1. Department of Chemistry, National Taiwan University, Taipei, Taiwan
2. Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taipei, Taiwan
3. Institute of Physics, Academia Sinica, Taipei, Taiwan
4. Department of Physics, National Taiwan University, Taipei, Taiwan
5. LAAS-CNRS, 7 Avenue du Colonel Roche, F-31077 Toulouse, France
6. Université de Toulouse, F-31077 Toulouse, France