Investigation Of Electronic Transport Properties For Graphene Nanoribbons And Three-Dimensional Graphene/Carbon Nanotube Composite Structure

Graphene nanoribbons such as a novel carbon-nanomaterials has some special performance due to its nanometer scale, and can adjust its electronic transport properties by controlling the geometry or doped. This means that graphene nanoribbons has important implications for research and production of the next generation of new nano-electronic devices.In this paper, we combined with density functional theory and non-equilibrium Green’s function method to simulate and compute electron transport properties of nanostructure systems. We studied the following nanostructures: different chiral graphene nanoribbons, cross graphene nano-junction and graphene / carbon nanotube composite three-dimensional structure. And electronic transport properties of this three structure were modeling, calculating and analysing, have the following conclusions:1. Graphene nanoribbons with the perfect boundary: Zigzag GNR is a metallic structure and Armchair GNR is a semiconducting structure, which is consistent with the analysis of the theoretical model; Changes in the width of the graphene nanoribbons not only affect the current suppression interval width and conductivity of metallic graphene nanoribbons, but also directly affect the amplitude of cutoff voltage and the current strength of the semiconducting graphene nanoribbons; And the study of nitrogen doping case found that there are significant changes in bandgap after doping from metal to semiconductor properties. While the electronic density of states and transmission coefficients near the Fermi level have significantly reduced, thus the electron transport properties have a various kinds of reduction.2. Cross grapheme nano-junction: With the arms of this structure, it destroyed the original electron transporting channel at the edge of the structure, and increased several electron tunneling channel. Namely with the quantum size effect and quantum interference effects, its electron transport capacity is significantly less than Zigzag GNR; For undoped cross nanostructure it showed some metallic properties, but with the arm width, height and asymmetry varied, the transmission spectral line has a clear oscillation; Since the doped nitrogen atom intensified electron scattered, so that the electron transport properties decreased and the phenomenon of negative resistance emerged in certain bias range.3. Three-dimensional graphene / carbon nanotube composite structure: Two types of the three-dimensional composite structures have some metallic properties; The hole type of the G16-C60 composite structure will appear the phenomenon of negative resistance between +1.5 and + 2.0V bias voltage; The plane type of G16-C60 and G16-C66 composite structure will appear the phenomenon of current suppression in multiple bias voltage; With the depression plane, the aperture of carbon nanotubes and the area of depression plane varied, it will make electron tunneling channel increased and oscillation intensified; The G16-C66 composite structure has a greater electronic density of states than the G16-C60 composite structure.