1. College of Mechanical Engineering; Shanghai University of Engineering Science; Shanghai 201620 P. R. China
2. Division of Interfacial Water and Key Laboratory of Interfacial, Physic and Technology; Shanghai Institute of Applied Physics; Chinese, Academy of Sciences, P.O. Box 800-204; Shanghai 201800 P. R. China
3. College of Physics Science and Technology; Yangzhou University; Jiangsu 225009 P. R. China
4. Department of Physics and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education; School of Physics and Technology; Wuhan University; Hubei 430072 P. R. China