H钝化Si(001)表面上Cu的亚表面扩散的从头算研究
Ab initio study of subsurface diffusion of Cu on the H-passivated Si(001) surface
AI总结：
本研究通过密度泛函理论计算，揭示了Cu在H钝化Si(001)表面的亚表面扩散机制，发现沉积Cu与体相污染Cu遵循不同的扩散路径，为理解Cu-Si界面行为提供了理论依据。
摘要：
本文利用密度泛函理论计算，分析了Cu吸附原子在H钝化Si(001)表面附近及表面的稳定性和扩散行为。考虑了两种不同的Cu来源：从真空中沉积的Cu，以及从体相Si中向外扩散的污染Cu。从真空中沉积的Cu迅速移动到第三硅层中的间隙位点（T2）。一旦到达该位置，Cu吸附原子便沿着二聚体行方向进入T2与另一个亚表面位点之间的亚表面之字形迁移路径，即T2->HSL->T2。研究发现，从体相向外扩散的污染Cu在远离表面时，沿平行和垂直于二聚体行的方向都是快速扩散体。它被吸引到靠近表面的层中，并被困在第六硅层（T3）的间隙位点。当向外扩散的Cu原子更接近表面时，沿二聚体行方向的通道化之字形扩散（类似于从真空沉积的Cu所遵循的路径）比沿垂直方向的扩散更受青睐。这些结果与先前在类似系统上进行的实验工作一致，并将激发关于Cu与Si表面之间有趣相互作用的进一步实验。
英文摘要：
In this paper we use density-functional theory calculations to analyze both the stability and diffusion of Cu adatoms near and on the H-passivated Si(001) surface. Two different Cu sources are considered: depositing Cu from vacuum, and contaminating Cu outdiffusing from bulk Si. Deposited Cu from vacuum quickly moves subsurface to an interstitial site in the third Si layer (T2). Once there, Cu adatoms enter a subsurface zigzag migration route between T2 and another subsurface site, T2->HSL->T2, along the dimer row direction. Contaminating Cu outdiffusing from bulk is found to be a fast diffuser along both parallel and perpendicular directions to the dimer row when far from the surface. It is attracted to the layers close to the surface and becomes trapped at an interstitial site located at the sixth Si layer (T3). As the outdiffusing Cu atoms get closer to the surface, a channeling zigzag diffusion along the dimer row direction, similar to that one followed by deposited Cu from vacuum, is favoured over diffusion along the perpendicular direction. These results are consistent with previous experimental work done on similar systems and will motivate further experiments on the interesting interaction between Cu and Si surfaces.
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