1. Department of Materials and Optoelectronic science National Sun Yat‐sen University Kaohsiung 80424 Taiwan
2. Department of Materials Science and Engineering National Chiao Tung University Hsinchu 30010 Taiwan
3. Computer, Electrical, and Mathematical Sciences and Engineering Division King Abdullah University of Science and Technology (KAUST) Thuwal 23955‐6900 Saudi Arabia
4. Center for Condensed Matter Sciences and Center of Atomic Initiative for New Materials National Taiwan University Taipei 10617 Taiwan
5. Department of Physics Chung Yuan Christian University Chung‐Li Jhongli 32023 Taiwan
6. National Synchrotron Radiation Research Center Hsinchu 30076 Taiwan
7. Institute of Atomic and Molecular Sciences Academia Sinica Taipei 10617 Taiwan
8. Department of Physics and Astronomy Clemson Nanomaterials Institute Clemson University Clemson 29634‐0978 USA
9. Department of Materials Science and Engineering Northwestern University Evanston IL 60208 USA