CAREER: Nanoscale temperature mapping across interfaces using scanning transmission electron microscopy

从晶体管到发光二极管和热辅助磁记录设备，材料之间的界面构成了纳米技术热管理的主要障碍。对这些界面上的纳米尺度热流机制的基本理解的改进，可以使工程师定制界面的组成和结构，以优化冷却策略，从而提高设备的耐用性和效率。然而，目前很难在纳米尺度上测试相互竞争的界面热传输理论的预测，因为热实验无法在相关的近原子长度尺度上绘制温度图。这项工作将发展扫描透射电子显微镜纳米热测量实验，并使用原子计算来阐明界面热传输的机制，并为界面结构-热性质关系提供高空间分辨率的见解。该项目还将建立在莱斯大学和休斯顿地区社区学院之间现有的合作基础上，为社区大学生提供暑期研究经验，并开展推广活动，促进纳米技术和热管理方面的就业机会。这个项目的目标是测试界面声子热传输模型，通过映射温度与亚纳米空间分辨率跨强键合界面。纳米热测量将利用在扫描透射电子显微镜衍射图和环形暗场图像中检测到的温度相关的热扩散散射。这种热扩散散射与局部原子振动幅值直接相关，局部原子振动幅值随温度的升高而增大。校准和绘制作为光束位置函数的热扩散散射将允许亚纳米电子束直径的实验以超高空间分辨率测量温度分布。这些热电子显微镜实验将与理论预测进行比较，通过结合界面附近温度相关原子振动的原子模型和多层电子衍射计算来量化热扩散散射。该结果将提供对半导体-半导体和半导体-金属结界面热传输的潜在物理机制的见解。这些基础知识的未来应用可以让工程师改进纳米电子学和信息存储技术中接口的热设计，目标是实现更高效的设备性能。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。

Interfaces between materials pose a major barrier to the thermal management of nanotechnologies ranging from transistors to light-emitting diodes and heat-assisted magnetic recording devices. Improvements in the fundamental understanding of nanoscale heat flow mechanisms across these interfaces could allow engineers to tailor the composition and structure of interfaces for optimized cooling strategies, leading to improved device durability and efficiency. However, it is currently difficult to test the predictions of competing interfacial thermal transport theories at the nanoscale because thermal experiments are not able to map temperature at the relevant near-atomistic lengthscales. This work will develop scanning transmission electron microscopy nanothermometry experiments and use atomistic calculations to elucidate the mechanisms of interfacial thermal transport and to provide high spatial resolution insight into the interface structure-thermal property relationship. This project will also build upon existing collaborations between Rice University and Houston-area community colleges to implement summer research experiences for community college students and to develop outreach events that promote career opportunities in nanotechnology and thermal management. The goal of this project is to test models for interfacial phonon heat transport by mapping temperature with sub-nanometer spatial resolution across strongly bonded interfaces. The nanothermometry measurements will leverage the temperature-dependent thermal diffuse scattering that has been detected in scanning transmission electron microscopy diffraction patterns and annular dark field images. This thermal diffuse scattering is directly related to the local atomic vibration amplitudes, which increase with increasing temperature. Calibrating and mapping the thermal diffuse scattering as a function of beam position will allow experiments with sub-nanometer electron beam diameters to measure the temperature profile with ultrahigh spatial resolution. These thermal electron microscopy experiments will be compared with theoretical predictions by combining atomistic modeling of temperature-dependent atomic vibrations near interfaces with multislice electron diffraction calculations to quantify the thermal diffuse scattering. The results will provide insight into the underlying physical mechanisms of interfacial thermal transport across semiconductor-semiconductor and semiconductor-metal junctions. Future application of this fundamental knowledge could allow engineers to improve the thermal design of interfaces in nanoelectronics and information storage technologies, with the goal of enabling more efficient device performance.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.