1. Department of Chemistry, National Taiwan University, Taipei 106, Taiwan,
2. Department of Materials Science and Engineering, Hongik University, Seoul 121-791, Korea
3. Green Energy & Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 300, Taiwan
4. Institute of Atomic & Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
5. National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
6. Department of Physics, National Taiwan University, Taipei 106, Taiwan