CAREER: Development of A Scalable Spin-Coating Technological Platform for Colloidal Self-Assembly and Templating Nanofabrication

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0744879JiangPhotonic crystals and plasmonics are two key techniques that will ultimately enable alloptical integrated circuits and quantum information processing. Unfortunately, the development and implementation of these techniques have been greatly impeded by expensive and painstaking topdown nanofabrication (e.g., electron-beam lithography), which limit the available sample size to less than 1 mm2. By contrast, bottom-up colloidal self-assembly and templating nanofabrication provide a much simpler, faster, and inexpensive alternative to nanolithography in creating highly ordered photonic crystals and plasmonic nanostructures. However, the traditional colloidal self-assembly and templating approach suffers from low throughput, incompatibility with standard microfabrication, and limited crystal structures which greatly hamper the mass-production and on-chip integration of practical nanooptical devices.Intellectual Merit. This proposal aims to develop understanding and control of a robust spin-coating technology that combines the simplicity and cost benefits of bottom-up self-assembly with the scalability and compatibility of top-down microfabrication. This will enable the creation of wafer-scale photonic crystals and a large variety of functional subwavelength-structured materials. The research plan has four specific objectives: (1) elucidate the basic crystallization mechanisms by which unusual nonclose-packed colloidal crystals form during spin-coating, (2) determine the photonic band gap properties of shear-aligned colloidal photonic crystals, (3) investigate the surface plasmon properties of templated periodic metallic nanostructures, including enhanced optical transmission through subwavelength nanohole arrays and surface-enhanced Raman scattering (SERS) on nanovoid gratings, and (4) develop biomimetic subwavelength-structured antireflection coatings for high-efficiency solar cells. The proposed experimental and theoretical investigation will lead to significant breakthroughs in a wide spectrum of fields ranging from all-optical integrated circuits to plasmonic sensors to sustainable energy. Improved fundamental understanding of flow-induced crystallization and melting within non-uniform shear flows, a topic that has received little or no examination, will also result. The creative and original components of the research plan rely on the integration of the above four objectives. Insights gained into basic mechanisms facilitate better control over the crucial crystalline parameters for tailoring the optical properties in the later objectives. Most importantly, the periodic plasmonic nanostructures and subwavelength-structured antireflection coatings are indeed 2-D photonic crystals, and are thus studied with similar experimental (optical spectroscopy) and modeling (rigorous coupled-wave analysis) techniques as photonic crystals. The unification of these apparently different but intrinsically interconnected fields under one umbrella ? the spin-coating platform could lead to new optical features that are interesting fundamentally and technologically.Broader Impacts. In conjunction with student mentorship and curriculum development activities, the closely integrated educational plan focuses on developing several outreach activities to educate K-12 students and teachers as well as the general public on nanooptics and self-assembly. An educational display for the Florida Museum of Natural History?s ?Butterfly Rainforest Center? will be created to disseminate the nanooptical mechanisms of the striking blue colors of morpho butterfly wings and the antireflection properties of butterfly eyes, along with how to mimic these natural photonic crystals and antireflection coatings using colloidal self-assembly. Direct participation of high school students from underrepresented groups in the research program and development of educational modules on making brilliant artificial opals through collaboration with high school teachers will be sought through several successful programs at the university. The spin-coating platform will advance many other areas that depend on the creation of large-area periodic nanostructures not covered by this proposal, ranging from high-density magnetic recording to bio-microanalysis. The integrated educational program will impact students at all education levels. Outreach efforts through a local museum will bring modern nanooptics to young students and adults through a fun learning experience and participation of high school students in the research program will benefit the students and their larger communities. Collaborative efforts with high school teachers to develop colorful demonstration modules will favorably impact hundreds of students per year at the secondary level with a low annual cost ($1,000) and help the program to spread outside the State of Florida.