Pd thickness and temperature dependence of the sheet resistance of Pd/Y bilayers under vacuum, O2, and D2

Le résumé fourni par la source

Pd/Y bilayers have a high hydrogen sorption ability suitable for their use as low temperature hydrogen getter for vacuum packaging and for hydrogen sensing applications. Pd/Y bilayers with variable Pd thicknesses in the 4–40 nm range were e-beam evaporated on silicon in ultrahigh vacuum. Deposition rate of the Pd ultrathin films was calibrated by grazing incidence X-Ray reflectivity measurements on films deposited on silicon. Sheet resistance measurements of the Pd/Y bilayers were performed as function of temperature in high vacuum, under a low partial pressure of deuterium, and under a low partial pressure of oxygen. Results show that Pd thicknesses above 15 nm efficiently passivate the yttrium surface against oxidation up to at least 250 °C and that the onset temperature of formation of yttrium dihydride does not vary significantly with Pd overlayer thickness. For thinner Pd films, because of Pd film discontinuity allowing yttrium oxidation, yttrium hydrogenation is slowed down.

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