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Master thesis: Nanoscale superconducting quantum interference devices (nano-SQUIDs)

Advertising institute: PGI-5 - Microstructure Research
Reference number: D035/2018, Physics

Unique quantum effects in superconducting nano-devices are providing them a great advantage in achieving the low noise, energy-saving and ultrahigh-speed processing. Scanning nanoscale superconducting quantum interference devices (nano- SQUIDs) are of particular interest for magnetic imaging in the fields of nanomagnetism and spintronics due to their high sensitivity, negligible reverse effect on the object and a large frequency bandwidth. Nano-SQUIDs can be potentially implemented also for non-destructive readout of the final states of superconducting flux qubits after their protection by sufficiently high potential barriers. Nano- SQUIDs demonstrated unprecedented spin sensitivity (Vasyukov et al., Nature Nanotechnology 8, 639, 2013) and spatial resolution (Anahory et al., Nano Lett. 14, 6481, 2014). Implementation of electrically tunable multi-terminal nano-SQUID’s configuration (Uri et al., Nano Lett. 16, 6910, 2016) provided the optimal flux bias conditions by direct injection of the flux modulation and feedback current into the SQUID loop. It is planned to develop a nano-SQUID measurement system that would be used at PGI-5 and ER-C to study magnetic effects that are occurring in small samples on a nanometer scale as a technique complementary to the electron holography measurements that are currently performed at ER-C.

This work will be embedded in the international team at the Institute for Microstructure Research (PGI-5) and Ernst-Ruska-Centre. The candidate will perform nanofabrication of superconducting devices: nanobridges, Josephson junctions and nano-SQUIDs and characterize their microstructural and electron-transport properties.

Deposition of thin films of Au, Pt, C, low-Tc superconductor Nb, epitaxial high-Tc superconductor YBa2Cu3O7-x and different epitaxial insulating metal-oxide materials will be performed at PGI-5. Nanostructuring down to 20 nm will be performed using electron beam lithography and (reactive) ion (beam) etching. For this purpose, work in the Cleanroom of the Helmholtz Nano Facility (HNF) is essential.

Study of microstructural properties of the superconducting devices will be performed using scanningand transmission electron microscopes at Ernst-Ruska-Centre. Characterization of electron-transport and noise properties will be performed at 4.2 K, 77 K and at room temperature using different measurement systems at PGI-5. Estimations and comparison with theoretical models will be performed. The best nanoSQUIDs will be placed on cantilever in a low temperature piezo scanning system with ultra large scan range for imaging of magnetic field of different nanoscale objects that are related to the rapidly evolving research fields of topological materials, spintronics, quantum
computation and artificial intelligence.

Contact person:
Prof. Dr. Michael Faley
Forschungszentrum Jülich
Ernst Ruska-Centre for Electron microscopy