Transport and Noise Properties of sub-100-nm Planar Nb Josephson Junctions with Metallic Hf – Ti Barriers for nano-SQUID Applications
Authors: V. Morosh, J. Linek, B. Müller, M.J. Martínez-Pérez, S. Wolter, T. Weimann, J. Beyer, T. Schurig, O. Kieler, A.B. Zorin, R. Kleiner, and D. Koelle
Phys. Rev. Applied 14, 054072
Abstract: We analyze electric transport and noise properties at 4.2 K of self-shunted superconductor-normal metal-superconductor (SNS) sandwich-type Josephson junctions, comprising Nb as the superconductor and Hf–Ti as the normal conducting material, with lateral dimensions down to approximately 80 nm. The junctions are fabricated with an optimized multilayer Nb technology based on nanopatterning by electron-beam lithography and chemical-mechanical polishing. The dependence of transport properties on the junction geometry (lateral size and barrier thickness dHf−Ti) is studied, yielding a characteristic voltage Vc up to approximately 100μV for the smallest dHf−Ti=17 nm. The observed small hysteresis in the current-voltage curves of devices with high Vc and large size can be attributed to self-heating of the junctions and fitted with an extended version of the resistively shunted junction model. Measurements of voltage noise of single junctions are consistent with the model including self-heating effects. The potential of our technology for further miniaturization of nanoscale superconducting quantum interference devices and for the improvement of their performance is discussed.