1. Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan
2. Taiwan Semiconductor Research Institute, 26, Prosperity Road I, Hsinchu Science Park, Hsinchu 300091, Taiwan
3. National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan
4. Department of Physics, National Tsing Hua University, 101 Section 2, Kuang Fu Road, Hsinchu 300044, Taiwan