1. Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern Polytechnical University, Xi’an, China
2. Department of Materials Forming and Control Engineering, School of Materials, Northwestern Polytechnical University, Xi’an, China
3. Key Laboratory of Physical Electronics and Devices of Ministry of Education, School of Electronic Science and Engineering, Xi’an Jiaotong University, Xi’an, China