1. Department of Electrical and Electronic Engineering, College of Technology, University of Buea, P.O. Box 63, Buea, Cameroon
2. Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005, India
3. Department of Physics, Faculty of Science, University of Ngaoundere, P.O. Box 454, Ngaoundere, Cameroon
4. Laboratory of Analysis, Simulation and Test, University of Ngaoundere, P.O. Box 455, Ngaoundere, Cameroon
5. Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India