Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

Abstract

In this work, we apply low energy ion beam analysis to examine directly how the adsorbed hydrogen concentration and binding configuration on W(100) depend on temperature. We exposed the tungsten surface to fluxes of both atomic and molecular H and D. We then probed the H isotopes adsorbed along different crystal directions using 1–2keV Ne+ ions. At saturation coverage, H occupies two-fold bridge sites on W(100) at 25°C. The H coverage dramatically changes the behavior of channeled ions, as does reconstruction of the surface W atoms. For the exposure conditions examined here, we find that surface sites remain populated with H until the surface temperature reaches 200°C. After this point, we observe H rapidly desorbing until only a residual concentration remains at 450°C. Development of an efficient atomistic model that accurately reproduces the experimental ion energy spectra and azimuthal variation of recoiled H is underway.