Crystal structure and electronic property modification of Ca2RuO4 thin films via fluorine doping

Shota Fukuma, Akira Chikamatsu, Tsukasa Katayama, Takahiro Maruyama, Keiichi Yanagisawa, Koji Kimoto, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Yasushi Hirose, Tetsuya Hasegawa

Research output: Contribution to journalArticlepeer-review


Layered ruthenium oxyfluorides have various crystal structures and Ru oxidation states and exhibit unique physical properties. While various layered ruthenates have reportedly been topochemically fluorinated with Sr as A sites, investigation of the fluorination of layered ruthenates containing smaller Ca ions is lacking. In this paper, we fabricated phase-pure and single-crystalline thin films of Ca2RuO2.5F2 on LaSrAlO4 (001) substrates via topochemical fluorination of the Ca2RuO4 precursor using polyvinylidene fluoride. The obtained fluorinated thin films had a chemical composition of Ca2RuO2.5F2 with the Ru3+ state, as determined by energy-dispersive x-ray spectroscopy and x-ray photoemission spectroscopy, whereas the film prepared via Sr2Ru4+O4 fluorination had a composition of Sr2Ru4+O3F2. Scanning transmission electron microscopy revealed that Ca2RuO2.5F2 has only 1 F- site in CaO rock-salt blocks, whereas Sr2RuO3F2 has two inequivalent F- sites in the SrO layers. The Ca2RuO2.5F2 film was insulating, with a resistivity (ρ) of 8.6×10-2ωcm at 300 K. Moreover, the temperature behavior of ρ was well described by the two-dimensional variable range hopping model. These results demonstrate that local distortion is an important factor that governs the topochemical fluorination of ruthenates and affects the crystal and electronic structures of the reactants.

Original languageEnglish
Article number035002
JournalPhysical Review Materials
Issue number3
Publication statusPublished - 2022 Mar

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)


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