Abstract
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.
Published Version
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