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Measurement of ultrafast carrier dynamics in epitaxial graphene Jahan M. Dawlaty,a
 

Summary: Measurement of ultrafast carrier dynamics in epitaxial graphene
Jahan M. Dawlaty,a
Shriram Shivaraman, Mvs Chandrashekhar,
Farhan Rana, and Michael G. Spencer
School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA
Received 29 November 2007; accepted 28 December 2007; published online 30 January 2008
Using ultrafast optical pump-probe spectroscopy, we have measured carrier relaxation times in
epitaxial graphene layers grown on SiC wafers. We find two distinct time scales associated with the
relaxation of nonequilibrium photogenerated carriers. An initial fast relaxation transient in the
70120 fs range is followed by a slower relaxation process in the 0.41.7 ps range. The slower
relaxation time is found to be inversely proportional to the degree of crystalline disorder in the
graphene layers as measured by Raman spectroscopy. We relate the measured fast and slow time
constants to carrier-carrier and carrier-phonon intraband and interband scattering processes in
graphene. 2008 American Institute of Physics. DOI: 10.1063/1.2837539
Graphene is a single two dimensional atomic layer of
carbon atoms forming a honeycomb crystal lattice.1,2
It is a
zero-bandgap semiconductor with a linear energy dispersion
relation for both electrons and holes.2
The unusual electronic

  

Source: Afshari, Ehsan - School of Electrical and Computer Engineering, Cornell University

 

Collections: Engineering