1,721,050 research outputs found
Toward YBa2Cu3O7-δ nanoscale structures for hybrid devices
No full textAn ex situ ozone annealing has been applied both on YBa2Cu3O7-δ (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
YBa2Cu3O7-δ nanorings to probe fluxoid quantization in High Critical Temperature Superconductors
Get PDFWe have realized YBa2Cu3O7-δ (YBCO) nanorings and measured the magnetoresistance R(B) close to the superconducting transition. The large oscillations that we have measured can be interpreted in terms of vortex dynamics triggering the nanowires to the resistive state. The Fast Fourier Transform spectrum of the magnetoresistance oscillations shows a single sharp peak for nanorings with narrower loop arm width: this peak can be univocally associated to a h/2e periodicity as predicted for optimally doped YBCO. Moreover it is a clear evidence of a uniform vorticity of the order parameter inside the rings, confirming a high degree of homogeneity of our nanostructures. This result gives a boost to further investigations of YBCO nanorings at different dopings within the superconducting dome, where in the underdoped regime a R(B) periodicity different from the conventional h/2e has been predicted
Improved nanopatterning for YBCO nanowires approaching the depairing current
Get PDFAn improved nanopatterning procedure has been developed to obtain YBa2Cu3O7-x nanowires with cross-sections as small as 50 × 50nm2, 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 108A/cm2 have been achieved at T = 4.2 K, approaching the theoretical depairing current limit. The resistance, measured as a function of temperature close to Tc, 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. © 2002-2011 IEEE
Fabrication and electrical transport characterization of high quality underdoped YBa2Cu3O7-δ nanowires
Get PDFWe present the fabrication and electrical transport characterization of underdoped YBa2Cu3O7-δ nanowires. The nanowires have been realized without any protective capping layer and they show transport properties similar to those of the parent thin film, demonstrating that they have not been damaged by the nanopatterning. The current-voltage characteristics of the underdoped nanowires show large hysteretic voltage switching at the critical current, in contrast to the flux-flow like characteristics of optimally doped nanostructures, indicating the formation of a self-stabilizing hot spot. These results open up new possibilities for using the underdoped nanowires as single photon detectors and for exploring the underdoped side of the YBa2Cu3O7-δ phase diagram at the nanoscale
Toward ultra high magnetic field sensitivity YBa2Cu3O7-δ nanowire based superconducting quantum interference devices
No full textWe report on measurements of YBa2Cu3O7-δ nanowire based Superconducting QUantum Interference Devices (nanoSQUIDs) directly coupled to an in-plane pick-up loop. The pick-up loop, which is coupled predominantly via kinetic inductance to the SQUID loop, allows for a significant increase of the effective area of our devices. Its role is systematically investigated and the increase in the effective area is successfully compared with numerical simulations. Large effective areas, together with the ultra low white flux noise below 1 μ Φ 0 / Hz, make our nanoSQUIDs very attractive as magnetic field sensors
Probing the phase diagram of cuprates with YBa2Cu3O7-δ thin films and nanowires
Get PDFWe have grown and characterized 30-nm-thick YBa2Cu3O7-δ (YBCO) films, deposited by pulsed laser deposition on both MgO (110) and SrTiO3 (001) substrates, which induce opposite strain to the superconducting layer. By carefully tuning the in situ post-annealing oxygen pressure, we achieved, in a reproducible way, films at different oxygen doping, spanning from the slightly overdoped down to the strongly underdoped region of the phase diagram. The transport properties of the films, investigated through resistance versus temperature measurements, are in perfect qualitative agreement with single crystals. Starting from these films, we have also successfully fabricated nanowires with widths down to 65 nm, at different oxygen doping. The nanostructures exhibit characteristic temperatures (as the critical temperature Tc and the pseudogap temperature T∗) similar to those of the as-grown films and carry critical current densities Jc close to the critical depairing value, limited by vortex entry. This implies that the superconducting and the normal state properties of underdoped YBCO are preserved in our films, and they can be studied as a function of the dimensionality of the system, down to the nanoscale
Approaching the theoretical depairing current in YBa2Cu3O7-x nanowires
Get PDFYBa2Cu3O7-x nanowires, with lateral dimensions smaller that 50 nm have been fabricated by a soft etching procedure preserving an Au capping layer on top of the nanostructure. We have obtained YBCO nanowires carrying critical current densities Jc close to the theoretical depairing limit. The resistive transition and the Jc as a function of temperature of the Au capped nanostructures have been compared with those where the Au protective layer was subsequently removed. We conclude that the Au capping layer together with the soft etching procedure are instrumental in preserving shape pristine superconducting properties very close to the as grown film. Our results open new perspective for the use of YBCO nanostructures in fundamental studies aiming at shedding light on the mechanism for high critical temperature superconductivity. © 2013 Elsevier B.V. All rights reserved
Doping dependence of the upper critical field in untwinned YBa2Cu3O7−δ thin films
Get PDFWe report on measurements of the doping dependence of the upper critical field Hc,2 in 50 nm thick YBa2Cu3O7−δ films. The films are untwinned and are characterized by a small in-plane compressive strain. We find that the Hc,2 shows a strong decrease in the underdoped region of the phase diagram, in agreement with that which has been measured in relaxed single crystals. The origin of the decrease of Hc,2 in the underdoped regime is discussed within a scenario where charge density wave (CDW) order competes with superconductivity. This demonstrates the potential of using thin films to study the phase diagram of high-Tc materials under strain, and opens up the possibility for investigating the interplay between CDW order and superconductivity tuned by strain
Microwave response of superconducting YBa2Cu3O7-δ nanowire bridges sustaining the critical depairing current: Evidence of Josephson-like behavior
No full textWe have investigated the zero-field critical supercurrent of YBa2Cu3O7-δ bridges patterned from 50 nm thick films as a function of bridge width, ranging from 2 μm to 50 nm. The critical current density monotonically increases for decreasing bridge width even for widths smaller than the Pearl length. This behavior is accounted for by considering current crowding effects at the junction between the bridge and the wider electrodes. Comparison to numerical calculations of the current distributions in our bridge geometries of various widths yields a (local) critical current density at 4.2 K of 1.3×108 A/cm2, the Ginzburg Landau depairing current density. The observation of up to 160 Shapiro-like steps in the current voltage characteristics under microwave irradiation substantiates the pristine character of our nanobridges with cross sections as small as 50×50 nm2. © 2013 American Physical Society
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