Preparation and Properties of [Ca2CoO3]x[CoO2] Thin Films Using Pulsed Laser Deposition.

Abstract

c-axis oriented films of a layer-structured oxide in the [Ca2CoO3]x[CoO2] (CCO) system were prepared on MgO(100), SrTiO3(100) substrates and MgO substrate with a Pt-buffer layer by pulsed laser deposition using on ArF excimer laser. In addition, the dependence of electrical resistivity of the c-axis oriented CCO thin films on MgO substrates on film thickness and their thermoelectric properties have been examined. c-axis oriented CCO thin films on MgO substrates had been fabricated by optimizing the deposition conditions, but they mainly tended to orient along the (204) plane of CCO, unless those on SrTiO3 substrates and MgO substrates with Pt buffer which did not show a (204) plane of CCO. The CCO films on MgO (100) substrates had showed a dependence on film thickness of their measured resistivity below 300K. Measurement of thermoelectric properties showed that the resistivity along the ab-plane hardly varied with increasing temperature from 300 to 700K, while the Seebeck coefficient increased up to 150μV/K with increasing temperature.