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LL2.03 - Molecular Functionalization of Exfoliated Graphene and Transferred CVD Graphene 
Date/Time:
April 22, 2014   11:00am - 11:15am
 
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C 
 
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Monolayer graphene, single-atom sheets of carbon atoms arranged in a honeycomb pattern is an attractive candidate due to its high transparency (97.7%) and flexibility. However the intrinsic sheet resistance of graphene (~ 6.5 kilo-ohms per square) is two orders of magnitude too high for transparent electrode applications. Further, the sensitivity of the electrical properties of monolayer graphene to ambient adsorbates or organic processing residue (from transfer or patterning) represents a serious obstacle to exploitation of this novel nanomaterial. Molecular functionalization offers a route to overcome these difficulties, through passivation and/or controlled adsorbate doping via charge transfer. We report a systematic study of molecular functionalization of graphene comprising optical microscopy, atomic force microscopy, scanning electron microscopy, Raman spectroscopy, together with initial electrical characterization results of as-fabricated and post-functionalized graphene field-effect devices. Candidate molecules screened included both p-dopants and n-dopants and deposition techniques include evaporation, spin-coating and drop-casting.Initial data on exfoliated graphene indicate that films formed by evaporation of small molecules, e.g. tetracyanoquinodimethane (TCNQ, a p-dopant) grow by nucleation and coalescence of ultra-thin islands (< 2 nm layer thicknesses). Efficient coupling between TCNQ and graphene is evidenced by molecular signatures observed in Raman data acquired from ultra-thin films deposited on both exfoliated graphene and graphene grown using chemical vapor deposition (CVD) on copper foil. Initial data from micron-scale field-effect devices fabricated from CVD graphene show net p-doping after evaporation of TCNQ, albeit with reduced mobility (ie increased sheet resistance). This work was supported by the European Commission under the FP7 project GO-NEXTs (309201), and by the Irish Government HEA PRTLI programmes (INSPIRE & TYFFANI)
 


 
 
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