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We have synthesized superconducting YBa2Cu3Ox thin films in situ using magnetron cosputtering with three metallic targets (Y, Ba, Cu). We present details of the sputtering chamber, as well as the growth conditions necessary to obtain superconducting films. We discuss the effects of oxygen and ozone partial pressure, differential pumping, O2–Ar plasma deposition and Ba–Cu alloy targets. We elaborate on our ozone condensing and delivery system. Finally, we describe the difficulties encountered with the deposition system and provide details of possible improvements.

Artificially-structured superconducting multilayers of amorphous Mo-Ge alloys separated by insulating layers of amorphous Ge are used as a model system to study the resistive transition in quasi two-dimensional superconductors. By comparing the behavior of the multilayers with that of a single layer, a transition line corresponding to the decoupling of the vortices in adjacent layers is empirically established. It is found that this line corresponds to the kink commonly seen in the resistive transitions of quasi twodimensional superconductors. Current theories are found to be only qualitatively in agreement with the data.

In a prospective study, 50 fractures of the distal fifth of the tibia with additional involvement of the ankle joint in 18 patients were stabilized by unreamed nailing. In all, 90% of all fractures healed uneventfully without further surgical Intervention after unreamed nailing, the highest ratio of complications (22%) being seen in all patients with distal fractures of the fibula without additional plating (of the fibula). Tibial fractures close to the ankle joint can be managed by unreamed nailing; distal fractures of the fibula should be additionally stabilized by fibular plating.

This study was designed to evaluate the effects of tissue-type plasminogen activator (tPA) and 21- amino steroid (U74006F) in experimental embolic stroke in rabbits. The size of infarction from embolism was compared to controls with tPA alone, 21-amino steroid alone, and in combination. The middle cerebral artery of the rabbit was embolized by injecting an arterial ('white') thrombus in the right internal carotid artery. The rabbit treatment was 2 mg kg-1 of tissue-type plasminogen activator and/or 3 mg kg-1 of 21 amino steroid started at 2 h post-embolization. The animals were terminated 4 h post-treatment and brains were examined for evidence of ischemia and/or hemorrhage. Administration of tissue-type plasminogen activator and/or 21-amino steroid in the raw data show that there is a tendency for all treatments to reduce the ischemic volume when compared to the control group, also it is evident the standard deviation of these estimates is rather large when compared to the differences between treatments. The results of the analysis of variance shows that the differences expressed are not statistically significant. (No statistical differences were found between the treatment groups and the control group.) The results show that administration of tissue-type plasminogen activator and/or 21 amino steroid at 2 h post-embolization alone or in simultaneous administration does not significantly reduce the volume of infarction. Further studies need to be addressed in regards to the region of viable brain in the peri-infarct area, in reducing the time to treatment.

Measurments of the ac penetration depth of a-MoGe films in the presence of a perpendicular magnetic field reveal an anomaly in the ac response of the vortex lattice at a characteristic temperature below the ${\mathit{H}}_{\mathit{c}2}$(T) line. The field and frequency dependence of this anomaly is found to be consistent with a Kosterlitz-Thouless-type melting of the two-dimensional vortex lattice. Moreover, we observe a crossover in the frequency dependence which suggests that the vortex lattice remains disordered on long length scales below the melting temperature.

Superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ films of thicknesses ranging from 500 AA to 5 mu m have been successfully made by the reactive magnetron sputtering technique. The effects of composition, annealing condition, and thickness of an epitaxial film on its orientation are discussed. films show anisotropic resistivities and critical-current densities that are orientation-dependent. >

We report results of the study of electron tunneling into thin films of the new high-${T}_{c}$ superconductor La-Sr-Cu-O. Both sandwich-type tunneling with a Pb counterelectrode and point-contact tunneling have been successfully achieved. The results show exceptionally large energy gaps in these materials (roughly 20, 30, and possibly even 60 mV), larger than previously obtained on bulk sintered powders. We interpret these results as due to large anisotropy in this material or due to the presence of a a very high-${T}_{c}$ layer near the surface of the films. The method of preparation of this new superconductor in thin film form is also discussed.

