Affiliation: | (1) Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 1 Nanyang Walk, Block 5, 637616 Singapore, Singapore;(2) School of Materials Science and Engineering, Nanyang Technological University, 1 Blk N4.1, 50 Nanyang Avenue, 639798 Singapore, Singapore;(3) Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore, Singapore;(4) National University of Singapore Nanoscience and Nanotechnology Initiative, Blk S13, Science Drive 3, 117542 Singapore, Singapore;(5) Institute of Advanced Materials (IAM), Fudan University, 220 Handan Road, Shanghai, 200433, P.R. China; |