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HL: Fachverband Halbleiterphysik

HL 26: Ultra-fast phenomena

HL 26.3: Vortrag

Mittwoch, 14. März 2018, 10:00–10:15, EW 202

Ultrafast quasi-particle dynamics in graphene nanoribbons. — •Raphael German, Jingyi Zhu, Boris Senkovskiy, Alexander Grüneis, and Paul H.M. van Loosdrecht — II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

The opening of a bandgap in one-dimensional graphene nanoribbons paves the road toward carbon based optical applications. Here, we report on a study of the optical dynamics in N=7 armchair graphene nanoribbons (7-AGNR) using steady state and time-resolved spontaneous Raman spectroscopy. The Raman spectra show a strong resonance behavior for excitation energies around 2.2 eV, which is interpreted as an excitonic Raman resonance. We use the resonant enhancement to study both the phonon as well as the exciton population dynamics in 7-AGNRs. The observed lifetime of the D and G phonons is found to be limited to about 2 ps due to optical-acoustical phonon scattering. The exciton population dynamics shows a multi-exponential decay which is interpreted in terms of the presence of an inhomogeneous distribution of defect bound excitons and dark states.