1. Quantum Materials & Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu 641 046, India
2. UGC-CPEPA Centre for Advanced Studies in Physics for the Development of Solar Energy Materials and Devices, Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, 641 046, India
3. KPR Institute of Engineering and Technology, Coimbatore, Tamil Nadu, 641 407, India