CVD growth of carbon nanotube bundle arrays

Recent discovery of enhanced field emission current intensity from arrays of bundles of carbon nanotubes (CNT) has prompted this investigation of the growth of CNT bundle arrays by metal-catalyzed chemical vapor deposition (CVD), in order to understand and control the growth of these arrays. CNT bundle array growth has been characterized as a function of array geometric parameters: the CNT bundle diameter and inter-bundle spacing. We find that CNT bundle array growth varies significantly with bundle size and spacing, which we suggest is due to the formation of a volatile molecular byproduct of ethylene decomposition that enhances CNT growth in areas with high concentrations of metal catalyst. We have also studied and optimized CNT growth with respect to a variety of CVD process parameters, in order to control the length of the resultant CNT bundles. We find that the length of the CNT can be reliably controlled by varying either the reaction time or the gas pressure. Such control over CNT bundle length will be crucial in the incorporation of these bundle arrays into high-intensity electron field emission devices.