Preparation Of 3 Inches YBa₂Cu₃O_7-x Films By Sol-Gel Process

YBCO thin films with excellent electrical properties have a wide market prospect in the microelectronic field for that the devices fabricated by them are smaller,lighter,and with lower insertion loss and noise.However,with the integration and industrialization of these microelectronic devices,preparation of large area films is required urgently which makes the fabrication of YBCO thin films with perfect properties to be the most important research. Fortunately,sol-gel method is a very potential method to fabricate large area YBCO thin films which has a great of advantages such as low cost,simple process and feasibility to prepare many films with any sizes and shapes on various substrates.In this paper,the low fluoride solution process with acrylic acid as the chelator of copper ion was employed and furthermore the influences of stoichiometric ratios and heat-treatment process of the precursors to the properties of YBCO films were explored.The XRD,SEM and the superconductivity test analysis results showed that the YBCO thin film with the stoichiometric ratio of Y:Ba:Cu=1:2:4 had the optimal c-axis growth orientation,and its critical transition temperature T_c was about 90 K,and changing widthâ–³T_c less than 1K(77K,0T).In the heat-treatment process,when the calcining temperature was 500℃,and the firing temperature was 800℃,the YBCO films had the highest T_c and the narrowestâ–³T_c.Meanwhile,an exploration of the variation of micro-morphologies as a function of thickness of the YBCO film has been made,which indicated that YBCO films on LaAlO₃(LAO) substrates possessed priority of c-axis growth orientation,and the orientation of them changed from c-axis axis to a-axis with the thickness increasing. At the last,the YBCO films with good c-axis growth orientation and surface quality were prepared onΦ3 inches LAO substrate using an optimized sol-gel and heat treatment process. The average surface roughness of these films withâ–³T_c ranged from 0.46 to 0.92 and thickness of 0.83μm was 38nm,and the thickness deviation was reduced to less than 3.71%.