Microstructural Analysis and Electrical Property Studies on BaxSr1-xTiO3 Ferroelectric Thin Films

9711044麦克特里克高质量铁电薄膜的开发是在动态随机存取存储器(DRAM)设备上实现千兆位存储容量的主要挑战之一。体相铁电材料，如BaTiO_3，已经得到了很好的表征；然而，对于薄膜的铁电性质，人们还没有从基础甚至技术层面上加以了解。晶粒度、晶向(多晶与外延)、化学计量比、薄膜厚度、残余应力、掺杂浓度和表面粗糙度等微结构特征尚未得到系统的研究或表征。为了使用铁电薄膜，它们必须夹在导电电极之间。这些电极已被发现是电流泄漏的来源，增加了疲劳和老化损伤。为了充分利用优化的薄膜结构，对电极的基本了解也是必要的。这项为期两年的计划旨在系统地研究用于兆字节动态随机存取存储器应用的顺电BaxS L-xTiO_3的微结构-电性能关系。本工作的目标有四个方面：(A)优化用于铁电薄膜沉积的导电氧化物电极，(B)量化化学计量比、颗粒尺寸、厚度和残余应力在铁电薄膜中的作用，并优化铁电薄膜的电学性能，(C)研究添加施主掺杂到BaxSr1-xTiO_3中的影响，目的是改善电学性能，以及(D)制备BaTiO_3和SrTiO_3的超晶格结构，并将微结构特征与电学性能联系起来。这项工作将在加州大学圣地亚哥分校和墨西哥恩塞纳达的物理研究所进行，这两个机构拥有不同但互补的设施。***

9711044 McKittrick The development of high quality ferroelectric thin films is one of the main challenges to achieving giga-bit storage capacity on dynamic random access memory (DRAM) devices. Bulk ferroelectrics such as BaTiO3 are well characterized; however, the ferroelectric properties of thin films are not understood at a fundamental or even technical level. The microstructural features such as grain size, grain orientation (polycrystalline vs. epitaxial), stoichiometry, thickness of the film, residual stress, dopant concentrations and surface roughness have not been systematically studied or characterized. In order to use ferroelectric thin films, they must be sandwiched between conductive electrodes. These electrodes have been found to be the source of current leakage, increasing fatigue and aging damage. To fully exploit the optimized thin film structures, a basic understanding of the electrode is also necessary. This two year proposal seeks to systematically investigate the microstructure-electrical property dependence of paraelectric BaxS l-xTiO3, for megabyte DRAM applications. The objectives of this work are fourfold: (A) to optimize a conductive oxide electrode for the deposition of the ferroelectfic films, (B) to quantify the role of stoichiometry, grain size, thickness, and residual stress in thin film ferroelectrics and optimize the electrical properties, (C) investigate the effect of adding donor dopants to BaxSrl-xTiO3 with the goal of improving the electrical properties and (D) to fabricate superlattice structures of BaTiO3 and SrTiO3 and correlate the microstructural features with the electrical properties. This work will be performed at UC-San Diego and the Institute of Physics in Ensenada, Mexico which have different but complementary facilities. ***