Myoung-Jun Cha

Homogeneous and stable p-type doping of graphene by MeV electron beam-stimulated hybridization with ZnO thin films

In this work, we demonstrate a unique and facile methodology for the homogenous and stable p-type doping of graphene by hybridization with ZnO thin films fabricated by MeV electron beam irradiation (MEBI) under ambient conditions. The formation of the ZnO/graphene hybrid nanostructure was attributed to MEBI-stimulated dissociation of zinc acetate dihydrate and a subsequent oxidation process. A ZnO thin film with an ultra-flat surface and uniform thickness was formed on graphene. We found that homogeneous and stable p-type doping was achieved by charge transfer from the graphene to the ZnO film.

Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

Abstract We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G). Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication.

Formation of uniformly sized gold nanoparticles over graphene by MeV electron beam irradiation for transparent conducting films

Highly flexible, transparent, and conducting sheet was fabricated by decoration of uniformly sized gold nanoparticles (Au NPs) with high-density on large-area graphene by MeV electron beam irradiation (MEBI) at room temperature under ambient conditions. The Au NPs with an average size of 13.6 ± 3.5 nm were clearly decorated on the graphene after MEBI with an irradiation energy of 1.0 MeV. The sheet resistances of the Au NPs/graphene significantly decreased. For the Au NPs/trilayer graphene, the sheet resistance reached to ∼45 Ω/sq, and the optical transmittance was ∼90.2% which is comparable to that of conventional indium tin oxide film.

Long-term air-stable n-type doped graphene by multiple lamination with polyethyleneimine

We demonstrate homogeneous and air-stable n-type doping of graphene grown by thermal chemical vapor deposition. Laminated Polyethyleneimine (PEI) layers fabricated by a simple polymer solution coating were employed. The doping stability of multiple laminated structures (graphene/PEI, PEI/graphene, and graphene/PEI/graphene) was systematically investigated. The resulting graphene/PEI/graphene laminated structure was highly stable in air. Moreover, the work function and carrier concentration of doped graphene can be tuned by altering the laminated structure.

P-Type Doping of Graphene Films by Hybridization with Nickel Nanoparticles

Here, we demonstrate the decoration of Ni nanoparticles (NPs) on graphene films by simple annealing for p-type doping of graphene. Scanning electron microscopy and atomic force microscopy revealed that high-density, uniformly sized Ni NPs were formed on the graphene films. The density of the Ni NPs increased gradually, whereas the size of the Ni NPs decreased with increasing NiCl26H2O solution concentration. The formation of Ni NPs on graphene films was explained by heat-driven dechlorination and subsequent nano-particlization, as investigated by X-ray photoelectron spectroscopy. The doping effect of Ni NPs onto graphene films was verified by Raman spectroscopy and electrical transport measurements. This method may provide a facile and universal way to obtain metal NPs on graphene if the metal forms a compound with Cl.