1. Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
2. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
3. Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
4. Department of Electrical Engineering, Yuan Ze University, Taoyuan 32003, Taiwan
5. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan