POSITIVE-ION CURRENT TO A SPHERICAL ELECTRODE IN A NEGATIVE-ION PLASMA

Critical parameters for the development of the plasma-source ion impla ntation process are the ion implantation current and the sheath expans ion characteristics. Recently, Xia and Chan [J. Appl. Phys. 73, 3651 ( 1993)] have investigated these parameters for small spherical electrod es inserted in a two component positive ion-electron plasma. This inve stigation is extended to a plasma that consists of three components: p ositive ions, negative ions, and electrons.