The Fabrication Of Layered Cobalt Oxide Thin Films By Pulsed Laser Deposition And Their High Temperature Thermoelectric Properties

In this thesis, the cobalt oxides based thermoelectric thin film, Bi2Sr2Co2Oy、Ca3Co4O9and NaxCoO2were fabricated by pulsed laser deposition(PLD) on a variety of single-crystal. The main conclusions are obtained as follows:1) Epitaxial Bi2Sr2Co2Oy thin film has been prepared by PLD, and the effects of substrate temperature and oxygen pressure on the crystal structure and the transport properties of the films were investigated. The films obtained under the optimum deposition conditions are fully textured in the ab plane and c-axis direction, the thermoelectric properties of which are comparable to single crystal samples both at room temperature and at high temperature.2) The effect of Fe doping on the thermoelectric properties of Ca3Co4-xFexO9(x=0、0.05、0.1、0.15) thin films was studied. Under the Fe doping concentration x≤0.1, the hole carrier concentration and the electrical conductivity increases with the doping, while the electrical conductivity decreases with the further doping x>0.1, which may originate from the enhanced carrier scattering caused by the distortion of lattice and the formation of second phase induced by the Fe doping. For the Seebeck coefficient is less affected by the Fe doping, a small amount of Fe doping can improve the thermoelectric performance of Ca3Co4O9thin films more effectively.3) Epitaxial NaxCoO2thin films have been grown by PLD combined with the ion diffusion technique. The power factor of the films is comparable to single crystal samples. Large open-circuit voltage signals was observed when the surface is irradiated by the laser pulses of308nm. The results suggest that the NaxCoO2thin films have great potential applications both in the thermoelectric devices and wide-band laser photo-detectors.