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Author (up) 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 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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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 0167-577x ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 850
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Author (up) 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 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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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 (up) Hofer, J.A.; Ginzburg, M.; Bengio, S.; Haberkorn, N.
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 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.
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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 0921-5107 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ pedrazp @ Serial 871
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Author (up) Hofer, J.A.; Haberkorn, N.
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 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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