The influence of ion irradiation on hydrogen chemisorption and diffusion on gadolinium surfaces

The role of irradiation induced surface defects on the chemisorption process of hydrogen and inward penetration of chemisorbed H atoms was studied on sputtered, with 4.5 keV Ar + ions and on annealed gadolinium surfaces. A combination of Direct Recoil Spectrometry (DRS) and Contact Potential Difference (CPD) enabled to distinct between topmost surface and subsurface processes. Simulations of irradiation-induced defects, which assume two types of defects-vacancies due to sputtering and Frenkel pairs, taking account of the annealing processes occurring at different temperatures, have reasonably reproduced the experimental Ar scattering peaks in the DR spectra. It has been concluded that the presence of surface defects has a significant effect on the binding energies of the chemisorbed hydrogen, resulting in hydrogen trapping on the surface and affects the surface to subsurface inward penetration process.