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  • 1.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    The effect of nano-confinement on hydrogen uptake in metallic superlattices2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The absorption of hydrogen is exothermic in vanadium whereas it is endothermic in iron and chromium. Investigations of the hydrogen uptake within Fe/V(001) and Cr/V(001) superlattices allow therefore a detailed exploration of finite size effects and the influence of boundaries on hydrogen absorption. Fe/V(001) and Cr/V(001) superlattices can be grown as single crystal structures with a small mosaic spread, as determined by X-ray reflectometry and diffraction. Furthermore when the thickness ratio of the constituents is kept constant the crystal quality can be retained in the range from a few up to 40 monolayer repeat distances (Λ). Neutron reflectometry was used to simultaneously determine the volume expansion and concentration of hydrogen in the vanadium layers. Large differences are found in the expansion of Fe/V(001) and Cr/V(001) superlattices, in good agreement with density functional theory (DFT) calculations. The findings are consistent with tetrahedral and octahedral site occupancy in Cr/V(001) and Fe/V(001) superlattices, respectively. Full fitting of the reflectivity pattern is required to obtainan accurate measure of expansion if the number of repeats is small. Under these conditions, the shift of the first order superlattice peak can be an inaccurate measure of the volume changes. By using a specially designed neutron scattering chamber, allowing simultaneous neutron and optical transmission measurements, it is found that the optical transmission scales linearly with hydrogen concentration. By comparing the experimental results to ab-initio DFT calculations, it is shown that optical transmission scales with electron density changes in the samples, explaining the linearity with concentration. This change is dominated by the hydrogen induced expansion of the lattices and depends therefore strongly on the site occupancy of the hydrogen. Finally, X-ray diffraction was used to address the local strain fields and the α to β phase transition, typically observed in bulk vanadium. Below 448 K the results are consistent with an α to β phase co-existence, separated along the surface normal of the samples.

    List of papers
    1. Crystal perfection by strain engineering: The case of Fe/V (001)
    Open this publication in new window or tab >>Crystal perfection by strain engineering: The case of Fe/V (001)
    Show others...
    2017 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 636, p. 608-614Article in journal (Refereed) Published
    Abstract [en]

    We study the effect of bilayer thickness at fixed volume fraction on the structural quality of Fe/V (001)superlattices. We find that such artificial metallic superlattices can be manufactured with excellent crystalquality and layering up to at least 50 Å in repeat distance (K = LFe +LV). For an intended fixed ratio of theconstituents: LFe/LV= 1/7, out-of-plane coherence lengths comparable to the thicknesses of the sampleswere obtained. We evaluate the strain in- and out-of-plane of both layers as a function of the bilayer thicknessand comment on the growth using the framework of linear elasticity theory. We interpret the stabilityof the superlattice against crystal degradation due to the alternating compressive and tensile strain, yieldingclose to ideal lattice matching to the substrate.

    Keywords
    Superlattice; Iron/Vanadium; Sputtering; Epitaxy; Reciprocal space mapping; X-ray diffraction; X-ray reflectivity; Linear elasticity
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:uu:diva-332050 (URN)10.1016/j.tsf.2017.07.005 (DOI)000408037800086 ()
    Available from: 2017-10-23 Created: 2017-10-23 Last updated: 2019-12-06Bibliographically approved
    2. Beating effects in multilayer systems studied with neutron reflectometry
    Open this publication in new window or tab >>Beating effects in multilayer systems studied with neutron reflectometry
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    We demonstrate the limitations of a partial, phenomenological tting approach comparedto full simulations, including reection and refraction at all interfaces on theexample of hydrogen loading in ultra thin vanadium layers. Fe/V superlattices areloaded with deuterium and the lattice expansion and deuterium concentration isextracted from neutron reectivity data. We nd a noticeable dierence betweenthe direct extraction of concentrations and bilayer thicknesses from the superlatticepeaks and ts of the full density prole using the Parratt formalism. Our results underlinethe importance of carefully considering the limitations of phenomenologicalapproaches, in order to obtain robust results.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-350582 (URN)
    Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-09-14Bibliographically approved
    3. Using interfaces to influence thermodynamic properties of metal hydrides
    Open this publication in new window or tab >>Using interfaces to influence thermodynamic properties of metal hydrides
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    We report profound proximity effects on the enthalpy of solution and critical temperature ofnano-sized vanadium hydrides. We use single crystalline Cr/V and Fe/V (001) superlattices forthese studies, in which the V layers are under close to identical strain. The thermodynamic propertiesare determined using isothermal pressure and optical transmission measurements, utilisingthe fully reversibel hydrogen uptake and release.The underlying mechanism is argued to be rootedin a radically different volume expansion in the two systems, arising from different site occupancyof hydrogen in Fe/V(001) and Cr/V(001). The optical transmission is found to be linear withconcentration in both types of superlattices, while exhibiting different slopes. The differences areattributed to changes in electron density arising from the volume expansion, rather than a directinfluence from a redistribution of electronic states.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-350589 (URN)
    Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-09-14Bibliographically approved
    4. The influence of site occupancy on diffusion of hydrogen in vanadium
    Open this publication in new window or tab >>The influence of site occupancy on diffusion of hydrogen in vanadium
    Show others...
    2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 6, article id 064310Article, review/survey (Refereed) Published
    Abstract [en]

