[1] Vel Tech Rangarajan Dr Sagunthala R&D Inst Sci &, Dept Phys, Chennai 600062, Tamil Nadu, India
[2] Vels Inst Sci Technol & Adv Studies VISTAS, Sch Basic Sci, Dept Phys, Chennai 600117, Tamil Nadu, India
[3] Anna Univ, Dept Chem, CEG Campus, Chennai 600025, Tamil Nadu, India
[4] SRMIST, Dept Phys, Vadapalani Campus, Chennai 600026, Tamil Nadu, India
[5] Univ Madras, Natl Ctr Nanosci & Nanotechnol, Chennai 600025, Tamil Nadu, India
[6] C Kandaswami Naidu Coll Men, Dept Phys, Chennai 600102, Tamil Nadu, India
[7] Anna Univ, Ctr Crystal Growth, Chennai 600025, Tamil Nadu, India