1. Department of Material Science & Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2. International College of Semiconductor Technology, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
3. Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States
4. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan