【作者】 刘晓梅；

【导师】 赵高扬；

【作者基本信息】 西安理工大学 ， 材料科学与工程， 2008， 硕士

【摘要】 由于YBa₂CH₃O_7-x（YBCO）高温超导薄膜具备优异的电学性能,用其制作的高温超导微波无源器件具有体积小、重量轻、损耗低、噪声小、低色散等优点,因此其在微电子应用领域有很好的市场前景。然而,这些微电子器件的集成化和产业化对大面积薄膜材料的制备提出了迫切的要求,因此制备性能良好的大面积YBCO薄膜成为高温超导薄膜的研究重点。溶胶-凝胶法具备成本低廉,工艺简单,可以在任意尺寸和形状的衬底上成膜等特点,是一种制备大面积YBCO薄膜极具潜力的方法。本文采用以丙烯酸作为铜离子络合剂的低氟溶胶工艺,探讨前驱物的不同化学计量比和热处理工艺对YBCO薄膜微观结构和超导相的影响。通过XRD、SEM和超导电性等测试分析发现:前驱物中阳离子的化学计量比为Y:Ba:Cu=1:2:4的YBCO薄膜具有较好的c轴生长取向,其临界转变温度T_c约为90K,转变宽度△T_c＜1K（77K,0T）:热处理工艺中,预处理温度为500℃、终处理温度为800℃时,样品的超导临界转变温度T_c最高,转变宽度△T_c最窄。同时对薄膜微观形貌随厚度的变化规律进行了探讨,研究发现,YBCO薄膜在LaAlO₃（LAO）衬底上是优先c轴生长的,且随着薄膜厚度的增大YBCO薄膜由c轴生长取向转为a轴生长取向。最后采用合适的溶胶配比和热处理工艺,在3英寸LAO单晶衬底上制备出了具有较好c轴生长取向和面内均匀性的YBCO薄膜。薄膜表面平均粗糙度为38nm、平均厚度为0.83μm、膜厚偏差为3.71%、△T_c分布在0.46-0.92之间。更多还原

【Abstract】 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 width△T_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 narrowest△T_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 with△T_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%.更多还原