Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 6: Superconductivity: Tunnelling & Josephson Junctions
TT 6.7: Vortrag
Montag, 11. März 2013, 11:00–11:15, H18
Towards π Josephson Junctions with Fe, Si based Barriers — •Nico Ruppelt1, Ondrej Vavra1, Hanna Sickinger2, Edward Goldobin2, Dieter Koelle2, Reinhold Kleiner2, and Hermann Kohlstedt1 — 1Nanoelektronik, Technische Fakultät, Christian-Albrechts Universität zu Kiel, Germany — 2Physikalisches Institut, Experimentalphysik II, Universität Tübingen, Germany
π Josephson junctions are promising elements for RSFQ logic [1] and flux qubits [2]. We fabricate and investigate Josephson junctions with barriers made of Si-Fe alloy aiming to achieve high critical current densities jc in the π state. In order to vary parameters like composition and thickness independently in a single wafer run, a combinatorial sputtering technique for alloy and multi layer deposition of Fe and Si is presented. Our approach is based on a common planetary-type sputter system. Both materials were deposited with monotonic thickness gradients which were aligned perpendicular to each other. Alloys are formed by stacking of alternately deposited submonolayers of Fe and Si. Various Nb/Al based Josephson junctions with FeSi alloy interlayers and different combinations of Si|Fe multilayers were prepared. Electrical I–V characteristics and Ic(B) look as expected (RSJ-like and Fraunhofer-like), while the critical current density jc as a function of the Fe content demonstrates non-trivial behavior.
[1] T. Ortlepp, et al., Science 312, 1495–1497 (2006)
A. K. Feofanov, et. al., Nature Physics 6, 593–597 (2010)