Structure of Germanium Treated in a Planetary Mill
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Structure of Germanium Treated in a Planetary Mill T. A. Gordeevaa, b, *, D. A. Ovsyannikova, M. Yu. Popova, b, B. A. Kulnitskiya, b, and V. D. Blanka a Technological b
Institute of Superhard and Novel Carbon Materials, Moscow, Troitsk, 108840 Russia Moscow Institute for Physics and Technology, Dolgoprudny, Moscow oblast, 141701 Russia *e-mail: [email protected] Received April 9, 2020; revised April 9, 2020; accepted April 24, 2020
Abstract—The structure of a powder germanium treated in a planetary mill in the presence of small (5–25%) additions of diamond powder has been studied by high-resolution transmission electron microscopy using a JEM-2010 electron microscope. As a result of the treatment, twins and stacking faults have been detected in germanium along plane (111). The germanium deformation is shown to lead to the polytypism. The studies show the existence of phase 9R with the following sequence of lay6ers: …BABCBCACA…. Some particles demonstrate the partial or complete GeI → GeIV and GeI → GeIII phase transitions. Keywords: germanium, twinning, transmission electron microscopy, plastic deformation DOI: 10.1134/S106378342010008X
1. INTRODUCTION The methods of high-energy treatment of materials have been long in use [1]. Now they are extensively used to produce nanocrystals. The processes that take place during the treatment of a material in a planetary mill attract attention of many researchers. In addition to the grinding itself, of interest are also processes that take place in material particles: defect formation and phase transformations. In the relation with the fact that, in nanoparticles, a great fraction of atoms is in a thin surface layer, these processes can go alternatively than in coarse particles. The size and deformation effects in powder particles are studied using the neutron diffraction and X-ray diffraction methods [2, 3]. X-ray diffraction lines are known to be often broadened after the treatment of a material in a planetary mill. This fact is related to a decrease in the particle sizes and the existence of microstresses in them. The authors of [4] succeeded in the partitioning of the size and deformation components. However, there are only few reports in which the formation of defects and high-pressure phases was illustrated by the data of transmission electron microscopy [5–8]. In this work, we study the features of the structure of Ge particles treated in a planetary mill using the electron microscopy methods. Germanium is a material that is commonly used in electronics and metallurgy; it is added in a ceramics, thermoelectrics and so on. The existence of defects in germanium is known to lead to a shift of the Fermi level, which, in turn, leads to an increase in the free charge carrier concentration and an increase in the electrical conductivity [9] due to the existence of nonequilibrium
vacancies and interstitial atoms at grain boundaries. A deformation of germanium also influences its optical properties. A planetary mill can be considered as original shear high-p
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