Morphology and quantum transport in defective graphene and at graphene/solid interfaces


David Tománek


Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824, USA * tomanek@pa.msu.edu


Defect-free 2D graphitic carbon combines high strength with structural flexibility and displays extraordinary charge and heat transport properties. Structural defects abound especially in graphene grown by CVD on a lattice mismatched substrate. I will discuss, to what degree specific defects in 2D graphene reduce thermal and electric conductivity by reducing the mean free path of the carriers. Computational results indicate that thermal conductivity suffers even from the presence of 12C/13C isotopic impurities. Even stronger conductivity reduction occurs in sp2 bonded carbon systems, where the hexagon-based honeycomb structure has been replaced by a 2D haeckelite lattice containing pentagons, heptagons and octagons. Monatomic vacancies effectively quench thermal and electrical transport. To best accommodate the lattice mismatch with the substrate, defects are usually not distributed uniformly, but concentrate near graphene grain boundaries. Computer simulations indicate that a periodic arrangement of parallel grain boundaries reduces thermal and electric transport not only normal, but also parallel to these defect lines due to scattering and state quantization. An intriguing alternative way to accommodate lattice mismatch between graphene and substrates like Si(111) and diamond-C(111) benefits from the structural flexibility of graphene. While maintaining the honeycomb lattice, the graphene overlayer may transform to a wavy structure that becomes commensurate and covalently connected to the substrate. The subdivision of the graphene overlayer into detached conductive strips, separated by semiconducting regions, yields intriguing electronic structure and transport properties.

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