1. Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
2. Department of Physics, National Taiwan University, Taipei 10617, Taiwan
3. Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan
4. Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
5. Department of Mathematics and Science (Pre-college), National Taiwan Normal University, New Taipei City 24449, Taiwan
6. Department of Physics, Tamkang University, New Taipei City 25137, Taiwan