1. Helmholtz-Zentrum-Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, D-01328 Dresden, Germany
2. Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan
3. Institute of Experimental Physics, Technische Universität Bergakademie Freiberg, Freiberg, Germany
4. Technische Universität Dresden, 01062 Dresden, Germany
5. National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
6. Institute of Physics, Technische Universität, Chemnitz, Germany
7. Institute of Physics, Academia Sinica, Taipei, Taiwan
8. Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan