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TT: Fachverband Tiefe Temperaturen
TT 11: Superconductivity: Tunneling, Josephson Junctions, SQUIDs
TT 11.6: Talk
Monday, February 25, 2008, 17:00–17:15, H 3010
Fabrication and performance of Niobium-microsquids — •Martin Batzer1, Georg Schmidt1, Charles Gould1, Laurens Molenkamp1, and Wolfgang Wernsdorfer2 — 1Julius-Maximilians-Universität Würzburg — 2Institut Néel, CNRS Grenoble
Microsquids are useful instruments to detect and measure strongly localized ultrasmall magnetic moments. Here we present the fabrication and characterization of Niobium-based microsquids with diameters equal to or less than 1 µm by dry-etching. In order to avoid degradation during processing, the Nb-layer needs to be covered by a protective layer directly after the Nb-deposition. This protective layer mainly determines the further processing steps. The layers used for our experiments either consist of 15 nm of Nb covered by 2 nm of Si or of 30 nm of Nb covered by a bi-layer of 10 nm of Al and 10 nm of Ru. For the patterning process, a metal mask is patterned on top of the multilayer by electron beam lithography and lift-off. RIE-etching in a mixture of CHF3 and O2 is used to transfer the pattern into the niobium. For the tri-layer an additional Ar+-etch is necessary to remove the Ru and Al layer. For both layer systems working microsquids have successfully been fabricated. The best resolution that we obtain in preliminary measurements is Φ0/200. We anticipate that additional shielding and optimization of the read out electronics will allow for a lower noise level and thus higher resolution.