1. Department
of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 680-749, Republic of Korea
2. Semiconductor
Physics Research Center, School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea
3. Department
of Nano Science and Technology, SKKU Advanced Institute of Nano Technology
(SAINT), Sungkyunkwan University, 2066 Seobu-ro,
Jangan-gu, Suwon, Gyeonggi-do 440-746 Korea
4. Department
of Materials Engineering, Korea Aerospace University, Seoul 412-791, Republic of Korea