JPH03201583A - Superconducting bond and manufacture thereof - Google Patents

Abstract

PURPOSE:To operate at a high temperature using oxide superconductor and to provide a superconducting bond having excellent performance by forming a nonsuperconducting layer of oxide of an element selected from Ti, Nb, Mn, Fe and Al and a part of the superconductor in contact with the oxide of the element from which superconducting properties are deprived. CONSTITUTION:A first oxide superconducting thin film 1 formed on an MgO single crystalline substrate 4, a nonsuperconductor layer 3 formed on a part except the right end on the film 1, a second oxide superconducting thin film 2 formed on the layer 3, and terminals 5, 6 connected to the first and second thin films are provided. Metals Ti, Nb, Mn, Fe or Al deposited on the first superconductor in a oxygen atmosphere to form a nonsuperconducting layer. Accordingly, the metal element reduces the part of the boundary of the superconductor to be deposited for the purpose of obtaining nonsuperconductor. The element layer may be extremely thin, and may not be completely continuously formed.

Description

[Detailed description of the invention] Industrial applications The present invention relates to superconducting junctions and manufacturing methods.

More specifically, the present invention relates to a novel horizontally drawn superconducting junction using an oxide superconductor and a manufacturing method.

Although there are various configurations for realizing a superconducting junction called a Josephson junction, the most preferred structure is a tunnel-type junction in which a thin non-superconductor is sandwiched between a pair of superconductors. Generally, such a superconducting junction is realized in the form of an element, and the above pair of superconductor and non-superconductor is a so-called thin film.

For example, when realizing a tunnel-type superconducting junction using an oxide superconductor as a superconductor, a first oxide superconducting thin film, a non-superconducting thin film, and a second oxide superconducting thin film are laminated in order on a substrate. do.

The thickness of the non-superconductor in a tunnel-type superconducting junction is determined by the coherence length of the superconductor.

Oxide superconductors have very short coherence lengths, so
In a tunnel-type superconducting junction using an oxide superconductor, the thickness of the non-superconductor must be on the order of several nanometers.

Problems to be Solved by the Invention Since it is difficult to uniformly form a thin film of a non-superconductor as described above, there are few examples of producing a tunnel-type superconducting junction using an oxide superconductor.

Furthermore, in conventional tunnel-type superconducting junctions, the interface between the oxide superconductor and the non-superconductor film was not in good condition, and desired characteristics could not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and provide a superconducting junction using an oxide superconductor that operates at high temperatures and has excellent performance.

Means for Solving the Problems According to the present invention, in a superconducting junction comprising a non-superconducting layer sandwiched between first and second oxide superconductors, the non-superconducting layer comprises Ti, Nb, A superconducting junction characterized in that it is formed of an oxide of any element selected from Mn5Fe and Al and a portion of the oxide superconductor that is in contact with the oxide of the element and has lost superconductivity. provided.

Further, in the present invention, as a method for forming the superconducting junction, metal Ti, metal Nb, metal Mn, metal Fe, or metal Al is deposited on the first oxide superconductor in an oxygen atmosphere, and the non-superconductor A method for producing a superconducting junction is provided, the method comprising forming a layer.

Function The superconducting junction of the present invention has a so-called tunnel type structure using an oxide superconductor, and the non-superconducting layer is made of highly oxidizable elements selected from among Ti, Nb, Mn, Fe, and Al. Its main feature is that it is formed of an oxide of any element that has been added to the oxide layer, and a portion of an oxide superconductor that is in contact with the oxide of this element and has lost its superconductivity.

Further, in the method of the present invention, metal Ti, metal Nb, metal M
n, the first metal Fe or metal Al in an oxygen atmosphere
oxide superconductor to form a non-superconductor layer. In the method of the present invention, each of the above metal elements is deposited on the first oxide superconductor at a time of 1. It should be completely unoxidized. The above metal elements have strong oxidizability, so when they come into contact with an oxide superconductor, they take in oxygen from the oxide superconductor until a stable oxidation state is reached (oxygen getter effect). Therefore, the interface portion of the oxide superconductor is reduced, loses superconductivity, and becomes a non-superconductor layer.

In the superconducting junction of the present invention, the non-superconductor layer is mainly composed of the portion of the oxide superconductor that has lost its superconductivity. That is, the above metal element is deposited for the purpose of reducing the interface portion of the oxide superconductor and making it a non-superconductor.

