The oxidation state at tunnel junction interfaces
2003 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, Vol. 260, no 02-jan, 78-83 p.Article in journal (Refereed) Published
The oxidation state at the interfaces of Nb/Al-AlOx/Pb junctions is discussed. Conductance-voltage curves below and above the superconducting temperature suggest tunneling conduction, while X-ray photoelectron spectroscopy shows the existence of a thin AlOx layer at the Nb/Al interface. We demonstrate that at the usual 10(-7) Torr range of base pressures in the sputtering chamber, this is due to the time elapsed between the deposition of the Nb and Al bottom layers, in both Nb/Al-AlOx/Pb tunnel junctions and Nb/Al bilayers. We also give some direct evidence of the oxidation of the top Pb electrode on the Nb electrode surface. Such oxidation probably occurs at the pinholes of the intermediate Al-AlOx layer of the tunnel junctions, as a consequence of the oxidation state at the Nb/Al interface, which helps to avoid barrier shorts and enhances the quality of the tunnel barrier. We therefore suggest that there is oxide formation in other places besides where there is an actual oxide deposited. This is relevant for the performance of magnetic tunnel junctions since in most tunneling studies it is assumed that once the oxide is deposited, that is the only place where there is an oxide. This is also a very general statement applicable to thin film systems.
Place, publisher, year, edition, pages
2003. Vol. 260, no 02-jan, 78-83 p.
tunnel junctions, oxidation at interfaces, X-ray photoelectron spectroscopy, barriers, magnetoresistance, temperature, resistance, bilayers
IdentifiersURN: urn:nbn:se:kth:diva-22402ISI: 000182069300011OAI: oai:DiVA.org:kth-22402DiVA: diva2:341100
QC 201005252010-08-102010-08-10Bibliographically approved