1. Samsung Advanced Institute of Technology, Samsung Electronics Company, LTD, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-803, Republic of Korea
2. IBS Center for Integrated Nanostructure Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea
3. Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, Zabrze 41-819, Poland
4. IFW Dresden, Institute of Complex Materials, P.O. Box 270116, D-01171 Dresden, Germany
5. Department of Energy Science, Department of Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea