1. Department of Physics, Center for Nanotubes and Nanostructured Composites, Sungkyunkwan University Advanced Institute of NanoTechnology, Sungkyunkwan University, Suwon 440-746, Republic of Korea, BK-21 Polymer BIN Fusion Research Team, Research Center of Industrial Technology, Chonbuk National University, Chonju, Chonbuk 560-756, Korea, and Korea Research Institute of Standards and Science (KRISS), Yuseung-Gu, Daejeon 305-600, Korea