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Author Amigó, M.L.; Haberkorn, N.; Pérez, P.; Suárez, S.; Nieva, G.
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 (up) 30 Issue 12 Pages 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.
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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
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Author Haberkorn, N.; Guimpel, J.; Suárez, S.; Troiani, H.E.; Granell, P.; Golmar, F.; Lee, J.-H.; Moon, S.H.; Lee, H.
Title Strong influence of the oxygen stoichiometry on the vortex bundle size and critical current densities J c of GdBa 2 Cu 3 O x -coated conductors grown by co-evaporation Type Journal Article
Year 2017 Publication Superconductor Science and Technology Abbreviated Journal Supercond. Sci. Technol.
Volume (up) 30 Issue 9 Pages 095009
Keywords
Abstract We report on the influence of oxygen stoichiometry on the vortex creep mechanism of GdBa 2 Cu 3 O x -coated conductors produced by co-evaporation. The oxygen stoichiometry of the films, x , was modified in a controlled way between 6.85 and 7, which resulted in systematic and reversible control of the superconducting critical temperature between about 78 and 93 K. The change in the oxygen stoichiometry produces a strong reduction in the self-field critical current densities J c without significantly modifying the power-law dependence at intermediate magnetic fields, which indicates a negligible contribution of oxygen vacancies to the pinning. In addition, the characteristic glassy exponent μ shows a systematic diminution from about 1.63 at x = 7 to about 1.12 at x = 6.85. The results are compared with those obtained for proton- and oxygen-irradiated films, in which the vortex dynamics is determined by a balance between the improved pinning, originating from nanocluster inclusion, and the suppressed superconducting properties due to disorder in the nanoscale.
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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 775
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Author Haberkorn, N.; Xu, M.; Meier, WR; Suárez, S.; Bud’ko, S.L.; Canfield, P.C.
Title Enhancement of critical current density in CaKFe4As4 single crystals through 3 MeV proton irradiation Type Journal Article
Year 2020 Publication Superconductor Science and Technology Abbreviated Journal Supercond. Sci. Technol.
Volume (up) 33 Issue 2 Pages 025008
Keywords
Abstract We study the influence of random point disorder on the vortex dynamics and critical current densities Jc of CaKFe4As4 single crystals by performing magnetization measurements. Different samples were irradiated with a proton (p) beam at constant energy of 3 MeV to fluencies from 2 × 1015 p cm−2 to 4 × 1016 p cm−2. The results show the addition of extrinsic random point disorder enhances the Jc values at low and intermediate temperatures over the entire range of magnetic fields applied. The optimum pinning enhancement is achieved with a proton fluence of 3 × 1016 p cm−2, increasing Jc at 5 K by factors ≈5 and 14 at self-field and μ0H = 3 T, respectively. We analyze the vortex dynamics using the collective creep theory. The enhancement in Jc matches with a systematic reduction in the flux creep relaxation rates as a consequence of a gradual increase in the collective pinning energy U0. The substantial increment in Jc produced by random point disorder, reaching values of 9 MA cm−2 at 5 K and self-field, makes CaKFe4As4 a promising material for applications based on current carrying capacity at high magnetic fields.
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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 857
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Author Haberkorn, H.; Xu, M.; Meier, W.R.; Schmidt, J.; Suárez, S.; Bud’ko, S.L.; Canfield, P.C.
Title Substantial reduction of the anisotropy in the critical current densities Jcof Ni-doped CaKFe4As4single crystals by chemical and irradiation-induced disorder Type Journal Article
Year 2021 Publication Superconductor Science and Technology Abbreviated Journal Supercond. Sci. Technol.
Volume (up) 34 Issue 3 Pages 035013
Keywords
Abstract We demonstrate that the anisotropy in the critical current densities, Jc, of CaK(Fe1-xNix)4As4 (x = 0, 0.015, 0.025, and 0.030) single crystals reduces with increasing chemical and irradiation-induced disorder. The magnetic field dependences of Jc are analyzed by performing magnetization measurements with H applied parallel and perpendicular to the crystallographic c-axis. The results show that undoped crystals display large anisotropies in Jc due to an enhancement of the vortex pinning with H applied parallel to the crystallographic ab-planes. This anisotropy reduces substantially as Ni addition increases. Moreover, we found that random disorder introduced by proton irradiation enhances mainly the vortex pinning for H parallel to the c-axis. Consequently, using adequate fluencies, the vortex pinning at low temperatures in both undoped and doped samples becomes close to isotropic. These results make the CaKFe4As4 system promising for applications that require isotropic Jc under magnetic fields.
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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 872
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Author Alcalde Bessia, F.; Pérez, M.; Sofo Haro, M.; Sidelnik, I.; Blostein, J.J.; Suárez, S.; Pérez, P.; Gómez Berisso, M.; Lipovetzky, J.
