Millimeter-Tall Carpets of Vertically Aligned Crystalline Carbon Nanotubes Synthesized on Copper Substrates for Electrical Applications

Eti Teblum, Chemistry, Bar-Ilan university, Ramat-Gan, Israel

We synthesized millimeter-tall, dense carpets of crystalline CNTs on non-polished copper substrates with a thin Al₂O₃ (below 10 nm) underlayer and Fe (1.2 nm) layer as a catalyst using chemical vapor deposition (CVD). Preheating of the hydrocarbon precursor gases and in-situ formation of controlled amounts of water vapor were critical process parameters. High-resolution microscopy showed that the CNTs were crystalline with lengths up to a millimeter. Electrical conduction between the CNTs and the copper substrate was demonstrated using multiple methods (probe-station, electrodeposition, and hydrolysis of water). Through TEM characterizations of cross-sections, we demonstrated that copper diffusion into the alumina layer during the thermal process was the key to explain the observed electrical conductivity. Additionally, the high electrical conductivity of a thermally-processed sample compared to the insulating behavior of a pristine sample confirmed the mechanistic hypothesis. Adsorption isotherm measurements showed the mesoporous structure of the vertically aligned carbon nanotubes (VACNTs) with a surface area of 342 m²/g. Electrical conduction and high surface area of this nanostructure make it a promising platform to be functionalized for future battery electrodes.