1. Department of Materials Science and Engineering, Yonsei University, Shinchon-Dong 134, Seodaemun-Gu, Seoul 120-749, Korea
2. R&D 4 Team, LGDISPLAY Co., Ltd., 1007 Deogeun-Ri, Wollong-Myeon, Paju-Si, Gyeonggi-Do 413-811, Korea
3. Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, 864-1 Yiui-Dong, Yeongtong-Gu, Suwon, Kyonggi-Do 443-270, Korea
4. Center for Intelligent Nano-Bio Materials and Division of Nano Science (BK21), Ewha Womans University, 11-1 Daehyun-Dong, Seodaemun-Gu, Seoul 120-750, Korea