Tunable graphene plasmonic structures with different gating schemes
Aygar, Ayşe Melis
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The aim of this thesis is to examine graphene plasmonic structures which yields actively tunable spectral resonances and compare two different ways to gate graphene. Plasmonic structures that consist of periodic fractal gold squares on graphene are used to increase light-graphene interaction. We show by simulations and experiments that higher degree fractal structures result in higher spectral tunability of resonance wavelength. This is explained by more plasmonic localization of light for higher degree fractal structures. Furthermore, spectral tunability of a plasmonic structure integrated with graphene is investigated comparing two different schemes for electrostatic gating. The fabrication methods and fabrication steps of the devices with different gating schemes is explained in detail. Comparison of back-gating and top-gating schemes confirms that top-gating using ionic liquid is a more efficient gating method. Top-gating yields the same amount of spectral tunability while requiring smaller gate voltages compared to that of back-gating experiments.