Layer number dependence of carrier lifetime in graphenes observed using time-resolved mid-infrared luminescence

Watanabe, Hiroshi; Kawasaki, Tomohiro; Iimori, Takushi; Komori, Fumio; Suemoto, Tohru

doi:10.1016/j.cplett.2015.07.046

Cited by 7 publications

(8 citation statements)

References 23 publications

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“…38,57 However, we assume that the strongly coupled phonon systems are in quasi-equilibrium states and define temperatures of these systems. 4,6,10,19,46 It is noted that early studies showed supercollision cooling of carriers in defective graphene, where carrier cooling is accelerated by enhanced carrier-acoustic phonon scattering via defect state. 58−61 In the supercollision cooling model, the cooling rate of T c is dependent on the average distance between defects.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Despite these advantages, the emission properties of BLG have been investigated less compared with those of MLG. Early time-resolved PL measurements showed that the PL from BLG was 2 times stronger than that from MLG at a photon energy of 0.3 eV, as evident by the 2-fold absorption of excitation light in BLG . However, the PL intensity was not only affected by absorption but also by relaxation in the excited state.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: ■ Results and Discussionmentioning

confidence: 99%

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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“…Moreover, we note that when the electron distribution approaches the Dirac point, the cooling of the electronic system may be further reduced through bottlenecks arising from the zero DOS at the Dirac point. 25,46 Specifically, an electron in an initial energy state well above the Dirac point (here we assume E D = E F ) can easily relax to a lower energy state whereas one initially near the Dirac point cannot because the DOS of the final state in the latter case is much smaller than that in the former case. Therefore, the relaxation of the electronic temperature is significantly restricted when the electron distribution for the Dirac point is approached (for example, see Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Spectroscopic experiments combined with pump-probe techniques, such as time-and angle-resolved photoemission spectroscopy (trARPES), [10][11][12][13][14][15][16] transient transmissivity (reflectivity) measurements, [17][18][19][20][21][22] and time-resolved photoluminescence spectroscopy, [23][24][25] have been applied to understand the carrier dynamics in graphene. According to previous research, photo-excited hot carriers lose a large part of their energy via electron-optical phonon scattering within the first several hundred femtoseconds and gradually return to their equilibrium state through electron-acoustic phonon scattering or optical phononacoustic phonon decay within 1 to 100 ps.…”

Section: Introductionmentioning

confidence: 99%

Suppression of supercollision carrier cooling in high mobility graphene on SiC( 0001¯ )

et al. 2017

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Graphene, a two-dimensional carbon crystal with a gas of massless Dirac fermions, has promise as a material that is useful in photonic and optoelectronic devices. A comprehensive understanding of carrier cooling in photo-excited graphene is necessary for their applications, however, as competing cooling processes, electron-phonon scattering, and supercollisions, complicates the problem. Specifically, in energy harvesting, supercollision promotes further carrier cooling and, therefore, leads to lower efficiency, placing doubt on the feasibility of device applications. Here we present evidence of suppressed supercollisions in trilayer graphene on a SiC(0001) substrate by directly observing photo-excited carriers and numerically analyzing a phenomenological two-temperature model. Knowing that supercollisions restrict the capabilities of graphene-based devices, our results provide a breakthrough for improving their performance.

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“…Extensive experimental and theoretical studies have been done to understand the electron dynamics in graphene excited by optical pulses [11][12][13][14][15][16][17][18] . From there, it has been possible to identify the main physical mechanisms responsible for the cooling of the excited electron: immediately after the optical excitation, a non-equilibrium carrier population is put into the conduction band with the same spectral distribution of the excitation pulse.…”

Section: Introductionmentioning

confidence: 99%

Effect of high-optical excitation on the ultrafast electron dynamics in stacked-monolayer graphene samples

Castañeda

Rosa

Gomes³

et al. 2016

SPIE Proceedings

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We report on transient absorption experiments performed at high optical excitation fluences and used to study the ultrafast dynamics in graphene. We employed a degenerated scheme of pump and probe at 800 nm (1.55 eV). The time resolution of our measurements was limited by the pulse duration ~ 100 fs. The samples were prepared by chemical vapor deposition (CVD) as single-layers on silica and, then staked layer-by-layer in order to make a stack of up to 5 graphene monolayers. We observed saturable absorption (SA) and fluence-dependent relaxation times. We see that the ultrafast carrier dynamics is composed by two decay mechanisms, one with response time of about 200 fs and a slower process of about 1 ps. The fast decay, due to both carrier-carrier and carrier-optical phonon scattering, becomes slower when the density of excited carrier was increased. We implemented a theoretical model and found that both the optical phonon rate emission and the optical phonon lifetime are affect by the pump fluence.

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Layer number dependence of carrier lifetime in graphenes observed using time-resolved mid-infrared luminescence

Cited by 7 publications

References 23 publications

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

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

Suppression of supercollision carrier cooling in high mobility graphene on SiC( 0001¯ )

Effect of high-optical excitation on the ultrafast electron dynamics in stacked-monolayer graphene samples

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