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，它们被广泛用作微电子、超声波设备和消费产品中的传感器、执行器以及能量和存储器存储部件。随着尺寸的减小，铁电材料的性能会发生显著变化。在铁电薄膜中，人们普遍认为当薄膜厚度在10 nm到1微米之间时，可以观察到显著的尺寸效应。在这些厚度下，这些材料在存储和转换能量方面的有效性大大降低--在某些情况下，其值被抑制到较大材料的20%。使用由合作研究团队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。这种理解使下一代设备的设计和实现具有卓越的性能和功能，其长度规模要小得多。技术细节：该项目的目标是对控制铁电薄膜外部尺寸效应的基本结构-性能-工艺关系有一个普遍的物理理解。具体目标包括证明影响铁电薄膜尺寸效应的外在机制(S)，量化内在和外在机制对性能的相对贡献，以及建立新的基本结构-性质-加工关系。为了实现这些目标，宾夕法尼亚州立大学的Ttrolier-McKinstry团队合成了高质量的薄膜，并使用Rayleigh和Preisach模型分析了性能测量。北卡罗来纳州立大学的琼斯小组在施加电压的同时，使用原位X射线衍射来量化同等电气负载条件下的本征和外在贡献。积分结果提供了对铁电薄膜中本征和外在效应对铁电薄膜介电和压电系数作为薄膜厚度和其他关键变量的函数的贡献的定量理解。这些机制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(铅)应用。研究生通过在阿贡国家实验室的高级光子源进行实验，获得了对设施和科学家的更多接触。教育推广计划包括让项目参与者参加针对小学生、初中生和高中生的研讨会和夏令营。来自任职人数不足群体的学生将通过有针对性的招聘和外联活动参与该项目。

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.