| 1. |
- Arpaia, Riccardo, 1985, et al.
(författare)
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Improved Nanopatterning for YBCO Nanowires Approaching the Depairing Current
- 2013
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 23:3
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Tidskriftsartikel (refereegranskat)abstract
- An improved nanopatterning procedure has been developed to obtain YBa2Cu3O7-x nanowires with cross-sections as small as 50 x 50 nm(2), protected by an Au capping layer. To probe the effective role of the Au protecting layer, we have measured the current-voltage characteristics and the resistive transition in temperature of the nanowires. Critical current densities up to 108 A/cm(2) have been achieved at T = 4.2 K, approaching the theoretical depairing current limit. The resistance, measured as a function of temperature close to T-c, has been fitted with a thermal activated phase slip model, including the effect of the gold layer. The extracted values of the superconducting coherence length and of the London penetration depth give current densities consistent with the measured ones. These results cannot be achieved with nanowires without the Au capping layer.
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| 2. |
- Baghdadi, Reza, 1984, et al.
(författare)
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Toward YBa2Cu3O7-δ nanoscale structures for hybrid devices
- 2015
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- An ex situ ozone annealing has been applied both on YBa2Cu3O7-d (YBCO) films and nanowires. From the investigation on bare films, by measuring the superconducting resistive transition in temperature and the X-ray diffraction pattern, we have observed that the ozonation can be a powerful tool to oxygenate the YBCO structure. To probe the effective role of this reactive annealing on nanostructures, we have fabricated nanowires with widths down to 100 nm, covered by a 20-nm-thick Au layer. We have compared the critical current density and the broadening of the resistance transition measured before and after the ozone treatment, concluding that the ozone is instrumental in recovering very high quality superconducting properties inside the nanostructures, which were degraded by the oxygen out-diffusion occurring during the nanopatterning.
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| 3. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
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Noise Properties of YBCO Nanostructures
- 2017
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- Voltage noise measurements on close to optimally doped YBa2Cu3O7-delta nanostructures have been performed. The measured resistance noise at temperature T = 96 K (above critical temperature T-C = 85 K) shows a quadratic dependence on the bias current, e.g., the voltage power spectral density S-V alpha V-2. Moreover, the normalized voltage noise S-V/V-2 is inversely proportional to the device volume. This is a clear indication that the noise is the result of an ensemble of independent resistive fluctuators, evenly distributed within the sample volume. For our structures, we obtain a product S-V/V-2 x Vol. = const. approximate to 6 x 10-(33) m(3)/Hz resulting in a Hooge's parameter 3.4 x 10(-4), which is among the lowest reported in literature. At lower temperature, T = 2 K (well below TC) the total voltage fluctuations are given by the combined effect of critical current fluctuations and resistance fluctuations. For the critical current noise, we obtain a product S-I/IC2 x Vol. = const. approximate to 6x10(-32) m(3)/Hz. The larger value of the relative critical current noise is most probably due to the fact that the critical current is determined by edge effects whereas the resistance is given by the total volume of the device.
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| 4. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
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SQUID magnetometer based on Grooved Dayem nanobridges and a flux transformer
- 2020
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 30:7
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Tidskriftsartikel (refereegranskat)abstract
- We report noise measurements performed on a superconducting quantum interference devices (SQUID) magnetometer implementing YBa2Cu3O7-δ grooved Dayem nanobridges as weak links. The magnetometer is realized by coupling the SQUID to a flux transformer with a two-level coupling scheme using a flip-chip approach to improve the effective area of the SQUID. The measured magnetic flux noise of the SQUID is as low as 10 μ Φ0/√Hz, which corresponds to an equivalent magnetic field white noise of 60 fT/√Hz above 100 Hz at T=77 K.
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