1. School of Information and Communication; Gwangju Institute of Science and Technology (GIST); Korea
2. School of Materials Science and Engineering; Gwangju Institute of Science and Technology (GIST); Korea
3. Korean Photonics Technology Institute; Gwangju 500-712 Korea
4. Department of Materials Science and Engineering; KAIST; Daejeon 305-701 Korea
5. Center for Nanomaterials and Chemical Reactions; Institute for Basic Science; Daejeon 305-701 Korea
6. Department of Nanobio Materials and Electronics; Gwangju Institute of Science and Technology (GIST); Korea
7. Department of Electrical and Computer Engineering; Applied Research Center; Old Dominion University; Newport News VA 23606 USA