Wagner, Stefan

[["dc.bibliographiccitation.firstpage","123"],["dc.bibliographiccitation.journal","JOURNAL OF NANO RESEARCH"],["dc.bibliographiccitation.lastpage","133"],["dc.bibliographiccitation.volume","26"],["dc.contributor.author","Cizek, Jakub"],["dc.contributor.author","Melikhova, Oksana"],["dc.contributor.author","Vlcek, Marian"],["dc.contributor.author","Lukac, Frantisek"],["dc.contributor.author","Vlach, Martin"],["dc.contributor.author","Dobron, Patrik"],["dc.contributor.author","Prochazka, Ivan"],["dc.contributor.author","Anwand, Wolfgang"],["dc.contributor.author","Brauer, Gerhard"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Uchida, Helmut"],["dc.contributor.author","Gemma, Ryota"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T09:46:42Z"],["dc.date.available","2018-11-07T09:46:42Z"],["dc.date.issued","2014"],["dc.description.abstract","Hydrogen interaction with defects and structural development of Pd films with various microstructures were investigated. Nanocrystalline, polycrystalline and epitaxial Pd films were prepared and electrochemically loaded with hydrogen. Structural changes of Pd films caused by absorbed hydrogen were studied by in-situ X-ray diffraction combined with acoustic emission and measurement of electromotorical force. Development of defects during hydrogen loading was investigated by positron annihilation spectroscopy. It was found that hydrogen firstly fills open volume defects existing already in the films and subsequently it occupies also interstitial sites in Pd lattice. Absorbed hydrogen causes volume expansion, which is strongly anisotropic in thin films. This introduces high stress into the films loaded with hydrogen. Acoustic emission measurements revealed that when hydrogen-induced stress achieves a certain critical level rearrangement of misfit dislocations takes place. The stress which grows with increasing hydrogen concentration can be further released by plastic deformation and also by detachment of the film from the substrate."],["dc.identifier.doi","10.4028/www.scientific.net/JNanoR.26.123"],["dc.identifier.isi","000330816600018"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34943"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Trans Tech Publications Ltd"],["dc.relation.issn","1661-9897"],["dc.relation.issn","1662-5250"],["dc.title","Hydrogen Interaction with Defects in Nanocrystalline, Polycrystalline and Epitaxial Pd Films"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1862"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Acta Materialia"],["dc.bibliographiccitation.lastpage","1870"],["dc.bibliographiccitation.volume","59"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T08:58:41Z"],["dc.date.available","2018-11-07T08:58:41Z"],["dc.date.issued","2011"],["dc.description.abstract","Palladium hydrogen thin films are used as a model system to investigate the impact of microstructure and mechanical stress release on the electrical resistivity of thin film metals and alloys that undergo structural phase transitions. The results are compared with bulk resistivity models. Nanocrystalline, multi-oriented and epitaxial films are investigated, yielding initial terminal resistivities rho(infinity)(0) = 152 - 200 Omega nm. The hydrogen-related resistivity changes of epitaxial films are shown to approach the predicted a-phase bulk increment Delta rho(H)/Delta c(H) = 451 Omega nm, while hydrogen trapping in nanocrystalline films strongly reduces the resistivity response. In the two-phase region, the resistivity is shown to be modified by the steric distribution and geometry of the hydride precipitates, yielding different proportions of serial and parallel conduction. Film delamination from the substrate strongly reduces the resistivity increment due to the Gorsky effect. (c) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft (DFG) [PU 131/7-2]"],["dc.identifier.doi","10.1016/j.actamat.2010.11.052"],["dc.identifier.isi","000287775400002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23703"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Pergamon-elsevier Science Ltd"],["dc.relation.issn","1359-6454"],["dc.title","Combined impact of microstructure and mechanical stress on the electrical resistivity of PdHc thin films"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1387"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Acta Materialia"],["dc.bibliographiccitation.lastpage","1394"],["dc.bibliographiccitation.volume","58"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T08:45:57Z"],["dc.date.available","2018-11-07T08:45:57Z"],["dc.date.issued","2010"],["dc.description.abstract","During hydrogen gas loading, Pd thin films exhibit an anomalous reduction of resistivity change with decreasing film thickness. In this paper we show that this effect can mainly be attributed to a stress-dependent reduction of hydrogen solubility at a given hydrogen pressure. Different stress states of the thin films result from different bonding to a rigid substrate. Strongly buckled thin films show bulk-like pressure-resistivity isotherms. The resistivity changes as a function of hydrogen concentration appear to be independent of film thickness. The apparent Sieverts' constant seems to be larger for thin films compared to bulk, and increases with cycling of the thin films. