Li Xin, Zhang Yijun, Li Mingxiao, Zhao Yang, Zhang Lingqian, Huang Chengjun
R&D Center of Healthcare Electronics, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Langmuir. 2021 Jan 12;37(1):249-256. doi: 10.1021/acs.langmuir.0c02851. Epub 2020 Dec 23.
Self-assembly at the air/water interface (AWI) has proven to be an efficient strategy for fabricating two-dimensional (2D) colloidal monolayers, which was widely used as the template for nanosphere lithography in nanophononics, optofluidics, and solar cell studies. However, the monolayers fabricated at the AWI usually suffer from a small domain area and quasi-double layer structure caused by submerged particles. To overcome this, we proposed an improved protocol to prepare 2D colloidal monolayers free of overlapping nanospheres at the AWI. Utilizing the stable suspension infusion to the water surface, a convex meniscus, whose height is related to viscous force, was formed adjoining the three-phase boundary. As a result of the resistance of the convex meniscus, the polystyrene nanospheres in the initial suspension directly self-assembled into a preliminary monolayer, which proved effective in preventing nanospheres' sinking and increasing the colloidal crystal domain size. An optimal parameter for transferring the monolayer was also developed based on the numerical simulation results. Finally, a wafer-scale monolayer, covered with less than one nanosphere per 100 μm × 100 μm area, was achieved on the desired substrate with an average domain size attaining centimeter scale. The high-quality 2D colloidal crystal may further promote the application of nanosphere lithography, especially in the fields that require a defect-free template.
在空气/水界面（AWI）进行自组装已被证明是制备二维（2D）胶体单层的有效策略，该策略在纳米声学、光流体学和太阳能电池研究中被广泛用作纳米球光刻的模板。然而，在AWI处制备的单层通常存在由浸没颗粒导致的小畴区面积和准双层结构的问题。为克服这一问题，我们提出了一种改进方案，以在AWI处制备无重叠纳米球的2D胶体单层。利用向水面稳定注入悬浮液，在三相边界附近形成了一个高度与粘性力相关的凸弯月面。由于凸弯月面的阻力，初始悬浮液中的聚苯乙烯纳米球直接自组装成初步的单层，这在防止纳米球下沉和增加胶体晶体畴区尺寸方面被证明是有效的。还基于数值模拟结果开发了转移单层的最佳参数。最后，在所需基板上实现了每100μm×100μm面积覆盖少于一个纳米球的晶圆级单层，平均畴区尺寸达到厘米级。高质量二维胶体晶体可能会进一步推动纳米球光刻的应用，特别是在需要无缺陷模板的领域。
