1. Department of Microelectronic Science and Engineering
2. Ningbo University
3. 315211 Ningbo
4. China
5. School of Physical Science and Technology
6. Department of Physics
7. Pukyong National University
8. Busan 608-737
9. South Korea
10. Institute for Advanced Study
11. Shenzhen University
12. Shenzhen 518060
13. College of Physics and Optoelectronics