1. Department of Electronics
and Telecommunications, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
2. School of Physics, Konkuk University, Seoul 143-701, Korea
3. CrayoNano AS, Otto Nielsens
vei 12, NO-7052, Trondheim, Norway
4. Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway