* Corresponding authors

^a Department of Physics, College of Science, University of Bahrain, PO Box 32038, Kingdom of Bahrain

^b Department of Physics, Faculty of Science, University 20 Août 1955 of Skikda, N. P. 26, Route d’El-Hadaiek, Skikda 2100, Algeria

^c Laboratory of Surfaces and Interfaces (LESIMS), Department of Physics, Faculty of Science, University Badji Mokhtar, Annaba, Algeria

^d Center of Research Excellence in Nanotechnology (CENT), King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia

^e School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, 2 West Wenhua Road, Weihai 264209, China
E-mail: sy@hitwh.edu.cn

^f Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Technology, Center for Environmental and Energy Nanomaterials, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, P. R. China