Affecting Graphene Based Absorbers

Today I had the pleasure of visiting Manchester University and specifically the physics buildings. Apart from being one of the absolute best physics departments in the UK for research it is also where graphene was invented over a decade ago. The two Nobel prize winners, Andre Geim and Konstantin Novoselov,  who discovered it still work there and I did see them although didn’t get the opportunity to talk to have a conversation. Coincidently tonight’s news is also about graphene and another one of its many uses. To simply greatly graphene ribbons composed of two layers instead of the normal one were placed near a metallic plate made of pure silver (Ag) periodically along the surface. In order to accomplish this they were embedded a small distance apart in silicon dioxide (SiO2) that acted as a dielectric. Then simulations were run to predict the absorption rate for different wavelengths of infrared radiation. The bilayer graphene ribbons were used as resonance can be set up between the layers to increase absorption. The silver plate is very thick compared to the rest of the system and was included to limit and infrared transmission from the device. As the width of the ribbons got bigger and bigger, the predicted peak absorption wavelength where the energy reflected is at a complete minimum, kept increasing as well. For instance at 150 nanometres wide the wavelength of light at peak absorption was about 11 micrometres, while at 240 nanometre width the wavelength had increased to 13.25 micrometres. It was also found that in addition to energy absorbed directly be the graphene, energy was also absorbed by the dielectric in between the graphene and the silver so the thicker this is the more efficient the absorber will be regardless of wavelength.


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