Exceptional ballistic transport in epitaxial graphene nanoribbons

TL;DR

Epitaxial graphene nanoribbons exhibit room temperature ballistic transport over micrometer scales with exceptionally high mobility, surpassing theoretical limits of 2D graphene, and behave as quantum waveguides with distinct temperature-dependent conduction modes.

Contribution

This study demonstrates that epitaxial graphene nanoribbons grown on SiC are not semiconductors but exhibit unprecedented ballistic transport properties at room temperature, with mobilities exceeding one million.

Findings

Mobility exceeding one million and sheet resistance below 1 Ohm.

Ballistic transport observed over lengths up to 16 micrometers.

Transport dominated by two ground state waveguide modes, one temperature-independent and one thermally activated.

Abstract

Graphene electronics has motivated much of graphene science for the past decade. A primary goal was to develop high mobility semiconducting graphene with a band gap that is large enough for high performance applications. Graphene ribbons were thought to be semiconductors with these properties, however efforts to produce ribbons with useful bandgaps and high mobility has had limited success. We show here that high quality epitaxial graphene nanoribbons 40 nm in width, with annealed edges, grown on sidewall SiC are not semiconductors, but single channel room temperature ballistic conductors for lengths up to at least 16 micrometers. Mobilities exceeding one million corresponding to a sheet resistance below 1 Ohm have been observed, thereby surpassing two dimensional graphene by 3 orders of magnitude and theoretical predictions for perfect graphene by more than a factor of 10. The graphene ribbons behave as electronic waveguides or quantum dots. We show that transport in these ribbons is dominated by two components of the ground state transverse waveguide mode, one that is ballistic and temperature independent, and a second thermally activated component that appears to be ballistic at room temperature and insulating at cryogenic temperatures. At room temperature the resistance of both components abruptly increases with increasing length, one at a length of 160 nm and the other at 16 micrometers. These properties appear to be related to the lowest energy quantum states in the charge neutral ribbons. Since epitaxial graphene nanoribbons are readily produced by the thousands, their room temperature ballistic transport properties can be used in advanced nanoelectronics as well.