Study of ultrafast dynamics in graphene by using high-order haromonic photoelectron spectroscopy

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To clarify ultrafast relaxation dynamics in high quality and large-area graphene which is grown on a silicon carbide substarate by sublimating silicon, we have developed femtosecond time-resolved surface photoelectron spectroscopy based on a high-order harmonics source. By using this system, we clarified the surfce transport of photoexcited electron and hole on a semiconductor surface, thus showing the potential of this system for measuring ultrafast relaxation dynamics in graphene. We have also studied the surface-enhanced Raman scattering (SERS)of graphene grown on SiC by depositing Ag. The enhancement of the Raman spectrum in graphene reached more than 60. Moreover, we have successfully estimated a electron dephasing time of monolayer graphene to be approxiamtely 50 fs by using a time-resolved transient diffraction technique.