1. Graduate Institute of Opto-Mechatronics, National Chung Cheng University, 168 University Road, Min-Hsiung Township, Chiayi County, Taiwan 62102
2. Department of Material Science and Engineering, National Cheng Kung University, Tainan, Taiwan 70101
3. Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan 31040
4. Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan 10617