Energy dependent wavelength of the ion induced nanoscale ripple
Energy dependent wavelength of the ion induced nanoscale ripple
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离子引起的纳米级波纹的能量依赖波长
DOI：
10.1103/physrevb.66.153404
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发表时间：
2002
影响因子：
3.7
通讯作者：
Satyaranjan Bhattacharyya
中科院分区：
文献类型：
--
作者：
T. K. Chini;Milan K. Sanyal;Satyaranjan Bhattacharyya
通过斜入射离子轰击在典型波长约为10 nm到1µm的各种材料上形成周期性起伏或波纹特征，由于其可能的技术应用，从光学器件、用于液晶取向的模板到用于异质外延生长的无应变图案化衬底，已经成为一个活跃的研究课题。对离子束诱导纳米波纹形成的系统研究将有助于我们了解沙漠中沙丘状结构形成的基本过程。虽然这种离子诱导现象最早是在20世纪60年代[1]和70年代[2，3]报道的，但实验条件的改善，如更好的真空和离子束参数以及改进的表面表征工具，使我们能够控制这些波纹状特征的生长[4，5，6，7，8，9，10，11]。第一个被广泛接受的描述离子轰击波纹形成过程的理论方法是由Bradley和Harper(BH)[12]发展起来的。这一线性理论[12]预测了波纹的波长和方向，这与许多实验研究相一致。然而，这一理论不能解释一些实验观测，如波纹幅度饱和[9]、旋转波纹的出现[11]和动力学粗糙[13]。此外，根据BH理论，波纹波长应该随着离子能量的增加而减小，但这一预测迄今尚未得到实验证实[5，6，7]。最近，一种基于非线性连续统理论的形式论[14，15，16]已经发展起来，用来解释这些线性理论没有预测到的实验观测。在这种新的形式中，不仅在侵蚀表面高度分布方程中考虑了非线性项和噪声项，而且承认了两种不同的表面扩散过程的存在。基于Sigmund的溅射理论[17]，根据这个非线性理论的离子侵蚀表面的高度演化h(x，y，t)可以用下式来描述
Formation of periodic undulations or ripple like features on various materials with typical wavelength ranging from about 10 nm to 1µm, obtained by obliquely incident ion bombardment, has become an active research subject due to its possible technological applications, as varied as optical devices, templates for liquid crystal orientation and strain-free patterned substrates for heteroepitaxial growth of quantum wires. It is also expected that systematic study of ion beam induced nano ripple formation will help us to understand the basic processes prevalent in formation of sand dune like structures in deserts. Although this ion induced phenomenon was reported first in 1960s [1] and then in 1970s [2, 3], the improvement in experimental conditions such as, better vacuum and ion beam parameters and improved surface characterizing tools, has enabled us to control the growth of these ripple like features [4, 5, 6, 7, 8, 9, 10, 11]. The first widely accepted theoretical approach describing the process of ripple formation due to ion bombardment was developed by Bradley and Harper (BH) [12]. This linear theory [12] predicts the ripple wavelength and orientation in agreement with numerous experimental studies. However, this theory cannot explain a number of experimental observations, such as the saturation of the ripple amplitude [9], the appearance of rotated ripples [11] and kinetic roughening [13]. Moreover, according to the BH theory ripple wavelength should decrease with ion energy but this prediction has not been confirmed experimentally so far [5, 6, 7]. Recently a formalism [14, 15, 16] based on nonlinear continuum theory has been developed to understand these experimental observations not predicted by linear theory. In this new formalism, not only nonlinear and noise terms were included in the equation of height profile for eroded surface but also existence of two different surface diffusion processes were recognised. Based on Sigmund’s theory of sputtering [17], the height evolution h(x,y,t) of an ion eroded surface according to this nonlinear theory [14, 15, 16] can be described by