Vertical Nb/TiOx/Nb Josephson Junctions Controlled by In-Plane Hot-Electron Injection (original) (raw)

Hybrid Josephson Junctions with Iron-based and Conventional Superconductor Electrodes

Journal of Superconductivity and Novel Magnetism, 2014

We investigate the iron-based superconductor Ba(Fe 1−x Co x ) 2 As 2 (Ba-122) regarding its superconducting properties and possible applications. Therefore Ba-122 thin films are used as base electrode to prepare different kinds of hybrid Josephson junctions with a counter electrode of the conventional superconductor Pb. Additionally, we use both c-axis and ab-plane transport geometries and different kinds of barriers like interface-engineered surfaces, sputtered titanium oxide and gold layers. Temperature dependent I-V characteristics as well as magnetic field dependence and microwave response of the junctions are shown. The examined I-V characteristics and I c R n -T behaviours of each junction type are compared and described according to the electrical behaviour of the respective normal conducting or insulating barrier. While the I c R n product of the interface-engineered barrier junction was 12 µV and the planar junction with Au barrier showed 18 µV, we could increase the I c R n to 90 µV for planar TiO x barrier junctions.

Tailoring of high-Tc Josephson junctions by doping their electrodes

Applied Physics Letters, 1999

Appropriate doping of the electrodes of high-T c Josephson junctions provides a means to systematically adjust the junctions' electronic properties. This is demonstrated for the exemplary case of grain boundary junctions in bicrystalline Ca-doped YBa 2 Cu 3 O 7Ϫ␦ films. It is found that the critical current density is strongly increased and the normal state resistivity significantly reduced in comparison with the values obtained for equivalent junctions in undoped films.

Characteristics of Nb-based Josephson junctions at a temperature below 1 K

IEEE Transactions on Magnetics, 1989

In nuclear r a d i a t i o n detection, superconductors have t h e inherent advantage of b e t t e r energy resolut i o n than t h a t of semiconductors. The ultimate energy r e s o l u t i o n has never been accomplished by t h e conventional method of f a b r i c a t i n g t h e tunnel junctions. In t h i s study, lithographic technique f o r Josephson LSI c i r c u i t s is applied t o t h e production of a superconducting tunnel junction f o r r a d i a t i o n detection. Nb-AUaluminum oxide/Nb tunnel junctions with d i f f e r e n t junction s i z e s and b a r r i e r oxidation times have been fabricated t o study t h e i r c h a r a c t e r i stics. The current-voltage curves were measured i n t h e temperature range from 4.2 t o 0.45 K. The junctions

Interface-Engineered High-Tc Josephson Junctions

Applied Superconductivity, 1998

ÐWe have developed a process for fabricating YBa 2 Cu 3 O 7 thin-®lm, ramp-type edge junctions in which no deposited barrier is employed. These devices display excellent RSJ-type current±voltage (I± V) characteristics with values of I c and R n tunable over a useful range for operation of digital circuits. Initial junction reproducibility and uniformity are very encouraging.

Low-T[sub c] Josephson junctions with tailored barrier

Journal of Applied Physics, 2007

Nb/Al2O3/Ni0.6Cu0.4/Nb based superconductor-insulator-ferromagnet-superconductor (SIFS) Josephson tunnel junctions with a thickness step in the metallic ferromagnetic Ni0.6Cu0.4 interlayer were fabricated. The step was defined by optical lithography and controlled etching. The step height is on the scale of a few angstroms. Experimentally determined junction parameters by current-voltage characteristics and Fraunhofer pattern indicate a uniform F-layer thickness and the same interface transparencies for etched and non-etched F-layers. This technique could be used to tailor low-Tc Josephson junctions having controlled critical current densities at defined parts of the junction area, as needed for tunable resonators, magnetic-field driven electronics or phase modulated devices.

Electron transport and microwave dynamics of hybrid Nb/Au/CaSrCuO/YBaCuO planar Josephson junctions

Journal of Physics: Conference Series, 2010

We report on measurements of dc electron transport and microwave dynamics of thin film hybrid Josephson junctions with an oxide antiferromagnetic interlayer. The base superconducting electrode YBaCuO and the antiferromagnetic (AF) interlayer CaSrCuO (with thickness d = 20-70 nm) were grown by laser ablation on NdGaO 3 substrates. I-V curves were well fitted to RSJ model and had no excess current, I C R N products were of order 0.2 mV at T=4.2 K. We did not observe any noticeable reduction of I C R N with increasing d. Such "tunnellike" behaviour also resulted in appearance of singularities on I-V curve when magnetic field was applied. Oscillating with microwave power integer and half-integer Shapiro steps were registered along with sub-harmonic detector response. Moreover, for some of junctions a "devil" staircase structure was observed on I-V curves and giant noise-like signals were measured in 1-2 GHz band at the certain levels of microwave power. Observed features, noise performance and the impact of the second harmonic in current-phase relation on junction dynamics are discussed taking into account data for structures without AF interlayer.

Intrinsically shunted Josephson junctions for electronics applications

Low Temperature Physics, 2017

Conventional Josephson metal-insulator-metal devices are inherently underdamped and exhibit hysteretic current-voltage response due to a very high subgap resistance compared to that in the normal state. At the same time, overdamped junctions with single-valued characteristics are needed for most superconducting digital applications. The usual way to overcome the hysteretic behavior is to place an external low-resistance normal-metal shunt in parallel with each junction. Unfortunately, such solution results in a considerable complication of the circuitry design and introduces parasitic inductance through the junction. This paper provides a concise overview of some generic approaches that have been proposed in order to realize internal shunting in Josephson heterostructures with a barrier that itself contains the desired resistive component. The main attention is paid to self-shunted devices with local weak-link transmission probabilities so strongly disordered in the interface plane that transmission probabilities are tiny for the main part of the transition region between two superconducting electrodes, while a small part of the interface is well transparent. We consider the possibility of realizing a universal bimodal distribution function and emphasize advantages of such junctions that can be considered as a new class of self-shunted Josephson devices promising for practical applications in superconducting electronics operating at 4.2 K.

Supercurrent in Nb/InAs-nanowire/Nb Josephson junctions

Journal of Applied Physics, 2012

We report on the fabrication and measurements of planar mesoscopic Josephson junctions formed by InAs nanowires coupled to superconducting Nb terminals. The use of Si-doped InAs-nanowires with different bulk carrier concentrations allowed to tune the properties of the junctions. We have studied the junction characteristics as a function of temperature, gate voltage, and magnetic field. In junctions with high doping concentrations in the nanowire Josephson supercurrent values up to 100 nA are found. Owing to the use of Nb as superconductor the Josephson coupling persists at temperatures up to 4 K. In all junctions the critical current monotonously decreased with the magnetic field, which can be explained by a recently developed theoretical model for the proximity effect in ultra-small Josephson junctions. For the low-doped Josephson junctions a control of the critical current by varying the gate voltage has been demonstrated. We have studied conductance fluctuations in nanowires coupled to superconducting and normal metal terminals. The conductance fluctuation amplitude is found to be about 6 times larger in superconducting contacted nanowires. The enhancement of the conductance fluctuations is attributed to phase-coherent Andreev reflection as well as to the large number of phase-coherent channels due to the large superconducting gap of the Nb electrodes.