On the identification of pristine and defected graphene nanoribbons by phonon signatures in the electron transport characteristics

TL;DR

This paper uses first-principles simulations to identify phonon signatures in electron transport that distinguish pristine from defected graphene nanoribbons, revealing characteristic IETS signals and spin effects.

Contribution

It introduces a detailed theoretical analysis of IETS in graphene nanoribbons, linking phonon modes to electron transport signatures and defect/spin states.

Findings

Identified IETS signals at 169 and 196 mV for armchair GNRs.

Linked IETS features to specific defect types and edge passivation.

Showed spin state impacts IETS spectra in zigzag GNRs.

Abstract

Inspired by recent experiments where electron transport was measured across graphene nanoribbons (GNR) suspended between a metal surface and the tip of a scanning tunneling microscope [Koch \textit{et al}., Nat. Nanotechnol. {\bf 7}, 713 (2012)], we present detailed first-principles simulations of inelastic electron tunneling spectroscopy (IETS) of long pristine and defected armchair and zigzag nanoribbons under a range of charge carrier conditions. For the armchair ribbons we find two robust IETS signals around 169 and 196 mV corresponding to the D- and G-modes of Raman spectroscopy as well as additional fingerprints due to various types of defects in the edge passivation. For the zigzag ribbons we show that the spin state strongly influences the spectrum and thus propose IETS as an indirect proof of spin polarization.