Basic elements for photodeposited high Tc thin film devices

Flat films, high quality insulating layers and adequately superconducting via contacts are basic elements for high Tc device fabrication. We studied the influence of the process parameters of laser deposition on the occurrence of droplets and outgrowths in YBaCuO films. The droplet density is minimal when a laser fluence below about 1.0 J cm-2 is used. The outgrowth density decreases with increasing laser pulse rate or decreasing deposition temperature. High quality flat films were obtained with a rate of 10 Hz and at a temperature of 720 °C. Wet chemical etching and etching with an Argon ion source were used for structuring multilayers with SrTiO3 as an insulating layer. Smooth edges were obtained with an argon gun. Bromine and EDTA etching are not adequate techniques for fabricating controllable well-defined edges. Cross-overs, via contacts and coils were prepared

Materials aspects of integrated high-Tc dc-SQUID magnetometer fabrication

An integrated high Tc dc-SQUID magnetometer is being developed. It has in total 10 layers of five different materials. Various materials aspects of the fabrication process will be discussed, especially the smoothness of the films and the techniques to obtain smooth edges. Cross-overs and superconducting window contacts were fabricated. The critical temperature of the window-contact is 84K (jc(77K)=2·105 A/cm2) and the resistivity of the insulating SrTiO3 layer in the cross-over is 6·105 Ωcm at 77K. The complete coil often shows a small resistive component down to about 50K. Ramp type and bi-epitaxial grain boundary dc-SQUIDs show voltage modulation up to 65K and 79K, respectively. Efforts to fabricate an integrated high Tc dc-SQUID magnetometer will be discussed

Multilayer studies and applications in template bi-epitaxial DC SQUIDS

Multilayer deposition for the creation of a well-defined grain boundary, based on different in-plane orientations of c-axis oriented thin YBa2O2Cu3O7-δ layers on a single substrate, has been performed on three different kinds of substrates: (1102)-oriented Al2O3 , (100) SrTiO3, and (100) MgO. The multilayers consist of combinations of SrTiO3, MgO, CeO2, and YBa2O2Cu3O7-δ. The YBa 2O2Cu3O7-δ top layers on (1102) Al2O3 and (100) SrTiO3 were polycrystalline. Josephson junctions and DC superconducting quantum interference devices (SQUIDs) have been structured in the layers on MgO. Shapiro steps were observed. The Jcρn-product of the junctions at 4.2 K is on the order of 1 mV. The critical current decreases in good approximation linearly with increasing temperature, whereas the normal state resistance is nearly temperature independent. Voltage modulation was observed at temperatures up to 77 K

Prediction of quantization of magnetic flux in double-layer exciton superfluids

JAN 24Theoretical Physic

Four layer monolithic integrated high Tc dc SQUID magnetometer

YBa2Cu3O7−x based monolithic integrated dc SQUID magnetometers, consisting of a dc SQUID integrated with a flux transformer on a single bicrystalline substrate, have been fabricated and characterized. The devices consist of four layers, including two superconducting layers, and first realizations operate up to 73 K. A maximum voltage modulation of 32 μV is observed at 40 K. A field sensitivity of 0.17 pT/√Hz is obtained above 200 Hz at 45 K and 0.49 pT/√Hz at 1 Hz and 65 K

Enhancement of spin propagation due to interlayer exciton condensation

Theoretical Physic

Exciton condensation in strongly correlated electron bilayers

Theoretical Physic

On the nature of ionic liquid gating of La2-xSrxCuO4

Quantum Matter and Optic