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Superconducting quantum interference filters, or SQIFs, are a promising class of highly sensitive magnetometers benefiting from a highly peaked and symmetric magnetic response at zero-input flux. They can be used in magnetometry, e.g., in wideband applications. A simple solution to increase further their sensitivity is to add a superconducting flux concentrator (SFC) to their design. Using the ion irradiation process, we designed a meander-shaped SQIF enhanced with an SFC. The SFC improved the SQIF transfer factor by a factor of 8.4. However, high temperature superconducting (HTSc) devices are vulnerable to flux pinning, which can severely hinder their response. On the one hand, HTSc technologies alleviate the burden of cryogenics. On the other hand, applications that use SFCs in noisy and unshielded environments will become possible only if a better understanding of how this flux impacts the device's properties is achieved. We studied the relationship between the field present during the cooling process of the SQIF antenna (thereafter called "cooling field") and the evolution of its DC response. We developed a simple and phenomenological model and were able to reproduce the degradation of the SQIF response. This work demonstrates the usability of SFC-enhanced SQIFs based on ion irradiated junctions in rather harsh conditions, in particular, an unshielded environment, and also gives an insight into the implications that such conditions cause on the application of SFCs in general. [ABSTRACT FROM AUTHOR]

Research describing the performance of microwave devices formed by pulsed laser ablation is presented. In particular the electrical properties of strontium titanate layered devices are investigated.

Research is presented concerning the use of Y-Ba-Cu-O/Sr-Ti-O//La-Al-O multi-layers to obtain an individual resonator Qo greater than 1000 and a 10% frequency shift in the design of a frequency agile microwave device.

A study evaluated the work on third-generation mobile communication systems that is being conducted as part of the EU's Advanced Communication Technologies and Services program. It also describes a transceiver for use in mobile and personal communications base transceiver stations (BTS). High temperature superconductivity technology undoubtedly furnishes one of a number of solutions to potentially enhance the performance of a BTS.

Product development of superconductive microwave filters linked to the use of cooled electronics is already in the critical phase of system integration. To optimize the aspects involved in the systems integration phase of the development of these devices, a study designed and fabricated microwave filters which eliminate the need for tuning. Good agreement was obtained between the computed response and the measurements for these filters.

A study was conducted to examine the physical and structural properties of YBa2Cu3O(sub 7-delta) (YBCO) thin films, which have been deposited on two sides of a 2' lathanium aluminate (LaAlO3) substrate. The composition of the fabricated YBCO thin films was analyzed using Rutherford Backscattering spectrometry, electron microscopy and ion channeling, electrical resistivity and x-ray diffraction experiments. Results show that both side deposits have grown similar films. These fabricated films were found to be useful in making passive microwave devices.

The theoretical conditions required to observe reduced nonlinearities in passive microwave devices made of a paraelectric (PE) thin layer and a high-temperature superconductor (HTS) thin film are presented. In a transmission line (TL) combining both materials, the nonlinear permittivity [variant_greek_epsilon]r(Vrf) of the PE generates a nonlinear capacitive contribution Cd(Vrf), whereas the nonlinear penetration depth λ(Irf) of the HTS produces a nonlinear inductive contribution Ld(Irf). These contributions act in opposite ways. Under determined conditions that will be defined, they may fully compensate or at least lead to the reduction of the spurious signal level. The HTS nonlinearities may be lowered by employing very thin layers of PE. In this case, the high dielectric loss tangent (tan δ) of PE should not be such an issue. Based on experimental results obtained with superconducting YBa2Cu3O7-δ resonators integrating different thicknesses of paraelectric SrTiO3 (STO) deposited on LaAlO3 substrates, the loss level could then be considered in the simulation of the proposed compensation effect. The results show that the reduction of the unloaded quality factor (Q0) as the thickness of STO increases also impacts the level of spurious signals. Then, an analytic expression for the Q0 of a resonant TL that integrates a PE and a HTS thin layer is proposed. It specifies the conditions for reducing the total nonlinear response. These results could then be applied to realize high power handling HTS passive microwave devices. [ABSTRACT FROM AUTHOR]

A high critical current density was obtained in the attempt to pattern microbridges in a superconducting line. Microbridges were patterned as narrow as 200 nanometers by a focused beam process without damaging the superconducting properties. A current density of six times 10(super 8) angstroms per square centimeters at 77 Kelvin was generated leading to a corrected value of 10(super 8) angstroms per square centimeters. These results validates the use of focused ion beam in the fabrication of superconducting devices.

An experimental chamber was connected to the 2.5 MV Van de Graaff accelerator allowing in situ sample annealing at T ≤ 700°C and under pO2 ranging from 10-8 to 1 bar. For the first time to our knowledge the 16O(3He,α)15O nuclear reaction has been employed to monitor in situ the oxygen loss and uptake in Y1Ba2Cu3O7-x (YBCO) thin films as a function of oxygen pressure and temperature (T ≤ 500°C). The role played by the presence of carbon contamination on YBCO surface was elucidated. Using the 12C(d,p)13C nuclear reaction the carbon loss was observed for T ≥ 250°C and it was associated with the oxygen loss enhancement in YBCO. It is found that in absence of carbon contamination, oxygen in-diffusion rate in YBCO is much faster than the out-diffusion rate, the later being surface reaction limited. The oxygen diffusion coefficients and the surface exchange coefficients of YBCO films have been evaluated. These results will be discussed in relation with the mechanism of high temperature YBCO thin film growth by cathodic sputtering and with the mechanism of the oxygen loss and/or uptake during the sample cooling. [ABSTRACT FROM AUTHOR]

Evaluates the performance of microwave devices containing electrically tunable layers of strontium titanate for samples produced by pulsed laser ablation. Range of deposition temperatures; Parameters relevant in determining frequency agility and dielectric loss of the samples.

RHEED controlled ultra-thin buffer layers of SrTiO3 have been deposited on (1 0 0) MgO by pulsed laser deposition to grow YBa2Cu3O7 films for microwave applications. A buffer layer with a thickness from 5 to 40 unit cells of SrTiO3 is sufficient to expand to more than 60°C the range of deposition temperatures for which a low microwave surface resistance [Rs(10 GHz, 77 K)<0.5 mΩ] is obtained. The Rs values are as low as those obtained on LaAlO3 substrates, furthermore they present a slightly lower magnetic field dependency. The XRD Φ-scans show that the SrTiO3 seed layer induces an oriented epitaxial growth with the [1 0 0] axis of YBCO parallel to the one of MgO over this broadened range of deposition temperatures. This seed layer promoting effect is not observed with other oxides such as Ba0.15Sr0.85TiO3, CeO2, Ce1− xLa xO2. [ABSTRACT FROM AUTHOR]