Proximity and dimensionality effects on interstitial hydrogen

• In this study, we investigate the proximity effects on hydrogen distribution in ultrathin single crystalline vanadium films, by comparing the absorption in Fe/V- and Cr/V-superlattices. Pressure concentration isotherms show higher absolute solubility of hydrogen in a Cr/V-superlattice. Isotherms of excess resistivity are used to locate phase boundaries which yielded a higher critical temperature and concentration in Cr/V. Measurements of hydrogen site location and thermal vibrations using 15N-nuclear reaction analysis demonstrate identical site occupation of 0Z at room temperature with a vibrational amplitude of 0.20‑0.25 Å over a wide range of hydrogen concentrations in both superlattices. The analysis excludes changes in site occupancy as the primary cause for variations in thermodynamics across different temperatures due to proximity. Our findings are consistent with a more extended region of hydrogen depletion in the vicinity of Fe and resolve previously puzzling differences in the hydrogen loading of Fe/V- and Cr/V-superlattices, implying an inverse spillover effect.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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