(142c) Electronic and Mechanical Properties of Hydrogenated Irradiated and Amorphous Graphene

Authors: 
Weerasinghe, A., University of Massachusetts Amherst
Maroudas, D., University of Massachusetts Amherst
Ramasubramaniam, A., University of Massachusetts Amherst

                                                                                         

Electronic and Mechanical Properties of

Hydrogenated Irradiated and Amorphous Graphene

Asanka Weerasinghe,(1) Ashwin Ramasubramaniam,(2) and Dimitrios Maroudas(3)

(1)Department of Physics, University of Massachusetts, Amherst

(2)Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst

(3)Department of Chemical Engineering, University of Massachusetts, Amherst

Defect engineering and chemical functionalization of graphene are promising routes for fabrication of carbon nanostructures and two-dimensional metamaterials with unique properties and function.  Toward this end, we have developed computer models of irradiated graphene through insertion of random distributions of vacancies, which have generated configurations with structural and morphological characteristics in very good agreement with experimental observations.  We have predicted the onset of an amorphization transition at an inserted vacancy concentration between 5% and 10%, with the transition becoming less abrupt with defect concentration as the temperature increases.  We have found that the electronic density of states of vacancy-amorphized graphene is characterized by introduction of localized states near the Fermi level.  We have also found that the vacancy-induced crystalline-to-amorphous transition is accompanied by a brittle-to-ductile transition in the failure response of irradiated graphene sheets. While point defects and larger voids appreciably degrade the strength of irradiated graphene compared to that of pristine graphene, even heavily damaged samples exhibit tensile strengths in significant excess of those typical of engineering materials.

In this presentation, we use hydrogenation of irradiated and irradiation-induced amorphized graphene to study the effects of chemical functionalization on the properties of graphene damaged by irradiation.  Our study is focused on the impact of hydrogenation on the electronic structure and properties and on the mechanical response of irradiated and irradiation-induced amorphized graphene.  We use molecular-dynamics simulations according to a reliable bond-order potential to prepare the hydrogenated configurations and to carry out mechanical tests of dynamic deformation of the prepared configurations at constant strain rate and temperature.  Computations of the electronic band structure and electronic density of states of fully relaxed hydrogenated configurations are performed based on a density functional tight binding approach.  We report results for the electronic properties, as well as the ultimate tensile strength, fracture strain, and toughness of a broad class of irradiated graphene structures as a function of the hydrogen concentration/coverage used in the hydrogenation process.