1. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, Dresden D-01328, Germany
2. Technische Universität Dresden, Dresden D-01062, Germany
3. State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, P. R. China
4. Key Laboratory of Novel Materials for Sensor of Zhejiang Province, Institute of Advanced Magnetic Materials, Hangzhou Dianzi University, Hangzhou 310018, P. R. China
5. Department of Applied Physics, Aalto University School of Science, Aalto FI-00076, Finland
6. College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China