Madi Charbel S, Bola George H, Aziz Michael J
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA.
J Phys Condens Matter. 2009 Jun 3;21(22):224010. doi: 10.1088/0953-8984/21/22/224010. Epub 2009 May 12.
We study the patterns formed on Ar(+) ion-sputtered Si surfaces at room temperature as a function of the control parameters ion energy and incidence angle. We observe the sensitivity of pattern formation to artifacts such as surface contamination and report the procedures we developed to control them. We identify regions in control parameter space where holes, parallel mode ripples and perpendicular mode ripples form, and identify a region where the flat surface is stable. In the vicinity of the boundaries between the stable and pattern-forming regions, called bifurcations, we follow the time dependence from exponential amplification to saturation and examine the amplification rate and the wavelength in the exponential amplification regime. The resulting power laws are consistent with the theory of nonequilibrium pattern formation for a type I (constant wavelength) bifurcation at low angles and for a type II (diverging wavelength) bifurcation at high angles. We discuss the failure of all sputter rippling models to adequately describe these aspects of the simplest experimental system studied, consisting of an elemental, isotropic amorphous surface in the simplest evolution regime of linear stability.
我们研究了室温下Ar(+)离子溅射硅表面形成的图案与控制参数离子能量和入射角之间的函数关系。我们观察到图案形成对诸如表面污染等伪像的敏感性，并报告了我们开发的控制这些伪像的程序。我们确定了控制参数空间中形成孔洞、平行模式波纹和垂直模式波纹的区域，并确定了表面平坦稳定的区域。在稳定区域和图案形成区域之间的边界（称为分岔）附近，我们跟踪从指数放大到饱和的时间依赖性，并研究指数放大区域中的放大率和波长。所得的幂律与低角度下I型（恒定波长）分岔和高角度下II型（发散波长）分岔的非平衡图案形成理论一致。我们讨论了所有溅射波纹模型都未能充分描述所研究的最简单实验系统的这些方面，该系统由处于线性稳定性最简单演化状态的元素性、各向同性非晶表面组成。
