1. a Faculty of Resource Science and Technology , Universiti Malaysia Sarawak , 94300 Kota Samarahan, Sarawak, Malaysia
2. b Faculty of Science and Mathematics , Universiti Pendidikan Sultan Idris , 35900 Tanjong Malim, Perak, Malaysia
3. c Oxford Diffraction Ltd. , 10 Mead Road, Oxford Industrial Park, OX5 1QU, UK