【作者】 方骏飞；

【导师】 杜丕一；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2012， 硕士

【摘要】 AB03型钙钛矿结构铁电薄膜由于具有独特的介电、压电、热释电及铁电性能,在很多领域中有着广泛的应用前景。(Pb,Sr)TiO3(PST)铁电薄膜由于具有很好的介电可调性,是当前介电可调薄膜的研究热点之一。然而,对于介电可调薄膜来说,要想获得最大介电调制,必须施加足够高的调制电压来产生高调制电场,但对于电子元器件来说工作电压不宜太高。同时,随着电子器件的微型化和集成化,对介电可调薄膜性能的要求也越来越高。显然降低介电调制电压、提高PST薄膜的介电可调性已经成为PST在相关领域得到应用的关键。采用小尺度间距叉指电极可有效地降低介电调制电压,提高介电可调性。随着纳米科学的不断发展,导电纳米线的应用也逐渐进入人们的视线,考虑到硅化钛由于其低电阻率、高热稳定性、可以制备成纳米线/薄膜一体化结构和与当前硅基制备工艺相匹配等特点,利用硅化钛导电纳米线/硅化钛薄膜作为薄膜电极,能使材料在较低电压下获得较大介电常数调制。而且,对这种纳米线复合电极降低调制电压、提高介电可调性的作用机制还不清楚,进而不能很好地控制相应薄膜性能。因此深入研究这种复合电极结构显得尤为重要,进一步探索介电可调薄膜的形成机制并揭示其性能改善的基本原理将有利于实现薄膜的制备和性能可控,对开发其在新型高性能器件中的应用起到极其重要的推动作用。本论文全面综述了AB03型钙钛矿结构铁电薄膜的主要制备方法及其应用现状,总结了硅化钛薄膜及其纳米线的制备与应用。描述了铁电薄膜的介电可调原理和基于边缘电场的边缘电场电容器概况。通过引入在纳米线电极周围产生强大边缘电场的思想,首先采用常压化学气相沉积法在玻璃基板上制备了TiSi纳米线/Ti5Si3薄膜复合电极,并采用射频磁控溅射法在TiSi纳米线/Ti5Si3薄膜复合电极上制备了PST薄膜。利用XRD、SEM、TEM、Agilent 4294A型阻抗分析仪等多种测试手段对薄膜的相结构、结晶性能、表面形貌及介电可调性等进行了研究,详细讨论了电极对PST薄膜结构形成和介电可调性的影响,给出了电极对PST薄膜形成的影响过程和诱导形成的形成机理,并通过模拟研究确认了基于边缘电场的低调制电压高介电可调PST薄膜的调制行为。研究表明,在TiSi纳米线/Ti5Si3薄膜电极上制备的PST薄膜受到TiSi和Ti5Si3电极结构诱导作用的影响,PST薄膜析晶温度下降,同时PST晶相含量提高。这有利于PST薄膜的制备优化,性能提高及在相关微电子器件中的应用。同时,在TiSi纳米线/Ti5Si3薄膜电极上制备的PST薄膜受纳米线产生的强大边缘电场的作用,其介电调制电压降低了约9倍,介电可调性提高约一倍。边缘电场的强度受纳米线密度和长度等因素影响,随着纳米线密度增大和长度增加,边缘电场的作用增强。这种利用边缘电场降低介电调制电压和提高介电可调性对于铁电薄膜在介电可调领域的应用来说是一个很大的突破。更多还原

【Abstract】 Ferroelectric thin film with ABO3 perovskite structure has a broad prospect for its application in many fields due to their sufficient advantages including dielectric, piezoelectric, pyroelectric and ferroelectric properties. (Pb, Sr)TiO3 (PST) ferroelectric thin film is a hot research material because it has great dielectric tunability. However, high tunability of dielectric tunable thin film has to be stimulated by high electric field, and high electric field is always obtained under high voltage. The high voltage contradicts with the development of micro-electric component. At the same time, with miniturazation and integration of micro-electric devices, the requirement of performances of PST thin film becomes higher and higher. Obviusly, in order to adapt miniturazation tendency of micro-electric devices, the decrease of modulation voltage and improvement tunability of PST thin film become an important factor to using PST in related application field. Interdigital electrodes with small distance would decrease modulation voltage and improve tunability effectively. With the development of nano science, applications of electric-conducted nanowire are put forward. Considering low resistivity, high heat-stability and great compatibility with silicon integrated technology of titanium silicide, embedding TiSi nanowires as electrode of ferroelectric thin film could improve tunability and decrease modulation voltage. What’s more, the mechanism of the decrease in modulation voltage and improvement of tunability haven’t clearly announced until now, and thus the properties of thin film couldn’t be controlled greatly. Therefore, it’s important to research the composite electrode structure, and the further study about the formation mechanism of dielectric tunable thin film and announcing the property improvement mechanism are beneficial for the preparation and properties comtrol of thin film, and promote its applications in high-performance devices greatly.This paper reviewed preparation methods and applications of ferroelectric thin film with ABO3 perovskite structure, described dielectric tunability theory and current situation of dielectric tunable thin film based on fringing electric. Through the introduction of idea of using TiSi nanowires to generate large fringing electric field for stimulating tunability of PST thin film, TiSi nanowires/Ti5Si3 thin films were prepared by chemical vapor deposition method, and PST thin films were prepared on TiSi nanowires/Ti5Si3 thin film electrodes by magnetron sputtering method respectively. The phase structure, crystalline condition, morphology, and tunability were measured by XRD, FESEM and Agilent 4294A respectively. Effect of TiSi nanowires/Ti5Si3 thin film electrodes on structure formation and tunability of PST ferroelectric thin films was detailedly analysised. and the effect of TiSi nanowires/Ti5Si3 thin film electrode on tunability of PST ferroelectric thin films was simulated.Reserch shows that:As inducing effect of TiSi and Ti5Si3 structure, PST thin films sputtered on TiSi nanowires/Ti5Si3 thin films electrode have lower crystalline temperature and more phase content. This is favorable for the optimization of preparation, the improvement of properties, and the application to micro-electric devices of PST thin films. At the same time, modulation voltage of PST thin film sputtered on TiSi nanowires/Ti5Si3 thin film electrode decreases by about nine times at the same condition because of large fringing electric field generated by TiSi nanowires, and tunability improves by one time. Fringing electric field is affected by density and length of nanowires:the larger the nanowires density and the longer the nanowires, the larger intensity of fringing electric field. The application of fringing electric field to decrease modulation voltage and increase tunability is a great breakthrough for the application of ferroelectric thin film in dielectric tunable field.更多还原