1. Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2. Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
3. Hsinchu Chien Kung Senior High School, Hsinchu 300046, Taiwan
4. Faculty of Science, University of the Ryukyus,1 Senbaru, Nishihara, Okinawa 903-0213, Japan