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.actamat.2009.10.045"],["dc.identifier.isi","000274616000020"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20574"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Pergamon-elsevier Science Ltd"],["dc.relation.issn","1359-6454"],["dc.title","Electrical resistivity and hydrogen solubility of PdHc thin films"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","S388"],["dc.bibliographiccitation.journal","Journal of Alloys and Compounds"],["dc.bibliographiccitation.lastpage","S391"],["dc.bibliographiccitation.volume","645"],["dc.contributor.author","Burlaka, Vladimir"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T09:50:22Z"],["dc.date.available","2018-11-07T09:50:22Z"],["dc.date.issued","2015"],["dc.description.abstract","Hydride precipitation in 25 nm and 40 nm epitaxial Nb-films was studied by Scanning Tunnelling Microscopy (STM) supported by X-ray diffraction (XRD) measurements. In combination, these methods yield information about the phase transition, the coherency state, the hydride precipitates' density and size as well as their lateral distribution, at 293 K. For both film thicknesses, hydride formation was detected with STM; it can be easily missed by XRD. While the 25 nm film showed a coherent phase transition, the phase transition was incoherent for the 40 nm film. This is in good accordance with theory. The phase transition features are found to strongly depend on the coherency state: a large number of small hydrides appear in the coherent regime while a small number of large hydrides evolve in the incoherent regime. (C) 2014 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.jallcom.2014.12.103"],["dc.identifier.isi","000360404100088"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/35693"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Sa"],["dc.publisher.place","Lausanne"],["dc.relation.conference","14th International Symposium on Metal-Hydrogen Systems (MH)"],["dc.relation.eventend","2014-07-25"],["dc.relation.eventlocation","Salford, ENGLAND"],["dc.relation.eventstart","2014-07-20"],["dc.relation.issn","1873-4669"],["dc.relation.issn","0925-8388"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","In-situ STM and XRD studies on Nb-H films: Coherent and incoherent phase transitions"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","515"],["dc.bibliographiccitation.journal","Acta Materialia"],["dc.bibliographiccitation.volume","122"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Kramer, Thilo"],["dc.contributor.author","Uchida, Helmut"],["dc.contributor.author","Dobron, Patrik"],["dc.contributor.author","Cizek, Jakub"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2022-01-25T09:58:14Z"],["dc.date.available","2022-01-25T09:58:14Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1016/j.actamat.2016.10.001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/98625"],["dc.identifier.url","https://publications.goettingen-research-online.de/handle/2/43670"],["dc.relation.iserratumof","/handle/2/40034"],["dc.relation.issn","1359-6454"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Corrigendum to “Mechanical stress and stress release channels in 10–350 nm palladium hydrogen thin films with different micro-structures” [Acta Mater. 114 (2016) 116–125]"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.subtype","erratum_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","87"],["dc.bibliographiccitation.journal","Journal of Alloys and Compounds"],["dc.bibliographiccitation.lastpage","92"],["dc.bibliographiccitation.volume","593"],["dc.contributor.author","Kuerschner, Jara"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T09:41:09Z"],["dc.date.available","2018-11-07T09:41:09Z"],["dc.date.issued","2014"],["dc.description.abstract","Hydride nucleation and growth is studied by electrochemical hydrogenography on Pd-thin films with modified adhesion between the film and the glass substrate. Modification was controlled by a Nb-adhesive. A clear influence of the adhesion on the hydride formation was found. The adhering films showed small hydrides far beyond the resolution limit of the method. Contrary to this, the weak-adhering films showed low nucleation densities and large separated hydrides extending in the mu m-range. The difference was attributed to enhanced hydride formation in quasi stress-free volumes and an easily propagating delamination front that supports hydride growth. (C) 2014 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.jallcom.2014.01.026"],["dc.identifier.isi","000331713800014"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/33667"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1873-4669"],["dc.relation.issn","0925-8388"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Delamination-supported growth of hydrides in Pd thin films studied by electrochemical hydrogenography"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","756"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Scripta Materialia"],["dc.bibliographiccitation.lastpage","759"],["dc.bibliographiccitation.volume","69"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Hamm, Magnus"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T09:18:20Z"],["dc.date.available","2018-11-07T09:18:20Z"],["dc.date.issued","2013"],["dc.description.abstract","Hydrogen absorption in metals causes volume expansion, which increases abruptly with phase transformation. This effect can stimulate hydrogen-induced percolation of discontinuous palladium thin films, yielding a drop in the films' electrical resistance. Long-term exposure to air and cyclic hydrogen loading of palladium films with optimized morphology (meander films of 15 nm thickness, islands gaps of about 14 nm) are shown to change the meander connectivity and, thereby, increase the films' resistance switching to -5900% in a narrow pressure range. