We report on the fabrication and electrical transport properties of gate-tunable superconducting quantum interference devices (SQUIDs), made of semiconducting PbS nanowire contacted with PbIn superconducting electrodes. Applied with a magnetic field perpendicular to the plane of the nano-hybrid SQUID, periodic oscillations of the critical current due to the flux quantization in SQUID are observed up to T = 4.0 K. Nonsinusoidal current-phase relationship is obtained as a function of temperature and gate voltage, which is consistent with a short and diffusive junction model.

The authors found experimentally that carbon nanotube field-effect transistors (CNFETs) could exhibit n-type characteristics even though their electrodes consist of a large-work-function metal such as Co. To explain their result, which is contrary to the general belief that CNFETs with large-work-function electrodes always lead to p-type characteristics, ab initio electronic structure calculation for the metal-carbon nanotube junction was performed, which showed that the Fermi level alignment at the junction could sensitively depend on microscopic structures of the metal-carbon nanotube junction. This suggests that deposition method of electrodes as well as the metal type could be utilized to obtain n-type CNFETs.

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We have fabricated MgB2 grain boundary nanobridges by focused-ion-beam etch and studied their transport properties. Nanobridges with a nominal width and length of 100 nm were patterned across naturally formed single grain boundaries in the microbridges, which were prepatterned by a standard argon ion milling technique. We have studied current-voltage (I-V) characteristics, the temperature-dependent critical current, and the normal-state resistance. The measured properties were interpreted based on a flux flow model. In the I-V curves, a typical resistively shunted-junction characteristic was observed near Tc, however, as temperature decreases, flux-flow behavior became dominant, in accordance with the crossover of the ratio of the bridge length to the coherence length from the single-phased regime to the flux-flow regime. The temperature-dependent critical current was Ic(T)∼(1−T/Tc)1–1.5, similar to that of a superconducting film. The normal-state resistance increased steeply as temperature approaches Tc, in agreement with the flux-flow theory.

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