摘要
本论文的目的是研究基片对薄膜结构和性能的影响关系，采用倒筒靶直流溅射技术在在LaAlO3(100)和R-平面的蓝宝石（Al2O3(102)）两种基片上制备出c轴取向的外延高温超导YBa2Cu3O7-δ薄膜。
本文结合AFM、SEM研究YBCO薄膜的表面形貌，XRD、FWHM分析薄膜的结晶情况，并结合成膜温度和基片的质量进行一系列结构与性能的对比研究，发现LaAlO3（LAO）基片的质量对YBCO薄膜的结构完整性有很大影响，不仅影响了薄膜的c轴取向性，而且影响了YBCO的超导性能。
在LaAlO3 (100)基片上制备出了c轴取向的YBa2Cu3O7-δ薄膜：Tc0=90K，ΔTc=0.3K，Rs(77K, 10GHz)=1.7mΩ。
通过在R-Al2O3基片上生长一层CeO2缓冲层，改善了Al2O3与YBCO晶格的严重失配，制备出了Tc0=90K，ΔTc=0.5K，Rs(77K, 10GHz)=2mΩ，性能较好的YBCO超导薄膜。
同时，本文运用成核、成膜理论分析了制备优质外延氧化物薄膜所要满足的必要条件，讨论了应力对薄膜取向的影响，发现晶格失配导致CuO2面中应力的产生，从而降低了YBCO的临界转变温度。
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.
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