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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.


Average conductance for a nitrogen-doped Na = 45 AGNR. Average conductance <g> as a function of the energy E for a nitrogen-doped Na = 45 AGNR of different lengths. Plotted values represent statistical averages over more than 500 equivalent replicas of the system. Charge neutrality points of pure and doped systems are aligned at E = 0 eV in the figure.
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Figure 1: Average conductance for a nitrogen-doped Na = 45 AGNR. Average conductance <g> as a function of the energy E for a nitrogen-doped Na = 45 AGNR of different lengths. Plotted values represent statistical averages over more than 500 equivalent replicas of the system. Charge neutrality points of pure and doped systems are aligned at E = 0 eV in the figure.

Mentions: In a real defected system, we expect a finite density of random distributed scattering centers and, as a consequence, the effect of multiple scattering processes should be evaluated in this kind of configuration. In Figure 1, we show the (small bias) average conductance of an ideally contacted Na = 45 AGNR doped with a 0.2% density of nitrogen atoms and for systems with increasing length L, from approximately 0.1 μm to approximately 0.8 μm. An asymmetric decrease of the average conductance due to the impurity scattering can be observed for the whole spectrum. This behavior is particularly important in the energy region near the single impurity resonance states (i.e., for energies E ≈ 0.2 eV) where a mobility gap appears also for the smaller systems. We note that the pure Na = 45 AGNR is a semiconductor GNR with an energy gap of approximately 0.2 eV.


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)

Average conductance for a nitrogen-doped Na = 45 AGNR. Average conductance <g> as a function of the energy E for a nitrogen-doped Na = 45 AGNR of different lengths. Plotted values represent statistical averages over more than 500 equivalent replicas of the system. Charge neutrality points of pure and doped systems are aligned at E = 0 eV in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Average conductance for a nitrogen-doped Na = 45 AGNR. Average conductance <g> as a function of the energy E for a nitrogen-doped Na = 45 AGNR of different lengths. Plotted values represent statistical averages over more than 500 equivalent replicas of the system. Charge neutrality points of pure and doped systems are aligned at E = 0 eV in the figure.
Mentions: In a real defected system, we expect a finite density of random distributed scattering centers and, as a consequence, the effect of multiple scattering processes should be evaluated in this kind of configuration. In Figure 1, we show the (small bias) average conductance of an ideally contacted Na = 45 AGNR doped with a 0.2% density of nitrogen atoms and for systems with increasing length L, from approximately 0.1 μm to approximately 0.8 μm. An asymmetric decrease of the average conductance due to the impurity scattering can be observed for the whole spectrum. This behavior is particularly important in the energy region near the single impurity resonance states (i.e., for energies E ≈ 0.2 eV) where a mobility gap appears also for the smaller systems. We note that the pure Na = 45 AGNR is a semiconductor GNR with an energy gap of approximately 0.2 eV.

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.