Therefore, the layer of the metal element may be extremely thin and may not be completely continuous.

In the method of the present invention, the thickness of the portion of the oxide superconductor that has lost its superconductivity is controlled by adjusting the oxidation state of the metal element during deposition. According to this method, the thickness of the non-superconductor layer can be accurately controlled. As a specific method for adjusting the oxidation state of the metal element during deposition, for example, when depositing the metal element by high frequency sputtering, the high frequency output is adjusted.

In the superconducting junction of the present invention, as described above, the non-superconductor layer is mainly formed from a part of the oxide superconductor, so the characteristics of the first and second oxide superconductors, the oxide superconductor and the non-superconductor layer are The result is a high-performance product with excellent interface conditions with the body layer.

Any oxide superconductor can be used for the superconducting junction of the present invention, but Y+BazCu+ 07-x-based oxide superconductors, especially Y+BazCu+ 07-x-based oxide superconductors, have a high critical temperature and high critical current density.
Bi, 5r2Ca, Cu, OX-based oxide superconductors or T12Ba2Ca2Cu30x-based oxide superconductors are preferred.

When using the above oxide superconductor and non-superconductor,
The thickness of the non-superconductor layer is preferably about 1 to 40 nm, and 2
~5 nm is more preferred. Such a superconducting junction of the present invention can be produced using a sputtering method, a physical vapor deposition method such as an MBE method, or a chemical vapor deposition method such as an MO-CVD method.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the following disclosure is merely an example of the present invention, and does not limit the technical scope of the present invention in any way.

EXAMPLE A cross-sectional view of an example of a superconducting junction according to the present invention is shown in FIG. FIG. 1 shows an element using superconducting bonding, and shows a first oxide superconducting thin film l formed on an Mg○ single crystal substrate 4 and a portion of the first oxide superconducting thin film 1 excluding the right end. a non-superconductor layer 3 formed on the non-superconductor layer 3, a second oxide superconductor thin film 2 formed on the non-superconductor layer 3, and terminals 5 and 6 connected to the first and second oxide superconductor thin films, respectively. and.

The above-mentioned superconducting junction device was fabricated by the MBE method using the superconductors and metal elements shown in Tables 1 to 3 below. In each superconducting junction element, the thickness of the oxide superconducting thin films 1 and 2 was 400 nm. The non-superconducting layer 3 is composed of a portion 11 of the first superconducting thin film l that has lost superconductivity, a metal oxide layer 31, and a portion 21 of the second superconducting thin film 2 that has lost its superconductivity, and its thickness is was set to 3 nm.

Table 1 Table 2 Table 3 Furthermore, the element profiles of each of the fabricated superconducting junction devices were measured using a micro Auger electron spectrometer (AE).
Measured at S>. As a result, T1, Nb, Mn, F
In both cases of e5Al, oxygen was deficient in the oxide superconducting thin film over 5 nm before and after the metal film, indicating that the metal film was oxidized.

As described in detail, in the superconducting junction of the present invention, the non-superconductor layer is mainly composed of a portion of an oxide superconductor that has lost its superconductivity. Therefore, even when an oxide superconductor is used, a non-superconductor layer having an appropriate thickness can be formed satisfactorily.

The present invention provides a high-performance superconducting junction element and further promotes the application of superconducting technology to electronic devices.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a superconducting junction element using an example of the superconducting junction of the present invention. [Main reference numbers] 1.2... Oxide superconductor, 3... Non-superconductor layer, 4... Substrate, 5.6... Terminal

Claims (2)

[Claims] (1) In a superconducting junction comprising a non-superconducting layer sandwiched between first and second oxide superconductors, the non-superconducting layer is selected from Ti, Nb, Mn, Fe, and Al. A superconducting junction characterized in that it is formed of an oxide of any of the elements and a portion of the oxide superconductor that is in contact with the oxide of the element and has lost superconductivity. (2) In the method for producing a superconducting junction according to claim 1, metal Ti, metal Nb, metal Mn, metal Fe, or metal Al is deposited on the first oxide superconductor in an oxygen atmosphere, and the A method for producing a superconducting junction characterized by forming a non-superconducting layer.