1. Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Malaysia
2. Faculty of Sciences, Technology and Human Development, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Malaysia
3. Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 Serdang, Malaysia