Enhanced field emission properties of vertically aligned double-walled carbon nanotube arrays

Abstract

Vertically aligned double-walled carbon nanotube (VA-DWCNT) arrays were synthesized by point-arc microwave plasma chemical vapor deposition on Cr/n-Si and SiO2/n-Si substrates. The outer tube diameters of VA-DWCNTs are in the range of 2.5 -3.8 nm, and the average interlayer spacing is approximately 0.42 nm. The field emission properties of these VA-DWCNTs were studied. It was found that a VA-DWCNT array grown on a Cr/n-Si substrate had better field emission properties as compared with a VA-DWCNT array grown on a SiO2/n-Si substrate and randomly oriented DWCNTs, showing a turn-on field of about 0.85 V mu m(-1) at the emission current density of 0.1 mu A cm(-2) and a threshold field of 1.67 V mu m(-1) at the emission current density of 1.0 mA cm(-2). The better field emission performance of the VA-DWCNT array was mainly attributed to the vertical alignment of DWCNTs on the Cr/n-Si substrate and the low contact resistance between CNTs and the Cr/n-Si substrate.