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Epitaxy

Researchers from Tohoku University Describe Findings in Chemicals and Chemistry

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— 1 min read

Researchers from Tohoku University have detail new data in the field of Chemicals and Chemistry, focusing on the growth of Ruddlesden-Popper-type Sr3Cr2O7-delta (001) epitaxial thin films using pulsed laser deposition. The as-grown thin films exhibit transparent color and high resistivity, indicating the existence of a number of oxygen vacancies as well as Cr3+ ions.

Key Takeaways:

  • The researchers utilized pulsed laser deposition to grow Ruddlesden-Popper-type Sr3Cr2O7-delta (001) epitaxial thin films, resulting in high crystallinity and flat surfaces.
  • The as-grown thin films exhibited transparent color and high resistivity, indicating the presence of oxygen vacancies and Cr3+ ions.
  • Air annealing caused a nonmonotonic variation in lattice constants and a color change to brownish, due to the compensation of ordered oxygen vacancies as well as oxidation of the Cr3+ ions to Cr4+ ions.
  • The room temperature resistivity showed a large decrease exceeding 5 orders of magnitude after air annealing.
  • Synchrotron-radiation photoemission spectroscopy revealed a wider Mott gap for the Cr3+ ions than that for Cr4+ ions.
  • The giant resistivity change was attributed to the synergistic effects of dimensionality variation in the electron conduction pathway and band-structure modulation, which depends on the Cr valence within the layered structure.
  • The research was funded by the Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research (KAKENHI), and the Program Advisory Committee, High Energy Accelerator Research Organization (KEK).
  • The research has been peer-reviewed and published in the journal Chemistry of Materials.

Statistics:

  • The researchers reported a transparent color and high resistivity with a resistivity change exceeding 5 orders of magnitude.
  • The wavelength of the laser used for deposition was not specified in the article.
  • The Mott gap for the Cr3+ ions was found to be wider than that for Cr4+ ions.

Sources:

  • NewsRx. Researchers from Tohoku University Describe Findings in Chemicals and Chemistry (Oxidation-induced Giant Resistivity Change Associated With Structural and Electronic Reconstruction In Layered Sr 3 cr 2 o 7-d ...). News of Science. November 2, 2025; p 4019.
  • Oxidation-induced Giant Resistivity Change Associated With Structural and Electronic Reconstruction In Layered Sr 3 cr 2 o 7-d Epitaxial Thin Films. Chemistry of Materials, 2025.
  • Amer Chemical Soc. (American Chemical Society - www.acs.org; Chemistry of Materials - www.pubs.acs.org/journal/cmatex)
  • Tohoku University, Graduate School of Science, Dept. of Chemistry, Sendai 9808578, Japan.

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