1. Department of Applied Physics, National Pingtung University, No. 4-18, Minsheng Road, Pingtung 90044, Taiwan, R. O. C
2. Division of Physics, Faculty of Science and Technology, Rajamangala University of Technology Thanyaburi, Rangsit-Nakhonnayok Rd. (Klong 6), Thanyaburi Pathum Thani 12110, Thailand
3. Department of Applied Physics, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nanzih District, Kaohsiung 811, Taiwan, R.O.C
4. Institute of Physics CAS, Na Slovance 1999/2, Praha 8, Czech Republic
5. National Synchrotron Radiation Research Center, No. 101, Hsin-Ann Road, Hsinchu 30013, Taiwan, R. O. C