Control of Epitaxial Growth Orientation and Anisotropic Thermoelectric Properties of Misfit-Type Ca3Co4O9 Thin Films

概要

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We have investigated the control of crystal orientation in misfit-type layered cobaltite Ca3Co4O9 thin films by rf-planar magnetron sputtering and succeeded in growing epitaxial films with $c$-axis, $a$-axis and $b$-axis orientations normal to the substrate. Anisotropic transport properties (parallel to the CoO2 layers and perpendicular to the CoO2 layers) were measured using the $b$-axis-oriented epitaxial films with a layered structure perpendicular to the substrate surface. The resistivity parallel to the CoO2 layers ($\rho_{a}$) is about 8 m$\Omega$ cm at room temperature while that perpendicular to the CoO2 layers ($\rho_{c}$) is about 300 m$\Omega$ cm; the anisotropy is estimated to be about 40. Thermoelectric anisotropy is not considerably pronounced; the parallel Seebeck coefficient $S_{a}$ is measured to be 110 μV/K and the perpendicular $S_{c}$ is 40 μV/K at room temperature.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2005-07-10