[1] Univ Teknol MARA, Inst Sci, Ctr Nanosci & Nanotechnol, NANO SciTech Ctr, Shah Alam 40450, Selangor, Malaysia
[2] Univ Teknol MARA, Fac Elect Engn, NANO Elect Ctr, Shah Alam 40450, Selangor, Malaysia
[3] Univ Sains Malaysia, Sch Phys, NOR, Pulau 11800, Pinang, Malaysia
[4] Univ Malaya, Dept Phys, Kuala Lumpur 50603, Malaysia