Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 11: Superconductivity: Tunneling, Josephson Junctions, SQUIDs

TT 11.6: Vortrag

Montag, 25. Februar 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.