1. Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Xiangtan University, Hunan 411105, China
2. Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan
3. Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
4. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
5. Institute of Physics, Academia Sinica, Taipei 11529, Taiwan