Affiliation: | 1. National Center for Nanoscience and Technology, Beijing 100080 (P.R. China);2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (P.R. China);3. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332‐0245 (USA);4. Institute of Physics, Beijing 100080 (P.R. China) |