Unconventional Terahertz Carrier Relaxation in Graphene Oxide: Observation of Enhanced Auger Recombination Due to Defect Saturation

Kim, Jaeseok; Oh, Ji Hye; In, Chihun; Lee, Yun Shik; Norris, Theodore B.; Jun, Seong Chan; Choi, Hyunyong

doi:10.1021/nn406066f

Cited by 32 publications

(45 citation statements)

References 61 publications

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“…Thus, the Dirac type band structure should be essentially maintained for the individual graphene sheets in the graphene sponge except with a slightly opened band gap, which should allow the material to behave as a collection of individual suspended graphene sheets with the intrinsic properties of graphene retained 17,27,28 . Note the photon energy of the lasers that we used is at least ~1.91 eV, which should be much higher than the possibly very small band gap 29,30 of the individual graphene sheets in the graphene sponge.…”

Section: Mechanism Of the Macroscopic And Direct Light Propulsionmentioning

confidence: 99%

Macroscopic and direct light propulsion of bulk graphene material

et al. 2015

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It has been a great challenge to achieve the direct light manipulation of matter on a bulk scale. In this work the direct light propulsion of matter is observed on a macroscopic scale using a bulk graphene-based material. The unique structure and properties of graphene, and the novel morphology of the bulk three-dimensional linked graphene material make it capable not only of absorbing light at various wavelengths but also of emitting energetic electrons efficiently enough to drive the bulk material, following Newtonian mechanics. Thus, the unique photonic and electronic properties of individual graphene sheets are manifested in the response of the bulk state. These results offer an exciting opportunity to bring about bulkscale light manipulation with the potential to realize long-sought applications in areas such as the solar sail and space transportation driven directly by sunlight.U sing beams of light, scientists have been able to trap 1 , move 2 , levitate 3 and even pull 4 small objects (such as atoms and molecules, living cells and viruses, and micro/nanoscopic particles) on the microscopic scale, as well as nano/micrometre-sized graphene sheets 5-7 on a small spatial scale, typically on the order of hundreds of micrometres 8 . There have also been reports of efforts to enlarge the optical manipulation distance by harnessing strong thermal forces 9 , and also the robust manipulation of airborne micro-objects photophoretically with a bottle beam 10 . Furthermore, the rotation and motion of a millimetre-sized graphite disk by photoirradiation has been realized with the graphite levitated magnetically 11 . If these optical operations were to be achieved with large objects on a macroscopic spatial scale, significant applications such as the long-sought direct optical manipulation of macroscale objects (including the proposed solar sail and space transportation via laser or beam-powered propulsion) could be realized. To acquire the required energy and momentum for propulsion, two main mechanisms have been proposed: the use of a laser to superheat a propellant (or air), which then provides propulsion in the same manner as a conventional rocket 4,12,13 , or obtaining propulsion directly from light pressure (radiation pressure) acting on a light sail structure (as with the IKAROS spacecraft) 14,15 .It has been a great challenge to realize the intrinsic properties of single-layer graphene in the bulk state, because stacking of the graphene sheets diminishes most of its properties (electronic, photonic and even mechanical). In this Article, we show that if graphene sheets are assembled in the proper manner into the bulk state, the resulting bulk material not only can retain the intrinsic properties of the individual graphene sheets, but also allows their manifestation on a macroscopic scale. Here, we demonstrate the directly lightinduced macroscopic propulsion and rotation of a bulk graphene sponge material with dimensions on the scale of a centimetre and milligram weight. The mechanism behind this novel phenomenon ...

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Section: Mechanism Of the Macroscopic And Direct Light Propulsionmentioning

confidence: 99%

Macroscopic and direct light propulsion of bulk graphene material

et al. 2015

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“…In general, in the plasmon model, the restoring force by the displacement from equilibrium is neglected to simplify the solution of the Maxwell equation. It has successfully been applied to the analysis of optical conductivity in metals including graphene over the THz regime as the frequency of electromagnetic waves is significantly higher, compared to the plasma frequency. Recently, the applications of graphene have been extended to microwave absorption in the gigahertz (GHz) regime .…”

Section: Introductionmentioning

confidence: 99%

Relaxation of Plasma Carriers in Graphene: An Approach by Frequency‐Dependent Optical Conductivity Measurement

