Spectral tunability of realistic plasmonic nanoantennas

Abstract

Single nanoantenna spectroscopy was carried out on realistic dipole nanoantennas with various arm lengths and gap sizes fabricated by electron-beam lithography. A significant difference in resonance wavelength between realistic and ideal nanoantennas was found by comparing their spectral response. Consequently, the spectral tunability (96 nm) of the structures was significantly lower than that of simulated ideal nanoantennas. These observations, attributed to the nanofabrication process, are related to imperfections in the geometry, added metal adhesion layer, and shape modifications, which are analyzed in this work. Our results provide important information for the design of dipole nanoantennas clarifying the role of the structural modifications on the resonance spectra, as supported by calculations.

Optical nanogap antennas as plasmonic biosensors for the detection of miRNA biomarkers

“…20 It has been reported that deviation on the nanofabrication process can hamper the figure of merit of LSPR sensing. 19 As expected, the evaluation of the sensitivity for parallel and perpendicular configurations shows a different sensitivity to RI bulk changes (ȠB). As can be noticed in Figure 4, there is a higher sensitivity for the TE polarized, parallel (422 nm/RIU) vs perpendicular (270 nm/RIU)) orientation respect to the axis of the nanogap antennas.…”

“…This fabrication strategy exhibits slightly lower resolution than other expensive and timeconsuming fabrication methods, such as e-beam lithography for gap sizes of the same range. 19 FDTD simulations performed for these nanostructures were compared with discrete nanodisks (see Figure 2). Ideal nanogap antennas with a gap size equal to 15 nm onto a glass substrate shows a large confinement of a higher intensity EM field within the nanogap separating the two nanodisks (see Figure 2a), resulting on a higher sensitivity to changes of the RI as illustrated in Figure 2b-d.…”

“…17,18 These effects are remarkably observed on the visible light frequencies for gap sizes below 20 nm, which represents a fabrication challenge when a large-area sensing surface is required. 19,20 Most nanogap antennas structures explored for biosensing applications have been fabricated through expensive and timeconsuming fabrication methods such as e-beam lithography 19 or focus ion beam (FIB), 21 which hinders their further transfer into more feasible and commercial-oriented products.…”

Highly sensitive SERS analysis of the cyclic Arg–Gly–Asp peptide ligands of cells using nanogap antennas

“…Nanogap antenna fabrication: Gold nanogap antennas were fabricated on glass substrates using lift‐off and electron‐beam lithography, as described elsewhere . Different nanogap sizes (15–30 nm) and arm's lengths (40–80 nm) were designed, whereas the width and thickness were kept constant at 40 nm.…”

“…A nanogap antenna enables nanoscale spatial resolution, leading to more precise spectral analysis than conventional averaged surface enhanced spectra. Dipole nanogap antennas allow fine‐tuning of the plasmon resonance condition used for SERS, as was experimentally demonstrated by precisely controlling geometrical parameters such as the gap dimension and the length of the arms . The tunability of the plasmon resonance constitutes a clear advantage of the dipole nanogap antennas compared to colloidal or randomly structured metal‐island films.…”