Fabrication and characterization of Y-Ba-Cu-O and Nd-Ba-Cu-O ramp-edge junctions with an interface-modified barrier

Author

Makita, Takehiko ; Toma, Kazuyasu ; Ishikawa, Kazuhiro ; Zama, Hideaki ; Utagawa, Tadashi ; Kawabe, Ushio ; Tanabe, Keiichi

Author_Institution

Supercond. Res. Lab., ISTEC, Tokyo, Japan

Volume

11

Issue

1

fYear

2001

fDate

3/1/2001 12:00:00 AM

Firstpage

155

Lastpage

158

Abstract

The fabrication process for YBa₂Cu₃O_7-δ (YBCO) ramp-edge junctions with an interface-modified barrier has been studied. The conditions of electron cyclotron resonance (ECR) ion etching and following annealing treatment were optimized by evaluating the mean roughness of the ramp surface using atomic force microscope (AFM) observation. We could obtain resistively-shunted junction (RSJ) type current-voltage characteristics for the junctions with the counterelectrode YBCO layer deposited at temperatures lower than 720°C, while a deposition temperature higher than 755°C resulted in a high-J_c superconducting contact. The junctions exhibited an I_cR_n product of 1.0-1.9 mV and magnetic field modulation of I_c more than 90% at 4.2 K. By applying the optimum etching condition to a NdBa₂Cu₃O_7-δ (NBCO) base electrode and employing a slightly higher annealing and deposition temperature, YBCO/NBCO ramp-edge Josephson junctions with a similar I _cR_n product were successfully obtained

Keywords

Josephson effect; annealing; barium compounds; critical current density (superconductivity); critical currents; high-temperature superconductors; neodymium compounds; sputter etching; superconducting junction devices; superconducting thin films; surface topography; yttrium compounds; 4.2 K; 720 to 775 C; AFM observation; I_cR_n product; Nd-Ba-Cu-O ramp-edge junctions; NdBa₂Cu₃O_7-δ base electrode; NdBa₂Cu₃O₇; Y-Ba-Cu-O ramp-edge junctions; YBa₂Cu₃O_7-δ; YBa₂Cu₃O₇; annealing treatment; counterelectrode YBCO layer; deposition temperature; electron cyclotron resonance ion etching; high-J_c superconducting contact; interface-modified barrier; magnetic field modulation; optimum etching condition; ramp surface roughness; resistively-shunted junction type current-voltage characteristics; Annealing; Atomic force microscopy; Cyclotrons; Electrons; Etching; Fabrication; Josephson junctions; Resonance; Temperature; Yttrium barium copper oxide;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.919308

Filename

919308