Field emission and anode etching during formation of length-controlled nanogaps in electrical breakdown of horizontally aligned single-walled carbon nanotubes.

Keigo Otsuka,Taiki Inoue,Yuki Shimomura,Shigeo Maruyama,Shohei Chiashi

doi:10.1039/c6nr05449h

Abstract

We observe field emission between nanogaps and voltage-driven gap extension of single-walled carbon nanotubes (SWNTs) on substrates during the electrical breakdown process. Experimental results show that the gap size is dependent on the applied voltage and humidity, which indicates high controllability of the gap size by appropriate adjustment of these parameters in accordance with the application. We propose a mechanism for the gap formation during electrical breakdown as follows. After small gaps are formed by Joule heating-induced oxidation, SWNTs on the anode side are electrochemically etched due to physically-adsorbed water from the air and the enhanced electric field at the SWNT tips. Field emission is measured in a vacuum as a possible mechanism for charge transfer at SWNT gaps. The relationship between the field enhancement factor and geometric features of SWNTs explains both the voltage dependence of the extended gap size and the field emission properties of the SWNT gaps. In addition, the similar field-induced etching can cause damage to adjacent SWNTs, which possibly deteriorates the selectivity for cutting metallic pathways in the presence of water vapor.

Highlights

Electrical breakdown[1] of single-walled carbon nanotubes has been performed to selectively cut metallic SWNTs (m-SWNTs) for field-effect transistor (FET) applications,[2,3,4,5] or to create SWNT nanogaps for use as nanoscale electrodes[6,7,8] to contact single molecules[9,10] and functional materials.[11]
Electrical breakdown on heated substrates resulted in smaller gap formation because the water molecules on the SWNT surfaces desorb at high temperature, even under the same water vapor pressure
We have reported on the field emission and voltage-driven gap extension phenomena for SWNTs on substrates

Summary

Introduction

Electrical breakdown[1] of single-walled carbon nanotubes (single-walled CNTs, SWNTs) has been performed to selectively cut metallic SWNTs (m-SWNTs) for field-effect transistor (FET) applications,[2,3,4,5] or to create SWNT nanogaps for use as nanoscale electrodes[6,7,8] to contact single molecules[9,10] and functional materials.[11]. Based on the experimental results, we have considered that electrochemical etching at the SWNT tips due to physisorbed water and enhanced electric field is the driving force behind the gap extension.

Results

Conclusion