Growth and characterization of Ca doped Eu-123 whiskers for intrinsic Josephson junction applications

Abstract

Single-crystal whiskers of Eu-123 were grown from Te and Ca doped precursor pellets. The Eu-123 whiskers contained a certain amount of Ca but were not contaminated with Te. Our composition analysis and superconducting property measurements reveal that the whiskers inherited certain site disorders and oxygen deficiencies in the as-grown state, which is reflected in the very low T c . High pressure oxygen annealing was required to increase the T c to about the 80 K level. Submicron sized junctions fabricated by focused ion-beam etching showed clear multi-branch structure with hysteresis in the I -V curve. The Eu-123 whiskers were found to possess excellent crystalline quality both in the as-grown state and after high pressure annealing, despite the site disorders. The critical current density J c of a Eu-123 whisker (T c = 45 K) was estimated to be 1.43 × 10 5 A cm −2 at 4.2 K, twice that observed for Y-123 having a similar T c .

Measurements of the switching current distribution in REBa2Cu3Oy(RE = Eu, Er) intrinsic Josephson junctions

“…Since RE123 IJJs has a large J c , so that they have a significantly high ω p0 [5,6]. On the other hand, in order to observe the intrinsic Josephson junction properties in RE123, the carrier doping state should be controlled to under-doped region to enhance the electrical isolation of its barrier layers, because the barrier layers of RE123 are not insulating around the optimal doped region.…”