Fabrication And Properties Of Bi₂Sr₂Co₂O_y Nanocomposite Thin Films

The misfit layered Bi2Sr2Co2Oy(BSCO) is a newly-discovered p-type oxide thermoelectric(TE) material. Besides, it has potential applications in transverse TE devices and transparent conducting electrodes due to its large Seebeck coefficient anisotropy and reasonable visible light transmission. In this thesis, we fabricated high quality BSCO/Au nanocomposite thin films and investigated the effect of Au nanoparticles(Au NPS) on the TE, transverse TE and transparent conducting properties of BSCO thin films. The main contents and conclusions as follows: 1. BSCO/Au(Au=0、0.8、1.59 at%)nanocomposite thin films have been successfullyDeposited on La Al O3(001)single crystal substrates by pulsed laser ablating a BSCO/Aucomposite target. The x-ray diffraction results indicates that the films are c-axis orientedwithout any impurities, and the high resolution transmission electron microscopy revealsthat Au NPs, with the diameter of 5-10 nm, are well dispersed in the BSCO films. 2. With the increase of Au NPs in the BSCO thin films, the resistivity of the films decreasesgreatly while both the Seebeck coefficient and the average visible light transmission keepalmost unchanged, leading to an significant enhancement in both thermoelectric powerfactor and photoelectric figure of merit. The results suggest that adding Au NPs is aeffective way to improve the thermoelectric and transparent conducting properties ofBSCO thin film. For example, BSCO/Au film with Au NPs content of 1.59 at% has theroom temperature resistivity of 3.0m?·cm, the average visible light transmission of 48%,resulting in a high FOM 2270 M?-1 which is one of the highest value so far reported forall p-type transparent conducting oxide coatings. 3. We deposited BSCO/Au nanocomposite thin films on 10° tilted La Al O3(001)singlecrystal substrates by pulsed laser deposition and investigated its transverse TE effect. Theresults show that adding Au NPs into the films can greatly improve the voltage sensitivityof the open circuit out-put voltage single. For example, the voltage peak of the BSCOfilms with 0.8 at% Au NPS is about 14 times larger than that of the pure BSCO films.