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A new fabrication process of Nb/Al-AlO(sub x)-Al/Nb junction is described. The sputtered Al2O3 layers with 10 nm thickness are used in the process as the protection layer for the upper surface of both the base and counter electrodes in the anodization process and also the etching stop layer for the formation of the contact hole by reactive ion etching process.

Two types of high-temperature Josephson junctions were developed using a focused ion beam approach. Junctions made by narrow-focused Ga-ion beam for substrate damaging exhibit geometrical defects prior to high-temperature layer deposition. Meanwhile, junctions fabricated on a narrow tungsten metal layer deposited on SrTiO3 and MgO substrates through focused ion beam chemical vapor deposition exhibit current-voltage characteristics that are consistent with a resistively shunted junction model.

An Nb Josephson junction with a Hf/HfN double overlayer structure was fabricated and presented. The characteristics of the device were not affected by annealing at temperatures up to 350 degrees celsius. The Hf layer acted as a layer for the tunneling barrier formation and as an effective etch stop for a reactive ion etching process during the fabrication of the junction. The HfN layer acted as a stop for grain boundary diffusion between the Nb and Hf layers.

Presents a study which investigated the fabrication process of niobium/aluminum-aluminum oxide[sub x]/niobium (Nb/Al-AlO[sub x]/Nb) Josephson junctions. Fabrication of the Nb/Al-AlO[sub x]/Nb; Junction defined by a reactive ion etching technique; Influence of Nb deposition condition on the junction characteristics; Optimization of the Al film thickness.

Presents information on a study which fabricated niobium (Nb)/AlO[subx]Nb Josephson junctions which showed excellent current-voltage characteristics. Deposition of Nb and aluminum layers to get a clear junction interface; Fabrication of 10[sup4] junctions connected in series; Estimation of the yield.

One of the most important factor of the superconducting tunnel junction for a particle and radiation detection is the sub-gap leakage current. An anodization of a junction edge is an effective method to reduce the sub-gap leakage current. In a new fabrication process of a Nb/Al - AlOx - Al/Nb junction, the sputtered Al2O3 layers with 10 nm thickness are used as not only the protection layer for the upper surface of both the base and counter electrodes in the anodization process, but also the etching stop layer for the formation of the contact hole by reactive ion etching process. [ABSTRACT FROM AUTHOR]

Focuses on the fabrication of an all refractory Josephson junction in which ytterbium (Yb) oxide is used as a tunneling barrier. Application of self-aligned contact process; Advantage of using Yb oxide over aluminum oxide; Background temperature for the sputtering and the oxidation.

High quality Nb/Al-AlOx/Nb Josephson junctions have been fabricated by a novel process named the self-aligned contact process. After the definition of the junction area by a reactive ion etching (RIE) technique, the exposed Nb layer and the junction edge are anodized to protect against electrical shorts and an Al film is deposited as the etching stopper layer. After base electrode patterning by RIE, an insulation layer is deposited. The contact hole, with the diameter of the junction, for connecting a counter electrode and a wiring layer, can be made without registration because of the deposited Al film. The junctions fabricated by this process have exhibited excellent current-voltage characteristics (Vm =70 mV at the critical current density jJ =1.8 kA/cm2, Vm =11 mV at jJ =20 kA/cm2). [ABSTRACT FROM AUTHOR]

We have improved the quality of Nb/Al-AlOx/Nb Josephson junctions and obtained the most excellent junction characteristics ever obtained for all refractory Josephson junctions. The Vm values (the product of the critical current and the subgap resistance measured at 2 mV) are 88 mV at the critical current density Ij =500 A/cm2 and 72 mV at Ij =1000 A/cm2. The Vm values are larger than 40 mV up to Ij of 2400 A/cm2. The high Vm values are important to obtain the low subgap leakage current and not to reduce the transfer current to the load in Josephson circuit. These characteristics have been achieved by improving the quality of the Nb film and optimizing the Al thickness. We have also confirmed that Ij can be controlled by both the oxidation pressure and time in the range of 40–4600 A/cm2. [ABSTRACT FROM AUTHOR]

Investigates the metal/niobium (Nb) junctions with thin overlayers using x-ray photoelectron spectroscopy. Preparation of the samples by direct current magnetron sputtering; Examination of the aluminum overlayer coverage of Nb; Factors influencing the quality of the fabricated junctions.

Reports the fabrication of a niobium Josephson junction with a hafnium (Hf) overlayer. Use of Hf native oxide formed by thermal oxidation as a tunneling barrier; Degradation of junction characteristics in deposition and annealing; Increase of subgap leakage current after annealing.

Investigates the fabrication of Nb/Al--AlO[sub x]--Al/Ta/Nb Josephson junctions as x-ray detectors. Observance of the current-voltage characteristics of the junction; Fabrication of the junction at different Al deposition rates; Dependence of the junction on Al deposition rates at leakage current.

Examines the fabrication of Josephson junction using Al/Ta/Nb structure for x-ray detection. Application of the junctions for integrated circuits; Use of niobium layer as buffer; Temperature dependence of current-voltage characteristics.

Investigates the interfaces of niobium (Nb) Josephson junctions with an overlayer structure using cross-sectional transmission electron microscopy. Factors attributing the interface roughness between aluminum (Al) and Nb; Application of McMillan's proximity theory for Al/Nb interface analysis; Impact of thermal annealing on interface roughness.

Presents an interface study of Nb/ZrO[sub x]-Zr/Nb Josephson junctions by using the secondary ion mass spectroscopy. Detachment of water vapor layer from the chamber wall; Absorption of argon sputtering gas in the ZrO[sub x]-Zr and niobium layers; Implication of zirconium melting point for the junction interface stability.

Examines the use of secondary ion mass spectrometry in observing niobium (Nb) Josephson junction structure changes. Significance of the absorbed water vapor layers in the junction structure; Comparison between the annealing changes of Nb base electrode and Nb counterelectrode; Effect of grain boundary diffusion on the interface.

Plasma polymerization using CHF3 gas, which prevents the degradation of high Tc oxide superconductors due to moisture and annealing, was developed. The resistive transitions of Y1Ba2Cu3Ox thin films, coated by plasma polymerization, did not change before and after soaking in 20 °C water for 60 min. In addition, the critical temperature of those films was unchanged after annealing at 200 °C for 30 min in air, and then soaking in 90 °C water for 10 min. We confirmed that the polymer film grown by this method was dense, and the Y1Ba2Cu3Ox film reacted with the fluorine at the interface using x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Responds to the commentary on the use of tantalum film as an absorber for a Josephson junction structure in a single photon x-ray detection. Reason for the use of tantalum as a counter electrode; Gap voltage in the symmetrical gap structure; Relationship of the gap voltage and energy resolution of the detector.