Charge transport mechanism in networks of armchair graphene nanoribbons

Nils Richter,Mischa Bonn,Klaus Müllen,Kamal Asadi,Mathias Kläui,Thorsten Prechtl,Zongping Chen,Akimitsu Narita,Alexander Tries

doi:10.1038/s41598-020-58660-w

Abstract

In graphene nanoribbons (GNRs), the lateral confinement of charge carriers opens a band gap, the key feature that enables novel graphene-based electronics. Despite great progress, reliable and reproducible fabrication of single-ribbon field-effect transistors (FETs) is still a challenge, impeding the understanding of the charge transport. Here, we present reproducible fabrication of armchair GNR-FETs based on networks of nanoribbons and analyze the charge transport mechanism using nine-atom wide and, in particular, five-atom-wide GNRs with large conductivity. We show formation of reliable Ohmic contacts and a yield of functional FETs close to unity by lamination of GNRs to electrodes. Modeling the charge transport in the networks reveals that transport is governed by inter-ribbon hopping mediated by nuclear tunneling, with a hopping length comparable to the physical GNR length. Overcoming the challenge of low-yield single-ribbon transistors by the networks and identifying the corresponding charge transport mechanism is a key step forward for functionalization of GNRs.

Highlights

We investigate charge transport in networks of bottom-up synthesized 5-AGNRs and 9-AGNRs grown by chemical vapor deposition (CVD)
The topography allows for inter-graphene nanoribbons (GNRs) charge carrier transfer, and macroscopic charge currents can be established via percolation paths
The Raman spectra are similar with identical peak positions before and after the transfer (Fig. 1(c) for 5-AGNRs and Fig. S1 in the Supplementary Information for 9-AGNRs)

Summary

Introduction

We investigate charge transport in networks of bottom-up synthesized 5-AGNRs and 9-AGNRs grown by CVD. We have developed a dependable and reproducible device fabrication protocol, optimized for stable and reproducible device features instead of high performance This fabrication scheme enables reliable transport measurements of the GNR networks and allows a direct comparison of the two ribbon types. Measurements over a previously inaccessible wide temperature range reveal the dominant charge transport mechanism to be nuclear tunneling-assisted carrier hopping. Based on this model, the universal scaling allows us to collapse all the charge current characteristics obtained across several orders of magnitude of bias voltages and temperatures onto a single curve. We determine a consistent charge carrier hopping distance

Methods

Results

Conclusion