1. Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan,
Republic of China
2. Materials
Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
3. Department of Physics, Tamkang University, New-Taipei 251, Taiwan, Republic of China
4. Crystal Growth Centre, Anna University, Chennai 600 025, India