Ultra-high density alignment of carbon nanotubes array by dielectrophoresis

TL;DR

This paper demonstrates the controlled assembly of ultra-high density aligned single-walled carbon nanotube arrays using ac dielectrophoresis, achieving the highest densities reported and enabling high-performance electronic devices.

Contribution

It introduces a method to produce ultra-high density aligned SWNT arrays with tunable density and demonstrates their application in high-performance FETs.

Findings

Maximum density of 30 SWNT/μm achieved

Dense arrays with multiple layers at higher concentrations

Low sheet resistance and high on-off ratio in FETs

Abstract

We report ultra-high density assembly of aligned single walled carbon nanotubes (SWNTs) two dimensional arrays via ac dielectrophoresis using high quality surfactant free and stable SWNT solutions. After optimization of frequency and trapping time, we can reproducibly control the linear density of the SWNT between prefabricated electrodes from 0.5 SWNT/\mum to more than 30 SWNT /\mum by tuning the concentration of the nanotubes in the solution. Our maximum density of 30 SWNT/\mum is the highest for aligned arrays via any solution processing technique reported so far. Further increase of SWNT concentration results dense array with multiple layers. We discuss how the orientation and density of the nanotubes vary with concentrations and channel lengths. Electrical measurement data show that the densely packed aligned arrays have low sheet resistances. Selective removal of metallic SWNTs via controlled electrical breakdown produced field effect transistors (FET) with high current on-off ratio. Ultra-high density alignment reported here will have important implications in fabricating high quality devices for digital and analog electronics.