1. Key
Laboratory for Micro-Nano Physics and Technology of Hunan Province,
State Key Laboratory of Chemo/Biosensing and Chemometrics, and School
of Physics and Electronics, Hunan University, Changsha 410082, People’s Republic of China
2. SEU-FEI
Nano-Pico Center, Key Lab of MEMS of Ministry of Education, Southeast University, Nanjing 210096, People’s Republic of China
3. Department
of Materials Science and Engineering, Department of Chemistry and
Biochemistry, and California NanoSystems Institute, University of California, Los
Angeles, California 90095, United States