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| Hauptseite > Publikationsdatenbank > Superconducting nanostructures and 2D superconducting materials for operation in transmission electron microscopes |
| Hauptseite > Publikationsdatenbank > Superconducting nanostructures and 2D superconducting materials for operation in transmission electron microscopes |
| Conference Presentation (After Call) | FZJ-2025-01992 |
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2025
Abstract: Transmission electron microscopy enables high-resolution imaging and spectroscopy on active quantum devices. Here, we develop new technologies for operation of low-Tc and high-Tc superconducting nanostructures inside transmission electron microscope (TEM) in order to study their functionality down to atomic level and temperatures down to 5 K. As thin-film materials for the nanobridges, metals Ti and Nb were combined into 3-layer heterostructures for adjusting superconducting parameters of the nanobridge Josephson junctions (nJJs) through the proximity effect. This allowed to reduce spread of parameters (Tc, Ic, etc.) in ultrathin superconducting films and to adjust operating temperature of nJJs to the most stable operating temperature of the commercial TEM sample holders cooled using liquid helium. Cross-sectional TEM images of the Ti-Nb-Ti thin-film heterostructure were obtained and revealed epitaxial growth. Electron beam lithography and high selectivity reactive ion etching with pure SF6 gas were used to pattern nJJs with down to 10 nm width that is comparable to coherence length in thin films of Nb. Nanoscale superconducting quantum interference devices (nanoSQUIDs) with nJJs were prepared on home-made SiN membrane and observed with TEM (Fig. 1a). NanoSQUIDs were also prepared at a distance of below 200 nm from the tip of a cantilever by using a focused ion beam to achieve bulk nanosculpturing of the substrate. Measurements revealed non-hysteretic I(V) characteristics of the nJJs and nanoSQUIDs at operation temperature 5 K. 100-nm-thick NbSe2 flakes were transferred onto SiN membrane with Au contact leads and a hole (Fig. 1b) and measured in TEM down to the temperature below its Tc =7 K. High-Tc nanoSQUIDs were realized with step-edge Josephson junctions. To realize hybrid superconductor-ferromagnetic nanostructures for further experiments in TEM, Permalloy nanodisks and triangles with dimensions down to ~100 nm were prepared on similar SiN membranes and studied by Lorentz microscopy and electron holography methods. These technologies are promising for the fabrication of superconducting electronics for operation inside a TEM.
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