Modeling the Optical Properties of Bowtie Antenna Generated By Self-Assembled Ag Triangular Nanoprisms

Self-organized metal nanoparticles often possess assembly defects that can have a profound impact on the optical properties of the resulting nanoparticle assembly. Modeling these defects and evaluating their optical outcomes can provide a better understanding of how to design the assembly process and can evaluate the quality of the resulting materials. Here, we use finite element methods to examine the fabrication of bowtie nanoantenna, a commonly sought-after plasmonic structure with resonances in the visible and near-infrared wavelengths, through the self-assembly of colloidal triangular Ag nanoprisms. We model perfect and defective antenna structures and examine the effects of commonly observed assembly defects such as imperfect nanoprism shapes, off-axis antenna structures, and trimer or tetramer formation. We also evaluate the ability to fabricate antenna structures that possess comparable structural parameters (e.g., thickness, gap distance) to top-down lithographic techniques. We find that structural defects in self-assembled bowties can shift the resonant wavelength of the antenna by as much as 200 nm. Our models also indicate that self-assembled bowties possess high defect tolerances with respect to near-field enhancement, suggesting that they are viable structures for nanophotonic and nanoplasmonic applications.