Thin Film Superconducting Devices

Techniques have been developed with which it is possible to fabricate superconducting thin film structures (“bridges”) which show Josephson-like phenomena, with a wide variety of electrical and superconducting parameters. These bridges—based on the proximity effect—are made in layered thin film substrates which have been fabricated from many different, both hard and soft, superconducting materials. The fabrication techniques and the electrical and superconducting characteristics for these proximity effect bridges including a simple low frequency (≤10 GHz) equivalent circuit will be discussed. These bridges have been incorporated into simple thin film circuits for use as galvanometers, magnetometers, gradiometers, detector arrays, etc. Extension of these techniques to more complex superconducting thin film bridge circuits including resistors, capacitors, and inductors will be indicated

Microelectronic fabrication of superconducting devices and circuits

It is expected that thin-film superconductors can be used as detectors or sources of infrared and microwave radiation, as magnetometers, as voltage standards, and for voltage and current measurements, for electronic signal processing, and in digital circuitry

Electrical Properties and Superconductivity of Rhenium and Molybdenum Films

Electrical and superconducting properties of rhenium and molybdenum films prepared by electron beam evaporation have been measured as a function of substrate temperature, film thickness, and substrate material. The films were prepared at residual pressures of 5×10^–8 Torr. In addition, films of each material were prepared by reactive deposition at nitrogen pressures in the 10^–5 Torr range. Rhenium films prepared at low residual pressures exhibited superconductivity with onset temperatures from 2.5–4.9 K depending on thickness and substrate temperature. However, rhenium films prepared by reactive deposition in nitrogen had onset temperatures from 4.6–5.5 K. Transition temperatures from 3.3–3.8 K were observed in molybdenum films at thicknesses greater than 6000 Å when deposited at substrate temperatures of 600 °C. Crystal structure and preferred orientation were determined by x-ray diffraction methods

Current-induced highly dissipative domains in high Tc thin films

We have investigated the resistive response of high Tc thin films submitted to a high density of current. For this purpose, current pulses were applied into bridges made of Nd(1.15)Ba(1.85)Cu3O7 and Bi2Sr2CaCu2O8. By recording the time dependent voltage, we observe that at a certain critical current j*, a highly dissipative domain develops somewhere along the bridge. The successive formation of these domains produces stepped I-V characteristics. We present evidences that these domains are not regions with a temperature above Tc, as for hot spots. In fact this phenomenon appears to be analog to the nucleation of phase-slip centers observed in conventional superconductors near Tc, but here in contrast they appear in a wide temperature range. Under some conditions, these domains will propagate and destroy the superconductivity within the whole sample. We have measured the temperature dependence of j* and found a similar behavior in the two investigated compounds. This temperature dependence is just the one expected for the depairing current, but the amplitude is about 100 times smaller.Comment: 9 pages, 9 figures, Revtex, to appear in Phys. Rev.