Theoretical study of the role of metallic contacts in probing transport features of pure and defected graphene nanoribbons

Antonino La Magna,Ioannis Deretzis

doi:10.1186/1556-276x-6-234

Antonino La Magna, Ioannis Deretzis

Open Access

https://doi.org/10.1186/1556-276x-6-234

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Abstract

Understanding the roles of disorder and metal/graphene interface on the electronic and transport properties of graphene-based systems is crucial for a consistent analysis of the data deriving from experimental measurements. The present work is devoted to the detailed study of graphene nanoribbon systems by means of self-consistent quantum transport calculations. The computational formalism is based on a coupled Schrödinger/Poisson approach that respects both chemistry and electrostatics, applied to pure/defected graphene nanoribbons (ideally or end-contacted by various fcc metals). We theoretically characterize the formation of metal-graphene junctions as well as the effects of backscattering due to the presence of vacancies and impurities. Our results evidence that disorder can infer significant alterations on the conduction process, giving rise to mobility gaps in the conductance distribution. Moreover, we show the importance of metal-graphene coupling that gives rise to doping-related phenomena and a degradation of conductance quantization characteristics.

Highlights

Graphene nanoribbons (GNRs) are the most promising graphene-based nanostructures for electronic applications since they are potentially suited for band-gap engineering, maintaining the excellent electronic properties of the parent two-dimensional graphene layer
GNRs have been already synthesized by means of different pattering techniques [1,2], and there exists convincing evidence that their electronic structure manifests subband formation which is a typical predicted signature of the one-dimensional (1D) confinement [3]
The terminology of Ref. [6] is applied to categorize them on the basis of the dimer lines Na along the ribbon width

Summary

Introduction

Graphene nanoribbons (GNRs) are the most promising graphene-based nanostructures for electronic applications since they are potentially suited for band-gap engineering, maintaining the excellent electronic properties of the parent two-dimensional graphene layer. Defected GNRs Isolated defect and impurity alter both the density of states distribution DOS(E) than conductance g(E) of quasi-1D GNRs. In particular n-type (p-type) impurities introduce electronic states ( called resonance states [3]) at energies above (below) the charge neutrality point (i.e., the Dirac point) of the pristine pure systems. Al has a lower work function with respect to graphene and the Al-GNR junction shows a quasi-ambipolar Schottky behavior (i.e., the I-V characteristic is almost symmetric for positive and negative bias). In the latter case, the dominant aspect is the strong scattering by the contacts and the related suppression of the contact transparency

Conclusion

Datta S: Electronic Transport in Mesoscopic Systems Cambridge