1. College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China
2. Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, P. R. China
3. Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, P. R. China
4. Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, P. R. China