Patterned Metal Arrays for LSPR and SERS Devices by Colloidal Lithography

Abstract

Surface plasmon resonance (SPR) is a coherent oscillation of the free electrons on the surface of metal excited by incident electromagnetic wave. The absorption of light and consequent enhancement of electromagnetic field by SPR results in the specific color and enhancement of scattering of light. Noble metal nanoparticles and their arrays are among the best materials for localized surface plasmon resonance (LSPR) due to intense surface plasmon resonance in the visible wavelength range. In addition, it is well-known that the electric field induced by SPR dramatically enhances surface-enhanced Raman scattering (SERS). Physical parameters such as shape, roughness, size and separation distance of noble metal nanoparticles were found to be the key factors influencing LSPR and the enhancement of SERS. Therefore, the development of an efficient method for fabricating noble metal nanoparticle arrays with controlled shape and size has been a hot issue in the field of nano-optics for variety of applications such as biological and chemical sensing, molecular spectroscopy and lithographic fabrication. However, the fabrication of well-ordered array of noble metal nanoparticles is still far from the mass production for the practical use because the optically active array of nanoparticles is usually in the size range from several tens to hundreds nanometer, which can be created by expensive advanced lithographic techniques such as e-beam or immersion lithography. Colloidal lithography (CL), in which self-assembled colloids are used as masks for fabricating 2-D nanostructures, is a simple and cost-effective alternative of advanced lithographic techniques frequently employed in nanofabrication. A variety of metal patterns, ranging from several tens nanometers to several micrometers, have been successfully fabricated via selective etching or deposition of metals on bare or modified colloidal masks. In this thesis, various methods for the creation of well-defined nanostructures ...