Deepak Pandey

Large-scale graphitic thin films synthesized on Ni and transferred to insulators: Structural and electronic properties

We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO2/Si substrates. Films of size up to several mm’s have been synthesized. Structural characterizations by atomic force microscopy, scanning tunneling microscopy, cross-sectional transmission electron microscopy (XTEM), and Raman spectroscopy confirm that such large-scale graphitic thin films (GTF) contain both thick graphite regions and thin regions of few-layer graphene. The films also contain many wrinkles, with sharply-bent tips and dislocations revealed by XTEM, yielding insights on the growth and buckling processes of the GTF. Measurements on mm-scale back-gated transistor devices fabricated from the transferred GTF show ambipolar field effect with resistance modulation ∼50% and carrier mobilities reaching ∼2000 cm2/V s. We also demonstrate quantum tra...

Surface Microscopy Characterizations of Large Size Graphene Films Grown by Surface Segregation on Ni and Transferred to Si/SiO2 Substrate

We report surface microscopy characterizations of large size graphene films (up to mm) grown on polycrystalline Ni foils and transferred to Si/SiO2. Wrinkles in such films are studied by both atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Local graphitic lattice structures of the films are imaged with atomic-resolution STM and compared with those of the highly ordered pyrolytic graphite (HOPG).