The Effect of Al Buffer Layer on the Catalytic Synthesis of Carbon Nanotube Forests

This study aims to reveal the effect of an Al buffer layer on the catalytic synthesis of carbon nanotube (CNT) forests. Thin films of Al buffer with thicknesses of 2, 5, 10, and 20 nm were deposited on copper, brass, stainless steel, Inconel® 600, silicon and alumina substrates under an Fe catalyst layer of 1 nm thickness. CNTs were synthesized from acetylene using hydrogen as a reducing gas at 660 °C in a low pressure chemical vapor deposition system. Vertically well-aligned CNTs were obtained on all substrates when an Al buffer layer of at least 10 nm was applied. The structure of the Al buffer layer and the nanotube forests were studied using scanning electron microscopy, atomic force microscopy and Raman spectroscopy. The effect of the Al buffer layer on the electrical properties of the substrate–buffer–catalyst–nanotube structures was evaluated by current–voltage measurements. Supercapacitor devices constructed from the nanotube forests grown on various types of conductive substrates were also studied. The specific capacitance of the double-layer capacitor electrodes was found to be ~10 F/g which is in the same range that we have measured in the absence of an Al buffer layer.