1. Department of Materials Science and Engineering, Yonsei University, 262 Seongsanno, Seoul 03722, Republic of Korea
2. Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 34133, Republic of Korea
3. Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 34113, Korea
4. Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea