1. Institute of Optoelectronic Material and Technology
2. South China Normal University
3. Guangzhou 510631
4. P. R. China
5. School of Natural Sciences (SNS)
6. National University of Sciences and Technology (NUST)
7. H-12 Islamabad
8. Pakistan
9. Institute of Applied Physics and Materials Engineering
10. University of Macau
11. China
12. Department of Physics
13. The University of Hong Kong
14. Hong Kong
15. People's Republic of China