Abstract Nanojoining is a promising nano-fabrication technique with the capability of assembling functional nanodevices with dissimilar nanoscale and/or molecular components. However, significant challenges are encountered in experimental studies owing to the extremely small scale (10−9 m), high heating rates (1016 K s−1), and high temperature gradients (1011 K m−1) inherent in the nanojoining process. A hybrid atomistic-continuum model comprised of a molecular dynamics simulation (MD) and a two-temperature model (TTM) was used to study the mechanical and thermal characteristics of copper/copper-nickel alloy nanowires during a femtosecond laser nanojoining process. The results show that the laser nanojoining of two identical copper nanowires leads to the deterioration of thermal conductivity and thermal stress due to lattice structural variations. The nanojoining process induces an interface when applied to nanowires with different crystal orientations, which leads to phonon scattering at the joining interface, significantly reducing the thermal conductivity but providing for better mechanical properties. Additional alloy impurities strongly affect the thermal and mechanical properties during the laser nanojoining process. The thermal conductivity decreases significantly with increasing of nickel content while the mechanical properties are improved with respect to the Young's modulus and elastic limit. The utility of the hybrid MD-TTM simulations employed in the present work can approximate the laser nanojoining process in accordance with reasonable physical scenarios and accurate thermal and mechanical property predictions, which can also provide an atomic-level understanding of ultra-small, ultra-fast phenomena.

中文翻译：

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飞秒激光加热诱导金属合金纳米线连接：混合原子连续谱解释

摘要 Nanojoining 是一种很有前途的纳米制造技术，能够组装具有不同纳米尺度和/或分子成分的功能性纳米器件。然而，由于纳米连接过程中固有的极小尺度 (10−9 m)、高加热速率 (1016 K s−1) 和高温度梯度 (1011 K m−1)，在实验研究中遇到了重大挑战。由分子动力学模拟 (MD) 和双温度模型 (TTM) 组成的混合原子连续体模型用于研究飞秒激光纳米连接过程中铜/铜镍合金纳米线的机械和热特性。结果表明，两条相同的铜纳米线的激光纳米连接会由于晶格结构变化而导致导热性和热应力的恶化。当应用于具有不同晶体取向的纳米线时，纳米连接过程会引起界面，这导致连接界面处的声子散射，显着降低热导率但提供更好的机械性能。在激光纳米连接过程中，额外的合金杂质会强烈影响热性能和机械性能。随着镍含量的增加，热导率显着降低，而杨氏模量和弹性极限方面的机械性能得到改善。本工作中采用的混合 MD-TTM 模拟的效用可以根据合理的物理场景和准确的热和机械性能预测来近似激光纳米连接过程，