1. Department of Advanced Materials Chemistry, Korea University, Sejong 339-700, Republic of Korea
2. Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Korea
3. Measurement and Analysis Division, National Nanofab Center (NNFC), Daejeon 305-806, Republic of Korea
4. Gyeongbuk Science & Technology Promotion Center, Gumi Electronics & Information Technology Research Institute, Gumi, 39171, Republic of Korea