1. International Ph.D. Program for Science (IPPS), National Sun Yat-sen University, Kaohsiung 80424, Taiwan
2. Department of Physics and Center for Crystal Research, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
3. Department of Applied Physics, National University of Kaohsiung, Kaohsiung 81148, Taiwan
4. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan