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Measurements of nonlinear microwave losses in doubble-sided YBCO and GBCO films are examined and reported.

Measurements of the microwave surface resistance of YBCO films simultaneously sputtered on both sides of CeO2 coated sapphire wafers are presented.

Research is presented concerning the use of sputtering from cylindrical targets which were hollow in the deposition of c-axis oriented YBa2Cu3O7-delta films for use as telecommunications microstrip filters.

Dielectric resonators for a two pole filter were developed and tested. They consist of LaAlO3 single crystalline cylinders covered on the cylindrical surface by 4 micrometer gold films and on the end faces by 350 nm YBa2cu3O7-delta thin films. The two-pole bandpass filters fabricated from the resonators have an insertion loss of -0.26 dB at their center frequencies of 6.3 GHz at 77 K.

Analyzing the results of the two-tone intermodulation distortion (IMD) measurements for the 2.3 GHz YBa2Cu3O7− x and GdBa2Cu3O7− x microstrip resonators we described the IMD spectra by the normalized values of P IMDn/ P 0, where P IMDn is the output power of the n-th order IMD product and P 0 is that of the fundamental tone. The circulating power in the resonator was normalized by the power of the third-order intercept: P circ/ P TOI. It was found, that the examined resonators exhibited the same dependence of P IMDn/ P 0 versus P circ/ P TOI versus the change of the microwave surface resistance (Δ R IMDn/ P 0 versus the change of the microwave surface resistance (Δ R S) at any measurement temperature. We reproduced these measurements for the indium microstrip resonators of the same geometry and obtained the same results. We conclude, that the nonlinear response of the superconducting microstrip resonators in the high power range is strongly affected by a geometry-dominated hf loss mechanism (likely the hf hysteretic losses due to magnetic flux penetration), which overshadows other nonlinear mechanisms related to the intrinsic material properties. This conclusion is in agreement with the results of the indium disk resonator measurements. [ABSTRACT FROM AUTHOR]

Ultra-thin CeO2 films with thicknesses in the range of 0.3–10 nm were deposited on r-plane sapphire substrates by sputtering. The growth of the films was investigated by X-ray diffraction measurements and by Rutherford backscattering spectroscopy. At a substrate temperature of 735 °C and a deposition rate of 0.16 nm/min the films grow epitaxially, (100) oriented revealing in their mosaic distribution a twofold appearance, namely a very narrow part with a breadth depending on the resolution of the X-ray system and a broad part. Both parts are observed from the beginning of the growth; the narrow distribution is ascribed to pseudomorphic growth showing partial coverage of the substrate, the broad part grows simultaneously but is relaxed by defect incorporation. The partial coverage starts with growth blocks with a minimum thickness of four unit cells up to a coverage of 36%; further growth proceeds on top of the first blocks and uncovered parts of the substrates until full coverage is achieved at thicknesses of around 8 nm. In the nominally thinnest films, i.e. at the shortest deposition times, the lattice constant shows a drastic increase of up to 3.7% in comparison to bulk material. This effect probably is due to oxygen loss in accordance with observations in CeO2 nanoparticles. [Copyright &y& Elsevier]

The absolute values of the London penetration depth λ[sub L], were measured in epitaxial (001) YBa[sub 2]Cu[sub 3]O[sub 7-x] (YBCO) thin films prepared by simultaneous sputter deposition on both sides of 3 in. r-cut sapphire wafers buffered with thin (001) CeO[sub 2] layers. The measurements were performed by using a technique, which is based on the effect produced on the quality factor Q of a microwave disk resonator by a gold layer deposited on the YBCO electrodes. The observed change of Q can be transformed into λ[sub L] value with an accuracy determined mainly by the uncertainty of the YBCO film thickness. The λ[sub L](T) data obtained by this technique revealed a good agreement with the variation of the resonant frequency with temperature, which is conventionally used for measurements of the variation of the effective London penetration depth δλ[sub L](T) [sub eff](T) with temperature. At temperatures above ∼60 K this λ[sub L](T) dependence was very close to the predictions of the Gorter-Casimir model. At lower temperatures a linear λ[sub L](T) behavior was observed with the slope higher for thinner YBCO films. The absolute λ[sub L] values were higher than those reported in literature for λ[sub ab] (screening currents flow in the crystallographic a-b plane) of YBCO single crystals. For example, our measured &lambda[sub L] (4.2 K) values were in the range of 195-220 nm compared to literature data for &lambda[sub ab] quoted around 140 nm. [ABSTRACT FROM AUTHOR]

Studies the effect of an Au contact layer on the microwave performance of YBa[sub 2]Cu[sub 3]O[sub 7-gamma] superconductor thick films. Microwave measurements; Power handling capability of a disk resonator made from thick YBCO superconducting film; Variation in the effective London penetration depth with temperature.

Power-induced nonlinear effects, i.e., the reduction of the quality factor, the distortion of the resonance peaks, and the two-tone intermodulation distortion (IMD), were experimentally examined by using 2.3 GHz microstrip resonators prepared from double-sided YBa[sub 2]Cu[sub 3]O[sub 7 − x] (YBCO) films on CeO[sub 2]-buffered sapphire. The resonators exhibited advanced performance with an unloaded quality factor of 80 000 at 63 K up to a circulating power P[sub circ] of 0.5 W and an IMD third-order interception point estimated at P[sub circ] ≈ 400 W. We found that the nonlinear effects in these resonators were produced by the power-dependent surface resistance R[sub s] of the YBCO films, whereas the variation of the surface reactance was negligible. Both the presence of the high-order IMD products and the dependence of their amplitude on the microwave power, indicate a R[sub s](H) ∝ cosh H relationship, where H is the amplitude of the microwave magnetic field at the film surface. Such a dependence agrees with the direct measurements of the power handling capability. © 2001 American Institute of Physics. [DOI: 10.1063/1.1425460]. [ABSTRACT FROM AUTHOR]

Measures the microwave surface resistance of YBa[sub 2]Cu[sub 3]O[sub 7-x] (YBCO) thin films sputtered simultaneously on both sides of CeO[sub 2] coated sapphire wafers. Use of disk resonator technique; Deposition of gold layers of various thicknesses on the unpatterned YBCO side of the disk resonator.

Thin superconducting films of YBa2 Cu3 O7 have been prepared by magnetron sputtering from targets of sintered material in an oxygen-argon atmosphere. The compositional and structural properties were studied by Rutherford backscattering and x-ray diffraction. The films were deposited at substrate temperatures between 580 and 800 °C. It was found that the material grows in the oxygen deficient tetragonal phase. In situ heat treatment at 430 °C in pure O2 atmosphere generates the orthorhombic structure and the films on sapphire and SrTiO3 coated sapphire substrates show the full superconducting transition at 83 K. [ABSTRACT FROM AUTHOR]

The contemporary expansion of investor-owned health care facilities has stimulated much controversy but little response from policymakers. We believe this results from the apparently ambiguous relationship between ownership and socially valued outcomes. In our assessment, this ambiguity occurs largely because the effects of ownership are mediated in complex ways by characteristics of the services being delivered and the training of health care providers. Reviewing both the history and current performance of nonprofit and for-profit health care facilities, we identify some of the more important of these mediating factors. Taking these into account, there is a consistent influence of ownership on the delivery of health services. On the basis of this analysis, we discuss appropriate policy responses to the future growth of investor-owned health care organizations.