1. Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic SystemsSchool of Materials Science & EngineeringBeijing Institute of Technology Beijing 100081 P. R. China
2. Center for Testing and Analyzing of MaterialsSchool of Materials Science and EngineeringTsinghua University Beijing 100084 P. R. China
3. School of Materials Science and EngineeringBeihang University No. 37 Xueyuan Road, Haidian District Beijing 100191 P. R. China
4. State Key Laboratory of Explosion Science and TechnologyBeijing Institute of Technology Beijing 100081 P. R. China
5. Department of Materials Science and EngineeringCollege of EngineeringPeking University Beijing 100871 P. R. China