1. Department of Physics National Taiwan University Taipei 10617 Taiwan
2. Advanced Research Center for Green Materials Science and Technology National Taiwan University Taipei 10617 Taiwan
3. Department of Physics and Center for Nanotechnology Chung Yuan Christian University Chung‐Li 32023 Taiwan
4. Department of Optoelectric Physics Chinese Culture University Taipei 11114 Taiwan
5. Department of Chemistry National Taiwan University Taipei 10617 Taiwan
6. Nano‐Science and Technology Program, Taiwan International Graduate Program, Institute of Physics Academia Sinica Taipei 10617 Taiwan