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普遍存在，但界面在其机械和热性能中的作用仍然难以捉摸，而且有限的理解给设计可靠和高效的器件带来了挑战。对于可能成为下一代电子产品潜在组成部分的半导体纳米线来说，情况尤其如此。在机械方面，使用硅纳米线的主要问题是它们的脆性。在热学方面，纳米线中导热系数的降低可能不利于散热，也可能有利于能量收集，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，通过实验和计算相结合的方法研究其机械和热性能。该项目的成果将使人们对异质纳米线的机械延展性和热导率的界面效应有了新的认识。研究成果将与教育活动相结合，这些活动将在材料力学和热传递的跨学科领域培训不同的学生群体。辅导和外展工作还将为任职人数不足的学生提供在私人投资机构实验室进行尖端研究的宝贵经验。虽然在过去的二十年里，人们对纳米材料的力学和热学性质进行了广泛的研究，但在纳米尺度上，特别是在金属-半导体界面上，我们对基本决定因素的了解仍然存在很大差距。本项目旨在揭示纳米线机械变形过程中的变形机制和位错过程。这项研究是基于这样一个假设，即半导体纳米线将通过结合金属-半导体界面而发生脆性到韧性的转变。原子模拟和原位电子显微镜将被用来研究力学性能，如屈服强度和断裂行为，以及与变形相关的原子过程。在热学方面，金属-半导体界面使以电子为主的金属与以声子为主的半导体相邻，从而使热和电的传输机制变得复杂，但这可能带来研究电子-声子耦合效应的特殊机会。基于微桥的纳米线导热系数测量将被用来研究不同界面密度下的热学性质。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-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。

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.