1. Department of Physics, Research Institute for Biomimetics and Soft Matter, Jiujiang Research Institute and Fujian Provincial Key Laboratory for Soft Functional Materials Research, Xiamen University 1 , Xiamen 361005, People’s Republic of China
2. Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong 2 , Shatin, N.T., Hong Kong 999077, People’s Republic of China
3. Department of Physical Chemistry, School of Chemistry, Tel Aviv University 3 , Tel Aviv 6997801, Israel
4. NTNU Nanomechanical Lab, Norwegian University of Science and Technology (NTNU) 4 , Trondheim 7491, Norway
5. College of Physical Science and Technology, Bohai University 5 , Jinzhou 121013, People’s Republic of China