1. Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
2. Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
3. Center for Condensed Matter Sciences, Center of Atomic Initiative for New Materials, National Taiwan University, Taipei 106, Taiwan
4. Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan