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Sandwich and superlattice structures composed of the high critical field superconducting alloy Nb0.53Ti0.47 (where the compositions refer to weight percent) and amorphous Ge were sputter‐deposited on sapphire substrates using a novel multi‐sputter‐gun system. The thicknesses of both the superconducting Nb0.53Ti0.47 and the insulating Ge layers were varied over a wide range in order to study the two‐dimensional (2D) and three‐dimensional (3D) superconducting properties of these structures. The observed suppression of the measured resistive superconducting transition temperature Tc with increasing sheet resistance is tentatively interpreted using the Maekawa–Fukuyama theory which incorporates contributions from localization and Coulomb interaction effects. The upper critical fields, with the field both normal Hc2⊥ and parallel Hc2∥ to the film, were measured up to 50 kG. Hc2∥ exhibited 2D behavior when the thickness of the superconducting layer was less than 200 A. The zero temperature values of Hc2∥(0) wer...

We describe a four‐gun sputtering system which has been used successfully to prepare composition‐modulated structures consisting of amorphous semiconductors and superconducting alloys or binary compounds. The substrates are mounted in ovens which can be individually heated to over 1000 °C. The ovens are mounted on a wheel which is driven by a computer‐controlled stepping motor. With appropriate programming of the movement of the stepping motor, the deposition sequence is determined.

A new composition modulated structure composed of semiconducting SnTe and semimetallic Sb has been grown epitaxially on mica substrates with differing SnTe to Sb ratios. The samples were characterized by x‐ray diffraction using the transmission Laue patterns and θ‐2θ diffractometer scans with scattering vectors both normal and in the plane of the film. We observed that the modulation satellites were 180° out of phase for films with short modulation wavelengths, but were in phase for long wavelengths. This change in the phase of the modulation can be understood by assuming that Sb adopts a quasicubic structure at short modulation wavelength, due to the coherency strain, but relaxes back to a distorted rhombohedral structure, with the loss of coherency, at long wavelengths. A simple 1‐D model was used to estimate the modulation wavelength dependence of the sublattice displacement of Sb.

V/Fe composition‐modulated structures have been grown on the (0001) surface of a sapphire substrate in an UHV evaporator. X‐ray θ‐2θ scans showed that the samples had a bcc (110) texture with a strong composition modulation. Samples with three atomic planes of Fe separated by thick layers of V showed a linear temperature dependence of the saturation magnetization over the range 5–400 K. This behavior is expected for the Bloch spin wave contribution to the magnetization of a 2D ferromagnet. Hysteresis measurements also confirmed that the samples were ferromagnetic. Superconductivity has been seen in samples with very thick V layers.

A versatile, compact, constant current‐voltage, bipolar power source for quasi‐static or derivative measurements of the characteristics of superconducting junctions has been developed. The circuitry is based on a negative feedback strategy that is effective in maintaining constant current‐voltage behavior at the junction itself and all lead resistances are included in the feedback loop. Constant currents and voltages can be delivered of up to ±0.5 A and ±0.75 V, respectively. Both fast and slow sweeps, as well as a single sweep mode, are available in variable ranges. The single sweep feature is used to avoid heating effects in low resistance junctions which are not in good thermal contact with a thermal reservoir (e.g., liquid 4 He).

Y‐Ba‐Cu‐O thin films have been deposited on MgO substrates by dc magnetron sputtering from a stoichiometric YBa2Cu3O7−δ target, after which they are subjected to a short heat treatment. Zero resistance is routinely achieved near 60 K, and one film shows zero resistance at 68.0 K.

The surface wave velocity in SnTe/Sb superlattices has been determined using Brillouin scattering. The velocity is independent of modulation wavelength over the range studied but is lower than would be expected if the layers of Sb and SnTe possessed their bulk properties. This is consistent with x‐ray data which can be interpreted as evidence of a cubic polymorph of Sb which is unstable in bulk form.