1. Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor Darul Ehsan, Malaysia
2. Institute of Advanced Technology, Universiti Putra Malaysia, 43400 Serdang, Selangor Darul Ehsan, Malaysia
3. Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor Darul Ehsan, Malaysia
4. Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia