1. Department of Physics, National Taiwan University, Taipei 106, Taiwan
2. Department of Physics, National Central University, Chung-Li 320, Taiwan
3. Molecular Science and Technology Program, Taiwan International Graduate Program, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 115, Taiwan
4. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 115, Taiwan
5. Nanoscience and Nanotechnology Program, Taiwan International Graduate Program, Institute of Physics, Academia Sinica, Taipei 106, Taiwan
6. Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan
7. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
8. Advanced Research Centre for Green Materials Science and Technology, National Taiwan University, Taipei 10617, Taiwan