Date of Award

2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Materials Science & Engineering

First Advisor

Ertugrul Cubukcu

Abstract

2-Dimensional materials are of great interest because of novel and intriguing properties that emerge at the monolayer limit in comparison to bulk materials. To that end, this thesis is split into the study of two different 2-dimensional materials in the realm of nanophotonics. First, graphene is utilized for both passivating the surface of metallic nanoparticles from oxidation and as a platform for functionalization and integration into specific molecule sensing. The nanoparticles act as plasmonic nanoantennas, enhancing the electric field near the surface of the antenna. It is shown that graphene-encapsulated silver nanoantennas are oxidation resistant and optically stable over a 30 day period. The performance of the graphene-passivated silver nanoantennas outpaces that of the traditional material, gold, by ~60% in sensing bulk index changes in the range of n = 1.40 1.45. Graphene encapsulation can be extended to other plasmonic metals such as aluminum and copper, as well as fully integrate graphene-passivated Ag nanoantennas into biomolecular sensing devices. The second topic of this thesis is to study and enhance the luminescence of molybdenum disulfide (MoS2), a 2-dimensional semiconductor. Atomic layer deposition of SiO2 was used to encapsulate and the effectively etch a layer of bilayer MoS2 through reactive processes, which result in a chemically-doped MoS2 monolayer with enhanced luminescence properties. This new enhanced layer is two orders of magnitude more luminescent than the original material and one order of magnitude over that of an exfoliated monolayer. By coupling the enhanced MoS2 to an optical microdisk cavity, highly narrow emission can be produced from the original, broad luminescence. These sharp peaks can be utilized in biomolecule sensing through functionalization of the MoS2 layer. The effects of high-intensity optical pumping of the MoS2 in these microdisk cavities are also studied. Heat generation from non-radiative recombination causes thermally enabled oxidation of the optical material. This effect is shown to be not limited to MoS2, but affects WSe2 as well. This effect is shown to be minimized through the use of pulsed excitation, and the luminescence from high Q-factor microdisks was investigated using high-fluence femtosecond optical pulses.

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