We report on point contact tunnelling experiments on preferentially c oriented Y1Ba2Cu3O7-δ (123) films deposited onto (100) SrTiO3 substrates using an ultra-high vacuum (UHV) triple electron-gun system with BaF2, yttrium and copper as source materials. The films were coated with a thin silver layer and annealed at 450°C. A niobium point was then carefully brought into contact with the surface, which was investigated by electron tunnelling. Using 10 GHz radiation we identified microwave-induced current steps in the current-voltage characteristic. Also, there was a strong decrease in Josephson current on application of a magnetic field. Moreover, UHV films were patterned into strips as narrow as 10 μm using a reactive ion etching technique. Critical current densities of about 106 A cm-2 at 20 K were obtained, which is an order of magnitude larger than for sputtered films, but smaller than for UHV laser-patterned thinner films.@en

The discovery of a new class of high-T//c superconducting materials has induced a renewed interest in the possibilites of superconducting thin film devices. As the thin YBa//2Cu//3O//7// minus // delta films appear to have a semi single-crystalline character they are also perfectly suited to study the physics of these materials. Both for materials characterization and the study of the physics of these materials the reproducibility is crucial. The authors demonstrate the possibilities of two structuring methods: reactive ion etching and local amorphisation by energetic (260 keV) ions.@en

High TC superconducting thin films were prepared on (100) SrTiO3 substrates by dc triode sputtering and subsequent annealing. In these films Hall-bar structures having a width down to 5 μm were patterned using a reactive ion etching technique. Superconductivity above 77 K was observed. When compared with the original film there is only a small reduction in TC. The critical current density determined by electrical measurements is substantially reduced. On the other hand, the critical current density in the bulk of the grains as measured by the torque on a film is not reduced by the patterning process. It is suggested that superconductor-normal metal-superconductor junctions between the grains account for this difference.@en