1. Center for Opto-Electronic Materials and Devices; Korea Institute of Science and Technology; Hwarangno 14-gil 5 Seongbuk-gu Seoul 136-791 Republic of Korea
2. Division of Nano & Information Technology; KIST School; Korea University of Science and Technology; Hwarangno 14-gil 5 Seongbuk-gu Seoul 136-791 Republic of Korea
3. Creative Research Center for Graphene Electronics; Electronics and Telecommunications Research Institute; Gajeong-ro 218 Yuseong-gu Daejeon 305-700 Republic of Korea
4. KHU-KIST Department of Converging Science and Technology; Kyung Hee University; Seoul 02447 Republic of Korea