Detailed examination of a well-ordered, high-${T}_{c}$ ${\mathrm{Y}}_{2}$${\mathrm{Ba}}_{4}$${\mathrm{Cu}}_{8}$${\mathrm{O}}_{16}$ (2:4:8) oriented thin-film sample revealed directly that the three crystallographic axes were unequal in length. Each layer of this high-${T}_{c}$ superconductor, like the closely related superconducting $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$ (1:2:3) phase, has structural anisotropy in the $a\ensuremath{-}b$ plane. The difference between $a$ (3.859 \ifmmode\pm\else\textpm\fi{} 0.002 \AA{}) and $b$ (3.874 \ifmmode\pm\else\textpm\fi{} 0.002 \AA{}) in 2:4:8 is significantly smaller than in 1:2:3, so many associated strains such as those occurring during oxidation or epitaxial growth will also be smaller. Well-ordered, high-${T}_{c}$ thin films of 2:4:8 using Er in place of Y have been produced. By comparing the x-ray-diffraction patterns of the Y and Er 2:4:8 samples, a one-dimensional electron density map has been produced directly, without structure refinement. The result demonstrates that relative to the 1:2:3 structure, 2:4:8 contains an additional -CuO- layer. Together, the results indicate, without appeal to indirect chemical analogy, that 2:4:8 contains double -CuO- layers with interlayer vacancy ordering.

The successful synthesis of high-Tc YBa2Cu3O7 films by means of electron-beam codeposition are reported. Several important growth parameters have been surveyed in a preliminary way. The substrates investigated include Al2O3, ZrO2, MgO, and SrTiO3, The films were characterized by resistivity measurements, x-ray diffraction, microprobe, and Rutherford backscattering analysis. Some TEM and critical current density studies were also carried out. The best results to date have been obtained on SrTiO3 substrates with which polycrystalline epitaxial growth has been achieved. Resistive superconducting transitions with zero resistance at 89.5 K and a 2 K width have been observed in these films.

The new high-${T}_{c}$ superconductor YBaCuO was prepared and characterized. Measurements were performed to determine the superconducting and magnetic properties of the samples. Onset of superconductivity was found above 90 K. Antiferromagnetism was also observed, probably associated with the nonsuperconducting pairs of the samples. Modest critical current density as well as large upper critical fields were inferred from the data.

High Tc superconductors exhibit significant flux motion due to a thermally activated creep process. The motion of the fluxoids dissipates energy. This dissipation causes a broadening of the resistive transition below Tc in a magnetic field as well as a logarithmic decay of the diamagnetic shielding moment in time. From the detailed structure of the broadened transition, empirical parameters are derived. The pinning strength is highly anisotropic, reflecting the anisotropy of the coherence length. Implications of an extraordinarily low activation energy are also addressed.

Optical transmission and reflection spectra (mid IR through uv) and Raman spectra of superior-quality 90-, 180-, 400-, and 1000-nm-thick superconducting Y-Ba-Cu-O films are reported. Characteristic excitonic bands, and in particular the absorption band at \ensuremath{\simeq}0.37 eV reported earlier, are not observed. It therefore seems unlikely that the high-${T}_{c}$ superconductivity in cuprates could arise from exciton-mediated electron pairing.

We report results of a study of electron tunneling into bulk samples of the new high-${T}_{c}$ superconductor Y-Ba-Cu-O using point-contact tunneling. Based on a superconductive tunneling interpretation, the results show exceptionally large energy gaps in these materials (roughly 2\ensuremath{\Delta}=100 meV), implying 2\ensuremath{\Delta}/${k}_{C}$${T}_{c}$\ensuremath{\sim}13. Similar values were found previously by us for La-Sr-Cu-O. We also see Structure in the I-V curves similar to that seen in La-Sr-Cu-O. On the basis of the asymmetries observed in the I-V characteristics, we believe that the natural tunneling barrier on this material is of the Schottky type.