Understanding the Reactions Between Fe and Se Binary Diffusion Couples

Dennice Roberts, Dylan Bardgett, Renae Gannon, Danielle Hamann, Sage Bauers, Ping Lu, David Johnson

Research output: Contribution to journalArticlepeer-review

2 Scopus Citations


Spurred by recent discoveries of high-temperature superconductivity in Fe-Se-based materials, the magnetic, electronic, and catalytic properties of iron chalcogenides have drawn significant attention. However, much remains to be understood about the sequence of phase formation in these systems. Here, we shed light on this issue by preparing a series of binary Fe-Se ultrathin diffusion couples via designed thin-film precursors and investigating their structural evolution as a function of composition and annealing temperature. Two previously unreported Fe-Se phases crystallized during the deposition process on a nominally room-temperature Si substrate in the 27-33 and 37-47% Fe (atomic percent) composition regimes. Both phases completely decompose after annealing to 200 °C in a nitrogen glovebox. At higher temperatures, the sequence of phase formation is governed by Se loss in the annealing process, consistent with what would be expected from the phase diagram. Films rich in Fe (53-59% Fe) crystalized during deposition as β-FeSe (P4/nmm) with preferred c-axis orientation to the amorphous SiO2 substrate surface, providing a means to nonepitaxial self-assembly of crystallographically aligned, iron-rich β-FeSe for future research. Our findings suggest that the crystallization of binary Fe-Se compounds at room temperature via near diffusionless transformations should be a significant consideration in future attempts to prepare metastable ternary and higher-order compounds containing Fe and Se.

Original languageAmerican English
Pages (from-to)2585-2592
Number of pages8
JournalChemistry of Materials
Issue number7
StatePublished - 13 Apr 2021

Bibliographical note

Publisher Copyright:
© Published 2021 by American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-79204


  • diffusion couples
  • iron selenide
  • solid state chemistry


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