1. School of Microelectronics and State Key Laboratory for Mechanical Behavior of Materials; Xi'an Jiaotong University; Xi'an 710049 China
2. College of Precision Instrument and Optoelectronic Engineering; Tianjin University; Key Laboratory of Optoelectronic Information and Technology (Ministry of Education); Tianjin 300072 China
3. State Key Laboratory for Mechanical Behavior of Materials and School of Materials Science and Engineering; Xi'an Jiaotong University; Xi'an 710049 China
4. State Key Laboratory of New Ceramics and Fine Processing & School of Materials Science and Engineering; Tsinghua University; Beijing 100084 China
5. Frontier Institute of Science and Technology; Xi'an Jiaotong University; Xi'an 710049 China
6. Center for Integrated Nanotechnologies (CINT); Los Alamos National Laboratory; Los Alamos NM 87545 USA
7. State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology; School of Microelectronics; Xidian University; Xi'an 710071 China
8. Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons; Forschungszentrum Jülich; D-52425 Jülich Germany