Graphene Based Thermal Emitters
Mahlmeister, Nathan Howard
Thesis or dissertation
University of Exeter
Mid-Infrared thermal emission sources based on graphene were investigated both experimentally and simulated using the finite element method modelling software package COMSOL. Devices were fabricated by transferring graphene onto various substrates. The thermal emission of few-layer and single graphene on SiO2/Si, under a pulsed square wave drive current, was characterised using spatially resolved thermal emission measurements. It was determined that the devices with single-layer graphene maintained characteristic properties of graphene, while few-layer graphene displayed properties typical of a semi-metal. The effect of thermal management on the emission was investigated by comparing simulations to the emission from these devices and a hexagonal boron nitride encapsulated few-layer graphene device. Limiting the vertical heat dissipation was shown to improve device modulation speed. The emission from the graphene devices was determined to be grey-body in nature. Metamaterial structures, including ring resonators and split ring resonators, were integrated with the encapsulated devices in order to narrow the emission spectra. The emission and reflectance of the devices was characterised using Fourier transform infrared spectroscopy. A tuneable electromagnetically induced transparency like spectral response was observed for devices with metamaterial structures. The resonance peaks were shifted by altering the unit cell parameters. Finally, gallium nitride nano-rod arrays were investigated for the potential to incorporate both spectral control and thermal management into the underlying substrate, in addition to the possibility of the optical generation of graphene plasmons. It was determined that the conventional wet transfer technique was inadequate to transfer the graphene onto the nano-rods. Therefore, a modified transfer technique was utilised, with a significant improvement in the graphene coverage observed. Optical characterisation of the nano-rods using Fourier transform infrared reflectance spectroscopy indicated the excitation of localised surface phonon polaritons, while no evidence was observed in the graphene reflectance spectra of the generation of graphene plasmons.
Luxmoore IJ, Adlem C, Poole T, Lawton LM, Mahlmeister NH, Nash GR. (2013) Thermal emission from large area chemical vapor deposited graphene devices, Applied Physics Letters, volume 103, no. 13, DOI:10.1063/1.4821939.
Lawton LM, Mahlmeister NH, Luxmoore IJ, Nash GR. (2014) Prospective for graphene based thermal mid-infrared light emitting devices, AIP ADVANCES, volume 4, no. 8, article no. ARTN 087139, DOI:10.1063/1.4894449.
Mahlmeister NH, Lawton LM, Luxmoore IJ, Nash GR. (2016) Modulation characteristics of graphene-based thermal emitters, Applied Physics Express, volume 9, no. 1, DOI:10.7567/APEX.9.012105.
Barnard HR, Zossimova E, Mahlmeister NH, Lawton LM, Luxmoore IJ, Nash GR. (2016) Boron nitride encapsulated graphene infrared emitters, APPLIED PHYSICS LETTERS, volume 108, no. 13, article no. ARTN 131110, DOI:10.1063/1.4945371.
PhD in Engineering