Senzu Yang

Preparation of YBa2Cu3O7−x superconducting thin films over large area substrates

Using facing targets and off‐axis direct‐current magnetron sputtering, we have prepared high quality YBa2Cu3O7−x (YBCO) superconducting thin films on ZrO2 (100) with Tc≤90 K (R=0) and Jc as high as 1.6×106 A/cm2 (78 K, zero magnetic field) over an area of 70 mm diameter. Over this large area, the fluctuations of Tc and film thickness are from less than +0.9% to −1.3% and from +6.3% to −10%, respectively. In this article, also discussed are the differences between two sputtering modes used in our experiments, one of which gives larger area of superconducting thin film, higher deposition rate, and better thickness uniformity than the other. It is found that the smoothness and the temperature uniformity of the substrate holder are a of extreme importance for the fabrication of large area superconducting thin films. An electroquartz with little deformation during deposition has turned out to be very successful as the substrate holder in our fabrication.

Fabrication and characteristics of intrinsic Josephson junctions in Bi2Sr2CaCu2O8+x single crystals

AbstractMesa-structured intrinsic Josephson junctions are fabricated in Bi2Sr2CaCu2O8+x single crystals. Typical current-voltage characteristics of intrinsic Josephson junctions are observed, which include multiple quasi-particle branches, surface junction with critical current lower than those of inner junctions, and subgap structures on quasiparticle branches. The corresponding physical explanations are also given. The energy gap voltage of the intrinsic Josephson junctions at 30 K is about 20 mV. Besides, the measuredIc-T relationship agrees quite well with the theoretical computations based on

Preparation of YBa2Cu3O7−δ thin films by magnetron sputtering with in situ plasma oxidation

d_{x^2 - y^2 } - wave

Quasi-particle injection into YBa2Cu3O7-δ micro-bridge

superconductor. Our measureddI/dV−V relationship shows theV-shaped gap structure, obviously differing from the U-shaped gap structure of the s-wave superconductor.

Simulation of Sub-harmonic SIS Mixers with a Full Five-Port Model

All currents through a superconducting tunnel junction, including quasiparticle tunneling current and Josephson current, are modeled on an electronic simulator. The current–voltage (I–V) curves of a rf‐driven superconducting tunnel junction are generated using this simulator so that the ranges of dc bias and rf excitation, over which chaotic behavior occurs, can be found for a given rf frequency. It turns out that the ranges are roughly the same as those for the resistively shunted junction model, although some differences exist. Contributions of either quasiparticle current or Josephson current to chaos in the junction are evaluated briefly.

Harmonic mixing of Bi2Sr2CaCu2O8+x intrinsic junction at millimeter waveband

Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films with surface roughness Ra{similar to}20 A have been successfully prepared by either rf or dc magnetron sputtering. The substrate temperature was kept at 600--670 {degree}C during deposition and a subsequent {ital in} {ital situ} plasma oxidation treatment was performed at 480--520 {degree}C. The films deposited on single-crystal SrTiO{sub 3} (100) exhibited zero resistance at 91 K and had the critical current density of 3{times}10{sup 6} A/cm{sup 2}. In this paper we describe the influences of fabrication conditions on film superconductivity.

Growth of YBCO Superconducting Thin Films by Magnetron Sputtering

Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films with surface roughness Ra{similar to}20 A have been successfully prepared by either rf or dc magnetron sputtering. The substrate temperature was kept at 600--670 {degree}C during deposition and a subsequent {ital in} {ital situ} plasma oxidation treatment was performed at 480--520 {degree}C. The films deposited on single-crystal SrTiO{sub 3} (100) exhibited zero resistance at 91 K and had the critical current density of 3{times}10{sup 6} A/cm{sup 2}. In this paper we describe the influences of fabrication conditions on film superconductivity.

In-situ Preparation of YBCO Thin Films on Single Crystal LaAlO3

Several types of quasi-particle injections into YBa2Cu3O7−δ (YBCO) micro-bridge have been studied, revealing the quasi-particle non-equilibrium effect, the current superposition effect and the heating effect. The current gain’s dependence on temperatures indicates that superconductivity of YBCO is really suppressed by quasi-particle injection. We propose a new type of quasi-particle injection which turns out to be a promising candidate for interface between superconductor and semiconductor circuits.