Raman Spectroscopy for Determination of Silicon Oxyfluoride Structure in Fluoride Melts

• Published in: Journal of fluorine chemistry 2020-10, Vol.238, p.109616, Article 109616
• Main Authors: Suzuki, Yuta, Park, Taebyung, Hachiya, Kan, Goto, Takuya
• Format: Article
• Language: English
• Subjects: Banded structure; Coordination; Coordination structure; Density functional theory; Fluoride melts; Fluorides; Ions; Lithium fluoride; Lithium oxides; Mathematical analysis; Melts; Molecular structure; Monomers; Oxyfluorides; Raman spectra; Raman spectroscopy; Silicon; Silicon dioxide; Silicon films; Spectroscopy; Spectrum analysis
• ISSN: 0022-1139; 1873-3328
• DOI: 10.1016/j.jfluchem.2020.109616

[Display omitted] •A coordination structure of Si ion in fluoride melts added SiO2 was investigated•A good agreement was observed between the DFT calculations and Raman spectra•Molecule-like and ion-like structures of silicon ion were identified•The formation of ion-like structure was promoted by addition of Li2O We investigated melt structures of eutectic LiF-KF, LiF-NaF and NaF-KF adding SiO2 through Raman spectroscopy and density functional theory calculations. The interactions between silicon ion and constituent ions of the fluoride melts have been identified. A good agreement was observed between the calculated and experimental Raman spectra for the melts. The spectra were characterized by two kinds of coordination structures: ion-like structure such as SiF2O22- and Si2O52-; and molecule-like structure such as SiF3O-Li and SiF2O2-2Li. Moreover, when Li2O as a source of O2- was added, remarkable bands appeared which were attributed to ion-like structure of SiFO33- and SiF3O-, indicating that O2- ions have potential to promote the formation of oxyfluoride monomers by cleaving the Si-O-Si bands of Si2O52- ions or SiO2. The information for the coordination structure around silicon ion in the fluoride melts are important towards electrodeposition process of silicon films in fluoride melt in terms of designing the electrolyte.