The Microscopic Structure And Properties Of Ybco Thin Films

The purpose of this dissertation is to study the effect of substrate on the characteristics and microstructure of High Temperature Superconducting YBa2Cu3O7-δ thin film, and well c-axis oriented epitaxial YBCO thin films have been deposited on both LaAlO3 (100) and R-plane sapphire Al2O3 (102) substrates by Inverted Cylindrical DC Sputtering (ICDS) technique.The properties of thin films have been investigated with modern analysis technique, such as AFM (atom force microscopy), SEM (scanning electron microscope), XRD (X-ray diffraction) and Rocking curve (ω-scan). And the properties of YBCO thin film and its substrate and deposition temperature have been analysed, comparing with LAO substrate's crystallization quality, YBCO thin film properties, such as morphology and degree of grain alignment, was concluded to correlate with the crystal orientation uniform of LAO substrate as revealed by XRD. In the optimum deposition conditions, c-axis oriented epitaxialYBCO/LAO thin films with propertities: Tc0=90K,ΔTc=0.3K,Rs(77K, 10GHz)=1.7mΩ have been obtained.The lattice misfit of YBCO film and Al2O3 substrate can be improved by (001) CeO2 bufer layer, YBCO/CeO2/Al2O3 thin film with good superconducting properties: Tc0=90K,ΔTc=0.5K,Rs(77K, 10GHz)=2mΩ have been obtained.Moreover, the epitaxial growth conditions, the orientation and epitaxy mechanisms of oxide thin film have been explained according to the theory of nucleation and film forming. At last, the film strain due to the lattice misfit is an important factor to make the Tc decreased, because of the strain effect on CuO2 planes.