1. Department of Physics, National Taiwan University, Taipei 106, Taiwan
2. Nano-Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 106, Taiwan
3. J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Prague 8, Czech Republic
4. Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan
5. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
6. School of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, Pennsylvania 19104, United States