Investigating the influences of the precise manufactured shape of dipole nanoantennas on their optical properties

Abstract

Fabrication of small nanoantennas with high aspect ratios via electron beam lithography is at the current technical limit of nanofabrication and hence significant deviations from the intended shape of small nanobars occur. Via numerical simulations, we investigate the influence of geometrical variations of gap nanoantennas, having dimensions on the order of only a few tens of nanometers. We show that those deviations have a significant influence on the performance of such nanoantennas. In particular, their resonance wavelength as well as the magnitude of absorption and scattering cross section and the electric field distribution in the near field is strongly altered. Our findings are thus of importance for applications based on near field as well as those based on far field interactions with nanoantennas and have to be carefully and individually considered in both cases.

Oxide mediated spectral shifting in aluminum resonant optical antennas

“…We neither included the surface roughness, nor the exact realistic geometry, which is known to change the optical response and which can be deduced from scanning electron microscopy images and atomic force microscopy data [27], nor additional effects due to grain boundaries. Furthermore, we assumed a homogeneous oxidation and therefore a smooth oxide layer with constant thickness.…”

Fabrication of suspended metal–dielectric–metal plasmonic nanostructures

“…Dipole nano-antennas, consisting of two metallic nanostructures separated by a dielectric gap region, can be viewed as MDM nanostructures. As the resonance frequency of dipole nano-antennas is sensitive to nanometer variations in the feedgap dimensions [27,28] and roughness [29,30], achieving arrays of such dipole antennas with uniform resonances is a challenge. Arrays of laterally-oriented dipole antennas invariably introduce a distribution of gap sizes, as well as 'shorted' antennas where the individual structures are connected together [31,32].…”

Spectral tunability of realistic plasmonic nanoantennas

“…Some studies have evaluated the influence of shape variations of antennas produced using current nanofabrication technologies. [12][13][14] The optical response of these antennas, referred as realistic nanoantennas, is significantly different, since they do not consist of two ideal rectangular nanorods separated by a nanogap. Therefore, a more extensive study of such structures is of strong interest in order to optimize sensitivity, reliability, and estimate the limits of plasmonic biosensors.…”

“…Other nanofabrication-related effects reported in a recent study can affect the spectral response of dipole plasmonic nanoantennas. 12 Based on the analysis of the antennas SEM images, we found a close relation between the decreasing trend of the antenna's arm aspect ratio (AR) (length/width), with respect to the design values, and the decrease of the resonance peak position, as can be noticed in the inset of between the aspect ratio and the plasmon resonance frequency (x res ) of an elongated particle can be addressed through a simple mass-and-spring model. 20 Accordingly,…”