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Author Navarro, H.; Sirena, M.; Kim, J.; Haberkorn, N. url  doi
openurl 
  Title Josephson coupling in high-Tc superconducting junctions using ultra-thin BaTiO3 barriers Type Journal Article
  Year 2020 Publication Materials Science and Engineering: B Abbreviated Journal Mater. Sci. Eng. B  
  Volume 262 Issue Pages (up) 114714  
  Keywords Josephson junctionsHigh-Tc superconductorsThin films  
  Abstract We study the electrical transport of vertically-stacked Josephson tunnel junctions using GdBa2Cu3O7−δ electrodes and a BaTiO3 barrier with thicknesses between 1 nm and 3 nm. Current-voltage measurements at low temperatures show a Josephson coupling for junctions with BaTiO3 barriers of 1 nm and 2 nm. Reducing the barrier thickness bellow a critical thickness seems to suppress the ferroelectric nature of the BaTiO3. The Josephson coupling temperature reduces as the barrier thicknesses increases. The Josephson energies at 12 K are of ≈ 1.5 mV and ≈ 7.5 mV for BaTiO3 barriers of 1 nm and 2 nm, respectively. Fraunhofer patterns are consistent with fluctuations in the critical current due to structural inhomogeneities in the barriers. Our results are promising for the development of Josephson junctions using high-Tc electrodes with energy gaps much higher than those usually present in conventional low-temperature superconductors.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0921-5107 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 858  
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Author Ale Crivillero, M.V.; Amigó, M.L.; Haberkorn, N.; Nieva, G.; Guimpel, J. url  openurl
  Title Microstructural control of the transport properties of β-FeSe films grown by sputtering Type Journal Article
  Year 2019 Publication Journal of Applied Physics Abbreviated Journal Journal of Applied Physics  
  Volume 126 Issue 11 Pages (up) 115303  
  Keywords  
  Abstract  
  Address  
  Corporate Author Thesis  
  Publisher American Institute of Physics Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0021-8979 ISBN Medium  
  Area Expedition Conference  
  Notes doi: 10.1063/1.5094131 Approved no  
  Call Number BT @ gnieva @ Serial 847  
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Author Hofer, J.A.; Ginzburg, M.; Bengio, S.; Haberkorn, N. url  doi
openurl 
  Title Nanocrystalline superconducting γ-Mo2N ultra-thin films for single photon detectors Type Journal Article
  Year 2022 Publication Materials Science and Engineering: B Abbreviated Journal Materials Science and Engineering: B  
  Volume 275 Issue Pages (up) 115499  
  Keywords  
  Abstract We analyze the influence of the surface passivation produced by oxides on the superconducting properties of γ-Mo2N ultra-thin films. The superconducting critical temperature of thin films grown directly on Si (100) with those using a buffer and a capping layer of AlN are compared. The results show that the cover layer avoids the presence of surface oxides, maximizing the superconducting critical temperature for films with thicknesses of a few nanometers. We characterize the flux-flow instability measuring current-voltage curves in a 6.4 nm thick Mo2N film with a superconducting critical temperature of 6.4 K. The data is analyzed using the Larkin and Ovchinnikov model. Considering self-heating effects due to finite heat removal from the substrate, we determine a fast quasiparticle relaxation time ≈ 45 ps. This value is promising for its applications in single-photon detectors.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0921-5107 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 871  
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Author Hofer, J.A.; Bengio, S.; Rozas, G.; Pérez, P.D.; Sirena, M.; Suárez, S.; Haberkorn, N. url  doi
openurl 
  Title Compositional effects on the electrical properties of extremely disordered molybdenum oxynitrides thin films Type Journal Article
  Year 2020 Publication Materials Chemistry and Physics Abbreviated Journal Mater. Chem. Phys.  
