1. Electronic Materials Research Laboratory; Key Laboratory of the Ministry of Education & State Key Laboratory for Mechanical Behavior of Materials; Xi'an Jiaotong University; Xi'an 710049 China
2. Department of Materials Physics; School of Science; Xi'an Jiaotong University; Xi'an 710049 China
3. Electronic Materials Research Laboratory; Key Laboratory of the Ministry of Education; Xi'an 710049 China
4. School of Materials Science and Engineering; Shaanxi University of Science and Technology; Xi'an 710021 China