a residual index between observed quantitative images and simulated images was introduced. From minimizing the residual index with some parameters of thickness and defocus values, partial occupancy of metal atoms can be quantitatively evaluated and deficient oxygen atom positions can be detected.2. By using high-sensitive properties of the CCD camera, we observed high-resolution electron microscopic images of zeorites introduced with Ni, which are extremely weak for electron beam. From image processing and image analysis of the high-resolution electron micrographs, accurate structure analysis of Ni atoms can be evaluated.3. We demonstrate herein the application of a slow-scan CCD camera for improvement in the experimental resolution of contrast details in the synthetic zeorite structure ZSM-5 (MFI). The improvement in the amount and quality of structural detail through the use of the CCD camera is also shown by a comparison of a Fourier synthesis, made by using the observed electron diffraction intensities. R-factors based on the normalized diffraction intensities have been employed to evaluate the result of the structure analysis.