1. Institute for Superconducting and Electronic Materials University of Wollongong Wollongong 2500 Australia
2. School of Physics and Electronics Hunan University Changsha 410082 P. R. China
3. Department of Materials Science and Engineering South University of Science and Technology of China 1088 Xueyuan Blvd Shenzhen 518055 P. R. China
4. Materials Science and Engineering Program & Texas Materials Institute The University of Texas at Austin Austin TX 78712 USA