Yuying Zhao

On‐axis dc magnetron sputtering of large area high quality YBa2Cu3O7 superconducting thin films

It is demonstrated by our experiment that using the in situ dc magnetron sputtering method, it is possible to prepare high quality YBa2Cu3O7 (YBCO) thin films with substrates facing the region of plasma ring. The effect of oxygen resputtering can be greatly reduced with a high argon‐oxygen working gas ratio and a large target to substrate distance. It is shown that high quality YBCO thin films of more than 60 mm in diameter, that is about the same size of the diameter of the YBCO target, can be prepared with this process. The thin films were characterized by x‐ray diffractometry, and the critical temperatures were determined by both resistive and ac susceptibility techniques.

Critical current measurements in YBa2Cu3O7−x thin film grown on LaAlO3 substrate

The critical current density Jc(B,T) of epitaxial YBa2Cu3O7−x (YBCO) thin films on LaAlO3 was measured under different applied magnetic fields (0–7 T) with the temperature ranging from 65 to 79 K. At 65 K, the zero‐field critical current density of the best film was 5.8×106 A/cm2; even at magnetic fields up to 7 T, Jc could reach as high as 1×106 A/cm2. Strong anisotropy was observed at 79 K. The anisotropy behavior diminished with the decrease of temperature. Experimental results showed that Jc was proportional to (Tc−T)3/2 ; this was in accordance with the theoretical explanation by the Josephson junction model for granular superconductors.

The effect of Sc on the superconductivity of the BaYCu oxides

Abstract The oxide compounds of Ba 0.6 Y 0.4−x Sc x Cu (x=0.05−0.35) have been prepared. It was found that the superconducting transition temperatures of the samples vary with the contents of Sc and when Sc>0.325, the samples become nonsuperconducting.

The Hall coefficient of YBa2Cu3O7−x thin films with (100) orientation

The Hall coefficientRH and the resistivity ρ of an (100) orientated YBa2Cu3O7-x thin film was measured. A very smallRH was obtained. The resulting carrier density is very different from the widely accepted value of the order of 1021 cm−3 for the bulk sample. The result is explained with the influence of grain boundaries and the anisotropy of the thin films.

SUPERCONDUCTIVITY OF Sr-La-Cu-O THIN FILMS

High Tc Sr-La-Cu-O thin films have been successfully prepared by magnetron sputtering method. Their superconducting transition temperatures Tc are determined to be 25-27.3K and the transition widths 7.5-8.5K.

HIGH Tc SUPERCONDUCTIVITY OF Sr-La-Cu-O and Ba-Y-Cu-O THIN FILMS

In a very short time after it was reported1 that perovskite-type Ba-La-Cu oxide system could have high temperature superconductivity, many new results were reported.2,3 Later, Y was substituted for La to form Ba-Y-Cu oxides and the Tc rose to the liquid nitrogen region.4 In this report we describe the results obtained with the Sr-La-Cu-O and Ba-Y-Cu-O thin films.

Study of Ba-Y-Cu-O thin films with zero resistance at LN2 region prepared by magnetron sputtering

We briefly describe our results to date on the magnetron sputtering deposition of BaxY1+xCuO3-y thin films with Tc onset=96K and TR=0=83K. We emphasize the importance of the characteristics of the substrate material. The perovskite-SrTiO3 substrate deposits high TR=0 and Jc films. X-ray diffraction studies show that they are of single phase orthorhombic perovskite structure.

Point-contact tunneling investigation of the superconductors in Y-Ba-Cu-O system

Point-contact tunneling measurements of the oxide superconductor Y-Ba-Cu-O were carried out with both Nb and Mo tips. An energy gap, Δ=18.5meV and 2Δ/kTC=4.7 were obtained. The result is consistent with the strong-coupling theory. The tunneling conductance curves indicate a granular feature of the sample.

The superconductivity, structure and microstructure of BaYScCu oxides

Abstract We added small amount of Sc (0.05–0.35at.%) to BaYCu oxide and found that the superconductivity deteriorated drastically when the Sc content reached 0.325at.%. X-ray and electron diffraction showed that the orthorhombic perovskite structure changed to multi-phase structure with unidentified phases. The microstructures observed by TEM are of needle like morphology. Their phases are not yet identified.

Study of High Quality YBa2Cu3O7-y Thin Films

The high quality YBa2Cu3O7-y thin films were prepared by RF magnetron sputtering and ion beam sputtering methods with post annealing procedure. Zero resistance temperature (TR=0) and critical current density JC (at 77 K) are 9l K and 1.3 × 105 A/cm2 respectively. X-ray diffraction showed three types of orientation for these thin films: a-axis orientation, c-axis orientation and mixed a-axis and c-axis orientations. For a-axis and c-axis orientation thin films, anisotropic values were obtained in the measurement of JC(H) under high magnetiac field. It is possible that the anisotropic flux pinning force might exist in the oriented thin films.