Department of Chemistry & Chemical Biology, ‡Wyss Institute for Biologically Inspired Engineering, and §The Kavli Insitute for Bionano Science, Harvard University , Cambridge, Massachusetts 02138, United States.
ACS Nano. 2014 Nov 25;8(11):11061-70. doi: 10.1021/nn504214b. Epub 2014 Sep 11.
Optical metasurfaces-patterned arrays of plasmonic nanoantennas that enable the precise manipulation of light-matter interactions-are emerging as critical components in many nanophotonic materials, including planar metamaterials, chemical and biological sensors, and photovoltaics. The development of these materials has been slowed by the difficulty of efficiently fabricating patterns with the required combinations of intricate nanoscale structure, high areal density, and/or heterogeneous composition. One convenient strategy that enables parallel fabrication of periodic nanopatterns uses self-assembled colloidal monolayers as shadow masks; this method has, however, not been extended beyond a small set of simple patterns and, thus, has remained incompatible with the broad design requirements of metasurfaces. This paper demonstrates a technique-shadow-sphere lithography (SSL)-that uses sequential deposition from multiple angles through plasma-etched microspheres to expand the variety and complexity of structures accessible by colloidal masks. SSL harnesses the entire, relatively unexplored, space of shadow-derived shapes and-with custom software to guide multiangled deposition-contains sufficient degrees of freedom to (i) design and fabricate a wide variety of metasurfaces that incorporate complex structures with small feature sizes and multiple materials and (ii) generate, in parallel, thousands of variations of structures for high-throughput screening of new patterns that may yield unexpected optical spectra. This generalized approach to engineering shadows of spheres provides a new strategy for efficient prototyping and discovery of periodic metasurfaces.
光学超表面——由等离子体纳米天线组成的图案，可以精确地控制光与物质的相互作用——在许多纳米光子材料中崭露头角，包括平面超材料、化学和生物传感器以及光伏器件。这些材料的发展受到了以下因素的限制：难以高效地制造具有所需复杂纳米结构、高面积密度和/或异质组成组合的图案。一种方便的策略是使用自组装胶体单层作为阴影掩模来实现周期性纳米图案的平行制造；然而，这种方法尚未扩展到一小部分简单的图案之外，因此仍然与超表面的广泛设计要求不兼容。本文介绍了一种技术——阴影球光刻（SSL）——该技术通过等离子体刻蚀微球从多个角度进行顺序沉积，从而扩展了胶体掩模可实现的结构的多样性和复杂性。SSL 利用了整个相对未开发的阴影衍生形状空间，并通过引导多角度沉积的定制软件，包含了足够的自由度，可用于：(i) 设计和制造各种复杂结构的超表面，这些超表面具有较小的特征尺寸和多种材料；(ii) 并行生成数千种结构变体，用于高通量筛选可能产生意想不到的光学光谱的新图案。这种球体阴影的通用工程方法为周期性超表面的高效原型设计和发现提供了新策略。
