Advanced Materials for Micro- and Nano-Systems Programme, Singapore-MIT Alliance, Singapore 117576, Singapore.
Nanoscale. 2012 Dec 7;4(23):7532-9. doi: 10.1039/c2nr32350h.
Metal assisted chemical etching with interconnected catalyst structures has been used to create a wide array of organized nanostructures. However, when patterned catalysts are not interconnected, but are isolated instead, vertical etching to form controlled features is difficult. A systematic study of the mechanism and catalyst stability of metal assisted chemical etching (MACE) of Si in HF and H(2)O(2) using Au catalysts has been carried out. The effects of the etchants on the stability of Au catalysts were examined in detail. The role of excess electronic holes as a result of MACE was investigated via pit formation as a function of catalyst proximity and H(2)O(2) concentration. We show that a suppression of excess holes can be achieved by either adding NaCl to or increasing the HF concentration of the etching solution. We demonstrate that an electric field can direct most of the excess holes to the back of the Si wafer and thus reduce pit formation at the surface of Si between the Au catalysts. The effect of hydrogen bubbles, generated as a consequence of MACE, on the stability of Au catalysts has also been investigated. We define a regime of etch chemistry and catalyst spacing for which catalyst stability and vertical etching can be achieved.
金属辅助化学蚀刻（Metal Assisted Chemical Etching，MACE）结合互联催化剂结构已被广泛应用于制造各种有序纳米结构。然而，当图案化催化剂不相互连接而是相互隔离时，垂直蚀刻以形成可控特征就变得困难。本文系统研究了 HF 和 H₂O₂中 Au 催化剂辅助的 Si 金属辅助化学蚀刻（MACE）的机制和催化剂稳定性。详细研究了蚀刻剂对 Au 催化剂稳定性的影响。通过研究催化剂接近度和 H₂O₂浓度对孔形成的影响，探讨了过量电子空穴在 MACE 中的作用。结果表明，通过在蚀刻溶液中添加 NaCl 或增加 HF 浓度，可以抑制过量空穴。我们证明，电场可以将大部分过量空穴引导到 Si 晶片的背面，从而减少 Au 催化剂之间 Si 表面的孔形成。还研究了 MACE 产生的氢气泡对 Au 催化剂稳定性的影响。我们定义了一个蚀刻化学和催化剂间距的范围，在此范围内可以实现催化剂稳定性和垂直蚀刻。