  Volume 242 Issue Pages (up) 122075  
  Keywords Molybdenum; Oxynitrides; Thin films; Sputtering; Electrical transport  
  Abstract Molybdenum oxynitride (MoNxOy) thin films were grown by reactive sputtering on Si (100) substrates at room temperature. The partial pressure of Ar was fixed at 90%, and the remaining 10% was adjusted with mixtures N2:O2 (varying from pure N2 to pure O2). The electrical properties of the films depend on the chemical composition. Thin films grown using mixtures up to 2% O2 have γ-Mo2N phase and display superconductivity. The superconducting critical temperature Tc reduces from ∼6.8 K to below 3.0 K as the oxygen increases. On the other hand, the films are mostly amorphous for gas mixtures above 2% O2. The electrical conductivity shows a semiconductor-like behavior well described by variable-range hopping conduction. The analysis of the optical properties reveals that the samples do not have a defined semiconductor bandgap, indicating that the high structural disorder produces electron excitation for a wide range of energies.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0254-0584 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 860  
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Author Haberkorn, N.; Zhang, Y.Y.; Bi, Z.X.; Park, B.H.; Civale, L.; Jia, Q.X url  doi
openurl 
  Title Effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer assisted deposition Type Journal Article
  Year 2021 Publication Materials Chemistry and Physics Abbreviated Journal Materials Chemistry and Physics  
  Volume 259 Issue Pages (up) 124184  
  Keywords  
  Abstract We report the effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer-assisted deposition on c-cut sapphire (Al2O3). The films show a superconducting transition temperature of 10.4 K and an upper critical field Hc2(0) perpendicular to the film surface around 3 T. The latter corresponds to a relatively large coherence length ξ, which enhances the two-dimensional limit when the magnetic field is applied parallel to the film surface. In comparison with pure δ-MoN films, the inclusion of Co2N impurity in the δ-MoN films could significantly modify the critical current density at the vortex-free state. The ability to tune the superconducting properties of metal-nitride superconductors by introducing chemically and structurally compatible impurity may find potential applications for superconducting single-photon detectors.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0254-0584 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 873  
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Author Haberkorn, N.; Jeehoon, Kim; Suárez, S; Lee, Jae-Hun; Moon, S.H. url  openurl
  Title Influence of random point defects introduced by proton irradiation on the flux creep rates and magnetic field dependence of the critical current density J c of co-evaporated GdBa 2 Cu 3 O 7− δ coated conductors Type Journal Article
  Year 2015 Publication Superconductor Science and Technology Abbreviated Journal Supercond. Sci. Technol.  
  Volume 28 Issue 12 Pages (up) 125007  
  Keywords  
  Abstract We report the influence of random point defects introduced by 3 MeV proton irradiation (doses of 0.5 × 10 16 , 1 × 10 16 , 2 × 10 16 and 6 × 10 16 cm −2 ) on the vortex dynamics of co-evaporated 1.3 μ m thick, GdBa 2 Cu 3 O 7− δ coated conductors. Our results indicate that the inclusion of additional random point defects reduces the low field and enhances the in-field critical current densities J c . The main in-field J c enhancement takes place below 40 K, which is in agreement with the expectations for pinning by random point defects. In addition, our data show a slight though clear increase in flux creep rates as a function of irradiation fluence. Maley analysis indicates that this increment can be associated with a reduction in the exponent μ characterizing the glassy behavior.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0953-2048 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 725  
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Author Amigó, M.L.; Haberkorn, N.; Pérez, P.; Suárez, S.; Nieva, G. url  doi
openurl 
  Title Vortex dynamics in β -FeSe single crystals: effects of proton irradiation and small inhomogeneous stress Type Journal Article
  Year 2017 Publication Superconductor Science and Technology Abbreviated Journal Supercond. Sci. Technol.  
  Volume 30 Issue 12 Pages (up) 125017  
  Keywords  
  Abstract We report on the critical current density J c and the vortex dynamics of pristine and 3 MeV proton irradiated (cumulative dose equal to ##IMG## [http://ej.iop.org/images/0953-2048/30/12/125017/sustaa9518ieqn1.gif] {$2\times {10}^{16}$} cm −2 ) β -FeSe single crystals. We also analyze a remarkable dependence of the superconducting critical temperature T c , J c and the flux creep rate S on the sample mounting method. Free-standing crystals present T c = 8.4(1) K, which increases to 10.5(1) K when they are fixed to the sample holder by embedding them with GE-7031 varnish. On the other hand, the irradiation has a marginal effect on T c . The pinning scenario can be ascribed to twin boundaries and random point defects. We find that the main effect of irradiation is to increase the density of random point defects, while the embedding mainly reduces the density of twin boundaries. Pristine and irradiated crystals present two outstanding features in the temperature dependence of the flux creep rate: ##IMG## [http://ej.iop.org/images/0953-2048/30/12/125017/sustaa9518ieqn2.gif] {$S(T)$} presents large values at low temperatures, which can be attributed to small pinning energies, and a plateau at intermediate temperatures, which can be associated with glassy relaxation. From Maley analysis, we observe that the characteristic glassy exponent μ changes from ∼1.7 to 1.35–1.4 after proton irradiation.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0953-2048 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 770  
Permanent link to this record
 

 
Author Hofer, J.A.; Haberkorn, N. url  doi
openurl 
  Title Flux flow velocity instability and quasiparticle relaxation time in nanocrystalline β-W thin films Type Journal Article
  Year 2021 Publication Thin Solid Films Abbreviated Journal Thin Solid Films  
  Volume 730 Issue Pages (up) 138690  
  Keywords Thin films; Electrical transport; Vortex velocities  
  Abstract We characterized the superconducting properties of a micropatterned 23 nm thick β-W film using electrical transport measurements in magnetic fields. The film is nanocrystalline and displays a smooth surface. The superconducting critical temperature is 4.6 K. The critical current densities display a fast drop with the magnetic field, indicating weak vortex pinning. From the analysis of the instability in the vortex motion at low magnetic fields in the flux-flow state, we observe vortex velocities up 800 m/s. An inelastic lifetime of quasiparticles around 0.6 ns is estimated at low temperatures. Together with high uniformity in thickness and simplicity in the fabrication process, the superconducting properties make β-W films promising for applications in fast single-photon detectors.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0040-6090 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 870  
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Author Sutter, J.G.; Chávez, A.S.; Soria, S.; Granada, M.; Neñer, L.; Bengió, S.; Granell, P.; Golmar, F.; Haberkorn, N.; Leyva, A.G.; Sirena, M. url  doi
openurl 
  Title Tuning the magneto-electrical properties of multiferroic multilayers through interface strain and disorder Type Journal Article
  Year 2020 Publication Journal of Alloys and Compounds Abbreviated Journal J. Alloys Compd.  
