同轴多壳半导体纳米丝脆韧断裂行为及变形机理研究

Coaxial multi-shell semiconductor nanowires have recently attracted great attention for their distinctive electrical, optical and semiconductor properties and are envisioned as fundamental building blocks of future nano-electro-mechanical systems (NEMS). The reliability and robustness of NEMS is determined by the mechanical properties of its building blocks. The current proposed project will first study effects of cross-sectional shape and surface morphology on fracture behaviors of silicon nanowires by using molecular dynamics method, and then discuss their deformation mechanism by comparing simulations with experimental results. Secondly, fracture behaviors of 'core-shell' type nanowires, with the same silicon 'core' and different conductor 'shell', will be investigated. By performing atomistic simulations and experimental tests, the proposed project is intend to explore the roles of outermost surface and different inter-shell interfaces in determining the deformation mechanism of silicon nanowires. Finally, the mechanical properties of coaxial multi-shell silicon nanowires will be investigated theoretically and computationally, and a continuum theoretic foumulation, including the surface and interface elasticity, is to be provided. This research not only possesses high academic significance in revealing surface/interface effects on deformation mechanism, but also has important application value in directing the design of coaxial multi-shell semiconductor nanowires.

同轴多壳半导体纳米丝作为一种新颖的纳米元件，具有优异的电学、光学和半导体特性，有望大量应用于纳机电系统（NEMS）中。半导体纳米丝的力学行为决定了纳机电系统的稳定性和可靠性。本申请项目拟采用分子动力学方法，研究具有不同截面形状和表面形态硅纳米丝的脆性、韧性断裂行为，与实验结果对比讨论其变形机理。在此基础上，研究具有单晶硅核心和半导体外壳的"芯-壳"型半导体纳米丝的断裂行为和变形机理，结合实验结果揭示表/界面对半导体纳米丝变形机理的影响。最后，将计算模拟与理论分析结合，建立考虑表/界面弹性的同轴多壳纳米丝的理论模型，为同轴多壳半导体纳米丝的设计提供理论参考和应用指导。

表/界面效应是同轴多壳纳米结构研究中的关键科学问题。纳米结构的力学性能和物理性能与其独特的表/界面性能密切相关。本项目采用模拟计算与理论分析相结合的研究方法，对单晶硅和单晶碳化硅两种重要半导体材料的表/界面效应（包括表面效应，界面效应）展开研究。首先，基于能量理论推导出力学量预测公式，再运用分子动力学方法进行建模计算，从而验证理论。根据计算结果，我们揭示出半导体纳米丝和同轴多壳纳米丝在表面效应、粗糙度以及界面等共同作用下的力学行为和脆-韧变形机理。此外，我们还研究了含孪晶晶界和非晶/晶体界面的碳化硅材料的热传导性能。结果发现，在纳米尺寸范围内，界面热阻与界面之间的间距和服役温度密切相关。