The effect of gas-dynamic factors on selective carbon-nanotube synthesis by injection CVD method for field-emission cathodes

Reversible selective growth of carbon-nanotube (CNT) arrays on Si/SiO2 topologies was investigated for field-emission-display applications. The method used was that of high-temperature pyrolysis of fluid hydrocarbon (p-xylene [C8H10]) in a mixture with volatile catalyst (ferrocene [Fe(C5H5)(2)]) using Ar as the gas carrier. The synthesized CNT arrays were analyzed by SEM, TEM, Raman, and TGA analyses. Reversible CNT growth both on Si and SiO2 surfaces was found to be sensitive to the gas-carrier flow rate and the catalyst/hydrocarbon solution injection rate into the synthesis zone. This phenomenon can be explained by inverse domination of active sites on Si and SiO2 surfaces at different flow rates of gas mixture, causing different types of catalyst precipitation followed by subsequent CNT growth. In principle, the possibility of growing CNTs using the proposed technology will allow the creation of precise geometries of field-emission cathodes excluding the step of catalyst localization.