Effect of Anodization Process Parameters on Morphology of Porous Anodic Aluminum Oxide and Carbon Nanotubes Grown by CVD

M. K. Kushwaha; Harleen Kaur; Dr. Priyavrat Thareja

Abstract

Normal 0 false false false EN-US X-NONE X-NONE Synthesis of well-ordered carbon nanotubes (CNTs) can be achieved by chemical vapor deposition (CVD) of a carbon source onto a porous anodic aluminum oxide (PAAO) template. The structure of the PAAO template or film is a close-packed array of hexagonal cells, each containing a cylindrical central pore that is perpendicular to the surface of the underlying aluminum substrate. The diameter, depth and spacing between pores can be tailored by altering the anodization process parameters. A two-step anodization method was developed in the mid-nineties to get near-perfect honeycomb like hexagonal ordering in the pore arrangement, which has been also used in this work. Anodization was carried out in diluted phosphoric acid electrolyte and later CNTs were developed within the nanopores of PAAO using chemical vapor deposition (CVD). Acetylene gas was used as a carbon source and the CVD was carried out with catalyst embedding in the nanopores. The effect of PAAO structure obtained by pretreatment and using various anodization process parameters, e.g., applied voltage/current density, temperature, concentration and pH of the electrolyte, etc., on the growth and morphology of PAAO and subsequently CNTs grown within pores has been studied. This study clearly shows that the PAAO morphology is very important for ordered growth of CNTs. Diameter and length of the CNTs vary directly with the diameter and depth of the pores of the PAAO for pore diameter 100 nm and above. The PAAO characteristics were examined by FE-SEM and analysis was done using Image-J software. The produced CNTs were characterized by FE-SEM with EDAX facility and HR-TEM. This systematic study will help in devising a method of template synthesis for controlled growth of CNTs which is expected to assist in the development of high-density vertically oriented well-ordered CNT-based nanodevices. Keywords: Porous anodic aluminum oxide (PAAO), pore diameter, CNTs (carbon nanotubes), chemical vapor deposition (CVD)