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Reaction Mechanism and Kinetic Model of Fe Thin Film Transformation into Monosulfides (FeS): First Step of the Fe Films Sulfuration Process into Pyrite

  • The sulfuration of metallic iron layers into pyrite (FeS2) is preceded by an initial stage characterized by the iron transformation into monosulfide, which acts as a precursor of the disulfide. This work presents a comprehensive reaction and kinetic model of the sulfuration reaction of metallic iron thin films into monosulfides when a molecular sulfur (S2) atmosphere is used. By slowing down the sulfuration reaction, we have been able to follow in situ the evolution of the transport properties (electrical resistivity and Seebeck coefficient) of the Fe films during their sulfuration reaction to monosulfides. We show that two different stages characterize this initial sulfuration: (1) the transformation of Fe into hexagonal pyrrhotite (Fe → Fe1–xSH) and (2) a partial crystallographic transformation of this hexagonal pyrrhotite into orthorhombic pyrrhotite (Fe1–xSH → Fe1–xSO). A two-step process can explain the pyrrhotite hexagonal phase formation, being first controlled by the surface adsorption of S2 on the external sample interfaceThe sulfuration of metallic iron layers into pyrite (FeS2) is preceded by an initial stage characterized by the iron transformation into monosulfide, which acts as a precursor of the disulfide. This work presents a comprehensive reaction and kinetic model of the sulfuration reaction of metallic iron thin films into monosulfides when a molecular sulfur (S2) atmosphere is used. By slowing down the sulfuration reaction, we have been able to follow in situ the evolution of the transport properties (electrical resistivity and Seebeck coefficient) of the Fe films during their sulfuration reaction to monosulfides. We show that two different stages characterize this initial sulfuration: (1) the transformation of Fe into hexagonal pyrrhotite (Fe → Fe1–xSH) and (2) a partial crystallographic transformation of this hexagonal pyrrhotite into orthorhombic pyrrhotite (Fe1–xSH → Fe1–xSO). A two-step process can explain the pyrrhotite hexagonal phase formation, being first controlled by the surface adsorption of S2 on the external sample interface (S2/pyrrhotite) and second by the diffusion of Fe atoms through the formed pyrrhotite layer. By deducing the corresponding kinetic equations in terms of the experimental parameters (S2 partial pressure and thicknesses of the layers of present species), we can explain the evolution of the electrical resistance and Seebeck coefficient of the original Fe film during its transformation into monosulfide. At the same time, the appearance of the Kirkendall effect during the monosulfide phase formation is experimental and formally justified. The comprehensive description of this first stage of the complete sulfuration process of the Fe film into pyrite provides a layout to deeply discuss the influence of these intermedium phases on the final iron disulfide film characteristics and the appearance of potential film defects related to the experimental growth conditions.show moreshow less

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Author: Carlos MoralesORCiD, Antonio Pascual, Dietmar LeinenORCiD, Eduardo FloresORCiD, Esmeralda Muñoz-CortesORCiD, Fabrice LeardiniORCiD, José Ramón AresORCiD, Jan Ingo FlegeORCiD, Leonardo SorianoORCiD, Isabel J. FerrerORCiD, Carlos SanchezORCiD
DOI:https://doi.org/10.1021/acs.jpcc.2c02060
ISSN:1932-7455
ISSN:1932-7447
Title of the source (English):The Journal of Physical Chemistry C
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2022
Tag:Fe thin films; Kirkendall effect; Seebeck coefficient; kinetics; resistivity; sulfuration; transport properties
Volume/Year:126
Issue number:32
First Page:13870
Last Page:13883
Faculty/Chair:Fakultät 1 MINT - Mathematik, Informatik, Physik, Elektro- und Informationstechnik / FG Angewandte Physik und Halbleiterspektroskopie
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