there is disclosed an apparatus and method for focused electric field enhanced plasma - based ion implantation . the apparatus includes an implantation chamber , a vacuum pump for maintaining the pressure in the implantation chamber at a desired level , a sample holder , means for applying a negative potential to the sample holder , and means for supplying a gaseous or vaporized implantation material . the supplying means takes the form of a feed conduit having an exit opening located in the implantation chamber above the sample holder , and when a negative potential is applied to the sample holder the exit opening of the feed conduit is maintained at a potential that is positive relative to the sample holder .