1. Department of Microelectronic Science and Engineering Ningbo University Ningbo 315211 China
2. School of Materials Science and Engineering Ningbo University of Technology Ningbo 315000 China
3. The Institute of Technological Sciences Wuhan University Wuhan 430072 P. R. China
4. State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai 200240 China
5. School of Physics and Technology Wuhan University Wuhan 430072 P. R. China