Particle-scattering phenomenon of powders caused by charging voltage of the surface during ion implantation

The particle-scattering phenomenon caused by charge-up in ion implantation into spherical dielectric powders in a stationary state or in a vibrational state with no neutralizer was studied theoretically and experimentally. The theoretical threshold charging voltage for scattering was obtained from the force balance equation between the Coulomb repulsive force and the attractive van der Waals force and gravity. The estimated charging voltage which starts scattering of powders agrees well with experimental results for positive-ion implantation into powders both in a stationary state and a vibrational state. Scattering took place even at an ion acceleration voltage of about 1 kV for positive-argon-ion implantation. Conversely, no scattering was observed for negative-carbon-ion implantation at an ion acceleration voltage of 20 kV in a stationary state. The negative-ion implantation technique was found to be a non-scattering implantation method for dielectric powders.