1. Center for Neuromorphic Engineering, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
2. Department of Materials Science & Engineering, Seoul National University, Seoul 08826, Republic of Korea
3. Department of System Semiconductor Engineering, Yonsei University, Seoul 03722, Republic of Korea
4. Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
5. Nanophotonics Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
6. Division of Nanoscience and Technology, Korea University of Science and Technology (UST), Daejeon 34113, Republic of Korea