Thin film deposition for permeability increase of gas being implanted (theoretical consideration)

Abstract

A theoretical model has been developed for diffusive permeation of gas injected by ion bombardment through thin metallic targets, including membranes with thin films deposited onto the surface. The film material differs from the substrate material. Calculations for gas atom distribution in the film and substrate have been carried out, as well as gas fluxes to the source and sink sides in such a system in a quasi-stationary régime. The possibility of a permeability increase is revealed under implantation of gas ions both with low (∼ keV) and higher energies (of the order of tens of keV) by deposition onto an irradiated target surface having a film of material with a lower diffusion coefficient for the gas being implanted than the substrate material itself. It has been shown that the most significant effect may be obtained under relatively high energy implantation for deposited film thicknesses markedly less than the mean ion range, and where the film permeability (diffusion coefficient and/or gas solubility) is much smaller than that of the substrate material itself. Periodic or simultaneous with implantation film renewal on the target surface has been suggested to compensate for sputtering.