Adaptive graphene electronics and plasmonics

Abstract

Graphene, the world’s first two dimensional material, has attracted great interest in the scientific community due to its unique behaviours such as the dramatic tunability of its electronic and optical properties, strong lightmatter interactions, and high values of carrier mobility which render graphene as a fascinating material for photodetection, plasmonic devices, and modulation of terahertz frequency radiation. To realise the next generation of graphene devices we must find new ways to adaptively control the electronic and optical properties of graphene and other two dimensional materials. In this thesis I propose a method to optically control the electronic properties of graphene in a spatially resolved, non-volatile, yet reversible manner via the use of photorefractive lithium niobate. The method I propose relies on the ability of lithium niobate to sustain optically defined charge distributions which result in large electrostatic fields at the surface of the crystal.
By transferring graphene onto lithium niobate crystals I show that the optically defined electrostatic surface charges in the substrate are capable of tuning the DC electrical conductivity of graphene in a behaviour which is non-volatile yet reversible under thermal annealing.
Further, I utilise this effect in a plasmonic device consisting of a hybrid graphene-metal metasurface on lithium niobate where the optical tuning effect is capable of altering the transmissive properties of the device at terahertz frequencies.
Finally, I show through simulations that by spatially patterning charge distributions it is possible to create optically defined plasmonic devices on graphene on lithium niobate. Such devices would not need permanent lithographic patterning of metasurfaces, yet instead would rely on optically defined regions of high and low conductivity graphene to sustain a plasmonic resonance. If such devices can be experimentally achieved this would allow for rewritable yet non-volatile plasmonic structures in graphene and open the doors to a truly reconfigurable plasmonic platform for two dimensional materials.

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Identifiers

ORCID for Jonathan Gorecki: orcid.org/0000-0001-9205-2294

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