Research Institute for Technical Physics and Materials Science, Konkoly Thege u. 29-33, 1125 Budapest, Hungary.
J Chem Phys. 2009 Nov 28;131(20):204704. doi: 10.1063/1.3264887.
The wavelength-dependence of ion-sputtering induced growth of repetitive nanostructures, such as ripples has been studied by molecular dynamics (MD) simulations in Si. The early stage of the ion erosion driven development of ripples has been simulated on prepatterned Si stripes with a wavy surface. The time evolution of the height function and amplitude of the sinusoidal surface profile has been followed by simulated ion-sputtering. According to Bradley-Harper (BH) theory, we expect correlation between the wavelength of ripples and the stability of them. However, we find that in the small ripple wavelength (lambda) regime BH theory fails to reproduce the results obtained by molecular dynamics. We find that at short wavelengths (lambda<35 nm) the adatom yield drops hence no surface diffusion takes place which is sufficient for ripple growth. The MD simulations predict that the growth of ripples with lambda>35 nm is stabilized in accordance with the available experimental results. According to the simulations, few hundreds of ion impacts in lambda long and few nanometers wide Si ripples are sufficient for reaching saturation in surface growth for for lambda>35 nm ripples. In another words, ripples in the long wavelength limit seems to be stable against ion-sputtering. A qualitative comparison of our simulation results with recent experimental data on nanopatterning under irradiation is attempted.
利用分子动力学（MD）模拟研究了离子溅射诱导重复纳米结构（如波纹）生长的波长依赖性。在具有波浪形表面的预图案化 Si 条带上模拟了离子侵蚀驱动波纹早期发展。通过模拟离子溅射，跟踪了高度函数和正弦表面轮廓振幅的时间演化。根据 Bradley-Harper（BH）理论，我们预计波纹的波长与它们的稳定性之间存在相关性。然而，我们发现，在小波纹波长（λ）范围内，BH 理论无法再现分子动力学获得的结果。我们发现，在短波长（λ<35nm）下，原子的产率下降，因此没有表面扩散发生，这对于波纹生长是足够的。MD 模拟预测，具有 λ>35nm 的波纹的生长根据可用的实验结果得到稳定。根据模拟，在 λ 长且几纳米宽的 Si 波纹中进行几百次离子冲击足以在表面生长中达到饱和，对于 λ>35nm 的波纹。换句话说，长波长极限下的波纹似乎对离子溅射具有稳定性。尝试将我们的模拟结果与最近的辐照下纳米图案形成的实验数据进行定性比较。
