Study of the specific features of single-crystal boron microstructure
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CTION AND SCATTERING OF IONIZING RADIATIONS
Study of the Specific Features of Single-Crystal Boron Microstructure A. E. Blagova,b, A. L. Vasil’eva,b, V. P. Dmitrievc, A. G. Ivanovaa, A. G. Kulikova,b, N. V. Marchenkova,b,*, P. A. Popovd, M. Yu. Presnyakovb, P. A. Prosekova,b, Yu. V. Pisarevskiia,b, A. V. Targonskiia,b, T. S. Chernayaa†, and D. Yu. Chernyshovc a Shubnikov
Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” Russian Academy of Sciences, Moscow, 119333 Russia b National Research Centre “Kurchatov Institute,” Moscow, 123182 Russia c Swiss–Norwegian Beamlines at the European Synchrotron Radiation Facility, Grenoble, France d Bryansk State University, Bryansk, 241036 Russia * e-mail: [email protected] Received February 3, 2017
Abstract—A complex study of the structure of β-boron single crystal grown by the floating-zone method, with sizes significantly exceeding the analogs known in the literature, has been performed. The study includes X-ray diffraction analysis and X-ray diffractometry (measurement of pole figures and rocking curves), performed on both laboratory and synchrotron sources; atomic-resolution scanning transmission electron microscopy with spherical aberration correction; and energy-dispersive microanalysis. X-ray diffraction analysis using synchrotron radiation has been used to refine the β-boron structure and find impurity Si atoms. The relative variations in the unit-cell parameters a and c for the crystal bulk are found to be δa/a ≈ 0.4 and δc/c ≈ 0.1%. X-ray diffractometry has revealed that the single-crystal growth axis coincides with the [22013] crystallographic axis and makes an angle of 21.12° with the [0001] threefold axis. Electron microscopy data have confirmed that the sample under study is a β-boron crystal, which may contain 0.3–0.4 at % Si as an impurity. Planar defects (stacking faults and dislocations) are found. The results of additional measurements of the temperature dependence of the thermal conductivity of the crystal in the range of 50–300 K are indicative of its high structural quality. DOI: 10.1134/S1063774517050030
INTRODUCTION Boron occupies an intermediate place between metals and insulators in the periodic system of chemical elements. The boron atom has three valence electrons and should possess metallic properties; however, its electrons are strongly bound to the atomic nucleus, due to which boron behaves as an insulator. In this context, the manifestation of metallic, semiconducting, or insulating properties by a boron crystal is determined by external conditions or introduction of different impurities; hence, one can consider boron as a unique and very promising material. Boron crystals, which are of interest due to their high hardness, high melting temperature, and semiconducting properties, can be used in the production of integrated circuits operating under extreme conditions, in particular, intense radiation and high temperatures. Crystalline boron is widely applied in the production of amorphous iron-
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