Fabrication and Low Temperature Thermoelectric Properties of Na_xCoO_2 (x = 0.68 and 0.75) Epitaxial Films by the Reactive Solid-Phase Epitaxy

Abstract

We have fabricated Na_xCoO_2 thin films via lateral diffusion of sodium into Co_3O_4 (111) epitaxial films (reactive solid-phase epitaxy: Ref. 4). The environment of thermal diffusion is key to the control of the sodium content in thin films. From the results of x-ray diffraction and in-plane resistivity, the epitaxial growth and the sodium contents of these films were identified. The thermoelectric measurements show a large thermoelectric power similar to that observed in single crystals. The quasiparticle scattering rate is found to approach zero at low temperatures, consistent with the small residual resistivity, indicating high quality of the Na_xCoO_2 thin films.

arXiv comment16 pages. 4 figures. To appear in Applied Physics Letters

References in corpus (5)

• Spin entropy as the likely source of enhanced thermopower in $\rm\bf Na_xCo_2O_4
• Charge-ordering, commensurability and metallicity in the phase diagram of layered Na(x)CoO(2)
• Coupling between electronic and structural degrees of freedom in the triangular lattice conductor NaxCoO2
• Electrodynamics of correlated electron matter
• Structural and transport properties of epitaxial NaxCoO2 thin films