[1] Harbin Inst Technol, Shenzhen Grad Sch, Dept Mat Sci & Engn, Shenzhen 518055, Peoples R China
[2] Rajeev Gandhi Mem Coll Engn & Technol, Dept Phys, Nandyal 518501, Andhra Prades, India
[3] Sri Venkateswara Univ, Dept Phys, Tirupati 517502, Andhra Pradesh, India
[4] Chadalawada Ramanamma Engn Coll, Dept Phys, Renigunta Rd, Tirupati 517506, Andhra Pradesh, India