Hot electrons in carbon - graphite behaves like a semiconductor

Scientists at the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy in Berlin, Markus Breusing, Claus Ropers and Thomas Elsässer, have now studied the behavior of electrons in thin crystalline graphite layers in real time. As reported in the journal Physical Review Letters (Vol. 102, Issue 08, 086809 / 1-4, 2009), they recorded the movements of the electrons with an unprecedented time resolution of 10 femtoseconds (one femtosecond is one millionth of a billionth of a second) , To do so, they excited electrons with ultrashort laser pulses into high-energy states and observed their return to equilibrium. Individual steps in this process can be separated in time and thus determine the instantaneous distribution of the electrons to different states. Within 30 femtoseconds, the electrons emit a hot gas with an extremely high temperature of 2500 ° C, which cools down to about 200 ° C within only 500 femtoseconds. The released energy is transferred to the crystal lattice. Thereafter, the electrons return to their original states on a much slower time scale. For the first time, these studies clearly show that graphite behaves on ultrashort timesheets like a semiconductor, such as silicon or gallium arsenide, rather than a metal.
More information: Press release Forschungsverbund