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

La Magna A, Deretzis I - Nanoscale Res Lett (2011)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: 1CNR IMM, Z,I, VIII Strada 5, 95121 Catania, Italy. antonino.lamagna@imm.cnr.it.

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.

No MeSH data available.


Small- and finite-bias conductance spectra. Small-bias (points) and finite-bias (+0.5 V green line, -0.5 red line) conductances of a pure Na = 16 AGNR end-contacted with Au.
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Figure 4: Small- and finite-bias conductance spectra. Small-bias (points) and finite-bias (+0.5 V green line, -0.5 red line) conductances of a pure Na = 16 AGNR end-contacted with Au.

Mentions: The local electronic structure characteristics in the contact region can non-trivially influence the conduction mechanism since, e.g., localized states do not contribute to the conduction, giving rise to conductance asymmetries and an overall loss of the transport information with respect to the ideal case. In Figure 4, small- and finite-bias conductance spectra of a pure Na = 16 AGNR end-contacted with Au are plotted as a function of energy. These spectra show similar characteristics with the ones obtained considering metals with higher work functions than graphene (e.g., Pt, Pd). A Schottky barrier of the order of 0.2 to 0.3 eV can be determined by the difference between the gap in the conductance spectrum for the contacted GNRs at 0 V (Figure 4 dotted line) and the gap (approximately 0.6 eV) of the ideal non-contacted GNR.


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

La Magna A, Deretzis I - Nanoscale Res Lett (2011)

Small- and finite-bias conductance spectra. Small-bias (points) and finite-bias (+0.5 V green line, -0.5 red line) conductances of a pure Na = 16 AGNR end-contacted with Au.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211293&req=5

Figure 4: Small- and finite-bias conductance spectra. Small-bias (points) and finite-bias (+0.5 V green line, -0.5 red line) conductances of a pure Na = 16 AGNR end-contacted with Au.
Mentions: The local electronic structure characteristics in the contact region can non-trivially influence the conduction mechanism since, e.g., localized states do not contribute to the conduction, giving rise to conductance asymmetries and an overall loss of the transport information with respect to the ideal case. In Figure 4, small- and finite-bias conductance spectra of a pure Na = 16 AGNR end-contacted with Au are plotted as a function of energy. These spectra show similar characteristics with the ones obtained considering metals with higher work functions than graphene (e.g., Pt, Pd). A Schottky barrier of the order of 0.2 to 0.3 eV can be determined by the difference between the gap in the conductance spectrum for the contacted GNRs at 0 V (Figure 4 dotted line) and the gap (approximately 0.6 eV) of the ideal non-contacted GNR.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: 1CNR IMM, Z,I, VIII Strada 5, 95121 Catania, Italy. antonino.lamagna@imm.cnr.it.

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.

No MeSH data available.