1. Beijing
National Center for Electron Microscopy, The State Key Laboratory
of New Ceramics and Fine Processing, Laboratory of Advanced Materials,
School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
2. Center
for Advancing Materials Performance from the Nanoscale (CAMP-Nano)
and Hysitron Applied Research Center in China (HARCC), State Key Laboratory
for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China