1. Key Laboratory of Photoelectronic/Electrophotonic Conversion MaterialsKey Laboratory of Cluster ScienceMinistry of Education of ChinaSchool of Chemistry and Chemical EngineeringBeijing Institute of Technology Beijing 100081 P. R. China
2. State Key Laboratory of Nonlinear MechanicsInstitute of MechanicsChinese Academy of Sciences Beijing 100190 P. R. China
3. Laser Micro‐/Nano‐Fabrication LaboratorySchool of Mechanical EngineeringBeijing Institute of Technology Beijing 100081 P. R. China
4. Key Laboratory for Adv. Mater. Processing TechnologyMinistry of Education of ChinaState Key Laboratory of TribologyDepartment of Mechanical EngineeringTsinghua University Beijing 100084 P. R. China
5. Department of ChemistryTsinghua University Beijing 100084 P. R. China