H.-U. Müller

Preparation of YBCO thin films by means of a hollow cathode discharge sputtering device

YBaCuO thin films have been grown in-situ on (100) SrTiO 3 from stoichiometric ceramic targets using a hollow cathode discharge sputtering device. The used linear hollow cathode sputter source can be advantageously up-scaled for uniform large area thin film deposition. Thin YBaCuO films have been produced with T c ≃90k, j c (77k)≃10 6 A/cm and p(100k)<0.1mΩcm. It ia shown that a substrate movement transversely to:he hollow cathode slot during the deposition guarantees both high film thickness homogenity and no degradation of the auperconducting properties

Effect of fluorine on the superconductivity of YBa2Cu3O7−y

In order to study the influence of fluorine on the superconductivity of YBa 2 Cu 3 O 7−y we have prepared samples of YBa 2 Cu 3 O 7−y with x = 0 – 2.5. For all samples the onset temperature is 91 K. The zero lesistence temperature To for samples with large x values decreases strongly and the lattice parameter c increases for about 0.5 %.

Large area deposition of YBaCuO thin films by means of hollow cathode sputtering

Abstract We report on a hollow cathode sputtering technique allowing the deposition of large area YBaCuO thin films on substrates up to 3″. The hollow cathode discharge takes place in a single slot with a length of 92 mm. Its walls are covered with YBaCuO bulk material of stoichiometric composition. In order to get a constant film thickness the substrate is moved perpendicular to the hollow cathode slot during the in-situ deposition. YBCO films with good superconducting properties have been obtained with a short sputtering source of 12 mm slot length. In first experiments with the 92 mm-sputtering source the homogeneity of the film thickness has been tested.

Evidence for the interaction between room-temperature annealing after quenching and persistent photoconductivity in oxygen-deficient Y1Ba2Cu3Ox thin films

Abstract Room-temperature annealing effects in oxygen-deficient YBaCuO thin films and persistent photoconductivity are correlated phenomena. A photoresponse was induced by laser illumination ( t = 60 s, λ = 670 nm) at various stages during the long-term relaxation of the resistivity after quenching to room temperature. The magnitude of the photoresponse generated during each illumination event follows the progress of the annealing process in time.

Cyclotron resonance in the n-inversion layer of InSb grain boundaries

Abstract We report the first observation of the cyclotron resonance of electrons in a grain boundary inversion layer. We provide transmission measurements on a p-type InSb bicrystal at discrete wavelengths between λ = 70.6 μm and 251 μm using an optically pumped molecular gas laser. The observed cyclotron resonance spectra consisting of the cyclotron resonance lines of at least three electric subbands do not allow a direct determination of the cyclotron masses of the different electtic subbands because of the large line-width of several lines.