    We investigate the effect of site occupancy on the chemical diffusion of hydrogen in strained vanadium. The diffusion rate is found to decrease substantially, when hydrogen is occupying octahedral sites as compared to tetrahedral sites. Profound isotope effects are observed when comparing the diffusion rate of H and D. The changes in the diffusion rate are found to be strongly influenced by the changes in the potential energy landscape, as deduced from first-principles molecular dynamics calculations.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-275058 (URN)10.1103/PhysRevB.95.064310 (DOI)000395988800002 ()
    Note

    The manuscript version of this article is part of two PhD theses: http://uu.diva-portal.org/smash/record.jsf?pid=diva2:900624

    http://uu.diva-portal.org/smash/record.jsf?pid=diva2:950756

    Available from: 2016-01-28 Created: 2016-01-28 Last updated: 2018-05-14Bibliographically approved
    5. Finite size effects: deuterium diffusion in nm thick vanadium layers
    Open this publication in new window or tab >>Finite size effects: deuterium diffusion in nm thick vanadium layers
    Show others...
    2017 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, article id 123004Article in journal (Refereed) Published
    Abstract [en]

    We investigate the effect of finite size on the chemical diffusion of deuterium in extremely thin V(001) layers. A five fold increase in the diffusion coefficient is observed at concentrations around 0.2 [D/V], when the thickness of the V is decreased from 28 to 14 atomic layers (approximate to 2.1-4.2 nm). The size dependent deuterium-deuterium interaction energy is argued to be the root of the observed changes as the diffusion rates are similar at low concentrations. The results demonstrate the feasibility of using finite-size effects to enhance the chemical diffusion of light interstitials in solids. We discuss the general applicability of these effects to other systems.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2017
    Keywords
    superlattices, optical transmission, deuterium diffusion, octahedral sites
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-347665 (URN)10.1088/1367-2630/aa94df (DOI)000424885300004 ()
    Funder
    Swedish Energy AgencySwedish Research Council
    Available from: 2018-04-05 Created: 2018-04-05 Last updated: 2018-05-14Bibliographically approved
    6. Concentration dependence of hydrogen diffusion in clamped vanadium (001) films
    Open this publication in new window or tab >>Concentration dependence of hydrogen diffusion in clamped vanadium (001) films
    Show others...
    2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 4, article id 045402Article in journal (Refereed) Published
    Abstract [en]

    The chemical diffusion coefficient of hydrogen in a 50 nm thin film of vanadium (0 0 1) is measured as a function of concentration and temperature, well above the known phase boundaries. Arrhenius analysis of the tracer diffusion constants reveal large changes in the activation energy with concentration: from 0.10 at 0.05 in II V-1 to 0.5 eV at 0.2 in II V-1. The results are consistent with a change from tetrahedral to octahedral site occupancy, in that concentration range. The change in site occupancy is argued to be caused by the uniaxial expansion of the film originating from the combined hydrogen induced expansion and the clamping of the film to the substrate.

    Keywords
    diffusion, hydrogen, single crystal
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-312024 (URN)10.1088/1361-648X/29/4/045402 (DOI)000389233200001 ()
    Funder
    Swedish Energy AgencySwedish Research Council
    Available from: 2017-01-05 Created: 2017-01-04 Last updated: 2018-09-14Bibliographically approved
    7. Experimental observation of hysteresis in a coherent metal-hydride phase transition
    Open this publication in new window or tab >>Experimental observation of hysteresis in a coherent metal-hydride phase transition
    Show others...
    2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 49, article id 495701Article in journal (Refereed) Published
    Abstract [en]

    We investigate the hysteresis obtained in the hydrogen absorption and desorption cycle for a single crystal Pd/V-28 [Fe-4/V-28](11) superlattice. Below the critical temperature, a small but clear hysteresis is observed in the pressure-composition isotherms, while it is absent above. The experimental results thereby prove the relevance of macroscopic energy barriers for obtaining hysteresis in coherent structural transformations. The textured Pd layer exhibits substantially larger hysteresis effects, which can be related to an irreversible energy loss caused by defect generation in Pd.

