Adsorption kinetics and energetics of atomic hydrogen (deuterium) on oxygen and carbon covered V(100)

The interaction of atomic and to some extent molecular hydrogen (deuterium) with oxygen and carbon covered V(100) surfaces has been studied. The oxyge n and carbon coverage has been well characterized with respect to compositi on and structure by low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). Thermal desorpt ion spectroscopy (TDS) has been used to investigate the kinetics of adsorpt ion, 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 hyd rogen to enhance the uptake of hydrogen into the bulk of a contaminated van adium sample. Surface, subsurface and bulk sites are occupied upon exposure to the atomic H (D) even at a surface temperature of 90 K, These adsorptio n states exhibit desorption peaks at 150 K (alpha-state), between 200 and 5 00 K (beta-states), and at 1000 K (gamma-state). The corresponding desorpti on 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 hyd rogen (deuterium) with V(100) is much less influenced by surface contaminan ts. (C) 2000 Elsevier Science B.V. All rights reserved.