Templated fabrication of periodic metallic nanopyramid arrays

This paper reports a simple self-assembly-based templating approach for fabricating wafer-scale, periodic metallic nanopyramid arrays with nanoscale tips and high tip density (6 x 10(8) tips cm(-2)). Spin-coated, non-close-packed monolayer colloidal crystals are used as templates to create chromium nanohole arrays, which are utilized as etching masks to fabricate inverted silicon pyramidal pits by anisotropic KOH etching. Wafer-scale metallic pyramid arrays with sharp nanotips can then be replicated from silicon templates by a simple adhesive peeling process. This nonlithographic technique combines the simplicity and cost benefits of bottom-up self-assembly with the scalability and compatibility of standard top-down microfabrication in creating periodic metallic nanostructures that are not easily available by conventional nanofabrication. The resulting nanopyramid arrays show stable surface enhancements for Raman scattering from benzenethiol molecules adsorbed at the metal surfaces, even though these sputtered films are not rough.