Wavelength-dependent ripple propagation on ion-irradiated prepatterned surfaces driven by viscous flow corroborates two-field continuum model
Wavelength-dependent ripple propagation on ion-irradiated prepatterned surfaces driven by viscous flow corroborates two-field continuum model
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DOI：
10.1103/physrevb.89.205422
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发表时间：
2014-05-20
影响因子：
3.7
通讯作者：
Gnaser, Hubert
中科院分区：
文献类型：
--
作者：
Kramczynski, Detlef;Reuscher, Bernhard;Gnaser, Hubert
在聚焦离子束(FIB)系统中，通过磨削波长从150 nm到750 nm的周期性沟槽结构来对玻璃表面进行图案化。在与表面法线成52角的30keV Ga+离子辐照下，发现这些图案转变为“波纹”状的纳米结构。使用安装在FIB中的扫描电子显微镜，原位监测了从5×1016到2.4×10(18)Ga+离子/cm(2)的离子通量的演变。随着通量的增加，波纹的波长保持不变(并且等于它们的原始特征尺寸)，同时它们在表面上传播的方向与离子束的入射方向在表面上的投影一致。在(60-100)nm/(1017个离子厘米(-2))范围内的传播速度v与波长成反比，v=A+B/lambda(2)(常数A和B由不同的离子束和靶材料参数得出)。这种依赖关系符合波纹形成的理论双场连续体模型的预测，该模型将表面视为由衬底上的一层可移动的物质组成。如果在该薄表面层中粘性流的存在是有效的，则实验结果与该模型的定量结果是一致的。用非原位原子力显微镜得到了波纹结构的波峰到波谷的最终幅度，它们的值类似于50-100 nm，因此与原始沟槽的深度相似。在原始的表面区域(没有图案化)，也通过离子轰击形成了涟漪。它们的波长随离子注量Phi从接近250 nm增加到接近420 nm，遵循与Phi(0.19)成正比的关系。
Glass surfaces were patterned by milling periodic trench structures with wavelengths from 150 to 750 nm in a focused ion-beam (FIB) system. Upon exposure to 30 keV Ga+ ion irradiation under an incidence angle of 52 with respect to the surface normal, those patterns were found to transform into "ripple"-like nanostructures. Their evolution was monitored in situ for ion fluence from 5 x 1016 to 2.4 x 10(18) Ga+ ions/cm(2) using the scanning electron microscope incorporated in the FIB. With increasing fluence, the wavelengths of the ripples remain constant (and equal to their original feature size) while they propagate across the surface, in a direction which coincides with the projection of the ion beam's incident direction onto the surface. The propagation velocities v, being in the range (60-100) nm/(1017 ions cm(-2)), were determined to be inversely proportional to the wavelengths lambda, with v = A + B/lambda(2) (the constants A and B derive from various ion beam and target material parameters). Such a dependence is in accordance with the predictions of a theoretical two-field continuum model of ripple formation which treats the surface as being composed of a thin layer of mobile species on the substrate. A quantitative agreement of the experimental findings with this model is obtained if the presence of a viscous flow is effective in that thin surface layer. Ex situ atomic force microscopy was employed to derive the final crest-to-valley amplitudes of the ripple structures; their values were similar to 50-100 nm and thus similar to the depth of the original trenches. On the pristine surface areas (which have not been patterned), ripples were also formed by ion bombardment. Their wavelength increases with ion fluence Phi from similar to 250 to similar to 420 nm, following a dependence lambda proportional to Phi(0.19).