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

doi:10.1143/APEX.2.035503

Structural transformation of ca-arrangements and carrier transport properties in Ca_0.33CoO₂ epitaxial films

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

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

The electrical properties of Ca_0.33CoO₂ 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 language	English
Article number	035503
Journal	Applied Physics Express
Volume	2
Issue number	3
DOIs	https://doi.org/10.1143/APEX.2.035503
Publication status	Published - 2009 Mar
Externally published	Yes

ASJC Scopus subject areas

Engineering(all)
Physics and Astronomy(all)

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

abstract = "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.",

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AU - Sugiura, Kenji

AU - Ohta, Hiromichi

AU - Ishida, Yukiaki

AU - Huang, Rong

AU - Saito, Tomohiro

AU - Ikuhara, Yuichi

AU - Nomura, Kenji

AU - Hosono, Hideo

AU - Koumoto, Kunihito

PY - 2009/3

Y1 - 2009/3

N2 - 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.

AB - 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.

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Structural transformation of ca-arrangements and carrier transport properties in Ca_0.33CoO₂ epitaxial films

Abstract

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