Structural transformation of ca-arrangements and carrier transport properties in Ca0.33CoO2 epitaxial films

Kenji Sugiura, Hiromichi Ohta, Yukiaki Ishida, Rong Huang, Tomohiro Saito, Yuichi Ikuhara, Kenji Nomura, Hideo Hosono, Kunihito Koumoto

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    11 Citations (Scopus)


    The electrical properties of Ca0.33CoO2 epitaxial films are investigated as the Ca2+-arrangement is transformed. Despite identical Ca-content, annealing the film caused the Ca-arrangement to change from a <!-Math-> hexagonal type to a 2a × <!-Math-> orthorhombic type, which was confirmed by X-ray diffraction and scanning transmission electron microscopy. A hexagonal Ca-arrangement type, Ca 0.33CoO2, exhibited a metallic resistivity as low as 7.5 × 10-4 Ω·cm and a moderately large thermopower (̃100μV·K-1), whereas the orthorhombic Ca-arrangement type displayed a thermally-activated resistivity (10-2 Ω·cm) with a slightly increase in thermopower, which led to about a one order of magnitude difference in the thermoelectric power factor.

    Original languageEnglish
    Article number035503
    JournalApplied Physics Express
    Issue number3
    Publication statusPublished - 2009 Mar 1

    ASJC Scopus subject areas

    • Engineering(all)
    • Physics and Astronomy(all)


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