(22h) Scalable Nanofabrication of Biomimetic Broadband Anti-Reflection Coatings
Millions of years before people began to fabricate functional nanostructures, biological systems were using nanometer-scale architectures to produce unique functionalities. Some nocturnal moths use hexagonal arrays of subwavelength nipples as anti-reflection (AR) coatings to reduce reflection from their compound eyes for the purpose of night camouflage. Similar periodic arrays of nanopillars have also been observed on the wings of cicada to render superhydrophobic surfaces for self-cleaning functionality. Inspired by these natural nanostructures, we have developed a simple and scalable templating technique for fabricating self-cleaning, broadband AR coatings on a large variety of technologically important substrates, such as single crystalline Si, multicrystalline Si, GaAs, GaSb, and glass. The technique is based on two colloidal self-assembly technologies that combines the simplicity and cost benefits of bottom-up self-assembly with the scalability and compatibility of standard top-down microfabrication. The resulting subwavelength-structured AR coatings exhibit improved broadband anti-reflection properties than traditional multilayer dielectric coatings, and show superhydrophobic surface states, promising for applications ranging from highly efficient solar cells and photodetectors to self-cleaning flat-panel displays.