Measurement of Hydrogen Solubility in PdxCu100–x Thin Films Prepared by Pulsed Laser Deposition: An Electrochemical in Situ X-Ray Diffraction Analysis

Pulsed laser deposition was used to prepare PdxCu100?x thin films. The whole composition range (0 ≤ x ≤ 100) was investigated by varying the Pd/Cu surface area ratio on the target. Films were prepared on both Ti and Si substrates, with thickness not exceeding 100 nm. All films are made of disordered (Pd,Cu) solid solutions that crystallized in the Fm3?m space-group lattice. The density of the films is ca. 100% and does not vary with the composition of the films. Depth profile analyses made by X-ray photoelectron spectroscopy indicate that the relative Pd and Cu content is constant throughout the entire thickness of the film. Hydrogen absorption in PdxCu100?x thin films was determined by electrochemical in situ X-ray diffraction measurements. It is shown that a few (ca. 2) absorption/desorption cycles (cold annealing) are needed to reach a steady state, during which the film rearrange itself in a less stressed configuration via plastic deformations. Hydrogen absorption is not observed for x < 50, whereas the H/M value increases drastically for [Pd] > 65 at %, consistently with data from the literature. For 50 ≤ x ≤ 65, H/M increases from 0 to ca. 4%. A detailed comparison with the most recent theoretical calculations indicates this effect is due to an augmentation of the Pd content and of the lattice parameter, which both lead to an increase in the hydrogen binding energy in the octahedral site of the fcc structure. Pulsed laser deposition was used to prepare PdxCu100?x thin films. The whole composition range (0 ≤ x ≤ 100) was investigated by varying the Pd/Cu surface area ratio on the target. Films were prepared on both Ti and Si substrates, with thickness not exceeding 100 nm. All films are made of disordered (Pd,Cu) solid solutions that crystallized in the Fm3?m space-group lattice. The density of the films is ca. 100% and does not vary with the composition of the films. Depth profile analyses made by X-ray photoelectron spectroscopy indicate that the relative Pd and Cu content is constant throughout the entire thickness of the film. Hydrogen absorption in PdxCu100?x thin films was determined by electrochemical in situ X-ray diffraction measurements. It is shown that a few (ca. 2) absorption/desorption cycles (cold annealing) are needed to reach a steady state, during which the film rearrange itself in a less stressed configuration via plastic deformations. Hydrogen absorption is not observed for x < 50, whereas the H/M value increases drastically for [Pd] > 65 at %, consistently with data from the literature. For 50 ≤ x ≤ 65, H/M increases from 0 to ca. 4%. A detailed comparison with the most recent theoretical calculations indicates this effect is due to an augmentation of the Pd content and of the lattice parameter, which both lead to an increase in the hydrogen binding energy in the octahedral site of the fcc structure.