STRUCTURAL EVOLUTION OF Pd-CAPPED Mg THIN FILMS UNDER H2 ADSORPTION AND DESORPTION CYCLES

In this paper we present a study on the relation between the evolution, upon successive H2 cycling, of the crystalline order and the H2 sorption properties of Pd-capped textured Mg thin films grown on Si and glass substrates. Using an asymmetric diffraction geometry suitable for thin films, it is found that: i) hydrogen desorption can be achieved at low temperatures exposing the samples to air and ii) already upon one hydrogen absorption–desorption cycle, the original texture is lost. Moreover metal-to-insulator transition following magnesium hydride formation is observed through spectrophotometry. However, cycling results in being detrimental to film properties, mainly due to the Pd cap degradation and correlated processes