Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 15: Focussed Session: Geometry- and Topology-Controlled Nanoarchitectures I
HL 15.12: Talk
Tuesday, March 13, 2018, 12:45–13:15, EW 015
Nano-SQUIDs with controllable weak links via electromigration — Wout Keijers1, Xavier D.A. Baumans2, Ritika Panghotra1, Jospeh Lombardo2, Vyacheslav S. Zharinov1, Alejandro V. Silhanek2, and •Joris Van de Vondel1 — 1INPAC-Institute for Nanoscale Physics and Chemistry, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium — 2Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège, B-4000 Sart Tilman, Belgium
This work deals with modifying the weak links of a thin film aluminum nano-SQUID beyond the limit of current lithography techniques using controlled electromigration (EM). In order to achieve this goal, a nano-SQUID is designed and fabricated using e-beam lithography (EBL) and molecular beam epitaxy (MBE) techniques. Since the design of the SQUID consists of two weak links in parallel, the next step was to experimentally verify that this design is indeed compatible with parallel EM. This is achieved by the, direct and in-situ, observation of the parallel EM process using scanning electron microscopy. Hereafter, we investigated the evolution of the superconducting properties of the SQUID using low temperature measurements as function of the cross section of the weak links. The behavior of the SQUID's critical current perfectly matches the numerical calculations based on a SQUID model which takes into account the kinetic inductance and asymmetry of the device. Moreover, it is observed that when EM has sufficiently reduced the junction cross section, the SQUID can be operated in the dissipative state, where magnetic flux readout from voltage is possible.