1. Department of Physics and Materials Science
2. City University of Hong Kong
3. Hong Kong SAR, P. R. China
4. Shandong Academy of Sciences
5. Jinan 250014, P. R. China
6. Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
7. Ministry of Education
8. Shandong University
9. Jinan 250061, P. R. China