Lattice dynamics and phase transitions in multifunctional oxide nanomaterials studied by ultraviolet Raman spectroscop

非技术描述：近年来，电子材料的科学和技术已经朝着纳米级(十亿分之一米)的人工工程薄膜和多层结构发展。纳米材料表现出与宏观材料截然不同的物理行为，从而为新型器件的应用开辟了新的机会。该项目研究纳米级铁电体和多铁性材料，这类材料既对基础研究感兴趣，又由于在各种设备中的高应用潜力而具有重要的实践意义，如计算机存储器、微波电子器件或下一代晶体管。这项研究与博伊西州立大学的教育项目紧密结合，让本科生和研究生参与研究和培训，从而为他们在物理科学和材料工程领域的职业生涯做好准备。这样的毕业生是电子和材料行业的需求，如美光科技、惠普和博伊西大都市区的其他高科技公司。该项目促进为教育目的积极使用最先进的仪器，并支持开发新的研究生课程。它扩大了来自代表性不足群体的学生对尖端科学研究的参与。该项目增强了博伊西州立大学在凝聚态物理和材料科学方面的实力。技术描述：复合金属氧化物是一类广泛的材料，具有广泛的功能特性，对新型器件应用具有吸引力。在这些功能中，铁电性和铁磁性是材料具有自发电极化或磁化的特性，它们可以分别通过施加电场或磁场来切换。铁电体和多铁体是同时表现出磁性和铁电有序的材料，在过去的几年里一直是密集的研究活动的焦点，因为由于电序和磁序参数之间的耦合而产生了潜在的新的器件应用功能。纳米尺度的人工工程薄膜和多层结构因其新的物理现象和性质与均匀的块状铁电材料显著不同而引起人们的极大兴趣。本项目利用紫外光激发的变温拉曼光谱研究了纳米铁电材料和多铁性材料的行为，重点研究了纳米铁电材料中的尺寸效应和薄膜中的温度-应变相图，以及预测具有应变薄膜形式的铁电和多铁性的新材料的异质结构。这些结果被用来检验热力学和第一性原理理论的预测，并结合结构、电和磁性质的彻底表征，导致对纳米尺度铁电和磁电耦合的更全面的理解。这项拟议的研究将与博伊西州立大学的教育计划紧密结合，积极吸引本科生和研究生参与研究和培训，并促进最先进的光学仪器继续有效地用于教育目的。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical description:In recent years, science and technology of electronic materials have moved towards artificially engineered thin films and multilayer structures at nanometer scales (one billionth of a meter). Nanoscale materials exhibit physical behavior drastically different from that of macroscopic materials, thus opening new opportunities for novel device applications. This project studies nanoscale ferroelectrics and multiferroics, a class of materials both interesting for fundamental research and practically important due to high potential for applications in various devices, such as computer memories, microwave electronic devices or in next-generation transistors. The research is closely integrated into the educational program at Boise State University, involving undergraduate and graduate students in research and training, thus making them well prepared for careers in physical sciences and materials engineering. Such graduates are on demand by electronics and materials industries, such as Micron Technology, Hewlett Packard, and other high-tech companies in Boise metropolitan area. The project promotes an active use of the state-of-the-art instrumentation for educational purposes and supports the development of new graduate programs. It broadens the involvement of students from under-represented groups in the cutting-edge scientific research. The project enhances Boise State’s strength in condensed-matter physics and materials science. Technical description:Complex metal oxides are a vast class of materials that have a wide variety of functional properties attractive for novel device applications. Among these functionalities are ferroelectricity and ferromagnetism, properties of materials to possess spontaneous electric polarization or magnetization, which can be switched by applying electric or magnetic field, respectively. Ferroelectrics and multiferroics, materials that exhibit both magnetic and ferroelectric ordering, have been in the focus of intensive research activity in the last several years, driven by potential new functionalities for novel device applications arising from the coupling between the electrical and magnetic order parameters. Artificially engineered thin films and multilayer structures at nanometer scales are of particular interest, due to new physical phenomena and properties dramatically different from those of homogeneous bulk ferroelectrics. This project utilizes variable-temperature Raman spectroscopy with ultraviolet excitation to address several issues of major importance for understanding the behavior of nanoscale ferroelectrics and multiferroics, focusing on size effects in ferroelectric nanomaterials and temperature-strain phase diagrams in thin films and heterostructures of novel materials predicted to have ferroelectric and multiferroic properties in strained thin film form. These results are used to test the predictions of thermodynamic and first-principles theories and combined with thorough characterization of structural, electrical and magnetic properties, leading to a more comprehensive understanding of nanoscale ferroelectricity and magnetoelectric coupling. The proposed research will be closely integrated into the educational program at Boise State University, actively involving undergraduate and graduate students in research and training and promoting the continued effective use of the state-of-the-art optical instrumentation for educational purposes.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.