金包覆硅纳米片的力学性能：一项原子尺度研究
Mechanical Properties of Au Coated Si Nanowafer: an Atomistic Study
AI总结：
本文利用分子动力学拉伸与压缩模拟，系统研究温度、金层厚度、应变速率及晶体取向对金包覆硅纳米片力学性能和失效机制的影响。
摘要：
金与硅复合纳米体系因其在各类金属-半导体电子器件及太阳能驱动分解水电池中的应用，在科学界引发了广泛关注。制备于金层上的硅，其表面容易发生金原子扩散。本研究通过开展分子动力学拉伸与压缩模拟，详细分析了金包覆硅纳米片的力学性能。研究考察了温度、金包覆层厚度、应变速率以及硅的晶体学取向对该纳米片力学性能的影响。结果发现，极限抗拉强度和抗压强度均与温度呈反比关系。当沿[100]方向加载时，纳米片主要因过大剪切而沿{110}晶面滑移失效；而在300 K时则出现滑移与裂纹混合型失效。在拉伸过程中，对于最大金层厚度，金层内观察到从fcc到hcp晶体结构的有趣晶体学转变。研究还考察了拉伸和压缩中应变速率的影响。最后，改变硅的晶体取向，研究了金包覆硅纳米片中的拉压不对称性。在沿[110]晶体取向加载时观察到反向拉压不对称性。失效机制表明，压缩过程中硅发生了有趣的晶体转变，导致材料提前屈服。
英文摘要：
Combined gold and silicon nano-system has spurred tremendous interest in the scientific community due to its application in different metal-semiconductor electronic devices and solar driven water splitting cells. Silicon, fabricated on gold layer, is prone to gold atom diffusion at its surface. In this study, detailed analysis of mechanical properties of gold coated silicon nanowafer is studied by performing molecular dynamics tensile and compressive simulations. The effects of temperature, gold coating thickness, strain rate and crystallographic orientation of silicon on the mechanical properties are observed for the nanowafer. It is found that both the ultimate tensile and compressive strength show inverse relationship with temperature. The nanowafer fails mainly by slipping along {110} plane due to excessive shear when loaded in [100] direction while a mixed slip and crack type failure occurs for 300K. Interesting crystallographic transformation from fcc to hcp crystal is observed in gold layer for the highest gold layer thickness during tension. The effects of strain rate in tension and compression is also studied. Finally, the crystal orientation of silicon is varied and the tension-compression asymmetry inn the gold coated silicon nanowafer is investigated. Reverse tension-compression asymmetry is observed in case of loading along [110] crystal orientation. The failure mechanism reveals that interesting crystal transformation of silicon occurs during compression leading to early yielding of the material.
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