1. Beijing National
Center for Electron Microscopy, School of Materials Science and Engineering,
The State Key Laboratory of New Ceramics and Fine Processing, Laboratory
of Advanced Materials (MOE), Tsinghua University, Beijing 100084, China
2. Center for Advanced Materials and Nanotechnology,
Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
3. Department of NanoEngineering, Program
of Materials Science and Engineering, University of California, San Diego, La Jolla, California 92093, United States