The control of carbon nanotubes density by gas-phase catalytic chemical vapor deposition

In this study, we are focusing on the detailed control of the size and density of nanoparticles on the substrate by employing the gas-phase catalyst. To fabricate iron (Fe) nanoparticles as catalyst, Fe(CO)₅ gas was used. Size and density of the nanoparticles can be controlled by varying the experimental parameters, such as the molar flow rate, the decomposition temperature and the flow time. Quartz and Si plate was used as the substrate. The nanoparticles were formed at a substrate temperature from 200 to 700degC. It was found that Fe nanoparticle size decreased from 36.8 nm to 7.6 nm with the increasing the substrate temperature. After the formation of nanoparticles, CNTs were successively grown by thermal CVD at 800degC. Acetylene gas was used as a carbon source. The density of CNTs also depends on Fe nanoparticle density. This density control of CNTs is useful for controlling the electron emission from CNT emitter devices.