1. Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
2. Colleage of Semiconductor Research, National Tsing-Hua University, Hsinchu 30013, Taiwan
3. Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
4. Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
5. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
6. Department of Photonics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan