Anomalous Structure of Palladium-Capped Magnesium Thin Films

Abstract: Pd capped pure Mg thin film (50 nm thick) was prepared by magnetron sputtering and its hydrogenation at room temperature has been investigated. After exposure to 4% hydrogen gas diluted by argon, the Pd/Mg thin films show drastic optical changes from the metallic state to the transparent state within five seconds by hydrogenation. Transmission electron microscope observation reveals that this sample has an anomalous structure; Mg grain is surrounded by Pd. This structure may be the reason why Pd/Mg films can be hydrogenated so quickly at room temperature.