Effect of Angled-Wall Etch Design on CNT Growth and Propellant Ionization

LT Brandi Gilbert, US Navy

Abstract: The carbon nanotube configurations that have been analyzed for ion thrusters usually only ionize a small fraction of the propellant particles flowing close enough to the tip of the nanotubes to interact with the strong electric field. Rearranging the current configuration from a perpendicular pillar array to an angled array grown on the sidewalls of nozzles normal to the flow of the propellant would produce a greatly increased surface area for propellant ionization and would increase the overall mass utilization factor (MUF) of the ion thruster system. Several methods were investigated to modify a Bosch etching recipe and create tapered etch profiles on silicon wafers, and carbon nanotubes were grown several different profiles including an angled surface. The carbon nanotubes were successfully grown on 45-degree angle wall and a promising recipe for Bosch etching nozzles was established. The carbon nanotubes grew perpendicular to the surface of a 45-degree nozzle sidewall which ultimately offers potential for increase of overall mass utilization factor.