1. Center of Electron Microscopy
and State Key Laboratory of Silicon Materials, Department of Materials
Science and Engineering, Zhejiang University, Hangzhou 310027, China
2. Department of Physics, Applied
Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
3. Department of Electrical Engineering, University of California, Los Angeles, California 90095,
United States