1. School
of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
2. Department
of Applied Physics, Chongqing University, Chongqing 400044, China
3. Department
of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan
4. Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, National Center for Nanoscience and Technology (NCNST), Beijing 100083, P. R. China