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

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.

Automated summary

Understanding the plasmonic coupling between metallic nanoparticles (NPs) in a 2D array and the effect of a semiconductor substrate is crucial for optimizing optoelectronic structures. This study presents a simple semi-analytical approach based on the discrete dipole approximation (DDA) to simulate the far-field and near-field properties of NP arrays, taking into account particle coupling and the presence of a semiconductor substrate. The method is validated for Ag NP dimers and single Ag NPs on a GaN substrate, and then applied to square and random arrays of Ag NPs. It is found that increasing the NP surface density on a GaN substrate results in a redshift of the dipolar resonance frequency and enhanced near-field properties. The single dipole approach used in this model allows for efficient computational times, making it advantageous for predicting optical properties in large NP arrays on semiconductor substrates for various applications.