1. Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan
2. Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan
3. Taiwan Semiconductor Research Institute, Hsinchu 30078, Taiwan
4. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
5. Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan