Hot electrons in nanoplasmonic devices

Localised surface plasmonic resonance is the oscillation of conduction electrons in metallic nanoparticles when it is illuminated with photons of a certain frequency. Nowadays, there is increasing effort to harness the energy or hot carriers from the metallic nanoparticles under plasmonic resonance. For example, researchers have used the plasmonic resonance effect to build photodetectors, photocatalysis, solar cells, etc. Despite the numerous experimental research, most theoretical studies are based on the classical approach such as solving Maxwell's equation. Little insights into the hot carriers are known as this is a quantum mechanical effect. To model the hot carriers, researchers have to solve Schrodinger's equation, which is computationally expensive. Researchers have attempted to model the hot-carrier processes using simplified wavefunctions such as the spherical-well approach, but this is less accurate and it is only limited to certain geometries of nanoparticles. Some other researchers uses ab-inito approaches to model these nanoparticles such as GW-perturbation method or time-dependent density functional theory calculations, but this can only be applied to very small (≤2000 atoms) nanoparticles or bulk-like nanoparticles. In this research project, we used a semi-classical approach, we used the tight-binding method to compute the wavefunction of the nanoparticles and used the quasi-static method to compute the perturbation induced by the photon. We used an efficient kernel polynomial method that scales linearly with the number of atoms. We managed to simulate the hot carrier distribution of nanoparticles with from 249 atoms(~0.5 nm) up to 1,000,000 atoms(~30 nm). Based on the finite-element quasi-static method, we managed to calculate the classical potential for arbitrary geometry. This allows us to calculate the hot-carrier generation rate of more complicated structures, such as Au@Pd core-shell nanoparticle surrounding a big Au nanoparticle and metallic Janus nanoparticles with a neck.