[¦plaz·mə ‚sȯrs ′ī·ən ‚im·plan‚tā·shən] (engineering) A method of ion implantation in which the workpiece is placed in a plasma containing the appropriate ion species and is repetitively pulse-biased to a high negative potential so that positive plasma ions are accelerated to the surface and implant in the bulk material. Abbreviated PSII.