ترغب بنشر مسار تعليمي؟ اضغط هنا

Atomistic quantum transport modeling of metal-graphene nanoribbon heterojunctions

326   0   0.0 ( 0 )
 نشر من قبل Ioannis Deretzis
 تاريخ النشر 2010
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We calculate quantum transport for metal-graphene nanoribbon heterojunctions within the atomistic self-consistent Schrodinger/Poisson scheme. Attention is paid on both the chemical aspects of the interface bonding as well the one-dimensional electrostatics along the ribbon length. Band-bending and doping effects strongly influence the transport properties, giving rise to conductance asymmetries and a selective suppression of the subband formation. Junction electrostatics and p-type characteristics drive the conduction mechanism in the case of high work function Au, Pd and Pt electrodes, while contact resistance becomes dominant in the case of Al.



قيم البحث

اقرأ أيضاً

The success of all-graphene electronics is severely hindered by the challenging realization and subsequent integration of semiconducting channels and metallic contacts. Here, we comprehensively investigate the electronic transport across width-modula ted heterojunctions consisting of a graphene quantum dot of varying lengths and widths embedded in a pair of armchair-edged metallic nanoribbons, of the kind recently fabricated via on-surface synthesis. We show that the presence of the quantum dot enables the opening of a width-dependent transport gap, thereby yielding built-in one-dimensional metal-semiconductor-metal junctions. Furthermore, we find that, in the vicinity of the band edges, the conductance is subject to a smooth transition from an antiresonant to a resonant transport regime upon increasing the channel length. These results are rationalized in terms of a competition between quantum-confinement effects and quantum dot-to-lead coupling. Overall, our work establishes graphene quantum dot nanoarchitectures as appealing platforms to seamlessly integrate gap-tunable semiconducting channels and metallic contacts into an individual nanoribbon, hence realizing self-contained carbon-based electronic devices.
Results of quantum mechanical simulations of the influence of edge disorder on transport in graphene nanoribbon metal oxide semiconductor field-effect transistors (MOSFETs) are reported. The addition of edge disorder significantly reduces ON-state cu rrents and increases OFF-state currents, and introduces wide variability across devices. These effects decrease as ribbon widths increase and as edges become smoother. However the bandgap decreases with increasing width, thereby increasing the band-to-band tunneling mediated subthreshold leakage current even with perfect nanoribbons. These results suggest that without atomically precise edge control during fabrication, MOSFET performance gains through use of graphene will be difficult to achieve.
As a critical way to modulate thermal transport in nanostructures, phonon resonance hybridization has become an issue of great concern in the field of phonon engineering. In this work, we optimized phonon transport across graphene nanoribbon and obta ined minimized thermal conductance by means of designing pillared nanostructures based on resonance hybridization. Specifically, the optimization of thermal conductance was performed by the combination of atomic Green` s function and Bayesian optimization. Interestingly, it is found that thermal conductance decreases non-monotonically with the increasing of number for pillared structure, which is severed as resonator and blocks phonon transport. Further mode-analysis and atomic Green` s function calculations revealed that the anomalous tendency originates from decreased phonon transmission in a wide frequency range. Additionally, nonequilibrium molecular dynamics simulations are performed to verify the results with the consideration of high-order phonon scattering. This finding provides novel insights into the control of phonon transport in nanostructures.
The quantum transport formalism based on tight-binding models is known to be powerful in dealing with a wide range of open physical systems subject to external driving forces but is, at the same time, limited by the memory requirements increasing wit h the number of atomic sites in the scattering region. Here we demonstrate how to achieve an accurate simulation of quantum transport feasible for experimentally sized bulk graphene heterojunctions at a strongly reduced computational cost. Without free tuning parameters, we show excellent agreement with a recent experiment on Klein backscattering [A. F. Young and P. Kim, Nature Phys. 5, 222 (2009)].
We fabricate a graphene p-n-p heterojunction and exploit the coherence of weakly-confined Dirac quasiparticles to resolve the underlying scattering potential using low temperature scanning gate microscopy. The tip-induced perturbation to the heteroju nction modifies the condition for resonant scattering, enabling us to detect localized Fabry-Perot cavities from the focal point of halos in scanning gate images. In addition to halos over the bulk we also observe ones spatially registered to the physical edge of the graphene. Guided by quantum transport simulations we attribute these to modified resonant scattering at the edges within elongated cavities that form due to focusing of the electrostatic field.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا