1. Department of Materials Science and Advanced Coatings Research Center of Ministry of Education, Fudan University, Shanghai 200438, P. R. China
2. State Key Laboratory of Mechanical Transmissions/College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, P. R. China
3. Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200438, P. R. China