Ultrafast Photoluminescence from Suspended Gold/Graphene Hybrid Structures

Abstract

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 by the bandgap.

A Review on Graphene-Based Light Emitting Functional Devices

“…The high carrier mobility [ 64 , 65 , 66 , 67 ] and high thermal conductivity [ 68 , 69 , 70 ] of graphene make it a candidate material for future high-speed optoelectronic devices. For the design and development of graphene-based light-emitting devices, the non-equilibrium process of electron-hole combination is not efficient, because of the zero bandgap nature of graphene, due to the rapid relaxation of electron-phonon and electron-electron interaction [ 64 ].…”

“…The high carrier mobility [ 64 , 65 , 66 , 67 ] and high thermal conductivity [ 68 , 69 , 70 ] of graphene make it a candidate material for future high-speed optoelectronic devices. For the design and development of graphene-based light-emitting devices, the non-equilibrium process of electron-hole combination is not efficient, because of the zero bandgap nature of graphene, due to the rapid relaxation of electron-phonon and electron-electron interaction [ 64 ]. On the other hand, the high strength, high current densities (10 9 A/cm 2 in nanoribbons) [ 71 ], particularly high current density 10 7 A/cm 2 reported in micron-sized graphene fibber synthesized by chemical vapor deposition (CVD) [ 72 ], with higher temperature stability enables broadband thermal emission from the graphene [ 32 ].…”

“…Likewise, the tunability of energy levels from the implication of external electrical excitations can improve radiation parameters such as direction, spectrum, and intensity. More significantly, the emission radiation behavior of graphene-based material such as high-frequency radians [ 32 , 64 , 122 ], saturation current [ 98 , 123 ], black body radiations [ 124 ], and tunable spectrum [ 125 ] can be explained by the following transition phenomenon. The quantum Cherenkov effect can be defined as the process of spontaneous emission from the charger carrier emitting into graphene plasmons, which can be calculated by Fermi’s golden (GPs) [ 126 , 127 ].…”

Enhanced Iron Uptake in Plants by Volatile Emissions of Rahnella aquatilis JZ-GX1

“…Studies have shown that the optimum pH environment for Fe 3+ reductase is 5.6 (Arikan et al, 2018). Although plants in alkaline soils initiate their own adaptive response to iron deficiency stress, they are quickly buffered by high pH values, which explains why some iron deficiency-sensitive plants are prone to yellowing in calcareous soils (Zhou et al, 2016b). Therefore, the VOCs released by R. aquatilis JZ-GX1 can enhance the ability of A. thaliana to absorb iron by activating the physiological response of the plant itself.…”

“…In contrast to animals, plants are fixed organisms, and their growth and development occur in the soil; thus, plants can suffer from a variety of biotic or abiotic stresses from the soil throughout their life cycle (Zhou et al, 2016a(Zhou et al, , 2019. As one of the essential micronutrients in plants, iron (Fe) plays a very important role in the electron transport chain and enzymatic reaction pathways in many physiological metabolic processes, such as photosynthesis, respiration, nitrogen fixation, protein, and nucleic acid synthesis (Zhou et al, 2016b). Although iron is abundant in most soils, its bioavailability is relatively low in alkaline or calcareous soils (Arikan et al, 2018).…”