Graphene nanoribbon based electronics and spintronics

Abstract

Modulation of orbitals in molecules or bands in materials is useful to tune the electron/spin transport in molecular/materials systems. Here, I discuss electron/spin transport and molecular fingerprinting using graphene nanoribbon (GNR) with density functional theory coupled to non-equilibrium Green function theory. By utilizing Fano-resonance driven 2-dimensional molecular electronics spectroscopy, the hyper-sensitive quantum conductance spectra of a GNR placed across a fluidic nanochannel can lead to fast DNA sequencing including cancerous methylated nucleobases detection [1, 2]. There was a difficulty in studying transport phenomena using the bottom-gate control of zigzag GNR (zGNR), because the chemical equilibrium between electrons in zGNR and electrodes requires electron reservoir. It is now possible to study the top/back-gate effects in field effect transistor (FET) under external potential using the iso-chemical potential approach [3]. It is also interesting to study graphene edges which show intriguing spin states [4]. By utilizing magnetic field control, a GNR spin-valve device shows the super magneto-resistance behavior as a spin filter which transmits near perfect spin-polarized current [5]. Such an intriguing behavior can also be obtained for chemically edge functionalized zGNRs under transverse electric field without magnetic field control [6]. Since on-site Coulomb repulsion governs spin splitting under electron accumulation/depletion, the current-voltage characteristics of the edge-modified zGNR under in-plane transverse electric field show the perfect spin filtering as a chemical spintronic device. Alteration of magnetic properties of zGNR by tuning the transverse electric field would be a promising method to construct magnetic/nonmagnetic switches.