Limits...
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.


Current-voltage characteristics. I-V characteristics derived by the NEGF in the Landauer-Buttiker scheme for a Na = 16 AGNR, end-contacted with three different metals Au (black line), Pd (green line), and Al (red line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211293&req=5

Figure 5: Current-voltage characteristics. I-V characteristics derived by the NEGF in the Landauer-Buttiker scheme for a Na = 16 AGNR, end-contacted with three different metals Au (black line), Pd (green line), and Al (red line).

Mentions: Current-voltage (I-V) characteristics of the junction in the case of a pure Na = 16 AGNR contacted with different metals are reported in Figure 5. Larger I values obtained for a negative bias in the case of Pd with respect Au are due to its slighter more pronounced p-type character (while in turn Au seems transparent near the Fermi level with the conductance arriving at the 1 G0 = 2e2/h plateau of the ideal case). 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). However, in the latter case, the dominant aspect is the strong scattering by the contacts and the related suppression of the contact transparency.


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)

Current-voltage characteristics. I-V characteristics derived by the NEGF in the Landauer-Buttiker scheme for a Na = 16 AGNR, end-contacted with three different metals Au (black line), Pd (green line), and Al (red line).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Current-voltage characteristics. I-V characteristics derived by the NEGF in the Landauer-Buttiker scheme for a Na = 16 AGNR, end-contacted with three different metals Au (black line), Pd (green line), and Al (red line).
Mentions: Current-voltage (I-V) characteristics of the junction in the case of a pure Na = 16 AGNR contacted with different metals are reported in Figure 5. Larger I values obtained for a negative bias in the case of Pd with respect Au are due to its slighter more pronounced p-type character (while in turn Au seems transparent near the Fermi level with the conductance arriving at the 1 G0 = 2e2/h plateau of the ideal case). 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). However, in the latter case, the dominant aspect is the strong scattering by the contacts and the related suppression of the contact transparency.

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.