1. Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan
2. Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan
3. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 31013, Taiwan
4. Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 31040, Taiwan