1. Nanomaterials
and System Lab, Department of Mechatronics Engineering, Jeju National University, Jeju 690-756, Republic of Korea
2. School
of Material Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
3. Research
Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan