Density control of vertically aligned carbon nanotubes and its effect on field emission properties

Abstract

Vertically aligned carbon nanotubes (VACNTs) were synthesized directly on stainless steel substrate and their surface densities were tuned by an order of magnitude via growing them at different temperatures. The surface density of the VACNTs was correlated with the surface evolution of the substrate, a process in which catalyst nano hills were generated at different growth temperatures in the presence of reducing gas environment. Enhanced field emission (FE) properties including low turn-on electric field (ETurn-on = 0.66 V μm-1), low threshold electric field (ETh = 1.07 V μm-1), high field enhancement factor (β = 4084), and high FE stability for 600 min were obtained from VACNT arrays synthesized at 650 °C. It is speculated that the inherent features of our sample such as the conductive substrate, the low contact resistance between the substrate and the VACNTs, the uniform length and the appropriate spacing between the VACNTs have contributed to the excellent field emission properties. Simulation on the electrostatic field of various VACNT arrays was performed and the result is in good agreement with the experimental data.