1. School of Materials Science and Engineering; Zhejiang University; Hangzhou 310027 P. R. China
2. State Key Laboratory of Silicon Materials; Hangzhou 310027 P. R. China
3. School of Information Science and Electronic Engineering; Zhejiang University; Hangzhou 310027 P. R. China
4. Laboratory of Glasses and Ceramics; Institute of Chemistry; CNRS-Université de Rennes I; Campus de Beaulieu 35042 Rennes Cedex France