Date of Award

Spring 5-2017

Embargo Period

5-25-2017

Degree Type

Dissertation (CMU Access Only)

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Advisor(s)

Alan McGaughey

Abstract

We explore the effects of surface plasmon hybridization in graphene nanostructures and silver nanoparticles as applied to novel plasmonic phenomena. The analysis is based on the theory of surface plasmon hybridization under the boundary charges method. This method, which is based in the electrostatic approximation, has been largely used to predict the resonant frequencies in strongly coupled nanoparticle clusters. Here, we extend this formalism to analyze novel plasmonic phenomena such as the blueshift of modes in graphene plasmonics, near-field radiation, thermal transport and plasmon-induced hot carrier generation in silver nanoparticles. Furthermore, we develop analytical solutions for graphene nanodisks and metallic spheres that allow for fast and accurate modeling. The analytic models provide the basis to derive a large number of results, including prediction of hybrid eigenmodes and bandstructures, far-field response, and near-field response under thermally induced fluctuations. We predict that the strong near-filed coupling in graphene nanodisk stacks can induce a blueshift in the resonant frequencies up to the near-infrared part of the spectrum. We find that the strong near-filed coupling between disks can also lead to large values of radiative thermal conductance when thermally induced fluctuations are included. In this regard, an enhancement over the blackbody limit of up to two and four orders of magnitude was observed for co-planar and co-axial disk configurations. The strong coupling between coplanar disks was also explored for the development of plasmonic waveguides by considering long co-planar disk arrays. It was observed that the array posseses great potential for plasmonic waveguiding, with a strong degree of confinement for disks smaller than 200 nm. Thermal activation of the guided modes showed a thermal conductivity of up to 4.5 W/m K and thermal diffusivity of up to 1:4 x 10-3 m2/s. The large values of thermal diffusivity suggest the potential of graphene disk waveguides for thermotronic interconnects. The plasmon-induced hot carrier generation in silver nanosphere dimers was also studied. The modeling considered analytical solution for metallic nanospheres, from which the electrostatic potential of each sphere was obtained. Using these results, the hot carrier generation was explored under the basis of the Fermi golden rule. The results show a large number of hot carriers at the low frequency modes. This values exceed the number of generated hot carriers on a single sphere. The energy distribution of photogenerated electrons and holes showed a large energy gap that can be explored in photocatalysis and photovoltaic energy conversion.

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