Choi

Nishiyama

Ogawa

et al. 2018

Advanced Optical Materials

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resulting in ultrahigh carrier mobilities, long mean free paths, and anomalous quantum Hall effects. [3][4][5][6][7] The most important advantage of graphene is the tunability of the carrier densities, which can be easily controlled by a gate bias or doping. [8][9][10][11][12] Consequently, graphene has been applied as convenient tunable terahertz (THz) metamaterials. [9,10,13,14] In photonics, the optical properties of graphene have been discussed with the surface plasmon model, corresponding to the Drude model with the free carrier concept. In general, in the plasmon model, the restoring force by the displacement from equilibrium is neglected to simplify the solution of the Maxwell equation. It has successfully been applied to the analysis of optical conductivity in metals including graphene over the THz regime [15][16][17][18] as the frequency of electromagnetic waves is significantly higher, compared to the plasma frequency. Recently, the applications of graphene have been extended to microwave absorption in the gigahertz (GHz) regime. [19,20] However, in most of these studies, the optical conductivity of graphene, related to the optical absorption, is discussed with the Debye model [21] or free carrier model. [22] The effective mass of electrons in graphene is extremely small, resulting in a high plasma frequency, comparable to the GHz regime. Hence, the analysis of the optical conductivity of graphene in the GHz regime should be modified from the free carrier model to the plasma carrier model considering the restoring force.In contrast, the field-induced time-resolved microwave conductivity (FI-TRMC) technique has recently been applied to complex permittivity analysis for organic semiconductors, leading to the assessment of the trap depth for charge carriers. [23] FI-TRMC is a microwave-based alternating current technique to evaluate the dielectric loss of materials with a resonant cavity. [23][24][25][26][27] In contrast to direct current (DC) methods represented by field-effect transistor (FET) and Hall effect measurements, FI-TRMC is advantageous in that it avoids the effect of extrinsic factors because of the small displacement distance of charge carriers. [28] For complex permittivity analysis with FI-TRMC, the real change in permittivity is estimated simultaneously with the dielectric loss, providing a detailed range of charge transport characteristics in the materials. FI-TRMC is suitable for investigation of the electronic properties The relaxation time and mobility of electrons on graphene are deduced quantitatively by complex permittivity analysis with microwave dielectric loss spectroscopy. Hexagonal graphene sheets with uniform domain sizes from 6 to 30 µm, which target the mean free path of electrons on graphene based on the significantly longer turnover time of microwave probing at gigahertz (GHz) frequencies as compared to the relaxation time of electrons, are employed to determine the factors for carrier relaxation at the intradomain and grain boundaries. The changes in the complex permittiv...

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“…In such 3D bulk graphene, these oxygen functional groups acted as electronically induced quantum confinement and electronic barriers between the graphene sheets, and as a result, a localized bandgap formed. When the photon energy of the laser was higher than the bandgap, the photon‐excited energetic electrons were ejected as free electrons, which generated inverted beam‐powered propulsion, pushing materials away from the laser beam . Herein, under continuous laser/light excitation, antigravity propulsion, rotation and translation of the graphene sponge were achieved.…”

Section: Actuating Schemes For Light‐to‐work Conversionmentioning

confidence: 99%

“…Such a sponge could be propelled by laser illumination inside a vacuum tube. When the laser was turned on, the photon‐excited energetic electrons were ejected to generate inverted beam‐powered propulsion, pushing materials away from the laser beam . Although the propulsion force was still small compared with that of conventional rockets, the force was already comparable to the weight of the graphene sponge‐based rocket.…”

Section: Applicationsmentioning

confidence: 99%

Photoresponsive Actuators Built from Carbon‐Based Soft Materials

Yang

Yuan

Liu

et al. 2019

Advanced Optical Materials

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Actuations triggered by light strongly depend on the energy density of light, energy conversion efficiency and actuator dimensions. Therefore, understanding the energy-conversion routes is crucial for effective photoresponsive actuations. As illustrated in Table 1, several actuating schemes have been demonstrated in carbon-based soft materials, including indirect light-to-work-conversion with heat energy, electric energy and chemical energy introduced as intermediate energy sources and

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Unconventional Terahertz Carrier Relaxation in Graphene Oxide: Observation of Enhanced Auger Recombination Due to Defect Saturation

Cited by 32 publications

References 61 publications

Macroscopic and direct light propulsion of bulk graphene material

Macroscopic and direct light propulsion of bulk graphene material

Relaxation of Plasma Carriers in Graphene: An Approach by Frequency‐Dependent Optical Conductivity Measurement

Photoresponsive Actuators Built from Carbon‐Based Soft Materials

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