1. State Key Laboratory of Silicon Materials and School of Materials Science and Engineering Zhejiang University Hangzhou 310027 P. R. China
2. State Key Laboratory of Silicon Materials and Department of Physics Zhejiang University Hangzhou 310027 P. R. China
3. School of Materials Science and Engineering Jingdezhen Ceramic Institute Jingdezhen Jiangxi 333403 P. R. China