Collaborative Research: Extrinsic Size Effects in Ferroelectric Thin Films

非技术描述：铁电材料用于耦合电能和机械能并存储信息。因此，它们在微电子、超声波设备和消费产品中广泛用作传感器、执行器、能量和存储组件。铁电材料的性能随着尺寸的减小而发生显著变化。在铁电薄膜中，现在人们普遍认识到，在10 nm和1 um之间的薄膜厚度上观察到显著的尺寸效应。在这样的厚度下，这些材料储存和传导能量的效率大大降低——在某些情况下，其数值被抑制到大尺寸材料的20%。利用由一个合作研究小组提供的最先进的实验方法，该项目阐明了铁电薄膜中这些尺寸效应的原子起源。这种理解使得下一代器件的设计和实现在更小的长度尺度上具有卓越的性能和功能。受本研究影响的器件包括压电微机电系统和缩放电容器。技术细节：该项目的目标是发展对铁电薄膜中控制外部尺寸效应的基本结构-性能-加工关系的普遍物理理解。具体目标包括证明影响铁电薄膜尺寸效应的外在机制，量化内在机制和外在机制对性能的相对贡献，以及建立新的基本结构-性能-加工关系。为了实现这些目标，宾夕法尼亚州立大学的Trolier-McKinstry小组合成了高质量的薄膜，并使用瑞利模型和Preisach模型分析了性能测量结果。北卡罗莱纳州立大学的Jones小组在施加电压的同时使用原位x射线衍射来量化等效电负载条件下的内在和外在贡献。综合结果提供了对铁电薄膜中介电和压电系数的内在和外在影响的定量理解，这些影响是薄膜厚度和其他关键变量的函数。机理的基本性质和本工作的结果将适用于许多铁电薄膜组合物，包括那些正在开发的高温和无铅应用。研究生通过在阿贡国家实验室的先进光子源进行实验，获得了更多的接触设施和科学家的机会。教育推广计划包括项目参与者参加针对小学、初中和高中学生的讲习班和营地。来自代表性不足群体的学生将通过有针对性的招聘和外展活动参与该项目。

NON-TECHNICAL DESCRIPTION: Ferroelectric materials are used to couple electrical and mechanical energy and store information. Therefore, they are used pervasively as sensors, actuators, and energy and memory storage components in microelectronics, ultrasonic devices, and consumer products. The properties of ferroelectric materials can change significantly as their size is reduced. In ferroelectric thin films, it is now widely recognized that significant size effects are observed at film thicknesses between 10 nm and 1 um. At these thicknesses, the effectiveness of these materials at storing and transducing energy is dramatically reduced - in some cases being suppressed to 20% of the values seen in their larger counterparts. Using state-of-the-art experimental approaches offered by a collaborative team of investigators, this project elucidates the atomistic origins of these size effects in ferroelectric thin films. This understanding enables the design and realization of next-generation devices at substantially smaller length scales with superior performance and functionality. Examples of devices impacted by this research include piezoelectric microelectromechanical systems and scaled capacitors.TECHNICAL DETAILS: The goal of the project is to develop a universal physical understanding of the fundamental structure-property-processing relationships that govern extrinsic size effects in ferroelectric thin films. The specific objectives include proving the extrinsic mechanism(s) affecting the size effects in ferroelectric thin films, quantifying the relative contributions from intrinsic and extrinsic mechanisms to properties, and establishing new fundamental structure-property-processing relationships. To accomplish these objectives, the Trolier-McKinstry group at Penn State synthesizes high-quality thin films and analyzes property measurements using Rayleigh and Preisach models. The Jones group at North Carolina State University uses in situ X-ray diffraction while applying voltage to quantify the intrinsic and extrinsic contributions under equivalent electrical loading conditions. The integrated results provide a quantitative understanding of contributions of intrinsic and extrinsic effects to the dielectric and piezoelectric coefficients in ferroelectric thin films as a function of film thickness and other key variables. The fundamental nature of the mechanisms and the results in the present work will be applicable to many ferroelectric thin film compositions including those being developed for high-temperature and lead(Pb)-free applications. Graduate students gain additional exposure to facilities and scientists through conducting experiments at the Advanced Photon Source at Argonne National Laboratory. The educational outreach program includes participation by the project participants at workshops and camps directed at elementary, middle school, and high school students. Students from underrepresented groups will be engaged in the project through targeted recruitment and outreach activities.