Exceptional ballistic transport in epitaxial graphene nanoribbons

Abstract

Graphene nanoribbons will be essential components in future graphene nanoelectronics. However, in typical nanoribbons produced from lithographically patterned exfoliated graphene, the charge carriers travel only about ten nanometres between scattering events, resulting in minimum sheet resistances of about one kilohm per square. Here we show that 40-nanometre-wide graphene nanoribbons epitaxially grown on silicon carbide are single-channel room-temperature ballistic conductors on a length scale greater than ten micrometres, which is similar to the performance of metallic carbon nanotubes. This is equivalent to sheet resistances below 1 ohm per square, surpassing theoretical predictions for perfect graphene by at least an order of magnitude. In neutral graphene ribbons, we show that transport is dominated by two modes. One is ballistic and temperature independent; the other is thermally activated. Transport is protected from back-scattering, possibly reflecting ground-state properties of neutral graphene. At room temperature, the resistance of both modes is found to increase abruptly at a particular length--the ballistic mode at 16 micrometres and the other at 160 nanometres. Our epitaxial graphene nanoribbons will be important not only in fundamental science, but also--because they can be readily produced in thousands--in advanced nanoelectronics, which can make use of their room-temperature ballistic transport properties.

Edge states in graphene-like systems

“…The recent report 113 of ballistic transport with a conductance of G = e 2 h in epitaxial graphene nanoribbons would imply time reversal symmetry breaking compatible with edge magnetism. Great care was taken by the authors of this paper to rule out a great number of possible experimental artifacts and the understanding of their data remains a very interesting challenge for theory.…”

Bulk properties of solution-synthesized chevron-like graphene nanoribbons

“…9 Later the solution-based synthetic approach for bulk quantities of chevron-like GNRs that relies on Yamamoto coupling of molecular precursors followed by cyclodehydrogenation via a Scholl reaction has also been demonstrated. 19,20 Considering the potential use of GNRs in electronics [27][28][29] it is very important to understand their electronic properties. Despite some recent attempts to measure the electronic properties of GNRs synthesized by the bottom-up approaches 30,31 the electrical characterization of GNRs remains challenging in general and no conductivity measurements have been performed on chevron-like GNRs in particular.…”

Wide-Gap Semiconducting Graphene from Nitrogen-Seeded SiC

“…Electron confinement in lithographically patterned narrow graphene ribbons has been plagued by lithographic limits and edge disorder, [8][9][10][11] although recent results from sidewall grown graphene ribbon are showing new progress that could lead to band-gaps larger than 0.6eV. 12,13 Functionalized graphene band-gaps can be produced by imposing a periodic potential in the graphene lattice through ordered adsorbates 14,15 or ordered impurities replacing carbon atoms. 16 In this work we demonstrate a novel approach to bandgap engineering in graphene using a nitrogen seeded SiC surface.…”