1. Hefei Innovation Research Institute, School of Microelectronics Beihang University Hefei 230013 P. R. China
2. National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230029 P. R. China
3. Division of Machine Elements, Luleå University of Technology Luleå 97187 Sweden
4. Applied Physics, Division of Materials Science, Department of Engineering Sciences and Mathematics Luleå University of Technology Luleå 97187 Sweden
5. College of Physics and Optoelectronic Engineering Shenzhen University Shenzhen 518060 China