Ultrafast Photoluminescence from Suspended Gold/Graphene Hybrid Structures

Gold is a classical metal with the Fermi level lying in the sp-band, while graphene is a zero-bandgap semiconductor with Dirac band structure. Thus, the photon emission from both gold and graphene can not be effectively achieved by electron–holes recombination as direct bandgap semiconductors. Alternatively, optical emission from hot carriers is possible in graphene and gold, but usually with very low efficiency. This is because the hot carrier relaxation time is much faster than the radiative lifetime in both graphene and gold. To solve this problem, here we show that in suspended graphene structures the photon emission intensity can be enhanced by increasing the hot carrier relaxation time, while in suspended gold/graphene hybrid structures, the photon emission intensity also increased with increasing holes sizes. Since nowadays most semiconductor light sources are based on bandgap design and also restricted by it, the study could help to develop materials with the emission wavelength not being limited ...