▎ 摘　　要

Graphene has attracted much interest for its potential applications due to its unique band structure. Although much work with graphene has recently been conducted in the time domain, questions about how the electronic properties of graphene behave in the vicinity of the linearly dispersive region remain. In this experiment, the authors use the technique of time-resolved photoemission to directly measure quasiparticle lifetimes. The results are in qualitative agreement with the predictions of a tight-binding model where lifetime is evaluated from the imaginary part of the electron self-energy. The results indicate that the excited carriers decay faster at higher excitation energies-an effect the authors attribute to increasing phase space for electron-electron and electron-phonon interactions for energies away from the Dirac point. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4715440]