二元共掺BST薄膜介电性能及掺杂机理研究

【作者】 傅向军；

【导师】 廖家轩；

【作者基本信息】 电子科技大学 ， 材料科学与工程， 2010， 硕士

【摘要】 本论文主要研究二元共掺对Sol-gel法制备的钛酸锶钡(Ba0.6Sr0.4TiO3,BST)薄膜介电性能的影响。围绕提高BST薄膜介电性能而展开,结合目前优化BST介电性能的研究趋势,对一元掺杂与二元共掺进行研究,并对BST进行了交替掺杂的研究尝试。利用XRD、AFM、XPS等现代材料分析方法对薄膜微结构、表面形貌和成分进行表征,并就相关成分、工艺、结构及性能之间的联系进行探讨。首先,研究掺杂前后BST相结构的变化,结合试验结果,从容差因子等角度判断了掺杂元素对BST相结构的影响。通过AFM和XPS分析了BST薄膜表面形貌和表面成分。分析表明:掺杂后BST晶粒尺寸的变化与掺杂的元素有关,一元掺杂后钙钛矿结构BST的含量发生了变化。选取铈、锰对BST进行了A位掺杂、B位掺杂与AB位共掺杂对比研究。结果表明:掺杂后BST薄膜的介电性能得到了优化,其中,铈锰二元共掺的介电性能更具有优势,介电损耗最低可以降到0.014,20V的偏压下的优值因子为16.9;铈锰共掺克服了铈单掺杂耐压性差的问题。其次,为进一步降低BST薄膜的介电损耗,本论文进行了交替掺杂的研究尝试。研究了掺杂浓度和薄膜层数对交替掺杂BST薄膜介电性能的影响。交替掺杂在保持一定的优值因子基础上显著降低了介电损耗,同时,该薄膜还具有良好的耐压特性、平稳的损耗-偏压特性。此外,测试频率从100KHz提高到1MHz后,BST薄膜介电性能显示出良好的频率稳定性能。更多还原

【Abstract】 This thesis studied the dielectric properties and surface morphology of doped Barium strontium titanate (BST) films prepared by sol-gel method. The research was focused on the improvement of dielectric tunability properties and the reduction of dielectric loss of BST. According to the current research trend of performance optimization of BST, not only the single doping and the co-doping were studied, but also the new alternative doping method was analyzed. The as-prepared BST films are characterized by XRD, AFM and XPS. Meanwhile, the relationships between the Sol-gel method, film structure, film composition, and film properties have been examed and discussed.First, variance of microstructure of BST affected by cerium, yttrium, manganese doping was studied. The change of BST film surface roughness and surface composition was analyzed by AFM and XPS method. The results showed that the grain size of doped BST was closely related to doping elements. The proportion of perovskite structure of single doped BST also showed strong dependence on doping elements. Cerium and manganese were chosen as the objects of comparative study between single doping and co-doping. In general, the cerium-manganese-doped BST obtain competitive advantage of dielectric properties. Its dielectric loss can be reduced to as low as 0.014. Figure of merit (FOM) can reach 16.9 at 20V bias. The disadvantage of resistance to pressure in single doped BST was overcomed.Secondly, to further reduce the dielectric loss of BST thin films, the research attempt to investigate the alternative doping. The influence of doping concentration and the number of film layer on the dielectric properties of BST thin film was analyzed in the thesis. Introduction of alternative doping method can significantly reduce the dielectric loss. Additionally, the alternating doped BST films display high voltage-resistance and good loss tangent-voltage properties. In addition, when the test frequency was rised from 100KHz to 1MHz, the dielectric properties of alternative doped BST thin film exhibit little change. This phenomenon implied good frequency invariance of the alternative doped BST thin film.更多还原