1. Department
of Electronic Engineering and Materials Science and Research Technology
Center, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong
SAR, China
2. Siyuan
Laboratory, Department of Physics, Jinan University, Guangzhou, Guangdong, P. R. China
3. Instrumental Analysis & Research Center, Sun Yat-sen University, Guangzhou 510275, P. R. China