Self-diffusion in intermetallic AlAu4: Molecular dynamics study down to temperatures relevant to wire bonding
Self-diffusion in intermetallic AlAu4: Molecular dynamics study down to temperatures relevant to wire bonding
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DOI：
10.1016/j.commatsci.2016.11.012
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发表时间：
2017-03
影响因子：
3.3
通讯作者：
M. Guerdane
中科院分区：
文献类型：
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作者：
M. Guerdane
我们证明了长时间（101 μs）的分子动力学模拟的能力，以提供定量的扩散系数的化合物Al Au 4（β-Mn型），下降到温度（10200 ° C），是相关的Al单键Au引线键合。关于Au扩散，我们的结果与DFT计算的空位形成能，激活能，和扩散机制。我们的模型低估了，但是，空位形成能量的Al，其扩散率被发现是至少10个数量级慢于Au之一。货车霍韦关联函数分析表明，Au的扩散主要发生在维科夫B亚晶格上。此外，我们揭示了高温区，作为稳定性限制T★的AlAu 4的接近和不利的跳跃有助于扩散。例如，这涉及产生反位缺陷的跳跃。后者导致大量的无序，最终在T★处相变为扭曲的fcc结构。在势拟合过程中包括熔化温度似乎是测量温标和正确捕获扩散数量级的有效方法。
We demonstrate the ability of long time (∼ 1 μs) molecular dynamics modeling to provide quantitative diffusion coefficients for the compound AlAu 4 (β-Mn type), down to temperatures (∼ 200° C) that are relevant to Alsingle bond Au wire bonding. Concerning Au diffusion, our results agree quite well with DFT calculations of the vacancy-formation energy, the activation energy, and the diffusion mechanisms. Our model underestimates, however, the vacancy-formation energy of Al, whose diffusivity is found to be at least 10 orders of magnitude slower than Au one. The van Hove correlation-function analysis shows that Au diffusion takes place mainly on the Wyckoff b sublattice. Moreover, we shed light on the high-temperature region, as the stability limit T★ of AlAu 4 is approached and unfavorable jumps contribute to the diffusivity. This concerns, for instance, jumps generating antisites defects. The latter lead to a massive disorder which ends up in a phase change to a distorted fcc structure at T★. Including the melting temperature in the potential-fitting procedure seems to be an effective way to gauge the temperature scale and properly capture the order of magnitude of diffusion.