FRG: Unit Defect and Microstructural Processes at Metal/Dielectric Interfaces: An Integrated Experimental and Simulation Approach

非技术描述：尽管铅与环境和生物不相容，但铅基介电材料继续被用于许多电子设备，如通信、声纳、非易失性存储器和超声。在这些设备中使用的一种常见金属是铂，因为它导电性能好，抗氧化和耐高温。在高温下，铅基材料和铂之间的界面经常发生混合，这最终限制了器件的性能和性能。该项目的重点是了解铂-铅基介电界面的这些影响，并利用这些信息来生产具有改进电气性能的结构。该项目同时培养下一代科学家，包括研究生，本科生和高中生，在最先进的实验和计算材料科学与工程方面。培训代表性不足的本科生和通过暑期研究项目向高中生推广也是该活动的重点。技术细节：铅基钙钛矿，最突出的是钛酸铅及其衍生物，尽管铅在环境和生物上不相容，但仍然是许多应用中主要的介电材料。在这些设备中使用的一种常见金属电极是铂，因为它是一种优良的导体，具有很高的抗氧化性和耐热性。在高温加工过程中，这些材料中的本构元素在界面上相互扩散，控制了晶体织构和成分的发展，从而定义了随后的性能特征。本项目的重点是了解在金属-介电界面中起作用的基本机制，并利用这些机制信息来合成具有改善电性能的受控界面的材料和异质结构。采用实验和计算相结合的方法来确定(i)铅在钛酸铅中扩散的机制，以及（ii）铂/钛酸铅界面温度驱动的晶界迁移和织体演化。计算方法包括利用密度泛函理论和原子尺度分子动力学模拟进行电子结构计算。作为后一种努力的一部分，正在开发新的电荷优化的多体反应电位，并将其作为开源LAMMPS软件的一部分传播给计算社区（http://lammps.sandia.gov/）。实验中，采用原位衍射技术表征了高温加工过程中的相和织构演变，并通过定量电镜检查了界面上的扩散。此外，宽带阻抗和电测量被用来确定结构对介电和铁电行为的影响。该项目旨在培养最先进的实验和计算材料科学与工程领域的下一代科学家。夏季研究项目将吸引代表性不足的本科生和高中生。

NON-TECHNICAL DESCRIPTION: Lead-based dielectric materials continue to be the used in many electronic devices for communication, sonar, non-volatile memory, and echography, despite the fact that lead is environmentally and biologically incompatible. One common metal used in these devices is platinum because it conducts electrical current well and is resistant to oxidation and high temperatures. At high temperatures it is common for mixing to occur at the interface between the lead-based materials and the platinum, which ultimately limits the properties and performance of the devices. This project is focused on understanding these effects in platinum-lead-based dielectric interfaces and using this information to produce structures with improved electrical performance. The project concurrently trains the next generation of scientists, including graduate students, undergraduate students, and high school students, in state-of-the-art experimental and computational materials science and engineering. The training of underrepresented undergraduate students and outreach to high school students through summer research projects are also a focus of this activity.TECHNICAL DETAILS: Lead-based perovskites, most prominently lead titanate and its derivatives, continue to be the dominant dielectric material for many applications despite the fact that lead is environmentally and biologically incompatible. One common metal electrode used in these devices is platinum because it is an excellent conductor and exhibits high oxidation and heat resistance. During high-temperature processing, the constitutive elements in these materials interdiffuse across the interface, controlling the development of crystallographic texture and composition and thereby defining the subsequent properties and performance characteristics. This project is focused on understanding the fundamental mechanisms at play at the metal-dielectric interface and using this mechanistic information to synthesize materials and heterostructures with controlled interfaces with improved electrical properties. A combination of experimental and computational methods is used to determine the mechanisms by which (i) lead diffuses into and out of lead titanate, and (ii) temperature-driven grain-boundary migration and texture evolution occurs at the platinum/lead titanate interface. The computational approaches include electronic structure calculations using density functional theory and atomic-scale molecular dynamics simulations. As part of the latter effort, new charge-optimized, many-body reactive potentials are being developed and disseminated to the computational community as part of the open-source LAMMPS software (http://lammps.sandia.gov/). Experimentally, phase and texture evolution during high-temperature processing are characterized using in situ diffraction techniques and diffusion across the interface is examined via quantitative electron microscopy. In addition, broadband impedance and electrical measurements are being used to determine the influence of structure on dielectric and ferroelectric behavior. The project is training the next generation of scientists in state-of-the-art experimental and computational materials science and engineering. Summer research projects will engage underrepresented undergraduate and high school students.