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Quantum transport simulations of graphene nanoribbon devices using Dirac equation calibrated with tight-binding π-bond model.

Chin SK, Lam KT, Seah D, Liang G - Nanoscale Res Lett (2012)

Bottom Line: The approach has the advantage of the computational efficiency of the Dirac equation and still captures sufficient quantitative details of the bandstructure from the tight-binding π-bond model for graphene.We demonstrate how the exact self-energies due to the leads can be calculated in the NEGF-Dirac model.We apply our approach to GNR systems of different widths subjecting to different potential profiles to characterize their device physics.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of High Performance Computing, A*STAR, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore. chinsk@ihpc.a-star.edu.sg.

ABSTRACT
We present an efficient approach to study the carrier transport in graphene nanoribbon (GNR) devices using the non-equilibrium Green's function approach (NEGF) based on the Dirac equation calibrated to the tight-binding π-bond model for graphene. The approach has the advantage of the computational efficiency of the Dirac equation and still captures sufficient quantitative details of the bandstructure from the tight-binding π-bond model for graphene. We demonstrate how the exact self-energies due to the leads can be calculated in the NEGF-Dirac model. We apply our approach to GNR systems of different widths subjecting to different potential profiles to characterize their device physics. Specifically, the validity and accuracy of our approach will be demonstrated by benchmarking the density of states and transmissions characteristics with that of the more expensive transport calculations for the tight-binding π-bond model.

No MeSH data available.


Related in: MedlinePlus

The E(k) calculated from the TBDE matching that of the TB-π with different best fit l0 for different subbands for the (a) W12 and (b) W14 devices. Only conduction bands for E ≥ 0 are shown. The valance bands are symmetric about E = 0.
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Figure 3: The E(k) calculated from the TBDE matching that of the TB-π with different best fit l0 for different subbands for the (a) W12 and (b) W14 devices. Only conduction bands for E ≥ 0 are shown. The valance bands are symmetric about E = 0.

Mentions: To incorporate the material details of GNR into the TB-π model, we first fit (3) of different GNR widths with that of the TB-π model, which is widely used to calculate the bandstructures of GNR, for a flat potential (i.e., U = 0). Both real and imaginary parts of (3) are fitted for multiple subbands with different values of l0 for a particular GNR system. Figure 3 shows the comparisons of E(k) for the GNRs with width 1.0 nm and 1.4 nm, labeled as W10 and W14, respectively. At larger k, the E(k) calculated using (3) deviated from the that of the TB-π model. This is expected as the TBDE model for GNR is most accurate near the Dirac points at small k[15]. Since we are interested in semiconductor properties of GNRs, only the wide bandgap armchair GNRs (families with indices of m = 3p and 3p+1) [8,21] are considered here. The GNRs associated with m = 3p + 2 have Eg that are too small and are not considered here. Table 1 shows the best-fit l0 at different subbands for the m = 3p and m = 3p + 1 GNRs obtained under this study. With these calibrations, the adequate bandstructure details based on TB-π model can be incorporated in the TBDE model. Figure 4 compare the DOS(E) and T(E) for the same W12 and W14 systems using TBDE model (with the fitted-lo values from Table 1) and that of the TB-π model. The very good agreements of results between the two models is a good first step to demonstrate the validity of the TBDE model in tackling quantum transport problems at which accurate T(E) and DOS(E) are the keys.


Quantum transport simulations of graphene nanoribbon devices using Dirac equation calibrated with tight-binding π-bond model.

Chin SK, Lam KT, Seah D, Liang G - Nanoscale Res Lett (2012)

The E(k) calculated from the TBDE matching that of the TB-π with different best fit l0 for different subbands for the (a) W12 and (b) W14 devices. Only conduction bands for E ≥ 0 are shown. The valance bands are symmetric about E = 0.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368727&req=5

Figure 3: The E(k) calculated from the TBDE matching that of the TB-π with different best fit l0 for different subbands for the (a) W12 and (b) W14 devices. Only conduction bands for E ≥ 0 are shown. The valance bands are symmetric about E = 0.
Mentions: To incorporate the material details of GNR into the TB-π model, we first fit (3) of different GNR widths with that of the TB-π model, which is widely used to calculate the bandstructures of GNR, for a flat potential (i.e., U = 0). Both real and imaginary parts of (3) are fitted for multiple subbands with different values of l0 for a particular GNR system. Figure 3 shows the comparisons of E(k) for the GNRs with width 1.0 nm and 1.4 nm, labeled as W10 and W14, respectively. At larger k, the E(k) calculated using (3) deviated from the that of the TB-π model. This is expected as the TBDE model for GNR is most accurate near the Dirac points at small k[15]. Since we are interested in semiconductor properties of GNRs, only the wide bandgap armchair GNRs (families with indices of m = 3p and 3p+1) [8,21] are considered here. The GNRs associated with m = 3p + 2 have Eg that are too small and are not considered here. Table 1 shows the best-fit l0 at different subbands for the m = 3p and m = 3p + 1 GNRs obtained under this study. With these calibrations, the adequate bandstructure details based on TB-π model can be incorporated in the TBDE model. Figure 4 compare the DOS(E) and T(E) for the same W12 and W14 systems using TBDE model (with the fitted-lo values from Table 1) and that of the TB-π model. The very good agreements of results between the two models is a good first step to demonstrate the validity of the TBDE model in tackling quantum transport problems at which accurate T(E) and DOS(E) are the keys.

Bottom Line: The approach has the advantage of the computational efficiency of the Dirac equation and still captures sufficient quantitative details of the bandstructure from the tight-binding π-bond model for graphene.We demonstrate how the exact self-energies due to the leads can be calculated in the NEGF-Dirac model.We apply our approach to GNR systems of different widths subjecting to different potential profiles to characterize their device physics.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of High Performance Computing, A*STAR, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore. chinsk@ihpc.a-star.edu.sg.

ABSTRACT
We present an efficient approach to study the carrier transport in graphene nanoribbon (GNR) devices using the non-equilibrium Green's function approach (NEGF) based on the Dirac equation calibrated to the tight-binding π-bond model for graphene. The approach has the advantage of the computational efficiency of the Dirac equation and still captures sufficient quantitative details of the bandstructure from the tight-binding π-bond model for graphene. We demonstrate how the exact self-energies due to the leads can be calculated in the NEGF-Dirac model. We apply our approach to GNR systems of different widths subjecting to different potential profiles to characterize their device physics. Specifically, the validity and accuracy of our approach will be demonstrated by benchmarking the density of states and transmissions characteristics with that of the more expensive transport calculations for the tight-binding π-bond model.

No MeSH data available.


Related in: MedlinePlus