1. Division
of Physics and Applied Physics, School of Physical and Mathematical
Sciences, Nanyang Technological University, Singapore 637371
2. Department
of Mechanical and Aerospace Engineering, School of Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong
3. NOVITAS,
Nanoelectronics Centre of Excellence, School of Electrical and Electronic
Engineering, Nanyang Technological University, Singapore 639798