Nanoline-gap controlled self assembly of plasmonic nanoparticles inside plasmonic nanolines

Abstract

This paper presents plasmonic substrates fabricated by a gap—controlled, template-assisted self assembly of plasmonic nanoparticles—such as spherical nanoparticles and nanorods—inside one dimensional plasmonic nanoline templates fabricated using Deep-UV lithography. This hybrid fabrication process—which combines the bottom-up process of capillary-force self assembly with the top-down process of Deep-UV lithography—can potentially be employed for large-area fabrication (6 inch or 12 inch wafers) of plasmonic substrates with sub-10 nm gaps. These small gaps lead to a high electromagnetic enhancement which can be highly beneficial if these substrates are employed for sensing based on surface enhanced Raman scattering (SERS). We demonstrate that the templates of plasmonic nanolines act as lithographed traps and direct the capillary-force assembly of metallic nanoparticles. The gaps between the nanolines, along with the shape and dimensions of the nanoparticles, together determine the interparticle distance, packing pattern and the orientation of the assembled nanoparticles inside these nanolines. Moreover, the electromagnetic behavior of these substrates is exhaustively analyzed using Finite Difference Time Domain (FDTD) modeling. Thus, we demonstrate template-directed, capillary-force assembly of plasmonic nanoparticles inside plasmonic nanolines such that the assembly can be controlled by modulating the structural parameters of the template or the assembled nanoparticles, and can be potentially carried out on a large area.