1. Laser Micro/Nano-Fabrication Laboratory School of Mechanical Engineering Beijing Institute of Technology Beijing 10081 P. R. China
2. School of Physics and Materials Science Nanchang University Nanchang 330031 P. R. China
3. Experimental Center of Advanced Materials School of Materials Science & Engineering Beijing Institute of Technology Beijing 10081 P. R. China
4. State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 P. R. China
5. School of Physics and Materials Science Guangzhou University Guangzhou 510006 P. R. China