**Author details**

S. Mukherjee1,2, T. H. Kao1 , H. C. Wu1 , K. Devi Chandrasekhar1 and H. D. Yang1\*

\*Address all correspondence to: yang@mail.nsysu.edu.tw

1 Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, Taiwan

2 UGC-DAE Consortium for Scientific Research, Mumbai Centre, Bhabha Atomic Research Centre, Trombay, Mumbai, India
