【作者】 李艳红；

【导师】 周科朝； 张斗；

【作者基本信息】 中南大学 ， 材料工程， 2014， 硕士

【摘要】 摘要：铁电材料由于具有良好的铁电性、介电性、热释电效应和压电效应等特性,被广泛应用于固态集成器件。随着电子器件向小型化和高度集成化的发展趋势,促进了薄膜化和集成化器件的发展。在铁电薄膜材料中钙钛矿相结构钛酸锶钡BaxSr1-xTiO3(BST)体系,具有介电常数高、介电非线性好、漏电流低和高温下稳定性好等优势,受到广泛关注,但其介质损耗较大。溶胶-凝胶法是制备BST薄膜一种重要的方法,但对于性能优异的薄膜的获得仍存在很多问题。研究表明通过系统的研究薄膜的制备工艺,可以优化其性能。因此,本文主要对比研究了Pechini法和醋酸盐法制备BST溶胶的机理,BST薄膜的热处理制度以及不同Ba/Sr比、厚度和Co掺杂对BST薄膜微观结构和性能的影响。论文主要完成的研究工作和取得的结果如下：(1)通过采用Pechini法和醋酸盐法制备澄清、稳定的BST溶胶,探讨了制备BST溶胶的机理。研究表明采用醋酸盐法制备出的BST溶胶与衬底的润湿性好,制备出的薄膜表面均匀、致密、无裂纹,晶粒生长较好。(2)研究了BST薄膜的热处理制度,Ba/Sr匕和厚度对其性能的影响。研究表明：在氧气气氛中,通过在400℃下热分解30min,旋涂几层后,在800℃下退火15min可以获得微观形貌较好的BST薄膜；BaxSr1-xTiO3(x=0.6,0.7,0.8,0.9)薄膜的居里温度随Ba含量的增加而升高；当Ba0.8Sr0.2TiO3薄膜的厚度在160～378nm时,晶粒尺寸与厚度呈线性关系,随着薄膜厚度增加,居里温度由于低介电常数层的影响发生了偏移,频率一定时,Ba0.8Sr0.2TiO3薄膜的介电常数和介质损耗随厚度的增加而增大,晶粒尺寸在30～40nm,厚度为300nm的Ba0.8Sr0.2TiO3薄膜由于尺寸效应在室温以上不能获得居里点。(3)研究了Co含量对Ba0.8Sr0.2CoxTi1-x/2O3(x分别为0,0.5,1,3,5,10,BSCT)薄膜性能的影响。研究表明Co的加入降低了BSCT薄膜的介电常数和介质损耗,但同时调谐率也降低。当Co含量为3mol%时,BSCT薄膜的综合性能适用于可调器件。图53幅,表20个,参考文献83篇。更多还原

【Abstract】 Abstract:Ferroelectric materials exhibit ferroelectric, dielectric, pyroelectric effect and piezoelectric effect and other properties, which are widely used in solid state integrated devices. The trends of miniaturization and high integration electronic device promote the development of thin films and integrated devices. Among the ferroelectric thin film materials, barium strontium titanate BaxSr1-xTiO3(BST) with perovskite structure, possessing a high dielectric constant, dielectric nonlinearity, low leakage current and high temperature stability, attracts lots of attention, but its dielectric loss is large. Sol-gel method is an important method for the preparation of BST thin films with high performances, which is of great problems during the preparation process. By systemly studying the process of film preparation can optimize its performance. This paper mainly studied the mechanisms of BST sols prepared by Pechini method and Acetate method, the heat treatment regime of BST thin films, the effect of Ba/Sr ratio, the effect of thickness and Co-doped on microstructure and properties of BST thin films. The main results are as follows:(1) Stable BST sols were prepared by Pechini method and Acetate method, repectively. The mechanisms of BST sols were studied. The results show that wettability between BST sol prepared by acetate and substrate is well, and the corresponding thin films are uniform, dense and crack-free.(2) The heat treatment regime BST films, effect of Ba/Sr ratio and the thickness on its performance were studied. The results show that BST thin films with good crystallinity and high density are obtained after pyralyzing at400℃for30min and annealing at800℃for15min under oxygen atmosphere. Curie temperature of BaxSr1-xTiO3(x=0.6,0.7,0.8,0.9) thin films increase with the increase of Ba content. The grain size increases linely with the increasing thickness of the Ba0.8Sr0.2TiO3thin films ranging from160to378nm. The Curie temperature shifts due to the dead layer. The dielectric constant and dielectric loss increase with the increase of the thickness under a constant frequency. The dielectric constant of the Ba0.8Sr0.2TiO3thin film whose Curie temperature is below the room temperature with the grain size of30～40nm and thickness of 300nm decreases with the increase of temperature because of size effect.(3) Ba0.8Sr0.2TiO3thin films doped with Co were characterized. The results show that the doping of Co not only contributes to dielectric constant and dielectric loss of BSCT thin films decreasing, but also the tunability decreasing. The samples doped with3mol%Co are suitable for tunable devices.更多还原