Institution: | 1. Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC;2. Department of Applied Physics, National Pingtung University of Education, Pingtung 900, Taiwan, ROC;3. Department of Physics, National Kaohsiung Normal University, No. 62, Shenjhong Rd., Yanchao District, Kaohsiung City 824, Taiwan, ROC |