[1] Chaudhary Charan Singh Univ, Dept Phys, Meerut 250004, Uttar Pradesh, India
[2] IIT Roorkee, Dept Phys, Roorkee 247667, Uttar Pradesh, India
[3] IIT Roorkee, Nanosci Lab, Inst Instrumentat Ctr, Roorkee 247667, Uttar Pradesh, India
[4] Univ Delhi, ARSD Coll, Dept Phys, New Delhi 110021, India