CAREER: Unusual phonons in bulk ferroelectric HfO2 single crystals

职业：块状铁电 HfO2 单晶中的异常声子

• 批准号: 2236543
• 负责人: Junjie Yang
• 金额: $ 57.08万
• 依托单位: New Jersey Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2028-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2236543&HistoricalAwards=false
• 关键词: CAREER; Unusual; phonons; bulk; ferroelectric

Non-technical Abstract: Due to extraordinary properties and compatibility with silicon technology, HfO2 is today's most promising material for next-generation non-volatile, high-density, and high-speed technologies. However, the microscopic origin of HfO2's properties remains elusive, hindering the development of HfO2-based devices. This project aims to fill the important gap in understanding by revealing the microscopic origin of HfO2's unique properties. The results will build the scientific foundation of HfO2 for future atomic-scale applications. The results of this project will provide new knowledge in the field of quantum materials, in addition to helping the rational synthesis and fabrication of better HfO2-based devices. The research activities involve the study of large crystals performed at world-class neutron facilities located at national labs. The PI effectively integrates the research activities with education at all academic levels (K-12 students, undergraduates, and graduates) to train the next generation of scientists. In particular, the PI collaborates with the Liberty Science Center, Franklin Mineral Museum, Rutgers University, and local high schools and develops a “Natural Minerals & Quantum Materials” educational project that provides great learning opportunities for K-12 students.Technical Abstract: HfO2 exhibits extraordinary ferroelectricity: it is the only binary compound with switchable polarization, which is robust down to atomic scales. More importantly, HfO2 shows excellent complementary metal-oxide semiconductor compatibility. Thus, HfO2 is today's most promising material for next-generation non-volatile, high-density, and high-speed ferroelectric memories. However, the microscopic origin of HfO2's ferroelectricity remains elusive, hindering the development of HfO2-based ferroelectric devices. Recent theoretical work suggested that HfO2's ferroelectricity may originate from exotic flat polar phonon bands, and these flat bands are directly associated with the atomic-scale separation of polar and space layers, which can enable atomic-scale manipulation of polarization. This project aims to fill the important gap: utilize the laser floating zone crystal growth method to stabilize the metastable ferroelectric phase in large bulk crystals and the inelastic neutron scattering technique on the crystals to validate the scenario of flat polar phonon bands. The inelastic neutron scattering method can detect phonon bands in a wide range of wavevectors and energies. Flat bands in quantum materials, such as flat bands of electrons, have been known to cause various novel quantum phenomena, such as superconductivity. However, the function of flat polar phonon bands is poorly understood. This project would reveal the effect of flat polar phonon bands on ferroelectricity, which can be directly relevant to atomic-scale ferroelectric manipulation. The results would also provide a new approach for improving the ferroelectric properties of HfO2-based materials, e.g., fine tunning the ferroelectric properties by engineering the flat polar phonon bands. The PI effectively integrates the research activities with education at all academic levels (K-12 students, undergraduates, and graduates) to train the next generation of scientists.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.

非技术摘要：由于非凡的特性和与硅技术的兼容性，HFO2是当今下一代非挥发性，高密度和高速技术的最有前途的材料。但是，HFO2属性的微观起源仍然难以捉摸，阻碍了基于HFO2的设备的开发。该项目旨在通过揭示HFO2独特属性的微观来源来填补理解的重要空白。结果将为未来的原子级应用建立HFO2的科学基础。该项目的结果还将在量子材料领域提供新知识，此外还可以帮助理性的综合和更好的基于HFO2的设备的结构。研究活动涉及对位于国家实验室的世界一流中子设施进行的大型晶体的研究。 PI有效地将研究活动与所有学术水平的教育（K-12）学生，本科生和毕业生）融合在一起，以培训下一代科学家。 In particular, the PI collaborates with the Liberty Science Center, Franklin Mineral Museum, Rutgers University, and local high schools and develops a “Natural Minerals & Quantum Materials” educational project that provides great learning opportunities for K-12 students.Technical Abstract: HfO2 exhibits extraordinary ferroelectricity: it is the only binary compound With switchable polarization, which is robust down to atomic scales.更重要的是，HFO2显示出极好的互补金属氧化物半导体兼容性。这是当今HFO2的下一代非挥发性，高密度和高速铁电回忆的最有前途的材料。但是，HFO2铁电性的微观起源仍然难以捉摸，阻碍了基于HFO2的铁电器的发展。最近的理论工作表明，HFO2的铁电性可能起源于外来的平面式声子带，这些平坦带与极性和空间层的原子尺度分离直接相关，这可以实现对极化的原子尺度操纵。该项目旨在填补重要的空白：利用激光浮动区晶体生长法以稳定大型散装晶体中亚稳态的铁电相和在晶体上的无弹性中子散射技术来验证平面极性声子带的情况。非弹性中子散射方法可以检测各种波形和能量的声子。已知量子材料中的平坦带（例如电子的平坦带，都会引起各种新型的量子现象，例如超导性。但是，平坦的极性声子条带的功能知之甚少。该项目将揭示平面声子带对铁电的影响，这可能与原子尺度的铁电操作直接相关。结果还将提供一种新的方法，用于改善基于HFO2的材料的铁电特性，例如，通过工程化平面极性声子条带来微调铁电特性。 PI有效地将研究活动与所有学术层面的教育（K-12学生，本科生和毕业生）培训，以培训下一代科学家。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准通过评估来获得的支持。