MODEL FOR EXPANDING SHEATHS AND SURFACE CHARGING AT DIELECTRIC SURFACES DURING PLASMA SOURCE ION-IMPLANTATION

Plasma source ion implantation utilizes negative high voltage pulses a pplied to targets immersed in a plasma. This produces an expanding she a which accelerates ions into the target. A model for expanding sheath s at dielectric surfaces is developed; the significant differences bet ween this and metal targets are the finite dielectric constant of the material and accumulation of charge in the nonconducting material. A m odel is developed for an expanding sheath at a dielectric surface and applied to a polyethylene sheet as an example. The most significant ef fect is the reduction of the energy at which ions are implanted in the material because of charging at the surface of the polyethylene.