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New insights into boron species in acidic digestion solutions of boron-doped silicon

  • The exact and precise determination of the boron concentration in silicon is still a challenge. A systematic investigation dealing with the digestions of 60 silicon samples with HF-HNO3 and subsequent boron determination by ICP-OES revealed that the concentration found could be up to 60% lower than the actual boron concentration depending on the composition of the sample solution. As the original boron–silicon compound that was identified was colloidally precipitated in the presence of an excess of hydrofluoric acid and then partially retained by filtration or by the sample introduction system, systematic lower boron concentrations were determined. In acidic, HF-free digestion solutions, this compound existed in a soluble form parallel to the borate in B(OH)4−. In an excess of hydrofluoric acid, the compound was converted into the colloidal form and, in parallel, B(OH)4− was converted to tetrafluoroborate, BF4−. For the composition of the colloidal compound, a molar ratio of boron to silicon of 1 : 4 could be determined. 11B-ss-NMRThe exact and precise determination of the boron concentration in silicon is still a challenge. A systematic investigation dealing with the digestions of 60 silicon samples with HF-HNO3 and subsequent boron determination by ICP-OES revealed that the concentration found could be up to 60% lower than the actual boron concentration depending on the composition of the sample solution. As the original boron–silicon compound that was identified was colloidally precipitated in the presence of an excess of hydrofluoric acid and then partially retained by filtration or by the sample introduction system, systematic lower boron concentrations were determined. In acidic, HF-free digestion solutions, this compound existed in a soluble form parallel to the borate in B(OH)4−. In an excess of hydrofluoric acid, the compound was converted into the colloidal form and, in parallel, B(OH)4− was converted to tetrafluoroborate, BF4−. For the composition of the colloidal compound, a molar ratio of boron to silicon of 1 : 4 could be determined. 11B-ss-NMR analysis revealed a tetrahedral geometry compound with a central boron atom surrounded by four silicon atoms. It is assumed that a soluble form with four –Si(OH)3 groups was present in the hydrofluoric acid-free solutions, while an insoluble form with four –SiF3 groups was present in HF-containing solution.show moreshow less

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Metadaten
Author: Anja RietigORCiD, Hans-Joachim GrafeORCiD, Jörg AckerORCiDGND
URL:https://pubs.rsc.org/en/content/articlelanding/2021/ja/d1ja00190f
ISSN:1364-5544
Title of the source (English):Journal of Analytical Atomic Spectrometry
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2021
Contributing Corporation:Leibniz Institute for Solid State and Materials Research (IFW) Dresden
Tag:11B-NMR; ICP-OES; boron; digestion; etching; high-precision chemical analysis; hydrofluoric acid; nitric acid; silicon
Volume/Year:36
Issue number:11
First Page:2492
Last Page:2500
Faculty/Chair:Fakultät 2 Umwelt und Naturwissenschaften / FG Physikalische Chemie
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