Affiliation: | (1) Department of Physics, Bahauddin Zakariya University, Multan, Pakistan;(2) Nanotechnology Research Institute, University of Ulster, Newtownabbey, Ulster, BT37 0QB, Northern Ireland, UK;(3) Department of Physics, University of Salford, Salford, M5 4WT, UK;(4) Birck Nanotechnology Center, College of Technology, Purdue University, 401 North Grant Street, West Lafayette, IN 47907-2021, USA; |