Artificial barriers for Ba-K-Bi-O tunnel junctions

Author

Baumert, B.A. ; Talvacchio, J.

Author_Institution

Dept. of Mater. Sci. & Eng., Carnegie Mellon Univ., Pittsburgh, PA, USA

Volume

3

Issue

1

fYear

1993

fDate

3/1/1993 12:00:00 AM

Firstpage

1567

Lastpage

1570

Abstract

The authors have grown epitaxial bilayers and trilayers which utilize Ba/sub 1-x/K/sub x/BiO/sub 3/ (BKBO) base electrodes, native or artificial (MgO or SrTiO/sub 3/) insulating barriers, and Ag or BKBO counterelectrodes, respectively. The layers were deposited in situ by RF magnetron sputtering and characterized in situ. Electron diffraction showed the layers to be epitaxial with the symmetry of the desired structure maintained even in the first monolayer at the surface. X-ray photoelectron spectroscopy (XPS) showed no evidence of a chemical reaction at the BKBO/barrier interfaces. Tunneling measurements through a native insulating layer grown by exposing BKBO surfaces to air showed a gap of approximately 25 mV to be present. In the range of thicknesses used for artificial barriers, 3-6 nm, the barriers apparently contained pin holes which caused the junctions to short. The BKBO films were K-rich with x approximately=0.5. Critical temperatures and lattice constants were consistent with reports for bulk superconductors with this composition. Normal-state resistivities of 70-100 mu Omega -cm at 30 K were the lowest ever reported in this system.<>

Keywords

X-ray photoelectron spectra; barium compounds; high-temperature superconductors; low energy electron diffraction; potassium compounds; reflection high energy electron diffraction; sputtered coatings; superconducting epitaxial layers; superconducting transition temperature; superconductive tunnelling; 3 to 6 nm; 30 K; Ag; Ba-K-Bi-O tunnel junctions; Ba/sub 1-x/K/sub x/BiO/sub 3/; HTSC; LEED; MgO; RF magnetron sputtering; RHEED; SrTiO/sub 3/; X-ray photoelectron spectroscopy; artificial barriers; base electrodes; counterelectrodes; critical temperatures; electron diffraction; epitaxial bilayers; epitaxial trilayers; insulating barriers; lattice constants; monolayer; native insulating layer; normal state resistivities; pin holes; tunnelling measurements; Chemicals; Electrodes; Electrons; Insulation; Radio frequency; Spectroscopy; Sputtering; Superconducting magnets; Tunneling; X-ray diffraction;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.233365

Filename

233365