    Place, publisher, year, edition, pages
    IOP PUBLISHING LTD, 2017
    Keywords
    hysteresis, coherent, incoherent, phase transition
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-342651 (URN)10.1088/1361-648X/aa9696 (DOI)000415854900001 ()
    Funder
    Swedish Energy AgencySwedish Research Council
    Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-05-14Bibliographically approved
  • 2.
    Droulias, Sotirios A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Komander, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Tailoring thermodynamic properties of metal hydrides with interfacesManuscript (preprint) (Other academic)
    Abstract [en]

    We report profound changes in the enthalpy of solution and critical temperature of nano-sizedmetal hydrides in proximity to dierent non-absorbing metals. We use Cr/V and Fe/V (001) superlatticesas model systems to map out these eects since the superlattices can be made singlecrystalline,have identical strain states and are fully reversible. The thermodynamic propertiesare determined using isothermal pressure and optical transmission measurements. We determinethe mechanism underlying the changes in the thermodynamic properties as well as the ecacyof optical transmission by utilizing simultaneous neutron reectometry and optical transmissionmeasurements, combined with rst principle calculations. The underlying mechanism, which issupported by quantitative agreement between theory and experiment is found to be rooted in aradically dierent volume expansion in the two systems. The commonly used optical transmissionmethod is found to be linear with concentration in both types of superlattices and is attributed tochanges in electron density, rather than a direct inuence from a redistribution of electronic states.The conclusions are generalized to other metal hydride systems and can open up for exploration ofproximity induced eects in metal hydrides.

  • 3.
    Droulias, Sotirios A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Komander, Kristina
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Using interfaces to influence thermodynamic properties of metal hydridesManuscript (preprint) (Other academic)
    Abstract [en]

    We report profound proximity effects on the enthalpy of solution and critical temperature ofnano-sized vanadium hydrides. We use single crystalline Cr/V and Fe/V (001) superlattices forthese studies, in which the V layers are under close to identical strain. The thermodynamic propertiesare determined using isothermal pressure and optical transmission measurements, utilisingthe fully reversibel hydrogen uptake and release.The underlying mechanism is argued to be rootedin a radically different volume expansion in the two systems, arising from different site occupancyof hydrogen in Fe/V(001) and Cr/V(001). The optical transmission is found to be linear withconcentration in both types of superlattices, while exhibiting different slopes. The differences areattributed to changes in electron density arising from the volume expansion, rather than a directinfluence from a redistribution of electronic states.

  • 4.
    Droulias, Sotirios A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Beating effects in multilayer systems studied with neutron reflectometryManuscript (preprint) (Other academic)
    Abstract [en]

    We demonstrate the limitations of a partial, phenomenological tting approach comparedto full simulations, including reection and refraction at all interfaces on theexample of hydrogen loading in ultra thin vanadium layers. Fe/V superlattices areloaded with deuterium and the lattice expansion and deuterium concentration isextracted from neutron reectivity data. We nd a noticeable dierence betweenthe direct extraction of concentrations and bilayer thicknesses from the superlatticepeaks and ts of the full density prole using the Parratt formalism. Our results underlinethe importance of carefully considering the limitations of phenomenologicalapproaches, in order to obtain robust results.

  • 5.
    Droulias, Sotirios A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Limitations of the kinematic approximation in neutron reflectivity measurements for the analysis of bilayers2018In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 51, p. 1556-1563Article in journal (Refereed)
    Abstract [en]

    The limitations of a phenomenological fitting approach compared to simulations of the optical model including reflection and refraction at all interfaces are demonstrated using the example of hydrogen loading in ultra-thin vanadium layers. Fe/V superlattices are loaded with deuterium and the lattice expansion and deuterium concentration are extracted from neutron reflectivity data. A noticeable difference is found between the extraction of concentrations and bilayer thicknesses directly from the superlattice peaks and fits of the density profile using the Parratt formalism. The results underline the importance of carefully considering the limitations of phenomenological approaches, in order to obtain robust results. The limitations of the kinematic approximation for the analysis are discussed in detail.

  • 6.
    Droulias, Sotirios A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ali, Hasan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Crystal perfection by strain engineering: The case of Fe/V (001)2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 636, p. 608-614Article in journal (Refereed)
    Abstract [en]

    We study the effect of bilayer thickness at fixed volume fraction on the structural quality of Fe/V (001)superlattices. We find that such artificial metallic superlattices can be manufactured with excellent crystalquality and layering up to at least 50 Å in repeat distance (K = LFe +LV). For an intended fixed ratio of theconstituents: LFe/LV= 1/7, out-of-plane coherence lengths comparable to the thicknesses of the sampleswere obtained. We evaluate the strain in- and out-of-plane of both layers as a function of the bilayer thicknessand comment on the growth using the framework of linear elasticity theory. We interpret the stabilityof the superlattice against crystal degradation due to the alternating compressive and tensile strain, yieldingclose to ideal lattice matching to the substrate.

