Interfacial Effects in Mechanical and Thermal Properties of Ductile Heterostructured Nanowires

虽然金属半导体异质结构在现代电子系统中无处不在，但界面在其机械和热性能中的作用仍然难以捉摸，并且对其有限的理解对设计可靠和高效的器件构成了挑战。对于可能成为下一代电子产品潜在基石的半导体纳米线来说尤其如此。在机械方面，使用硅纳米线的主要问题是它们的脆性。在热方面，纳米线的热导率降低可能不利于散热或有利于能量收集，但对边界的强烈依赖使得预测非常困难。该奖项支持使用金属硅纳米线作为模型材料，通过结合实验和计算方法来研究其机械和热性能的研究。该项目的研究结果将对异质结构纳米线的机械延展性和导热性的界面效应产生新的认识。研究成果将与教育活动相结合，在材料力学和热传递的跨学科领域培养不同的学生群体。指导和推广工作还将为未被充分代表的学生提供宝贵的经验，让他们在私人学院的实验室进行前沿研究。虽然在过去的二十年里，纳米材料的机械和热性能已经得到了广泛的研究，但我们对纳米尺度上的基本决定因素，特别是金属-半导体界面的基本决定因素的了解仍然存在很大的差距。本项目旨在揭示纳米线在机械变形过程中的变形机理和位错过程。该研究是由半导体纳米线通过结合金属-半导体界面将实现脆性到延性转变的假设驱动的。原子模拟和原位透射电子显微镜将进行研究的机械性能，如屈服强度和断裂行为，以及相关的原子过程的变形。在热方面，金属-半导体界面通过将电子占主导的金属与声子占主导的半导体相邻，使热和电的传输机制复杂化，但这可以为研究电子-声子耦合效应提供一个特殊的机会。将进行基于微桥的纳米线热导率测量，以研究相对于不同界面密度的热性能。通过结合先进的计算、纳米线计量技术和独特的材料处理，该项目将回答有关金属-半导体界面在脆性到延性转变和电子-声子耦合中的作用的重要问题。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。

While metal-semiconductor heterostructures are ubiquitous in modern electronic systems, the role of interfaces in their mechanical and thermal properties remains elusive, and the limited understanding poses challenges in designing reliable and efficient devices. This is particularly true for semiconductor nanowires that could be potential building blocks in next-generation electronics. On the mechanical side, the major concern of using silicon nanowires is their brittle nature. On the thermal side, thermal conductivity reduction in nanonowires could be either detrimental for heat dissipation or favorable for energy harvesting, yet the strong dependence on boundaries make predictions very difficult. This award supports research to use metal-silicon nanowires as a model material to investigate their mechanical and thermal properties through combined experimental and computational approaches. The outcome of this project will lead to new knowledge about interfacial effects in mechanical ductility and thermal conductivity of heterostructured nanowires. Research output will be integrated with educational activities that will train a diverse group of students in the cross-disciplinary areas of mechanics of materials and heat transfer. Mentoring and outreach efforts will also provide underrepresented students valuable experience in cutting-edge research in the PIs' laboratories. While mechanical and thermal properties of nanomaterials have been extensively studied over the past two decades, there remain significant gaps in our knowledge about fundamental determinants at the nanoscale and particularly across metal-semiconductor interfaces. This project aims to reveal deformation mechanisms and dislocation processes during mechanical deformation of nanowires. The study is driven by the hypothesis that the semiconductor nanowires will have brittle-to-ductile transition by incorporating metal-semiconductor interfaces. Atomistic simulations and in-situ transmission electron microscopy will be performed to study the mechanical properties such as yield strength and fracture behavior as well as the associated atomistic processes underlying deformation. On the thermal side, the metal-semiconductor interfaces complicate the transport mechanisms of heat and electricity by adjoining an electron-dominant metal to a phonon-dominant semiconductor, but this can lead to a special opportunity to study the electron-phonon coupling effect. Microbridge-based nanowire thermal conductivity measurements will be performed to study the thermal properties with respect to varying interface density. By combining advanced computations, nanowire metrology techniques, and unique materials processing, the project will answer the important questions regarding the role of metal-semiconductor interfaces in brittle-to-ductile transition and electron-phonon coupling.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.