CAREER: Novel Debye Waller Thermometry of Oxide Interfaces for Reducing Thermal Interface Resistance

非技术描述：要控制材料中的热传导，关键是要了解材料内部各种界面的热传输。界面通常表现出界面热阻(TIR)，对于广泛的电子、光子和能量采集材料，TIR会严重影响材料的性能和稳定性。然而，要确定TIR的确切来源往往是非常具有挑战性的，因为这需要准确地了解界面上发生了什么，包括界面的确切结构以及该结构如何影响热传输过程。该项目开发了一种新技术，使用一个小型电子探针直接测量界面温度，分辨率接近原子尺度，并以前所未有的精度测定TIR。通过对原子尺度结构和界面缺陷如何影响TIR提供了新的重要认识，验证了现有关于如何降低TIR的理论和模拟结果，并为如何通过改变界面结构和成分来控制TIR提供了新的材料设计规则，从而在许多方面对材料热工程产生了革命性的影响。该项目整合了代表不足的学生的教育和外展活动，为他们提供与研究人员接触的机会，激励并帮助他们在科学和工程领域攻读更高的学位或职业。该项目还包括开发交互式数据分析系统，使视力障碍者能够使用他们的听觉感知和处理科学数据。技术细节：正在开发的一种新的德拜-沃勒测温技术基于量化德拜-沃勒因子，即热振动引起的散射电子强度的衰减，在原子尺度上进行空间分辨，使用扫描透射式电子显微镜中对热振动高度敏感的高角度环形暗场信号。使用这种新的方法，可以在原子尺度上原位测量界面的温度分布，并且可以直接从分布高精度地确定TIR，超越了现有任何方法的限制。这一新的实验能力可以验证现有的关于如何降低TIR的理论和假设，包括声子匹配、声学匹配、外延应变和缺陷控制等理论。验证是使用精心设计的钙钛矿氧化物界面进行的，这些界面是使用不同的结构参数合成的，例如原子质量、键强度、应变、缺陷密度、层厚度和界面粗糙度。这项工作的错误分析部分得到了该项目开发的住宿技术的帮助，该技术使残疾人能够有效地感知、处理和分析科学数据。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: To control thermal conduction in materials, it is critical to understand heat transport through various interfaces within the material. Interfaces often display thermal interface resistance (TIR), and for a broad range of electronic, photonic, and energy-harvesting materials, TIR can critically affect the materials' performance and stability. However, it is often very challenging to identify the exact origin of TIR, since it would require an exact understanding of 'what really happens' at the interface, including the exact structure of the interface and how the structure affects the thermal transport process. This project develops a novel technique that uses a small electron probe to directly measure the temperature at the interface with near atomic scale resolution and determine TIR with unprecedented precision. This new approach can deliver transformative impact to the thermal engineering of materials in many ways, by providing the new important understanding on how the atomic scale structure and defects at the interface affect TIR, verifying the existing theories and simulation results on how to reduce TIR, and providing new material design rules on how to control TIR by modifying the interface structure and composition. This project integrates the education and outreach activities for underrepresented students to provide them with opportunities to engage with researchers, motivate, and help them potentially pursue advanced degrees or careers in science and engineering. The project also includes the development of the interactive data analysis system that allows people with visual impairment to perceive and process scientific data using their auditory senses.TECHNICAL DETAILS: A new Debye-Waller thermometry under development is based on quantifying Debye-Waller factor, the attenuation of the scattered electron intensity due to thermal vibration, spatially resolved at the atomic scale, using high angle annular dark field signal in scanning transmission electron microscopy that is highly sensitive to thermal vibration. Using this new approach, the temperature profile at the interface at the atomic scale can be measured in situ, and TIR is directly determined from the profile with high precision, beyond the limits of any existing methods. This new experimental capability can validate the existing theories and hypotheses on how to reduce TIR, including the theories involving phonon matching, acoustic matching, epitaxial strain, and defect control. The validation is carried out using carefully designed perovskite oxide interfaces, which are synthesized using different structural parameters, such as the atomic mass, bond strength, strain, defect density, layer thickness, and interface roughness. The error analysis part of this work is assisted by the accommodation technology developed in this project, which allows people with disabilities to efficiently perceive, handle, and analyze the scientific data.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.