Method for preparing high-temp. superconductive Josephson junction by using refractory micromask process

Abstract

A method for preparing a high-temperature superconducting Josephson (Josephson) junction by a refractory micromask method, using a refractory micromask method, selecting a conventional or twin crystal or step substrate, and preparing CeO on the substrate by an in-situ preparation method 2 / YBCO double-layer film, YBCO is used as the bottom dielectric film and plays a supporting role in suspending the micro-mask layer at the same time. A photoresist mask is prepared on the above-mentioned double-layer film, and a micro-bridge pattern is obtained after exposure and development; CeO in the microbridge region 2 CeO 2 Mask; use dilute phosphoric acid to etch the YBCO film in the microbridge area to completely remove the underlying YBCO; put it into the film forming system to grow a high-temperature superconducting film with the required pattern, and directly form the Josephson junction. Using this method can avoid the influence of etching process on the performance of superconducting devices, and prepare high-quality high-temperature superconducting Josephson junctions.

Description

1. Technical field [0001] The invention relates to a method for preparing a high-temperature superconducting Josephson (Josephson) junction, in particular to a method for preparing a high-temperature superconducting Josephson junction by using a refractory micromask. 2. Background technology [0002] Superconducting Josephson junctions are also known as weakly connected junctions. The so-called weak connection refers to the structure in which two superconductors form a weak coupling in some way. Josephson once predicted that in a superconductor-insulator (barrier layer)-superconductor (SIS) tunnel junction structure, the superconductors on both sides are coupled to each other through the barrier layer. When the barrier layer is thin enough, a strange physical phenomenon will appear, namely the Josephson effect. . In fact, the Josephson effect not only occurs in SIS-type superconducting tunnel junctions, but can also be observed in other types of weakly connected structures...

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Problems solved by technology

However, this step has a relatively large impact on the junction parameters, and either method will reduce the performance of the junction

In chemical etching, it is often unavoidable that some phosphoric acid solution remains, especially in tiny areas such as the junction area, where phosphoric acid is not easy to remove, resulting in slow corrosion of the film by phosphoric acid, while YB 2 C 3 o 7-δ The contact of the film with water can also negatively affect the film properties, which will affect the properties of the film, such as critical temperature, critical current, etc.

In reactive ion etching, although water and acid are avoided with YB 2 C 3 o 7-δ film contact, but due to the inevitable temperature rise, when the temperature is higher than 400 degrees Celsius, YB 2 C 3 o 7-δ The film is extremely prone to oxygen loss in a non-oxygen environment, which affects superconductivity

For example, in the experiment, it was found that the Tc of the same sample before and after chemical etching decreased by at least 3K, and some superconducting films even became semiconducting due to careless operation, and lost their superconducting properties at low temperatures.

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