A high-resolution core-level study of Ni-catalyzed absorption and desorption of hydrogen in Mg-films

Ultra-thin magnesium and magnesium-nickel films grown on Mo(1 1 0) under ultra-high vacuum (UHV) conditions are hydrogenated at room temperature with atomic H and studied by high-resolution core-level photoelectron spectroscopy (PES). For the Mg-film a layer of hydride is formed at the Mg/Mo interface and a sub-mono layer of hydride is formed at the surface, while an intermediate region remained non-hydrogenated. For the Mg-Ni-film a thick layer of surface hydride was detected, showing that Ni enhances formation of Mg-hydride at the surface. During the heat-up of the hydrogenated Mg-Ni-film hydrogen desorption started at 400 K.