1. Graduate School of Engineering, Osaka University, 2-1
Yamada-Oka, 565-0871 Suita, Osaka, Japan
2. Department of Materials
Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC
3. Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
4. Department of Physics, Tamkang University, Tamsui 251, Taiwan, ROC