Room-temperature hydrogen-induced resistivity response of Pd/Mg–Ni film

The structure and the response of the effective electrical resistivity 〈ρ〉 in hydrogenation–dehydrogenation processes of palladium-coated/magnesium-nickel (Pd/Mg–Ni) films were investigated as functions of Mg-to-Ni ratio, substrate temperature, and thickness of Pd overcoat. Films of noncrystalline structures with various Mg-to-Ni ratios showed prominent hydrogen-(H-)induced switching effect of 〈ρ〉. A film is supposed to contain segregated noncrystalline regions of different Mg-to-Ni ratios. The regions of an Mg-to-Ni ratio close to 2 are responsible for the switching processes. At room temperature, a dehydrogenation process is much slower than a hydrogenation process. Crystallization hindered the H-induced switching effect of 〈ρ〉. The use of a thicker Pd overcoat accelerated the change of 〈ρ〉 in the initial hydrogenating process but diminished the contrast. Results led to some discussions on the mechanisms governing the switching effects.