Self-shunted Nb/AlOx/Nb Josephson junctions (original) (raw)
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Fabrication of submicron Nb/AlO/sub x//Nb Josephson junctions using ECR plasma etching technique
IEEE Transactions on Appiled Superconductivity, 1997
A b s l r a c l-I t is important to develop a highyielding and reproducible fabrication process of submicron Nb/AIOxfNb Josephson junctions to improve the integration level and the operating speed of Josephson LSI circuits. For this purpose, we have developed a junction fabrication process by introducing an electron cyclotron resonance (ECR) plasma etching technique with CF4 gas. In the ECR plasma etching technique, highly anisotropic etching of Nb was achieved. Over-etching was reduced by 86 %. We have successfully fabricated NbfAlOxf-Nb junctions with critical current density of 104 A/cm2 using the cross-line patterning (CLIP) method and the electron beam (EB) lithography technique, where the size of the junctions was varied from 2 p n to 0.5 pm at 0.1 pm intervals. High-quality submicron junctions for integrated circuits with small spread of critical current IC was obtained. High uniformity of IC was achieved. The characteristics of the fabricated junctions are discussed and compared with the junctions fabricated by RIE technique.
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
Induced change of critical current density profile in Nb/Al-AlOx/Nb Josephson junctions
Journal of Physics: Conference Series, 2014
A technique to induce spatial modulation of critical current density in niobium based Josephson devices by using a selective thermal annealing is reported. By depositing a carbon film onto selected region of the Josephson element it is possible to induce a localized heating, with a spatial resolution less than 1µm, exploiting the much higher absorbance coefficient of carbon than the niobium one. The effectiveness of such technique is demonstrated by experimental measurement of the critical current vs. magnetic field, measured at T = 4.2 K, showing that the change of critical current density occurs only in the region corresponding to the absorber film area. Furthermore, the theoretical behaviour, by modelling a suitable step-like junction barrier shape, has been carried out to fit the experimental data in order to verify the selective modulation of critical current. This technique can be very useful in view of quantum computing experiments, Majorana fermions detection and superconducting magnetic sensors.
Investigation of low-temperature I-V curves of high-quality Nb/Al-AlOx/Nb Josephson junctions
Journal of Applied Physics, 1992
A detailed experimental temperature dependence of the subgap current of high-quality Nb/Al-AlO,/Nb Josephson tunnel junctions is reported. The presence of a pronounced current rise at V=A/e is observed. Comparison with the theoretical model for two-particle tunneling is performed, but a substantial disagreement is found. At V< A/e the measured current is in remarkably good agreement with the single particle tunneling predictions down to 2 K.
Stacked Josephson junction based on Nb/Si superlattice
Journal of Low Temperature Physics, 1997
We report on the technology and basic electrical properties of ten-fold stacked Nb/Si/Nb Josephson junction (J J). The problem of making a large number of stacked ,Lls with identical properties was solved by metallic superlattice preparation technology. The uniformity of Si barriers thickness was examined by low angle X-ray diffraction and cross-sectional transmission electron microscopy. To prevent pinholes in the Si barriers thc Nb/Si superlattice was sputtered at the regime at which smoothing of inteTfacial roughness occurs. The stacked junction exhibit both ac and dc Josephson effects. In the Ie( B) diffraction pattern there is an extra periodicity of about 2 -3 G in addition to a larger period of about 21 G.
Fabrication and properties of Nb/Al, Alox/Nb Josephson tunnel junctions with a double-oxide barrier
Journal of Applied Physics, 1990
High-quality Nb/ AI, At, /Nb Josephson tunnel junctions using double-oxide layers as barriers have been fabricated. The critical current density is controlled by the thickness of the second AI layer. This layer has to be oxidized completely through in order to obtain high-quality junctions. Typically, gap voltages of 2.8-3.0 m V and V", up to 70 m Vat 4.2 K were obtained.
IEEE Transactions on Appiled Superconductivity, 2003
Our Nb/AlO /Nb planarized process has been upgraded by adding extra dielectric and Nb wiring layers and the installation of an Inductively Coupled Plasma (ICP) etcher. Much higher quartz etch rates as well as reduced residue are achieved with ICP etch. Etch uniformities of both Nb and quartz are also improved significantly. Damage to Nb during the fabrication process has been investigated. We have found that dry etching in SF 6 plasma has a significant effect on the quality of Nb films under certain conditions with damage coinciding with the presence of in situ deposited Al.
Fabrication and properties of vertically stacked Nb/Al AlOχ/Nb Josephson tunnel junctions
Cryogenics, 1994
We present three novel processes for the fabrication of two or more vertically stacked Josephson tunnel junctions all based on the Nb/Al-AlOx/Nb technology. The dynamical properties of stacks of up to five, high-quality and low current density Josephson junctions have been investigated. In particular, we report the generation of two families of Fiske resonances in twofold stacks of electrically small junctions and on synchronized motion of fluxons having the same polarities but moving in opposite directions. Finally, we show why stacked junctions are very promising for application to the voltage standard maintenance.
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.