Silver is considered as one of the most desirable materials for plasmonic devices due to it having low loss, low epsilon<sub>2</sub>, across the visible spectrum. In addition, silver nanotriangles can self-assemble into complex structures that can include tip-totip or base-to-base arrangements. While the optical properties of tip-to-tip dimers of nanotriangles have been quite intensively studied, the geometric inverse, the base-to-base configuration, has received much less attention. Here we report the results of a computational study of the optical response of this latter configuration. Calculations were performed using the discrete dipole approximation. The effect of gap size and substrate are considered. The results indicate that the base-to-base configuration can sustain a strong coupled dipole and various multimode resonances. The pairing of the parallel triangle edges produces a strongly capacitive configuration and very intense electric fields over an extended volume of space. Therefore, the base-to-base configuration could be suitable for a range of plasmonic applications that require a strong and uniform concentration of electric field. Examples include refractometeric sensing or metal-enhanced fluorescence.
We investigated Si nanocrystal samples produced by high dose 600 keV Si+ implantation of fused silica and annealing using cathodoluminescence (CL). CL spectra collected under 5-25 keV electron irradiation show similar features to reported photoluminescence spectra, including the strong near IR peak. The CL intensity distribution is formulated as a linear inverse problem and two methods namely the regularisation method and maximum entropy method can be applied to determine the depth profile without making any assumptions concerning the profile function, i.e. a free form solution. We show using simulated CL data that the maximum entropy method is the most appropriate as it preserves the positivity and additivity of the depth profile. This method is applied to experimental CL data and we have localised the spatial origin of the near IR emission to the near-surface region of the implant, 400 nm from the surface, containing the smallest Si nanocrystals.