INFLUENCE OF METALLIC HOST STRUCTURE ON MOLECULAR HYDROGEN EMBEDDED AND STABILITY UNDER ION IMPLANTATION

With this study we would like to confirm previously predicted computationnal results regarding the formation of molecular hydrogen during ion-metal interactions.The formation of defects in iron and titanium and their binding to hydrogen were analyzed using the positron lifetime method using calculations made with the MIKA software package.The observed decrease in the positron lifetime indicates a structural saturation with hydrogen, probably in its molecular form, and suggests the formation of T(H)2 complexes in the induced cavities.These accumulations and additionnal hydride bonds act as barriers for hydrogen diffusion to the surface.For a perfect lattice in titanium in its hexagonal structure, a lifetime of 143 ps was calculated.For a vacancy with a few implanted atoms, we calculated a lifetime of 142 ps.For a perfect lattice for alpha iron, we obtained a value for the positron lifetime of 100 ps.An iron's vacancy with six implanted hydrogen atoms reports a lifetime of 101 ps.