Quantification of Hydrogen in Natural Diamond by Secondary Ion Mass Spectrometry (SIMS)
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Quantification of Hydrogen in Natural Diamond by Secondary Ion Mass Spectrometry (SIMS) Corresponding Member of the RAS F. V. Kaminskya,*, S. N. Shilobreevaa, B. Ya. Berb, and D. Yu. Kazantsevb Received May 9, 2020; revised July 2, 2020; accepted July 6, 2020
Abstract—The volumetric concentration of hydrogen in two Brazilian diamonds is determined using secondary ion mass spectrometry and implantation of hydrogen into an external standard sample (with a dose of 1 × 16 at/cm2 and energy of 120 KeV). The diamonds studied differ noticeably in their intensities of IR-active hydrogen from 0 to 1.5 cm–1 according to the analyses of their IR spectra. The results demonstrate that for both samples studied, the volumetric concentration of hydrogen does not exceed the reached detectable level of (1–2) × 1018 at/cm3 or 1.7–3.3 at. ppm; i.e., it is lower by an order of magnitude than in the early chemical analysis and by 2–3 orders of magnitude lower than the results of the ion-beam spectrochemical, nuclearphysical, and ERDA analyses. Only a part of the hydrogen forms optically active impurities in diamond crystals and can be determined by spectral methods. Keywords: diamond, hydrogen, secondary ion mass spectrometry DOI: 10.1134/S1028334X20090093
Hydrogen, together with nitrogen, is one of the main impurities in diamonds. Its presence affects the optical and electrical properties of diamonds. Geochemically, the study of this element in diamonds from kimberlites is incredibly important, since due to rapid outcropping of kimberlites, hydrogen contained in diamonds retains its mantle properties. It should be taken into account that, according to the latest research, the transformations of hydrogen and its compounds in the mantle are one of the main causes for magmatic and geodynamic processes. Moreover, hydrogen played an important role in the prebiological evolution of the early Earth. This determines the importance of studying hydrogen geochemistry in the deep Earth. However, not only the forms of hydrogen entry, but also its content in natural diamond have been studied insufficiently and the data of the studies in these areas are quite contradictory. In the early works that used chemical analysis of gases obtained by burning natural diamonds, the hydrogen concentrations were estimated at a few tenths, up to 0.5 wt % (which corresponds to over 5 at % and are obviously unreal). The ion-beam spectrochemical analysis (IBSCA) employa Vernadsky
Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia b Ioffe Physical–Technical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia *e-mail: [email protected]
ing bombardment with a flow of Ar+ argon accelerated ions was used to determine the total concentration of hydrogen impurities in natural diamonds of different physical types (Ia, Ib, and IIa) [1]. The results obtained showed hydrogen contents of about 1 at % in all types of diamonds, which is much smaller than in the early chemical analyses but still rather
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