1. State Key Laboratory of Precision Spectroscopy Engineering Research Center for Nanophotonics and Advanced Instrument Ministry of Education Department of Materials School of Physics and Electronic Science East China Normal University Shanghai 200241 P. R. China
2. School of Materials Science and Engineering Zhengzhou University Zhengzhou 450052 P. R. China
3. State Key Lab of Transducer Technology Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 P. R. China