Novel Mechanical Functionality in Nano-Architectured Ferroelectrics via Rational Design of Free Energy Landscapes

铁电体是传感和通信领域的重要材料。在铁电体中，可以通过施加电场来诱导机械运动，电场可以操纵纳米级电偶极子簇（称为畴）的方向。薄膜生长的进步现在允许通过将不同化学成分或域的层组合成单一结构（一次一个原子层）来制造人工铁电材料。与传统的铁电材料相比，人工系统提供了新的方法来操纵域，从而控制机械行为。该奖项旨在了解如何在人造铁电体中设计“智能”机械行为，例如用光诱导机械运动的能力或通过光或应力调节机械共振的能力。本研究将先进的计算技术与基于人工铁电体的微尺度机械装置的制造和表征相结合。该项目还将为材料科学、物理学、设备工程和数据科学等跨学科领域的研究生和本科生提供教育和培训机会。推广和传播工作将包括针对当地中学生和高中生的教育模块，以及达拉斯和沃斯堡地区科学博物馆的展览。铁电体是微机电系统（MEMS）中的关键材料。薄膜外延的最新进展使得人工铁电系统可以通过将不同的层组合成单片异质结构来创建。与同质组成的系统相比，人工系统提供了前所未有的途径来调整自由能景观，从而产生机械反应。该提案旨在阐明如何在人工铁电异质结构中合理地设计自由能景观，从而实现机械功能。特别令人感兴趣的是在自由能景观中接近不稳定的材料，这可能导致对扰动的剧烈机械响应。这种材料还可以表现出智能的功能特征，包括光诱导的机械驱动和可按需调整的机械共振。该方法涉及由不同成分的钙钛矿ABO3 （A = Sr, Ba; B = Ti, Zr）层组成的铁电异质结构的相场建模。通过高通量相场模拟生成的数据库上的机器学习将识别异质结构的关键材料特性（或“指纹”）并将其与机械响应关联起来。利用氧化分子束外延技术在硅表面外延生长，实验上实现了异质结构。这些异质结构将产生微光束谐振器和悬臂梁，并将在机械应力和光激励的扰动下探索机电行为，以形成闭环研究。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ferroelectrics are important materials used for sensing and telecommunication. Mechanical motion can be induced in ferroelectrics by applying electric fields, which manipulate the orientation of nanoscale clusters of electric dipoles, known as domains. Advances in the growth of thin films now allow artificial ferroelectric materials to be created by combining layers that differ in chemical composition or domains into a single structure, one atomic layer at a time. In comparison to traditional ferroelectric materials, artificial systems offer new ways to manipulate domains and thereby mechanical behavior. This award aims to understand how “smart” mechanical behaviors, such as the ability to induce mechanical motion with light or the ability to tune mechanical resonance with light or stress, can be engineered in artificial ferroelectrics. This research will integrate advanced computational techniques with the fabrication and characterization of microscale mechanical devices based on artificial ferroelectrics. The project will also provide opportunities to educate and train graduate and undergraduate students in the cross-disciplinary areas of materials science, physics, device engineering, and data science. Outreach and dissemination efforts will include educational modules for local middle and high school students, as well as displays for Dallas and Fort Worth area science museums. Ferroelectrics are key materials in microelectromechanical systems (MEMS). Recent advances in thin-film epitaxy have enabled artificial ferroelectric systems to be created by combining compositionally diverse layers into monolithic heterostructures. In contrast to systems of homogeneous composition, artificial systems offer unprecedented pathways to tune the free energy landscape, and thereby mechanical response. This proposal aims to elucidate how free energy landscapes, and thereby mechanical functionality, can be rationally engineered in artificial ferroelectric heterostructures. Of particular interest are materials poised near instabilities in the free energy landscape that may lead to dramatic mechanical response to perturbations. Such materials could also exhibit smart functional characteristics, including light-induced mechanical actuation and mechanical resonance that can be tuned on-demand. The approach involves phase-field modelling of ferroelectric heterostructures comprised of perovskite ABO3 (A = Sr, Ba; B = Ti, Zr) layers of varying composition. Machine learning on a database generated by high-throughput phase-field simulations will identify and correlate key material characteristics (or “fingerprints”) of heterostructures to mechanical response. Heterostructures will be experimentally realized through epitaxial growth on silicon using oxide molecular beam epitaxy. Microbeam resonators and cantilevers will be created from these heterostructures, and electromechanical behavior will be probed under perturbation of mechanical stress and optical excitation to form a close-loop study.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.