YBCO step-edge junctions with highI_cR_n

Abstract

Step-edge junctions represent one type of grain boundary Josephson junction employed in high-temperature superconducting junction technology. To date, the majority of results published in the literature focus on [001]-tilt grain boundary junctions (GBJs) produced using bicrystal substrates. We investigate the step morphology and YBCO (yttrium barium copper oxide) film structure of YBCO-based step-edge junctions on MgO [001] substrates which structurally resemble [100]-tilt junctions. High-resolution electron microscopy reveals a clean GBJ interface of width ∼1 nm and a single junction at the top edge. The dependence of the transport properties on the MgO step-edge and junction morphology is examined at 4.2 K, to enable direct comparison with results for other junction studies such as [001]-tilt and [100]-tilt junctions and building on previously published 77 K data. MgO step-edge junctions show a slower reduction in critical current density with step angle compared with [001]-tilt junctions. For optimized step parameters, transport measurements revealed large critical current and normal resistance (I c R N ) products (∼3-5 mV), comparable with the best results obtained in other kinds of [100]-tilt GBJs in YBCO at 4.2 K. Junction-based devices such as SQUIDs (superconducting quantum interference devices) and THz imagers show excellent performance when MgO-based step-edge junctions are used.

Enhancing Properties of High‐Temperature Superconducting Step‐Edge Josephson Junctions by Nano‐Multilayers with a Small Mismatch

“…[ 6 ] Single layer YBa 2 Cu 3 O 7 (YBCO) SQUIDs have already achieved remarkably low noise down to few hertz in a magnetically shielded environment. [ 7 ] However, in an unshielded environment (e.g. in the earth magnetic fi eld), the 1/f performance of these SQUIDs degrades at low frequency as a result of penetration of Abrikosov vortices and their thermally In addition, we show correlations between morphology and transport properties of HTS step-edge junctions grown by pulsed laser deposition on MgO substrates, which is one of the most important materials for practical applications.…”

“…[ 10 ] A range of different types of YBCO junctions have been engineered. [ 10 ] Among them, stepedge junctions are singled out due to their low cost, relatively high characteristic voltage (the so-called I R c n value of 100 to 400 μV at 77 K, [ 7,11 ] where I c is the critical current and R n is the resistance in the normal state), and excellent integrability and the scalability of the junctions. These features enable miniaturization and high effi ciency of electronic circuits, as well as applications in magnetic sensing and terahertz (THz) imaging.…”

“…The bottom edge of the step was made rounded [ 7 ] to attenuate the infl uence of the lower grain boundary. In the ideal case, it allows us to avoid formation the lower grain boundary (and the associated Josephson junction).…”

An overview of some of CSIRO’s “Underground Science” capabilities

“…An important outcome of this program was the development of a step-edge Josephson junction (SEJ) technology that allows a junction to be positioned anywhere on a MgO (001) substrate and is suitable for fabricating multiple devices or arrays on a single chip [8,9]. This technology has proven to be a cost effective process for fabricating HTS SQUIDs and other junction-based devices.…”

Monolithic high-temperature superconducting heterodyne Josephson frequency down-converter

“…11,12 The creation of the step-pattern on the MgO substrate and patterning of the YBCO film were done using photolithographic and Ar ion beam etching techniques (more details can be found in Refs. 5, 6, and 10).…”