Interplay of surface adsorption and preferential sputtering in metal plasma immersion ion implantation and deposition

Abstract

Formation of hard ceramic surface layer by metal plasma immersion ion implantation and deposition (MePIIID) can be a quite complex process as quite a number of different species, including condensable metallic ions, electrons and neutral gas, which can be partially ionised, are interacting in the vacuum chamber and impinging on the surface. The resulting growth rate and chemical composition will be determined by the complex interplay of surface adsorption, ion implantation and preferential sputtering. Here, an overview of these effects is given for the important systems ZnO, TiO 2, TiN and AlN prepared by MePIIID. In ZnO, the predominant mechanism is preferential oxygen sputtering. However, the oxygen adsorption from the background gas is stronger in the case of TiO 2, leading to a constant Ti/O ratio beyond a threshold in the oxygen gas flow for this compound. This effect is less pronounced for TiN, where a continuously varying Ti/N ratio was found only for a varying gas flow and independent of the pulse voltage. In contrast, a constant Al/N ratio over a broad range of nitrogen gas flows was observed for AlN.