基于聚合物衬底低温生长无定形铋基薄膜的结构调控与电性能研究

As electronic systems develop towards high computing speed, miniaturization, complanation and integration, it is being attempted embedding the passive components into printed circuit boards. Meanwhile, flexible electronic devices also show the potential applications. However, the polymer requires that the thermal process temperature should be below 200 °C, which limits the choice of capacitor materials, such as ferroelectrics. Ferroelectric materials with high dielectric constants can only be obtained for the crystalline phase with a high processing temperature. This research is intended to rely on the structure modulation and ionic substitution, The amorphous Bi-based thin films are prepared on the polymer substrates at low temparature. The influences of percolation structure, amorphous matrix, defect complexes, nanocrystallines,Chemical bonding on dielectric response and leakage behavior will be systematically investigated. The existing state, defect types and chemical bond of thin films will be analyzed. The formation mechanisms of the metal Bi and nanocrystallines will be discussed. By these methods: the modulation of micro and macro structures, the design of composite phase, improvement of interface features between the polymer substrate and thin film,the electric properties of thin films may be improved. The correlation between structure modulation and microscopic polarization response is established. The mechanisms and correlation of electric polarization, loss, charge transport characteristics, aging and resistivity degradaion of the amorhous Bi-based thin films are revealed. It can provide the theoretical reference and the material experimental basis for the development of the embedded thin film capacitors and flexible thin film devices.

电子系统正向高速、微型化、平面化和集成化快速发展，人们尝试将无源器件嵌入到线路板内部，同时柔性电子器件也显示出重要的应用前景。然而聚合物的应用要求工艺处理温度应低于200度，这就限制了电容器介质材料的选择，例如需要较高结晶温度的高介电常数的铁电体。本申请旨在通过结构调制和离子取代，在聚合物衬底上低温生长无定形铋基介质薄膜。系统研究无定形态基体、缺陷缔合、渗流结构、纳米晶体、化学键合对薄膜介电响应和漏导特性的影响规律；分析薄膜的局域精细结构，缺陷类型以及化学键合特性；阐明可能存在的纳米晶体与金属铋的形成机制。通过微观和宏观结构的调控、复相化设计、界面特性的研究，实现电性能改进，建立结构调制和微观极化响应之间的关联。同时揭示无定形铋基薄膜的极化、损耗、电荷输运、老化、电阻退化的微观机制与相互关联。为嵌入式薄膜电容器和柔性器件的发展提供理论参考和材料实验依据。

本课题自2015年立项以来，围绕铋基系列薄膜A2BB2O7、六方钙钛矿微波介质、MLCC薄层介质，系统探讨了晶体结构、多相设计、缺陷缔合对介电响应和漏导特性的影响规律。我们以立方铋基焦绿石Bi1.5ZnNb1.5O7配方为基点，通过改变Bi3+，Zn2+和O2-的浓度形成非化学计量比组成，正如Bi1.5Zn(1+y)Nb1.5O(7+y)(y=0, 0.1, 0.2, 0.4)，Bi(1.5+x)Zn(1+y)Nb1.5O(7+1.5x+y)(x=0, 0.075, 0.15, y=0 and x=0.075, y=0.05)，通过低温沉积无定形态的氧过量型铋基系列薄膜，来研究非化学计量比铋基系列薄膜的结构和性能的变化情况。另外，我们也借助了紫外-可见分光度计分析了Bi1.5ZnNb1.5O7结晶薄膜的光学特性，计算其折射率，进而得到光频下的介电常数和光学带隙宽度；并通过PL谱研究其在激发态下的发光特性。同时也制备了新型焦绿石陶瓷：立方Bi1.5CuTa1.5O7 和单斜Bi2(Cu1/3Ta2/3)2O7，研究其烧结特性、结构、性能，及其三者之间的相关性。我们也关注了超薄商用的Y5V型BaTiO3基MLCC，研究了缺陷与可靠性之间的相关性。研究了在强交流电场下的介电行为和高加速电阻退化行为，为了理解电阻退化的基本机制，对退化前和退化后的电容器介质进行了TSDC测试。我们也研究了在流动氧气氛下烧结的Ba0.6Sr0.4La4Ti4O15-TiO2复合陶瓷的相结构、烧结行为与微波介电特性。这些研究结果为功能电介质的实际应用提供了实验数据和理论参考依据。