1. School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore
2. School of Material Science and Engineering, Nanyang Technological University, 639798, Singapore
3. CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, Nanyang Technological University, 637371, Singapore
4. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin150001, P. R. China
5. School of Electronics and Information Engineering, Sichuan University, Chengdu, Sichuan610064, P. R. China
6. School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore