Research data supporting "Accessing Plasmonic Hotspots using Nanoparticle-on-Foil Constructs"

Figure 1c: Coupling of IMI + MIM = MIMI modes in a nanoparticle-on-foil cavity. Dispersion of MIMI modes for different t with d=1nm compared to IMI and MIM modes; surface plasmon on thick Au and free-space photon. Figure 1d: Effective propagation index of MIMI modes for increasing t at λ=633nm. Figure 1e: E_z near-fields from full-wave simulations of NPoF with plane wave excitation for t=15nm and t=5nm film thickness at the nanocavity resonance. The field null in the metal-film just above the substrate and the leakage of nanocavity fields into the substrate are clearly seen. Fig.1f: E_z near-fields from full-wave simulations of NPoF geometry with dipole source exciting the NPoF gap centre for t=10nm at λ=633nm, and IMI modes travelling away from the AuNP.

Figure 2a,b. Far-field scattering from NPoFs, dark-field scattering spectra obtained from different individual NPoF cavities for (a) t=20nm and (b) t=10nm along with the average spectra. Figure 2c: Simulated scattering spectra for NPoF cavities vs decreasing foil thickness t from 30nm to 5nm. Figure 2d: Simulated far-field radiated intensity for NPoF cavity.

Figure 3a: Average SERS enhancements in NPoFs Average SERS spectra for 3 different film thicknesses. Figure 3b: Histogram of extracted SERS 1585 cm-1 peak and background intensities. Figure 3c: Variation in the ratio of SERS background to SERS peak intensities.

Figure 4a: Wavelength-dependent near-field enhancements in NPoFs extracted from the centre of the BPT-gap layer and fields 2nm below the Au-foil for different film thickness. Figure 4b: Near-field enhancement map for t=10nm at the nanocavity resonance. Figure 4c: Extracted near-field profile along z-axis (at x=0) for different film thickness.