Electric transport across Sr{sub 1-x}La{sub x}CuO{sub 2}/Au/Nb planar tunnel junctions and x-ray photoelectron and Auger-electron spectroscopy on Sr{sub 1-x}La{sub x}CuO{sub 2} thin films

Journal Article · Mon Aug 01 00:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.84.064521· OSTI ID:21596845

Tomaschko, J; Kleiner, R; Koelle, D ^[1]; Raisch, C; Chasse, T ^[2]; Leca, V ^[1]

---

1. Physikalisches Institut-Experimentalphysik II and Center for Collective Quantum Phenomena in LISA, Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany)
2. Physikalische Chemie and LISA, Universitaet Tuebingen, Auf der Morgenstelle 18, 72076 Tuebingen (Germany)

Thin-film planar tunnel junctions with the electron-doped infinite-layer superconductor Sr{sub 1-x}La{sub x}CuO{sub 2} (SLCO) with x{approx}0.15 as bottom electrode, a thin Au interlayer, and Nb as top electrode were fabricated and characterized. Measurements of electric transport across these junctions provide information on the interface and surface properties of the SLCO thin films. No Cooper pair tunneling is observed; however, nonlinear current-voltage characteristics give evidence for quasiparticle (QP) tunneling across a thin insulating SLCO barrier at the SLCO/Au interface, with a single gap value {approx}1.4 meV, originating from superconducting Nb. The absence of a superconducting SLCO gap in the QP conductance curves indicates a thin normal-conducting SLCO layer below the insulating SLCO barrier. To examine its origin, x-ray photoelectron spectroscopy (XPS) and x-ray Auger-electron spectroscopy (XAES) on SLCO thin films were performed. We observe a Cu valence of +1 in the SLCO surface layer (within {approx}3 nm thickness) and of +2 in deeper regions, as expected for fully oxidized CuO{sub 2} planes in the bulk. Hence, the XPS and XAES results for the SLCO films are consistent with the QP tunneling spectra observed for our planar SLCO/Au/Nb junctions.

• OSTI ID: 21596845
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 6 Vol. 84; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
AUGER ELECTRON SPECTROSCOPY
COPPER COMPOUNDS
DIMENSIONS
DOPED MATERIALS
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ELEMENTS
FILMS
GOLD
HIGH-TC SUPERCONDUCTORS
IONIZING RADIATIONS
LANTHANUM COMPOUNDS
LAYERS
MATERIALS
METALS
NIOBIUM
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
RADIATIONS
RARE EARTH COMPOUNDS
REFRACTORY METALS
SPECTRA
SPECTROSCOPY
STRONTIUM COMPOUNDS
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTORS
SURFACE PROPERTIES
SURFACES
THICKNESS
THIN FILMS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNNEL EFFECT
TYPE-II SUPERCONDUCTORS
X RADIATION
X-RAY PHOTOELECTRON SPECTROSCOPY