[1] Univ Sidi Mohammed Ben Abdellah, Fac Sci Dhar el Mahraz, Lab Solid State Phys Lab, Grp Nanomat & Renewable Energies, POB 1796, Atlas Fez 30000, Morocco
[2] Univ South Africa, Dept Phys, Coll Sci Engn & Technol, Sci Campus,Cnr Christiaan Wet & Pioneer Ave, ZA-1709 Johannesburg, South Africa
[3] Univ South Africa, Africa Graphene Ctr, Dept Phys, Coll Sci Engn & Technol, Sci Campus,Cnr Christiaan Wet & Pioneer Ave, ZA-1709 Johannesburg, South Africa