Synthesis of Graphene and Carbon Nanotubes Hybrid Nanostructures and Their Electrical Properties

The gapless semimetallic nature of graphene-based nanoelectronics is a major hurdle for the advancement of graphene-based field-effect transistors. Here graphene-carbon nanotubes hybrid nanostructures (Gr-CNTs HNSs) were formed by synthesizing single-walled carbon nanotubes (SWCNTs) with a bandgap on monolayer graphene by thermal chemical vapor deposition. We systematically established optimum conditions for the synthesis of Gr-CNTs HNSs by adjusting catalytic layer formation. The structural features of Gr-CNTs HNSs were investigated by scanning electron microscopy and Raman spectroscopy. The surface morphologies and chemical states of the catalytic films used to optimize Gr-CNTs HNSs synthesis were explored by atomic force microscopy and X-ray photoelectron spectroscopy. In this process, graphene played a role as a barrier to prevent Fe nanoparticles from interdiffusing into Al2O3 layer. Based on these studies, we determined the catalytic structure (Fe/Graphene/Al2O3/SiO2) optimal for growing high-density SWCNTs on monolayer graphene. Electrical transport measurements revealed that Gr-CNTs HNSs exhibited p-type semiconducting behavior with combined properties of graphene and CNTs.