Electron beam splitting with crossed graphene nanoribbons

Abstract

Graphene exhibits many exceptional mechanical and electronic properties that make it attractive for the fabrication of electronic devices at the nanoscale, but the gapless spectrum is a major obstacle for carbon-based electronic applications, since the absence of an electronic gap makes it a poor candidate to build logic electronic devices, e.g. field-effect transistor. A gap can be however induced in different ways, among others, via lateral quantum confinement of the electrons, e.g., as it occurs in one-dimensional (1D) graphene nanoribbons (GNRs). On the other hand these GNRs can be produced and manipulated with atomistic precision. Here we analyze the effect of placing two GNRs one on top of the other interacting via the vander-Waals interaction (4-terminal device). Previous work based on DFT+NEGF showed that electrons injected from one terminal can be split into two outgoing waves with a tunable ratio that strongly depends on the intersection angle between the ribbons. In this work we complement this by adopting a simple and numerically efficient tight-binding description that captures the essential physics. In addition to the intersection angle, the precise stacking of the device results in a powerful tool to control the direction and intensity of the electron beam. Here we analyze different high-symmetry configurations as well as GNRs of varying width and edge chirality to reach a complete picture of the electron beam splitting effect.