Interfacial Effects in Mechanical and Thermal Properties of Ductile Heterostructured Nanowires

University Of California-Irvine, Irvine CA

Investigators

Abstract

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.