Non-catalyst and low temperature growth of vertically aligned carbon nanotubes for nanosensor arrays

In this paper we present a new technique to vertically grow aligned carbon nanotubes (CNTs) on nanosize pore anodic aluminum oxide (AAO) templates on a Si substrate. The CNTs are grown using methane in an RF PECVD system at only 400°C without using a transition metal catalyst. The AAO templates are prepared by a two-step anodizing process in oxalic acid at room temperature. The influence of preparation conditions, such as temperature, electrolyte, applied voltage and anodization time on the density, diameter, length and the shape of the pores is investigated. The diameter of the pores of AAO film varies from 30 nm to 70 nm. The average diameter and length of CNTs are approximately 40 nm and 1 μm respectively. This low temperature, IC-compatible process is very attractive as it allows integration of CNT devices with on-chip electronics.