Edge-type Josephson junctions with Co-doped Ba-122 thin films

Abstract

In this work we present preparation details and measurement results for an edge-type hybrid Josephson junction based on Co-doped BaFe2As2. The base electrode was formed by ion beam etching of a Ba-122 thin film, while the counter-electrode was patterned by evaporating lead. Finally, an indium protection layer was evaporated. The junction shows asymmetric I–V-characteristics with a total IC RN -product of about 12 μV . The characteristics can be fitted within a resistively shunted junction model assuming different fitting parameters for the positive and negative branches. There is a high excess current of unknown origin. The magnetic field dependence of the critical current indicates a non-homogeneous junction network and effects by flux trapping. It shows a variation of IC in the positive as well as in the negative bias branch, but does not suppress it completely. Also the influence of microwave irradiation on the junctions is shown. Thereby IC as well as the excess current can be suppressed, while first and higher order Shapiro steps can be observed.

Bicrystalline Grain Boundary and Hybrid SNS Junctions Based on Ba-122 Thin Films

“…In this temperature range, a nearly linear decay of I C can be seen when increasing the temperature. This behavior is similar to cuprate superconductor results [1] and the results of the planar SNS' and edge-type junctions [8], [9], where the temperature dependence is limited by the critical temperature of lead. The small I C value in Fig.…”

“…8). The resulting I C R N product is reduced from 12.6 µV (formal) to 7.5 µV (effective) at this junction [9].…”

Investigation of TiOx barriers for their use in hybrid Josephson and tunneling junctions based on pnictide thin films

“…In our investigations on iron pnictide superconductors we prepared planar Josephson junctions using a sputtered insulating layer as barrier. Up to now different works for Josephson junctions with single crystals, [1][2][3] for bi-crystal grain boundary junctions [4][5][6][7][8] and edge-type junctions 9,10 as well as for planar junctions 11 were published. The Josephson junctions presented therein used natural or engineered interfaces as well as normal metal layers as barrier, but up to now, no work with a deposited insulating barrier has been published.…”

Thin Film Growth and Device Fabrication of Iron-Based Superconductors

“…Regarding 122 compounds, a high-J c Ba122:Co film exhibiting above 1 MA/cm 2 was also demonstrated by Rall et al, 212) and Döring et al 213) fabricated an SNS junction using a Ba122:Co epitaxial film as a base electrode. Iida et al 214) proposed a new buffer layer, MgAlO 4 , which is effective between an Fe layer and an LSAT substrate.…”