Sebastian Döring

BaFe1.8Co0.2As2 thin film hybrid Josephson junctions

Josephson junctions with iron pnictides open the way for fundamental experiments on superconductivity in these materials and their application in superconducting devices. Here, we present hybrid Josephson junctions with a BaFe1.8Co0.2As2 thin film electrode, an Au barrier, and a PbIn counter electrode. The junction shows resistively shunted junction-like current-voltage characteristics up to the critical temperature of the counter electrode of about 7.2 K. The temperature dependence of the critical current shows nearly linear behavior near TC. Well-pronounced Shapiro steps are observed at microwave frequencies of 10–18 GHz. Assuming an excess current of 200 μA at 4.2 K the effective ICRN product calculates to 7.9 μV.

Planar hybrid superconductor-normal metal-superconductor thin film junctions based on BaFe1.8Co0.2As2

Abstract To investigate the transport properties of iron based superconductors, we prepared planar hybrid superconductor-normal metal-superconductor (SNS’) thin film junctions with BaFe 1.8 Co 0.2 As 2 as base electrode. As counter electrode we used a lead indium alloy, while the normal metal layer was formed by thin gold films. The junction design allows us to characterize the electrodes as well as the junction itself. Temperature dependent Andreev reflection studies of the junction show gap-like features but were also strongly influenced by the properties of the electrodes.

Preparation of hybrid Josephson junctions on Co-doped Ba-122 single crystals

In this paper we present a method for processing a hybrid Josephson junction on Co-doped (Ba-122) single crystals with a thin film Pb-counter electrode and a barrier layer of . This includes the leveling and polishing of the crystals and structuring them with thin film techniques such as photo lithography, sputtering and ion beam etching. The junctions show hysteretical resistively and capacitively shunted junction-like I?V characteristics with an -product of about 800 .

Bicrystalline Grain Boundary Junctions of Co-doped and P-doped Ba-122 Thin Films

We prepared GB junctions of Ba(Fe0.9Co0.1)2As2 thin films on bicrystalline [00 l]-tilt SrTiO3 substrates. The junctions show clear Josephson effects. Electrical characterization shows asymmetric I-V characteristics which can be described within the resistively shunted junction (RSJ) model. A large excess current is observed. Their formal ICRN product is 20.2 μV at 4.2 K, which is decreased to 6.5 μV when taking Iex into account. Fabrication methods to increase this value are discussed. Additionally, measurements on GB junctions of BaFe2(As0.66P0.34)2 thin films on LSAT bicrystalline substrates are shown. Their symmetric RSJ/flux flow-behavior exhibits a formal ICRN product of 45 μV, whereas the excess corrected value is ll μV.

Iron Pnictide Thin Film Hybrid Josephson Junctions

Thin films of iron pnictides open the way for fundamental experiments on superconductivity in this material. Thus we started to develop tunneling and Josephson junctions with pnictide film electrodes. Different preparation methods for Josephson junctions were investigated and the first results are presented. Resistive measurements show a high superconductive transition temperature of about 20 K even for the La-1111 electrode after patterning and preparation of the tunneling window. The hybrid junctions were completed with a PbIn counter electrode and normal conducting gold layers as barriers.

Charge transport under microwave irradiation in Josephson heterostrucrures superconductor - doped semiconductor - superconductor

Molybdenum-rhenium (MoRe) alloy based Josephson junction with various transparency distribution functions have been fabricated and studied. MoRe-Si(doped by tungsten)-MoRe junctions have been fabricated by using thin films deposition techniques. Bottom MoRe electrodes with a thickness of about 100 nm have been fabricated by magnetron sputtering in argon atmosphere. Silicon (Si) barriers doped by tungsten (W) have been fabricated by magnetron sputtering in argon atmosphere with the use of a complicated target assembled from a pure silicon wafer and a number of tungsten wires. Top MoRe electrodes with a thickness of about 100 nm have been fabricated by magnetron sputtering as well. Current-voltage characteristics (I-V curves) of the fabricated Josephson junctions have been measured at various temperature and magnetic field values.