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The interaction of atomic and to some extent molecular hydrogen (deuterium) with oxygen and carbon covered V(100) surfaces has been studied. The oxygen and carbon coverage has been well characterized with respect to composition and structure by low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). Thermal desorption spectroscopy (TDS) has been used to investigate the kinetics of adsorption, absorption and desorption quantitatively. In addition, the activation barriers for the individual reaction steps during adsorption and desorption have been determined. We have focused on the advantage of using atomic hydrogen to enhance the uptake of hydrogen into the bulk of a contaminated vanadium sample. Surface, subsurface and bulk sites are occupied upon exposure to the atomic H (D) even at a surface temperature of 90 K. These adsorption states exhibit desorption peaks at 150 K (alpha-state), between 200 and 500 K (beta-states), and at 1000 K (gamma-state). The corresponding desorption energies are 0.36 eV, 0.4 - 1.1 eV, and 0.9 eV, respectively. The kinetics of adsorption and absorption for molecular hydrogen depend strongly on the chemical composition of the surface, whereas the interaction of atomic hydrogen (deuterium) with V(100) is much less influenced by surface contaminants.
Corresponding author: A. Winkler (Graz). Reprints also available from P. Varga (varga).
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