Coupling of plasmonic nanoparticles on a semiconductor substrate via a modified discrete dipole approximation method

abstract

Understanding the plasmonic coupling between a set of metallic nanoparticles (NPs) in a 2D array, and how a substrate affects such coupling, is fundamental for the development of optimized optoelectronic structures. Here, a simple semi-analytical procedure based on discrete dipole approximation (DDA) is reported to simulate the far-field and near-field properties of arrays of NPs, considering the coupling between particles, and the effect of the presence of a semiconductor substrate based on the image dipole approach. The method is validated for Ag NP dimers and single Ag NPs on a gallium nitride (GaN) substrate, a semiconductor widely used in optical devices, by comparison with the results obtained by the finite element method (FEM), indicating a good agreement in the weak coupling regime. Next, the method is applied to square and random arrays of Ag NPs on a GaN substrate. The increase in the surface density of NPs on a GaN substrate mainly results in a redshift of the dipolar resonance frequency and an increase in the near-field enhancement. This model, based on a single dipole approach, grants very low computational times, representing an advantage to predict the optical properties of large NP arrays on a semiconductor substrate for different applications.

keywords

ENHANCED RAMAN-SCATTERING; OPTICAL-PROPERTIES; SILVER NANOPARTICLES; METALLIC NANOPARTICLES; RESONANCE; EXTINCTION; ARRAYS; MODES; SIZE; WAVELENGTH

subject category

Chemistry; Physics

authors

Carvalho, DF; Martins, MA; Fernandes, PA; Correia, MRP

our authors

acknowledgements

This work was partially developed within the scope of the projects i3N, UIDB/50025/2020 (BI/UI96/9549/2021 grant) & UIDP/50025/2020, and CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC. This research was also funded in part by the 2021.08228.BD FCT grant.

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