  Volume Issue Pages (up) 157820  
  Keywords multiferroic; superlattices; manganites; magnetism; disorder  
  Abstract Artificially engineered superlattices were designed and fabricated to induce different growth mechanisms and structural characteristics. DC sputtering was used to grow ferromagnetic (La0.8Ba0.2MnO3)/ferroelectric (Ba0.25Sr0.75TiO3 or BaTiO3) superlattices. We systematically modified the thickness of the ferromagnetic layer to analyze dimensional and structural disorder effects on the superlattices with different structural characteristics. The crystalline structure was characterized by X-ray diffraction and transmission electron microscopy. The magnetic and electronic properties were investigated by SQUID magnetometry and resistance measurements. The results show that both strain and structural disorder can significantly affect the physical properties of the systems. Ba0.25Sr0.75TiO3 based superlattices with a low thickness of the ferromagnetic layers (4 nm.) present compressive strain that decreases the ferromagnetic transition temperature from 250 K corresponding to the unstressed samples to 230 K. In these samples, the localization energy of the charge carrier through the electron-phonon interaction decreases at low temperatures (∼100 meV). Ba0.25Sr0.75TiO3 based superlattices with thicknesses of the ferromagnetic layers higher than 12 nm present tensile strain that reduces the charge carrier localization energy at low temperatures (∼1 meV), increasing the ferromagnetic transition temperature (Tc∼265K). Structural defects in BaTiO3 based superlattices have a stronger influence on the magnetic properties than on the transport properties. Nevertheless, disorder blocks the ferromagnetic transition for highly disordered samples (thickness of the ferromagnetic layer < 3 nm). These results help to further understand the role of strain and interface effects in the magnetic and transport properties of manganite based multiferroic systems.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0925-8388 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 861  
Permanent link to this record
 

 
Author Sutter, J.G.; Sarmiento Chávez, A.; Soria, S.; Granada, M.; Neñer, L.; Bengió, S.; Granell, P.; Golmar, F.; Haberkorn, N.; Leyva, A.G.; Sirena, M. url  doi
openurl 
  Title Tuning the magneto-electrical properties of multiferroic multilayers through interface strain and disorder Type Journal Article
  Year 2021 Publication Journal of Alloys and Compounds Abbreviated Journal J. Alloys Compd.  
  Volume 859 Issue Pages (up) 157820  
  Keywords  
  Abstract Artificially engineered superlattices were designed and fabricated to induce different growth mechanisms and structural characteristics. DC sputtering was used to grow ferromagnetic (La0.8Ba0.2MnO3)/ferroelectric (Ba0.25Sr0.75TiO3 or BaTiO3) superlattices. We systematically modified the thickness of the ferromagnetic layer to analyze dimensional and structural disorder effects on the superlattices with different structural characteristics. The crystalline structure was characterized by X-ray diffraction and transmission electron microscopy. The magnetic and electronic properties were investigated by SQUID magnetometry and resistance measurements. The results show that both strain and structural disorder can significantly affect the physical properties of the systems. Ba0.25Sr0.75TiO3 based superlattices with a low thickness of the ferromagnetic layers (4 nm) present compressive strain that decreases the ferromagnetic transition temperature from 250 K corresponding to the unstressed samples to 230 K. In these samples, the localization energy of the charge carrier through the electron-phonon interaction decreases at low temperatures (∼100 meV). Ba0.25Sr0.75TiO3 based superlattices with thicknesses of the ferromagnetic layers higher than 12 nm present tensile strain that reduces the charge carrier localization energy at low temperatures (∼1 meV), increasing the ferromagnetic transition temperature (Tc∼265 K). Structural defects in BaTiO3 based superlattices have a stronger influence on the magnetic properties than on the transport properties. Nevertheless, disorder blocks the ferromagnetic transition for highly disordered samples (thickness of the ferromagnetic layer < 3 nm). These results help to further understand the role of strain and interface effects in the magnetic and transport properties of manganite based multiferroic systems.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0925-8388 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 874  
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