Plasmon mediated polymerization on the surface of silver nanoparticles for advancements in photolithographic patterning

Abstract

Metal nanoparticles and their plasmon excitation have been used to enhance spectroscopic transitions and chemistry on metal nanoparticle surfaces. The size and shape of the enhancement area around the nanoparticles is dependant on the size, shape, dielectric constant of the matrix and the metal. We have recently reported on the use of plasmon excitation to induce acrylic polymerization on the surface of silver nanoparticles and have made ~10 nm polymer features far below the diffraction limit using visible LED irradiation. The acrylic polymerization takes advantage of plasmon enhanced excitation of azo photoinitiators in the vicinity of nanoparticles, causing cross-linking only in the enhancement region. The formation of a cross-linked polymer on the surface of the particles causes a solubility switch, where the regions unaffected by irradiation remain soluble and can be selectively washed away leaving behind the AgNP with a polymer coating. Plasmon excitation also generates a large local temperature gradients on the surface of nanoparticles and a measureable macroscopically amount of heat. The heat generated near the surface of particles can also be used to induce thermal processes with high spatial control. This spatial and temporal control over localized heating can also be used to initiate chemistry on the surface of particles relevant to the next generation of photolithography.