A theoretical investigation on the transport properties of overlapped graphene nanoribbons

The transport characteristics of overlapped junctions of Zigzag Graphene NanoRibbons (ZGNRs) are simulated and analyzed using Non-Equilibrium Green’s function combined with the Density Functional Theory. It is found that the carriers pass through an overlapped junction via several different energy states by tunneling process. In general, the current passing across the junction is mainly due to tunneling of carriers between many quasi-bound states. Meanwhile, few transmissions are observed between individual states. The latter behaviors cannot be explained by quasi-bound states; however, they are interpreted as the states which show long range resonance phenomenon. A combination of these states results in complex variations of transmission characteristics. These variations introduce several negative differential resistances by increasing the voltage across the junction of ZGNRs. In other words, misalignment in the states along the junction leads to periodic changes in the coupling of the quasi-bound states and long range resonant states. This makes an oscillation in the current voltage characteristics of the overlapped junction in ZGNRs. Consequently, the overlapped junction in ZGNR has a lower electrical transport comparing to that of an ideal (non-overlapped) ZGNR.