Thickness dependence of the hydrogen solubility in epitaxial Nb(110) films grown on Al2O3(11.0) substrates

Abromeit, A.; Siebrecht, R.; Song, Guang‐Ling; Zabel, H.; Klose, F.; Nagengast, D.; Weidinger, A.

doi:10.1016/s0925-8388(96)02972-6

Cited by 13 publications

(7 citation statements)

References 7 publications

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“…These results will be reported elsewhere. 23 It should, however, be mentioned here that preliminary analysis indicates a maximum hydrogen concentration on the order of only 95%. This is still much higher than in the bulk, but somewhat smaller than estimated using the bulk conversion factor f .…”

Section: ͑4͒mentioning

confidence: 75%

Solubility isotherms of hydrogen in epitaxial Nb(110) films

et al. 1996

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The solubility isotherms of hydrogen in epitaxial Nb͑110͒ films have been determined via in situ x-ray lattice-parameter measurements. The Nb films were grown by molecular-beam epitaxial techniques on Al 2 O 3 (1120) substrates with thicknesses ranging from 32 to 527 nm. All isotherms can be well described by the standard expression for the solubility of a monatomic lattice gas. Aside from the metal-hydrogen interaction, which appears to be bulklike, all other properties exhibit a strong thickness dependence, including the hydrogen-hydrogen interaction, the critical temperature for the ␣-␣Ј transition, and the maximum latticeparameter change that can be reached in saturation. For the critical temperature we find a scaling with the film thickness, which most likely is due to the elastic boundary condition provided by the rigid substrate. The clamping of the epitaxial film to the substrate hinders critical fluctuations of macroscopic hydrogen density modes from developing, thereby lowering the critical temperature for the ␣-␣Ј transition.

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Section: ͑4͒mentioning

confidence: 75%

Solubility isotherms of hydrogen in epitaxial Nb(110) films

et al. 1996

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“…In small angle neutron reflectivity measurements the position of the critical angle for total reflection depends sensitively on the hydrogen concentration and the isotope chosen. 22 At high angles the periodic modulation of deuterium atoms gives rise to additional Bragg reflections which cannot be seen using x rays. The structure factors of the individual Bragg reflections depend explicitly on the H or D concentration.…”

Section: Neutron Scatteringmentioning

confidence: 99%

Hydrogen and deuterium in epitaxial Y(0001) films: Structural properties and isotope exchange

et al. 1999

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Hydrogen in yttrium is of fundamental interest as a model system for driving metal-insulator transitions including switchable optical properties from reflecting to transparent in the visible region. We report on the structural properties of hydrogenated and deuterated thin, monocrystalline Y͑0001͒ films grown by molecular beam epitaxy on Nb/Al 2 O 3 substrates. X-ray diffraction reveals the response of the host metal lattice upon hydrogen loading. The structural coherence in all three spatial directions as well as the epitaxial relation to the substrate are maintained, though the sample undergoes structural phase transitions between the different hydride phases. With neutron reflectivity measurements we have determined the hydrogen and deuterium content since the critical angle for total reflection depends on their concentration in the sample. Measurements on hydrogenated and deuterated films show that H and D are completely interchangeable within the trihydride phase. Neutron scattering also allows us to determine the position of the deuterium atoms within the yttrium matrix. All structural information gained on thin films is in agreement with the space group P3 c1 which was previously determined from powder samples.

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“…Slight deviations from the continuous linear behavior associated with Sievert's law were observed and attributed to a different hydrogen absorption potential in the film near the substrate. 9 The validity of Vegard's law ͑the linear behavior of lattice strain versus concentration͒ in single-layer epitaxial Nb has been investigated at low hydrogen concentration by Reimer et al 6 and at high concentration by Abromeit et al 10 Enhanced out-of-plane expansion was observed at low concentration ͑ഛ0.02 ͓H͔ / ͓Nb͔͒ at room temperature that exceeds by a factor of 4 the anisotropic one-dimensional expansion expected from a clamped elastic medium. 6 The expected one-dimensional expansion was observed at high concentration ͑ϳ1͓H͔ / ͓Nb͔͒ above the critical point in a 320 Å thick film by Abromeit et al 10 The out-of-plane strain of a thicker film ͑780 Å͒, again above the critical point, exhibited the behavior expected from bulk Nb, 10 somewhat at variance, with the generally accepted behavior of thin film Nb.…”

Section: Introductionmentioning

confidence: 99%

Lattice strain measurements of deuteride (hydride) formation in epitaxial Nb: Additional results and further insights into past measurements

Allain

Heuser

2005

Phys. Rev. B

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The evolution of lattice strain during in situ gas-phase deuterium loading of epitaxial ͑110͒ Nb films on the ͑1120͒ sapphire was measured with x-ray diffraction. Two samples with film thicknesses 208 and 1102 Å were driven through the miscibility gap. Strains in three orthogonal directions were recorded, permitting the complete set of unit cell parameters to be determined for both the solid solution and deuteride phases. The overall film thickness was simultaneously measured by recording the glancing angle reflectivity response. The behavior of the two films was markedly different, with the thicker film exhibiting a much more compliant behavior and concomitant irreversible plastic deformation. The correlation between out-of-plane lattice and film expansion for both films is also consistent with this observation. These results help explain past inconsistencies observed by others.

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Thickness dependence of the hydrogen solubility in epitaxial Nb(110) films grown on Al2O3(11.0) substrates

Cited by 13 publications

References 7 publications

Solubility isotherms of hydrogen in epitaxial Nb(110) films

Solubility isotherms of hydrogen in epitaxial Nb(110) films

Hydrogen and deuterium in epitaxial Y(0001) films: Structural properties and isotope exchange

Lattice strain measurements of deuteride (hydride) formation in epitaxial Nb: Additional results and further insights into past measurements

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