a
Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology, and Research (A*STAR), 3 Research Link, Singapore 117602
E-mail: sonarp@imre.a-star.edu.sg
b
National University of Singapore, Department of Physics, Lower Kent Ridge Road, Singapore 117542
E-mail: chmcll@nus.edu.sg
c
National University of Singapore, Department of Chemistry, Lower Kent Ridge Road, Singapore 117543
d
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, USA
e
School of Natural Sciences, Shiv Nadar University, Greater Noida, India
f
Microelectronics Research Centre, The University of Texas at Austin, Austin, USA