The effect of an Al underlayer on Fe–Si thin film catalysts for the improved growth of carbon nanotubes

We report the positive effect of an Al underlayer for enhancing the growth of carbon nanotubes (CNTs) on Si substrates. The catalyst used for the growth was a sputter-deposited Fe–Si thin film and the growth temperature was 370 °C. The morphology, composition, microstructure, and crystalline structure of the Fe–Si films with and without an Al underlayer having different thicknesses were examined. Correlation between the Al underlayer thickness and the film characteristics is made. The effect of Al thickness on the growth of CNTs is discussed. It was found that the maximum growth increase occurs at an Al thickness of 4 nm, for which the growth is increased by 220%.