* Corresponding authors

^a Metallurgical Engg. and Material Sciences, Indian Institute of Technology Indore, India
E-mail: sens@iiti.ac.in

^b Department of Physics, Indian Institute of Technology Indore, India

^c Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai, India

^d Amity Institute of Nanotechnology, Noida, U.P., India

^e Institute of Nano Science and Technology, Mohali, Punjab, India

^f Department of Physics, Miami University, Oxford, Ohio 45056, USA

^g Electronic Engg., Ming Chi University of Technology, New Taipei City, Taiwan
E-mail: biring@mail.mcut.edu.tw