Title Displacement Damage in CMOS Image Sensors After Thermal Neutron Irradiation Type Journal Article
Year 2018 Publication IEEE Transactions on Nuclear Science Abbreviated Journal IEEE Transactions on Nuclear Science
Volume (up) 65 Issue 11 Pages 2793-2801
Keywords alpha-particle effects; boron; CMOS image sensors; lithium; neutron capture therapy; neutron effects; Rutherford backscattering; silicon; boron-10 thermal neutron capture; displacement damage; alpha particles irradiation; dark signal; thermal neutron irradiation; CMOS image sensors; Ionizing radiation; Thermal sensors; Radiation effects; Alpha particles; CMOS image sensors; Active pixel sensors; CMOS technology; X-rays; Active pixel sensors; alpha particles; borophosphosilicate-glass (BPSG); CMOS image sensors; CMOS technology; ionizing radiation; neutron radiation effects; thermal neutron; X-rays
Abstract In this paper, CMOS image sensors were exposed to thermal neutrons observing an increase in the dark signal of many pixels. The effect was found to be similar to the damage caused by alpha particles irradiation. Rutherford backscattering spectroscopy (RBS) and SIMNRA simulation were used to confirm that the sensors contain boron in the insulation layers. The damage produced by thermal neutrons is explained as displacement damage caused by alpha particles and lithium-7 ions in the silicon active volume of the sensors after boron-10 thermal neutron capture.
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Notes Approved no
Call Number BT @ pedrazp @ Serial 835
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Author Haberkorn, N.; Bengio, S.; Troiani, H.; Suárez, S.; Pérez, P.D.; Granell, P.; Golmar, F.; Sirena, M.; Guimpel, J.
Title Thickness dependence of the superconducting properties of γ- Mo<inf>2</inf>N thin films on Si (001) grown by DC sputtering at room temperature Type Journal Article
Year 2018 Publication Materials Chemistry and Physics Abbreviated Journal Mater. Chem. Phys
Volume (up) 204 Issue Pages 48-57
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Notes Cited By :1; Export Date: 14 March 2018 Approved no
Call Number BT @ jguimpel @ Serial 785
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Author Haberkorn, N.; Bengio, S.; Suárez, S.; Pérez, P.D.; Sirena, M.; Guimpel, J.
Title Effect of the nitrogen-argon gas mixtures on the superconductivity properties of reactively sputtered molybdenum nitride thin films Type Journal Article
Year 2018 Publication Materials Letters Abbreviated Journal Materials Letters
Volume (up) 215 Issue Pages 15-18
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Notes Cited By :1; Export Date: 14 March 2018 Approved no
Call Number BT @ jguimpel @ Serial 783
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Author Haberkorn, N.; Bengio, S.; Suárez, S.; Pérez, P.D.; Hofer, J.A.; Sirena, M.
Title Effect of thermal annealing and irradiation damage on the superconducting critical temperature of nanocrystalline γ-Mo2N thin films Type Journal Article
Year 2019 Publication Materials Letters Abbreviated Journal
Volume (up) 236 Issue Pages 252-255
Keywords Nitrides; Sputtering; Superconductivity; Irradiation
Abstract We report on the influence of the disorder and stoichiometry in the resulting superconducting critical temperature of γ-Mo2N thin films. Initially, three films (with Tc values of 7.6 K, 6.8 K and 6 K) were grown at room temperature by reactive sputtering, on Si (1 0 0) using different N2/(Ar+N2) mixtures. The influence of the thermal annealing up to 973 K and irradiation damage produced by 1 MeV Zr+(fluence up 2 × 1014 cm−2) is analyzed. The Tc of pristine films remains unchanged for increasing irradiation doses up 2 × 1014 cm−2. The Tc for annealed films decreases close to the value expected for bulk samples (≈5 K) for increasing the annealing temperature. Successive irradiations of the annealed films tend to increase their Tc up to its initial values (before annealing). The results indicate that the Tc in nanometric grain size γ-Mo2N thin films is affected by both nitrogen stoichiometry and disorder at the atomic scale.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0167-577x ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 850
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Author Hofer, J.A.; Bengio, S.; Rozas, G.; Pérez, P.D.; Sirena, M.; Suárez, S.; Haberkorn, N.
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 (up) 242 Issue Pages 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.
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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.; Suárez, S.; Bud'ko, S.L.; Canfield, P.C.
Title Strong pinning and slow flux creep relaxation in Co-doped CaFe2As2 single crystals Type Journal Article
Year 2020 Publication Solid State Communications Abbreviated Journal Solid State Commun.
Volume (up) 318 Issue Pages 113963
Keywords Iron based superconductors; Single crystals; Vortex dynamics; Magnetization
Abstract We report on measurements of critical current densities Jc and flux creep rates S of freestanding Ca(Fe1−xCox)2As2 (x ≈ 0.033) single crystals with Tc ≈ 15.7 K by performing magnetization measurements. The magnetic field dependences of Jc at low temperature display features related to strong pinning. In addition, we find that the system displays small flux creep rates. The characteristic glassy exponent, μ, and the pinning energy, U0, display exceptional high values for pristine crystals. We find that for magnetic fields between 0.3 T and 1 T, μ decreases from ≈ 2.8 to ≈ 2 and U0 remains ≈ 300 K. Analysis of the pinning force indicates that the mechanism is similar to the observed in polycrystalline systems in which grain boundaries and random disorder produce the vortex pinning. Considering the large U0 observed in the single crystal, we attempt to improve the pinning by adding random point disorder by 3 MeV proton irradiation with a fluence of 2 × 1016 proton/cm2. The results show that, unlike other iron-based superconductors, the superconducting fraction is sharply reduced by irradiation. This fact indicates that the superconductivity in the system is extremely fragile to an increment in the disorder. The superconducting volume fraction in the irradiated crystal systematically recovers after removal disorder by thermal annealing, which evidences as to the observation of critical state in curves of magnetization versus magnetic field. No features related to a reentrant antiferromagnetic transition are observed for the irradiated sample.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 859
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