  • 7.
    Huang, Wen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Mooij, Lennard P. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Concentration dependence of hydrogen diffusion in clamped vanadium (001) films2017In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 4, article id 045402Article in journal (Refereed)
    Abstract [en]

    The chemical diffusion coefficient of hydrogen in a 50 nm thin film of vanadium (0 0 1) is measured as a function of concentration and temperature, well above the known phase boundaries. Arrhenius analysis of the tracer diffusion constants reveal large changes in the activation energy with concentration: from 0.10 at 0.05 in II V-1 to 0.5 eV at 0.2 in II V-1. The results are consistent with a change from tetrahedral to octahedral site occupancy, in that concentration range. The change in site occupancy is argued to be caused by the uniaxial expansion of the film originating from the combined hydrogen induced expansion and the clamping of the film to the substrate.

  • 8.
    Huang, Wen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Diffusion of hydrogen in ultra-thin V(001) layers2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 723, p. 484-487Article in journal (Refereed)
    Abstract [en]

    We report on investigations of the influence of one dimensional confinement on the diffusion of hydrogen, in the low concentration limit (alpha-phase). The confinement is obtained by utilising single crystal Fe/V(001) superlattices, in which hydrogen preferably resides in the V layers. The diffusion along the [110] direction in the V(001) layers can thereby be determined. Activation energy and attempt jump rates are extracted from an Arrhenius analysis. No effects are observed from the confinement on the hydrogen diffusion in the thickness range 7-28 monolayers (approximate to 1.1-4.2 nm) of V(001).

  • 9.
    Huang, Wen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Brischetto, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Experimental observation of hysteresis in a coherent metal-hydride phase transition2017In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 49, article id 495701Article in journal (Refereed)
    Abstract [en]

    We investigate the hysteresis obtained in the hydrogen absorption and desorption cycle for a single crystal Pd/V-28 [Fe-4/V-28](11) superlattice. Below the critical temperature, a small but clear hysteresis is observed in the pressure-composition isotherms, while it is absent above. The experimental results thereby prove the relevance of macroscopic energy barriers for obtaining hysteresis in coherent structural transformations. The textured Pd layer exhibits substantially larger hysteresis effects, which can be related to an irreversible energy loss caused by defect generation in Pd.

  • 10.
    Huang, Wen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Brischetto, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Finite size effects: deuterium diffusion in nm thick vanadium layers2017In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, article id 123004Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of finite size on the chemical diffusion of deuterium in extremely thin V(001) layers. A five fold increase in the diffusion coefficient is observed at concentrations around 0.2 [D/V], when the thickness of the V is decreased from 28 to 14 atomic layers (approximate to 2.1-4.2 nm). The size dependent deuterium-deuterium interaction energy is argued to be the root of the observed changes as the diffusion rates are similar at low concentrations. The results demonstrate the feasibility of using finite-size effects to enhance the chemical diffusion of light interstitials in solids. We discuss the general applicability of these effects to other systems.

  • 11.
    Komander, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Humboldt Univ, Newtonstr 15, D-12489 Berlin, Germany.
    Moro, Marcos V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Müggenburg, J.
    Marburg Univ, Fac Math & Comp Sci, Hans Meerwein Str 6, D-35032 Marburg, Germany.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hydrogen site location in ultrathin vanadium layers by N-15 nuclear reaction analysis2019In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 455, p. 57-60Article in journal (Refereed)
    Abstract [en]

    We present a method using resonant nuclear reaction analysis combined with optical transmission and heavy-ion Rutherford backscattering spectrometry to study the absorption of hydrogen in single crystalline thin vanadium films. Probing with the resonant H-1(N-15,alpha gamma)C-12 reaction allows for highly resolved hydrogen depth profiling, while measurements along the crystal axes render possible the direct identification of the interstitial site occupancy. First experiments were performed on thin vanadium hydrides in Fe(Cr)/V superlattices revealing differences in site occupancy.

  • 12.
    Mooij, Lennard
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Huang, Wen
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Johansson, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Xin, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    The influence of site occupancy on diffusion of hydrogen in vanadium2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 6, article id 064310Article, review/survey (Refereed)
    Abstract [en]

    We investigate the effect of site occupancy on the chemical diffusion of hydrogen in strained vanadium. The diffusion rate is found to decrease substantially, when hydrogen is occupying octahedral sites as compared to tetrahedral sites. Profound isotope effects are observed when comparing the diffusion rate of H and D. The changes in the diffusion rate are found to be strongly influenced by the changes in the potential energy landscape, as deduced from first-principles molecular dynamics calculations.

  • 13.
    Mooij, Lennard
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Huang, Wen
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Xin, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Johansson, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Site-dependence of hydrogen diusion in vanadiumManuscript (preprint) (Other academic)
1 - 13 of 13
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