Controllable Fabrication Of Multi-Configuration Periodic Nanostructures And Their Optical Properties

Periodic nanostructures are finding applications in nanophotonics, biological sensing, chemical analysis, photovoltaic industry, and etc. Noble metallic nanostructure arrays with nanogaps or nanotips are of unique surface plasmon resonance properties,and regarded as ideal substrates for sensitive surface enhanced Raman scattering detection, whose controllable fabrication and properties have received considerable attention. They can be fabricated both by “top-down” and “bottom-up” strategies. However, some “top-down” methods, such as focus ions beam lithography and nanoprint lithography, are high-cost and low-throughput, which is not satisfied for the manufacture. Meanwhile, some “bottom-up’ methods, such as nanosphere lithography technique, are cost-effective and high-throughput. However, the time-assuming self-assembly process and the limited morphologies hindered its wide applications.To fabricate well-performance SERS substrates for practical application, we have explored a nanofabrication method based on micro-nano combination, realized the controllable fabrication of periodic nanostructure with nanogaps and nanotips, optimized the morphologies and parameters of the nanostructures, simulated the electromagnetic field distribution of nanostructures with nanogaps and nanotips, and realized the effective and controllable fabrication of sensitive SERS substrate. The main works and results are as follows:1. For effective and controllable fabrication of wafer-scale periodic nanostructures, we combined some standard MEMS fabrication process with nanosphere lithography technique, such as spin-coating and plasma etching technique, providing large-area and effective fabrication method for periodic nanostructure arrays. We have generated two-dimension crystal domain by spin-coating of PS spheres with various diameters. The coverage of the ordered crystal domain reached up to 90%. With the crystal domain as template, we successfully fabricated metallic, silicon nanohole arrays aided by plasma etching and metal deposition technique, which validated the efficiency and controllability of the proposed strategy.2. To fabricate periodic nanostructures with nanogaps for practical application, we have designed two separate fabrication procedures to fabricate nanostructures with nanogaps based on micro-nano combination. PIB and nanorod arrays were fabricated in a controlled manner, respectively. The results showed that the local EM enhancement factor of PIB arrays can reach up to 80, and the SERS enhancement factors was about 1.12×107; the density of nanogaps between nanorods was about 1.13×107/mm2, and detect limitation for R6 G solution was 10-8mol/L.3. To fabricate periodic nanostructures with nanotips for practical application, we have realized the controllable fabrication of two periodic nanostructures with nanotips based on micro-nano combination strategy. Pyramid and hexagram cone arrays were fabricated in a controllable manner, respectively. The pyramid arrays were lift-off from the anti-pyramid cavities in(100) silicon substrate. The pyramid arrays can be built both on hard and soft substrates using gold or gold-PDMS materials. Periodic hexagram cone arrays were built from the dynamic metal deposition with the etched double-layer PS spheres as shadow mask. The hexagram cone yielded high density tips and ridges. The calculation and experiment results showed that the EM fields of pyramid and hexagram cone tended to concentrate at the tips, which resulted in the good performance in SERS detection.4. To fabricate close-packed periodic structures in a robust manner, we brought out a procedure for periodic triangle cone fabrication based on dynamic shadow mask and over-etched substrate. The results showed that the close-packed triangle cone structure would not be affected by fabrication errors. This strategy is simple and robust for close-packed nanostructure array fabrication.