1. Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
2. Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan
3. Department of Physics and Astronomy, Hunter College of the City University of New York, New York 10065, USA
4. Donostia International Physics Center (DIPC), P de Manuel Lard Izabal, 4, 20018 San Sebastian, Basque Country, Spain
5. Hierachical Green-Energy Materials (Hi-GEM) Research Center, National Cheng Kung University, Tainan 701, Taiwan