FRG: Structural Phase Transformations in Polymorphic Nanostructures

技术描述：本项目旨在了解相变纳米结构材料，特别是In2Se3纳米线中晶体-非晶和多晶-晶体相变的潜在机制，并了解多层次相变记忆开关过程。具体任务包括：(1)通过构建温度-压力相图来理解相变的热力学；(2)研究相变动力学；(3)建立构物关系；(4)阐明多级存储器交换的多物理场过程。该方法结合了实验和理论研究。该实验方法结合了透射电子显微镜、拉曼和红外光谱、x射线衍射和多功能扫描探针显微镜技术，具有原位调节温度和压力的能力。作为实验方面的补充，基于第一性原理计算的理论部分研究了相稳定性及其对温度和压力的依赖，相变的动力学途径，以及相特有的电子结构和物理性质。非技术描述：本项目提供了对技术上重要的相变材料的结构相变的基本见解。与当前主流的非易失性存储器技术（如闪存）相比，相变存储器提供更快的随机访问时间、更高的耐用性和10nm范围内的可扩展性。本研究所获得的知识为在单一材料系统中开发具有多级存储能力的下一代非易失性相变存储器奠定了基础。该项目为本科生和研究生提供培训机会，包括那些代表人数不足的群体的学生。一个新的研讨会课程侧重于提供相变纳米材料的连贯理解，并由pi团队教授。通过制作视觉材料，包括在YouTube上发布的图像和电影，促进了与公众的接触。这些材料是探索纳米的一部分！在当地科学博物馆展出。

Technical Description: This project aims to understand the underlying mechanisms of crystalline-amorphous and polymorphic crystalline-crystalline phase transformations in phase-change nanostructure materials, particularly In2Se3 nanowires, and to understand the multi-level phase-change memory switching process. Specific tasks include (1) understanding the thermodynamics of phase transformations by constructing the temperature-pressure phase diagram; (2) investigating the phase transformation kinetics; (3) establishing the structure-property relation; and (4) elucidating the multiphysics process that underlies the multi-level memory switching. The approach combines experimental and theoretical investigations. The experimental approach utilizes a combination of transmission electron microscopy, Raman and infrared spectroscopy, x-ray diffraction, and multi-functional scanning probe microscopy techniques, with the capability to adjust the temperature and pressure in situ. Complementing the experimental aspect, the theory component based on first-principles calculations investigates the phase stability and its dependence on temperature and pressure, kinetic pathways of the phase transformation, and phase-specific electronic structures and physical properties.Non-technical Description: This project provides a fundamental insight into the structural phase transformation in a technologically important phase-change material. Compared to current mainstream non-volatile memory technologies, such as the Flash memory, phase-change memory offers faster random access time, higher endurance and scalability to the 10-nm range. The knowledge acquired in this study establishes a fundamental basis for developing next-generation non-volatile phase-change memory with multi-level storage capabilities in a single material system. This project provides training opportunities for undergraduate and graduate students, including those who are members of underrepresented groups. A new seminar course focusing on providing a coherent understanding of phase-change nanomaterials is developed and is team-taught by the PIs. The outreach to the general public is facilitated by developing visual materials, including images and movies, which are posted on YouTube. These materials are a part of the Explore Nano! exhibit in a local science museum.