Graphene nanoribbons from unzipped carbon nanotubes: atomic structures, Raman spectroscopy and electrical properties

TL;DR

This study explores the atomic structures, Raman spectra, and electrical properties of graphene nanoribbons derived from unzipped carbon nanotubes, revealing insights into their layer stacking, edge smoothness, and chiral angles.

Contribution

It provides detailed atomic-level characterization and correlates spectroscopic and electrical properties of GNRs from unzipped nanotubes, a novel approach in the field.

Findings

High percentage of two-layer GNRs with specific stacking angles

Edge roughness mostly below 1 nm

Correlation between Raman spectra and electrical properties

Abstract

We investigated the atomic structures, Raman spectroscopic and electrical transport properties of individual graphene nanoribbons (GNRs, widths ~10-30 nm) derived from sonochemical unzipping of multi-walled carbon nanotubes (MWNTs). Aberration-corrected transmission electron microscopy (TEM) revealed a high percentage of two-layer (2L) GNRs and some single layer ribbons. The layer-layer stacking angles ranged from 0o to 30o including average chiral angles near 30o (armchair orientation) or 0o (zigzag orientation). A large fraction of GNRs with bent and smooth edges was observed, while the rest showing flat and less smooth edges (roughness \leq 1 nm). Polarized Raman spectroscopy probed individual GNRs to reveal D/G ratios and ratios of D band intensities at parallel and perpendicular laser excitation polarization (D///D\bot). The observed spectroscopic trends were used to infer the average chiral angles and edge smoothness of GNRs. Electrical transport and Raman measurements were carried out for individual ribbons to correlate spectroscopic and electrical properties of GNRs.