Acceleration of Photocarrier Relaxation in Graphene Achieved by Epitaxial Growth: Ultrafast Photoluminescence Decay of Monolayer Graphene on SiC

Imaeda, Hirotaka; Koyama, Takeshi; Kishida, Hideo; Kawahara, Kenji; Ago, Hiroki; Sakakibara, Ryotaro; Norimatsu, Wataru; Terasawa, Tomo‐o; Bao, Jianfeng; Kusunoki, Michiko

doi:10.1021/acs.jpcc.8b06845

Cited by 12 publications

(27 citation statements)

References 47 publications

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“…However, a counterintuitive feature is that the temperature-dependent decreasing rate of emission intensity of BiOBr-V is much slower than that of BiOBr case, since promoted exciton-phonon couplings usually lead to faster decays in other systems. [36,37] Besides, time-resolved photoluminescence tests also give counterintuitive results. Time-resolved fluorescence spectra monitoring at 470 nm (corresponding to the short-lived excitonic emission peak; Figure 3d) verify that BiOBr-V possesses a slower excitonic radiative decay than BiOBr.…”

Section: Page 10 Of 22 Ccs Chemistrymentioning

confidence: 99%

Engineering Exciton–Phonon Interactions for Suppressing Nonradiative Energy Loss in Energy-Transfer-Initiated Photocatalysis

et al. 2023

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The prevalent excitonic effects in low-dimensional semiconductors enable energy-transfer-initiated photocatalytic solar-to-chemical energy utilization. However, the general strong interactions between excitons and lattice vibrations in these low-dimensional systems lead to robust nonradiative energy loss, which inevitably sets up obstacles to photocatalytic performance of energy-transfer-initiated reactions. Herein, we highlight the crucial role of engineering exciton-phonon interactions in suppressing nonradiative energy losses in low-dimensional semiconductor-based photocatalysts. By taking bismuth oxybromide (BiOBr) as an example,

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Section: Page 10 Of 22 Ccs Chemistrymentioning

confidence: 99%

Engineering Exciton–Phonon Interactions for Suppressing Nonradiative Energy Loss in Energy-Transfer-Initiated Photocatalysis

et al. 2023

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“…In addition, the extracted diffusion coefficient of the excitons was reduced by approximately four times from the bare WS 2 monolayer to the fully encapsulated monolayer due to the scattering by additional phonons introduced by hBN 42 . In a few studies on graphene, it has been found that the photocarrier lifetimes of CVD-grown graphene transferred to hBN are shorter than those of graphene transferred to SiO 2 81 , and photocarriers in graphene epitaxially grown on SiC substrates relax faster than those in graphene transferred to SiC substrates 82,83 . These discrepancies have been attributed to the difference in the coupling between photocarriers in the graphene layers and phonons in the substrates.…”

Section: Phonon-assisted Relaxationmentioning

confidence: 99%

Modulation of photocarrier relaxation dynamics in two-dimensional semiconductors

2020

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Due to strong Coulomb interactions, two-dimensional (2D) semiconductors can support excitons with large binding energies and complex many-particle states. Their strong light-matter coupling and emerging excitonic phenomena make them potential candidates for next-generation optoelectronic and valleytronic devices. The relaxation dynamics of optically excited states are a key ingredient of excitonic physics and directly impact the quantum efficiency and operating bandwidth of most photonic devices. Here, we summarize recent efforts in probing and modulating the photocarrier relaxation dynamics in 2D semiconductors. We classify these results according to the relaxation pathways or mechanisms they are associated with. The approaches discussed include both tailoring sample properties, such as the defect distribution and band structure, and applying external stimuli such as electric fields and mechanical strain. Particular emphasis is placed on discussing how the unique features of 2D semiconductors, including enhanced Coulomb interactions, sensitivity to the surrounding environment, flexible van der Waals (vdW) heterostructure construction, and non-degenerate valley/spin index of 2D transition metal dichalcogenides (TMDs), manifest themselves during photocarrier relaxation and how they can be manipulated. The extensive physical mechanisms that can be used to modulate photocarrier relaxation dynamics are instrumental for understanding and utilizing excitonic states in 2D semiconductors.

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“…Our recent study pertaining to PL from epitaxially grown and transferred MLG on SiC demonstrated that the PL decay of a transferred MLG was slower than that of an epitaxial MLG. 6 The distance between the graphene and substrate was longer in the transferred graphene sample than in the epitaxial graphene sample, thereby explaining the slower heat flow in the transferred graphene sample. A slow heat flow causes a slow PL decay, resulting in a strong steady-state PL.…”

Section: ■ Introductionmentioning

confidence: 99%

Photoluminescence Enhancement Exceeding 10-Fold from Graphene via an Additional Layer: Photoluminescence from Monolayer and Bilayer Graphene Epitaxially Grown on SiC

et al. 2021

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Graphene exhibits characteristic optical properties and has garnered significant attention for application in light-emitting devices. Bilayer graphene is expected to be more suitable than monolayer graphene for application because of its strong luminescence owing to weak substrate effects. To further investigate this, we analyze the femtosecond photoluminescence (PL) decay and time-resolved PL spectra of epitaxial monolayer and bilayer graphene on SiC. The bilayer graphene emits longer and more than 10-fold stronger PL compared with the monolayer graphene. The PL decay curves and spectra are analyzed using a three-temperature model. The time evolutions of the carrier temperature and coupling coefficients between the carriers of graphene and each of the phonons of graphene and the substrate are obtained. The carrier temperature in bilayer graphene after femtosecond laser pulse excitation is approximately 120 K higher than that in monolayer graphene under our experimental conditions, thereby explaining the longer and stronger PL from the bilayer graphene. This study demonstrates the superior ability of bilayer graphene as a light-emitting material compared with monolayer graphene and promotes research pertaining to graphene-based light-emitting devices.

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Acceleration of Photocarrier Relaxation in Graphene Achieved by Epitaxial Growth: Ultrafast Photoluminescence Decay of Monolayer Graphene on SiC

Cited by 12 publications

References 47 publications

Engineering Exciton–Phonon Interactions for Suppressing Nonradiative Energy Loss in Energy-Transfer-Initiated Photocatalysis

Engineering Exciton–Phonon Interactions for Suppressing Nonradiative Energy Loss in Energy-Transfer-Initiated Photocatalysis

Modulation of photocarrier relaxation dynamics in two-dimensional semiconductors

Photoluminescence Enhancement Exceeding 10-Fold from Graphene via an Additional Layer: Photoluminescence from Monolayer and Bilayer Graphene Epitaxially Grown on SiC

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