1. Key Laboratory for Advanced Materials Processing Technology; Ministry of Education of China; State Key Laboratory of Tribology; Department of Mechanical Engineering; Tsinghua University; Beijing 100084 P. R. China
2. Department of Chemistry; Tsinghua University; Beijing 100084 P. R. China
3. Laser Micro/Nano-Fabrication Laboratory; Beijing Institute of Technology; Beijing 100081 P. R. China
4. School of Chemistry and Chemical Engineering; Beijing Institute of Technology; Beijing 100081 P. R. China