1. School of Materials Science & Engineering Zhejiang Sci-Tech University Hangzhou 310018 P. R. China
2. State Key Laboratory of Silicon Materials Cyrus Tang Center for Sensor Materials and Applications School of Materials Science and Engineering Zhejiang University Hangzhou 310027 P. R. China
3. Chongqing No.1 Middle School Chongqing 400030 P. R. China