Nucleation Control of Carbon Nanowalls Using Inductively Coupled Plasma-Enhanced Chemical Vapor Deposition

Carbon nanowalls (CNWs), a self-organized network of vertically standing few-layer graphenes, were synthesized by inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD) employing methane and argon mixtures. Significant interest exists in clarifying the nucleation mechanism of CNWs and controlling their nucleation. We have investigated the early growth stage of CNWs on the catalyst-free substrate and the titanium (Ti)-nanoparticle-catalyzed substrate. In the case of catalyst-free growth of CNWs, there was an induction period of 1–5 min before the onset of vertical nanographene growth and an interface layer exists between the vertical nanographenes and the surface of Si and SiO2 substrates. Meanwhile, in the case of the growth on the Ti nanoparticle-coated SiO2 substrates, the nanographenes were directly nucleated from the Ti nanoparticles without forming a base layer within 30 s, while no nucleation was observed on the SiO2 surface at this period. These results suggest the possibility of area-selective growth of CNWs by controlling the substrate biasing to suppress the nucleation selectively from the catalyst-free surface.