A multiscale analysis of electronic structure and quantum transport in pure/defected/functionalized coronene-based graphene quantum dots

Description:
Coronene molecules can be seen as graphene-based quantum dots with a point symmetry. In this study we implement a bottom-up multiscale approach on their modeling, from density functional to semiempirical with different levels of accuracy (extended-Huckel with various bases and parameterizations and tight-binding). Using the ab initio calculations as a reference, the goal is to recognize the theoretical framework under which semiempirical methods describe adequately the electronic structure of the studied systems and thereon proceed to the calculation of quantum transport within the non-equilibrium Green's function formalism. Deviations from the ideal two-dimensional honeycomb lattice (confinement, deformations, vacancies and hydrogen impurities) challenge the traditional tight-binding picture of graphene-based complexes whereas the role of parameterization proves to be crucial even within the same semiempirical context. In terms of conduction, failure to capture the proper chemical aspects in the presence of generic local alterations of the ideal atomic structure sketches improperly the transport features, while contrary, a correct treatment of the latter by the semiempirical models can lead to massive transport calculations of realistic graphene-based devices. As an example, we show wavefunction localizations provoked by the presence of vacancies and how important is their modeling for the conduction characteristics of the studied systems.

Organised by Giovanni Piccitto
Support Email: Giovanni.Piccitto@ct.infn.it

 

Data: 
Giovedì, 22 Gennaio, 2009