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

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Proceedings of SPIE - The International Society for Optical Engineering
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Castaneda J.A.
Guimaraes Rosa H.
Gomes J.C.V.
De Souza E.A.T.
De Brito-Cruz C.H.
Fragnito H.L.
Padilha L.A.
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© 2016 SPIE.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.
Assuntos Scopus
Chemical vapor depositions (CVD) , Fluences , Optical phonon scattering , Saturable absorption , Saturation absorption , Ultra-fast spectroscopies , Ultrafast carrier dynamics , Ultrafast electron dynamics
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