1. School of Electrical Engineering,
WCU on Flexible Nanosystems, Korea University, Seoul 136-713, Korea
2. Institute of Applied Physics
and INCH, University of Hamburg, 20355
Hamburg, Germany
3. Division
of Quantum Phases and
Device, School of Physics, Konkuk University, Seoul 143-701, Korea
4. Department of Physics and Graphene
Research Institute, Sejong University,
Seoul 143-747, Korea