1. Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science; University of Malaya; 50603 Kuala Lumpur Malaysia
2. Department of Chemistry, Faculty of Science; Universiti Putra Malaysia; 43400 UPM Serdang Selangor Malaysia
3. Functional Device Laboratory, Institute of Advanced Technology; Universiti Putra Malaysia; 43400 UPM Serdang Selangor Malaysia