Profile studies of hydrogen trapping in metals due to ion damage

Abstract

The retention of hydrogen isotopes in Mo at room temperature after ion implantation damage has been studied by measurements of H depth profiles and total D retained in the near-surface region. Implantations of He, O, Ne, and Bi in a fluence range 3×1014–2×1017/cm2 were followed by 8-keV hydrogen bombardment to fluences of 2×1015–2×1017/cm2. Large enhancements in the amount of hydrogen retained in preimplanted samples over samples without prior implantation have been observed and are interpreted in terms of damage trapping. For a given predamage ion fluence hydrogen retention increases linearly with hydrogen fluence until a saturation level is reached. Increased predamage fluence results in increased saturation level for hydrogen trapping, with average concentrations as high as ∼10 at.% achieved. An ion-mass dependence indicates that the lighter ions, which create fewer primary displacements, are more effective in hydrogen trapping, suggesting a dependence on the damage density in the ion cascades.