▎ 摘　　要

Hot carrier dynamics in the Dirac band of n-type epitaxial graphene on a SiC substrate were traced in real time using femtosecond-time-resolved photoemission spectroscopy. The spectral evolution directly reflects the energetically linear density of states superimposed with a Fermi-Dirac distribution. The relaxation time is governed by the internal energy dissipation of electron-electron scattering, and the observed electronic temperature indicates cascade carrier multiplication. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.