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Imaging the Kirkendall effect in pyrite (FeS2) thin films: Cross-sectional microstructure and chemical features

  • This investigation provides novel data on the structure and chemical composition of pyrite thin films and new hints concerning their formation mechanism. From TEM-HAADF data, it has been found that the films are composed of two different layers: one is very compact and the other one is quite porous with many voids separating a few groups of grains. This porous layer is always in direct contact with the substrate, and its thickness is quite similar to that of the original Fe film. The average size of pyrite grains is equal in both layers, what suggests that the same process is responsible for their formation. Concentration profiles of sulfur, iron and some impurities (mainly sodium and oxygen from the glass substrate) through both layers are given in this work, and thus chemical inhomogeneities of the films are proved by the obtained stoichiometric ratios (S/Fe). Moreover, Na from sodalime glass substrates mainly accumulates at the pyrite grain boundaries and barely dopes them. The obtained results support the hypothesis that the ironThis investigation provides novel data on the structure and chemical composition of pyrite thin films and new hints concerning their formation mechanism. From TEM-HAADF data, it has been found that the films are composed of two different layers: one is very compact and the other one is quite porous with many voids separating a few groups of grains. This porous layer is always in direct contact with the substrate, and its thickness is quite similar to that of the original Fe film. The average size of pyrite grains is equal in both layers, what suggests that the same process is responsible for their formation. Concentration profiles of sulfur, iron and some impurities (mainly sodium and oxygen from the glass substrate) through both layers are given in this work, and thus chemical inhomogeneities of the films are proved by the obtained stoichiometric ratios (S/Fe). Moreover, Na from sodalime glass substrates mainly accumulates at the pyrite grain boundaries and barely dopes them. The obtained results support the hypothesis that the iron sulfuration process essentially induces the diffusion of iron atoms, what leads to the porous layer formation as a manifestation of the Kirkendall Effect. Therefore, it seems that the same mechanisms that operate in the synthesis of surface hollow structures at the nanoscale are also active in the formation of pyrite thin films ranging from several tens to hundreds of nanometers.show moreshow less

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Author: Carlos MoralesORCiD, 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/10.1016/j.actamat.2020.116582
ISSN:1359-6454
ISSN:1873-2453
Title of the source (English):Acta Materialia
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2021
Tag:Cross-section; Kirkendall effect; Pyrite; Sodium doping; Transmission electron microscopy (TEM)
Volume/Year:205
Number of pages:12
Article number:116582
Faculty/Chair:Fakultät 1 MINT - Mathematik, Informatik, Physik, Elektro- und Informationstechnik / FG Angewandte Physik und Halbleiterspektroskopie
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