Precision Measurements of the Intensity in the Electron Diffraction Analysis
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ion Measurements of the Intensity in the Electron Diffraction Analysis A. K. Kuligina, * and A. S. Avilova, ** aShubnikov
Institute of Crystallography Federal Research Center “Crystallography and Photonics,” Russian Academy of Sciences, Moscow, 119333 Russia *e-mail: [email protected] **e-mail: [email protected]
Received December 24, 2019; revised January 22, 2020; accepted January 25, 2020
Abstract—The problem of increasing the accuracy of an electron-diffraction experiment, on which the reliability of studying the nature of chemical bonding and the distributions of the electrostatic potential in nanoobjects by this method depends, is solved. For this, a recording system was created on the basis of an EMR-102 electron diffractometer, which operates in the single-electron mode with high time (60 MHz) and spatial (tens of thousands of steps at 1 Å–1) resolutions. Specialized software is developed that monitors the progress of the experiment and the processing of the obtained experimental data. With its help, the scanning system is controlled and the time and coordinate parameters of each event of operation of the electron detector are synchronously recorded. The developed diffractometer is used in a number of precision electron-diffraction studies, in which diffraction patterns are obtained with an accuracy of measuring the relative intensities and spatial (angular) resolution that is much better, compared to similar measurements described to date in publications. Keywords: electron diffraction, structure analysis, electron diffractometer, nano-objects DOI: 10.1134/S1027451020040308
INTRODUCTION Electron diffraction structural analysis is the main method for studying the atomic structure of nanomaterials (thin films and surface layers, nanocrystals, nanoparticles, etc.). Electron diffractometry is an effective method for obtaining experimental information on the structure and related properties of crystalline as well as amorphous materials. It was shown in [1, 2] that the accuracy and reliability of structural determinations in electron diffraction depends primarily on the accuracy of experimental observations of the reflection intensities. Improving the accuracy of structural determinations should make it possible to more successfully utilize a number of advantages of this method, for example, determining the positions of light atoms in the presence of heavy ones, studying the nature of chemical bonds, calculating the electron density distributions and electrostatic potential. This method (as was described in [3]) uses a photomultiplier (PMT) as a radiation detector in combination with a scintillator, which was subsequently successfully used to determine the nanostructures of minerals: brucite, lysardite, lepidocrocite, seladonite, nakrit [4–8]. Nevertheless, there are serious factors limiting its widespread use, namely: despite its high sensitivity, an important disadvantage of PMTs is the
nonlinear nature of the transmitted signal, even if it does not exceed 10–13–10–12 A (this is the result of the actio
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