1. Center for Emerging Electric Devices and Systems, Gwangju Institute of Science and Technology, Cheomdan Gwagiro 123, Buk-gu, Gwangju 61005, Korea
2. School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Cheomdan Gwagiro 123, Buk-gu, Gwangju 61005, Korea
3. Departmant of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Cheomdan Gwagiro 123, Buk-gu, Gwangju 61005, Korea