1. Department
of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
2. Center
for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan
3. Department
of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
4. Institute
of Electronics Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
5. National Synchrotron
Radiation Research Center, Hsinchu 30076, Taiwan