1. Department of Materials
Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
2. Department
of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
3. Center for
Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
4. Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
5. Institut für Angewandte Photophysik, Technische Universitat Dresden, Dresden 01069, Germany
6. Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
7. Institute
of Physics, Academia Sinica, Taipei 11529, Taiwan
8. Institute of Optoelectronic Science, National Taiwan Ocean University, Keelung 20224, Taiwan