1. Department
of Physics, National Cheng Kung University, Tainan, 701, Taiwan
2. National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
3. Advanced
Optoelectronic Technology Center, National Cheng Kung University, Tainan, 701, Taiwan
4. Taiwan
Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 106, Taiwan
5. Centre for
Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546, Singapore
6. Department
of Physics, National University of Singapore, 2 Science Drive 3, 117546, Singapore
7. Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
8. Institute
of Physics, Academia Sinica, Taipei 11529, Taiwan
9. Department
of Physics, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan
10. School
of Materials Science and Engineering and Anhui Provincial Key Laboratory
of Advanced Functional Materials and Devices, Hefei University of Technology, Hefei 230009, People’s Republic of China