1. Advanced Photonics Research Institute (APRI), Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea
2. GIST Advanced Institute of Instrumental Analysis (GAIA), Electron Microscopy Laboratory, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea
3. School of Materials Science and Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea