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nATuRE CommunICATIons | 3:646 | DoI: 10.1038/ncomms1656 | www.nature.com/naturecommunications 2012 Macmillan Publishers Limited. All rights reserved.
 

Summary: ARTICLE
nATuRE CommunICATIons | 3:646 | DoI: 10.1038/ncomms1656 | www.nature.com/naturecommunications
© 2012 Macmillan Publishers Limited. All rights reserved.
Received 12 Apr 2011 | Accepted 21 Dec 2011 | Published 31 Jan 2012 DOI: 10.1038/ncomms1656
Graphene, a two-dimensional layer of carbon atoms, is a promising building block for a wide
range of optoelectronic devices owing to its extraordinary electrical and optical properties,
including the ability to absorb ~2% of incident light over a broad wavelength range. While the
RC-limited bandwidth of graphene-based photodetectors can be estimated to be as large as
640GHz, conventional electronic measurement techniques lack for analysing photocurrents
at such frequencies. Here we report on time-resolved picosecond photocurrents in freely
suspended graphene contacted by metal electrodes. At the graphene­metal interface, we
demonstrate that built-in electric fields give rise to a photocurrent with a full-width-half-
maximum of ~4ps and that a photothermoelectric effect generates a current with a decay
time of ~130ps. Furthermore, we show that, in optically pumped graphene, electromagnetic
radiation up to 1THz is generated. our results may prove essential to build graphene-based
ultrafast photodetectors, photovoltaic cells and terahertz sources.
1 Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4a, 85748 Garching, Germany. 2 Research Center
for Exotic Nanocarbons, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano-shi 380-8553, Japan. 3 Department of Mechanical and
Materials Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, USA. 4 Institut für Experimentelle und Angewandte Physik, Universität
Regensburg, D-93040 Regensburg, Germany. 5 Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland. Correspondence and requests for

  

Source: Ajayan, Pulickel M. - Department of Mechanical Engineering and Materials Science, Rice University

 

Collections: Materials Science