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","DFG [Pu-131/7-2, Pu-131/9-1]"],["dc.identifier.doi","10.1016/j.scriptamat.2013.08.023"],["dc.identifier.isi","000325665800014"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/28387"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1359-6462"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Huge hydrogen-induced resistive switching in percolating palladium thin films"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","64"],["dc.bibliographiccitation.journal","Thin Solid Films"],["dc.bibliographiccitation.lastpage","71"],["dc.bibliographiccitation.volume","679"],["dc.contributor.author","Burlaka, Vladimir"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Hamm, Magnus"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2020-12-10T15:21:39Z"],["dc.date.available","2020-12-10T15:21:39Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1016/j.tsf.2019.04.002"],["dc.identifier.issn","0040-6090"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73103"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Tayloring surface morphologies and stress states of thin niobium epitaxial films on sapphire substrates"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","051914"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Applied Physics Letters"],["dc.bibliographiccitation.volume","92"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Pundt, Astrid"],["dc.date.accessioned","2018-11-07T11:18:22Z"],["dc.date.available","2018-11-07T11:18:22Z"],["dc.date.issued","2008"],["dc.description.abstract","Thermodynamic properties of thin films deviate strongly from those of bulk. The deviations are reported to originate from microstructure and from mechanical stress, whereas the contribution of both is unknown in particular. Focussing on the mechanical stress contribution and by using Pd(1-x)Fe(x)-H as a model system, it is shown that mechanical stress strongly changes phase transition pressures. The measured loading pressures shift up to 400 mbars in contrast to 18 mbars for bulk. These shifts relate to the film bonding to the substrate and can be affected by film detachment. (c) 2008 American Institute of Physics."],["dc.identifier.doi","10.1063/1.2841636"],["dc.identifier.isi","000253016500035"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/55017"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Inst Physics"],["dc.relation.issn","0003-6951"],["dc.title","Mechanical stress impact on thin Pd(1-x)Fe(x) film thermodynamic properties"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","S450"],["dc.bibliographiccitation.journal","Journal of Alloys and Compounds"],["dc.bibliographiccitation.lastpage","S453"],["dc.bibliographiccitation.volume","645"],["dc.contributor.author","Lukac, Frantisek"],["dc.contributor.author","Vlcek, Marian"],["dc.contributor.author","Vlach, Martin"],["dc.contributor.author","Wagner, Stefan"],["dc.contributor.author","Uchida, Helmut"],["dc.contributor.author","Pundt, Astrid"],["dc.contributor.author","Bell, Anthony"],["dc.contributor.author","Cizek, Jakub"],["dc.date.accessioned","2018-11-07T09:50:23Z"],["dc.date.available","2018-11-07T09:50:23Z"],["dc.date.issued","2015"],["dc.description.abstract","Gas phase loading of nanocrystalline and epitaxial 20 nm Pd films deposited on single crystalline sapphire substrates was studied in this work. The nanocrystalline film was deposited at room temperature and the epitaxial film deposited at 800 degrees C. The nanocrystalline film suffers from in-plane compressive stress imposed by atomic peening processes. The epitaxial film exhibits tensile stress caused by the different thermal expansion coefficients of Pd and sapphire substrate. Coherent phase transition into the hydride phase was observed both for the nanocrystalline and for the epitaxial film. For both films, the lattice parameters continuously increase during the phase transition to the hydride phase. Both films exhibit enhanced hydride formation pressure compared to bulk Pd. Misfit dislocations are formed at interface between Pd film and substrate during hydrogenation. This leads to irreversible change of stress state of the films subjected to sorption and desorption cycle with hydrogen. (C) 2014 Published by Elsevier B.V."],["dc.identifier.doi","10.1016/j.jallcom.2014.12.085"],["dc.identifier.isi","000360404100101"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/35695"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Sa"],["dc.publisher.place","Lausanne"],["dc.relation.conference","14th International Symposium on Metal-Hydrogen Systems (MH)"],["dc.relation.eventlocation","Salford, ENGLAND"],["dc.relation.issn","1873-4669"],["dc.relation.issn","0925-8388"],["dc.title","Stress release during cyclic loading of 20 nm palladium films"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]