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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.


Related in: MedlinePlus

Conductance fluctuation for nitrogen-doped and vacancy-damaged AGNRs. Conductance fluctuation σ as a function of the energy E for a nitrogen-doped Na = 45 AGNR (solid line), a nitrogen-doped Na = 47 AGNR (dashed line), and a vacancy-damaged Na = 47 AGNR (point) with fixed length: L~0.21 μm. Plotted values represent statistical averages over more of 500 equivalent replicas of the system. Charge neutrality points of pure and defected systems are aligned at E = 0 in the figure.
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Figure 3: Conductance fluctuation for nitrogen-doped and vacancy-damaged AGNRs. Conductance fluctuation σ as a function of the energy E for a nitrogen-doped Na = 45 AGNR (solid line), a nitrogen-doped Na = 47 AGNR (dashed line), and a vacancy-damaged Na = 47 AGNR (point) with fixed length: L~0.21 μm. Plotted values represent statistical averages over more of 500 equivalent replicas of the system. Charge neutrality points of pure and defected systems are aligned at E = 0 in the figure.

Mentions: From an analysis of the conductance spectra, we can derive same general features which can be useful for the interpretation of the electrical characterization of real GNRs. Indeed, we note that the conduction spectrum can be measured in a three terminal configuration [4] tuning the gate potential in order to modify the electron density in the nanostructure. Firstly, we note the persistence of the conduction modulation with energy in disordered systems, which is a marker of the conductance plateaus of the subband structure in pure GNRs. The effective transmission in the subbands is strongly reduced due to localization effects that suppress the conductance transparency in the spectral region where resonance states are located. Finally, the general occurrence of mobility gaps (see also Ref. [10]) can be hardly distinguished from the intrinsic bandgaps in semiconductor GNRs when experimentally measuring the conductance. A clear signature of the mobility gap is the occurrence of huge values of conductance fluctuations in the same spectral region of the gap due to its backscattering origin. In order to demonstrate this assumption, we have plotted in Figure 3 the statistically evaluated conductance variance


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)

Conductance fluctuation for nitrogen-doped and vacancy-damaged AGNRs. Conductance fluctuation σ as a function of the energy E for a nitrogen-doped Na = 45 AGNR (solid line), a nitrogen-doped Na = 47 AGNR (dashed line), and a vacancy-damaged Na = 47 AGNR (point) with fixed length: L~0.21 μm. Plotted values represent statistical averages over more of 500 equivalent replicas of the system. Charge neutrality points of pure and defected systems are aligned at E = 0 in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Conductance fluctuation for nitrogen-doped and vacancy-damaged AGNRs. Conductance fluctuation σ as a function of the energy E for a nitrogen-doped Na = 45 AGNR (solid line), a nitrogen-doped Na = 47 AGNR (dashed line), and a vacancy-damaged Na = 47 AGNR (point) with fixed length: L~0.21 μm. Plotted values represent statistical averages over more of 500 equivalent replicas of the system. Charge neutrality points of pure and defected systems are aligned at E = 0 in the figure.
Mentions: From an analysis of the conductance spectra, we can derive same general features which can be useful for the interpretation of the electrical characterization of real GNRs. Indeed, we note that the conduction spectrum can be measured in a three terminal configuration [4] tuning the gate potential in order to modify the electron density in the nanostructure. Firstly, we note the persistence of the conduction modulation with energy in disordered systems, which is a marker of the conductance plateaus of the subband structure in pure GNRs. The effective transmission in the subbands is strongly reduced due to localization effects that suppress the conductance transparency in the spectral region where resonance states are located. Finally, the general occurrence of mobility gaps (see also Ref. [10]) can be hardly distinguished from the intrinsic bandgaps in semiconductor GNRs when experimentally measuring the conductance. A clear signature of the mobility gap is the occurrence of huge values of conductance fluctuations in the same spectral region of the gap due to its backscattering origin. In order to demonstrate this assumption, we have plotted in Figure 3 the statistically evaluated conductance variance

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.


Related in: MedlinePlus