Observation of Nanosecond Hot Carrier Decay in Graphene.

An extremely long decay time of hot carriers in graphene at room temperature was observed for the first time by monitoring the photoinduced thermionic emission using a highly sensitive time-of-flight angle-resolved photoemission spectroscopy method. The emission persisted beyond 1 ns, two orders of magnitude longer than previously reported carrier decay. The long lifetime was attributed to the excitation of image potential states at very low laser fluencies.