Fabrication of high-density vertical CNT arrays using thin porous alumina template for biosensing applications

Abstract

This paper explores the process of forming arrays of vertically oriented carbon nanotubes (CNTs) localized on metal electrodes using thin porous anodic alumina (PAA) on a solid substrate. On a silicon substrate, a titanium film served as the electrode layer, and an aluminium film served as the base layer in the initial film structure. A PAA template was formed from the Al film using two-step electrochemical anodizing. Two types of CNT arrays were then synthesized by catalytic chemical vapor deposition. By electrochemically depositing Ni into the PAA pores in two different regimes—constant potential (DC deposition) and alternating current (AC deposition)—catalyst nanoparticles for CNT deposition are formed. It is shown that the size parameters of the CNTs and the proposed CNT growth mechanism depend on the size of the catalyst particles and their localization in the pores of the PAA. Thus, a Ti/PAA/Ni/CNT-based nanocomposite multilayered structure was formed on the Si substrate. Through the use of X-ray diffraction analysis, linear voltammetry, atomic force microscopy, and scanning electron microscopy, the morphological, structural, and electrochemical characteristics of the produced nanocomposite material were investigated. It is shown that the obtained nanostructures can be used for the fabrication of CNT electrodes for biosensing applications.