JPS63307614A - High-temperature oxide superconductor thin film - Google Patents

Abstract

PURPOSE:To aim at improvement of the critical current by arranging the crystal orientation of both the (a) axis and the (b) axis of crystal grains constituting a film so that they are parallel to a substrate. CONSTITUTION:In an Re1Me2Cu3O7-x thin film of the perovskite structure (Re; Y, Sc, rare earth element, Me; alkaline earth metal element), the (c) axis of the rhombic system structure is arranged to be perpendicular to a substrate, and both the (a) axis and the (b) axis thereof are arranged to be parallel to the substrate. When a film formed by a sputtering method or a deposition method is gradually heated in an atmosphere of oxidizing gas with a rate ranging from 10 deg.C/h to 300 deg.C/h, an oxide superconductor becomes highly c-axis oriented to the substrate. By thus forming a film having a high degree of the c-axis orientation, a high-quality film with a large critical current can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies to high-output magnets, Josephson elements, 5Q
The present invention relates to superconducting materials used in UIDs and the like, and particularly to the structure of a thin film of a ceramic-based high-temperature conductor that operates at temperatures above liquid nitrogen temperature and its manufacturing method.

Discovered by Bednorg and Muller in 1986, (La, S r)2Cu with N1F4 type structure
04 superconductors exhibit a high critical temperature of 30°C, then.

In 1987, YIBarcu307-x, which has a perovskite structure, was introduced from the United States and Japan with an even higher critical temperature T,
= 90 K, and is known to become superconducting even at liquid nitrogen temperature (77 K) or higher.

(Refer to the May 11, 1987 issue of Nikkei New Materials) [Problems that inventors are trying to solve] However, the production of thin films is essential for electronic devices, but the crystal structure of these oxide-based superconductors is Because of the complexity, there was a problem in that it was difficult to obtain a film of good quality.

The object of the present invention is to provide oxygen-deficient Y with short-range periodicity.
Regarding the quality of the 1Ba2Cu3O7-g-based high-temperature oxide superconductor, the object of the present invention is to provide a high-quality film with a particularly large critical current.

[Means for solving problems]

YlBarcus07-X-based high-temperature oxide superconductor belongs to the orthorhombic system, and the lattice constants are a = 3.88 and b = 3.83.
person, c=11.69 people. Electron conduction is two-dimensional conduction in a plane formed by the a-axis and b-axis.The purpose of the present invention is to improve efficiency by aligning the crystal orientations of the a-axis and b-axis of the crystal grains that make up the film parallel to the substrate. This is achieved by providing good two-dimensional conduction and greatly improving the critical current. In addition, by raising the temperature of a film formed by sputtering or vapor deposition in an oxidizing atmosphere gas in the range of 10°C/h to 300°C/h and causing a reaction between 800°C and 1000°C, a large critical current can be generated. An oxide superconductor film is obtained.

At this time, by selecting a substrate in which the lattice constant of the substrate surface matches the lattice constants of the a-axis and b-axis of the superconductor thin film in an integral ratio, an oxide superconductor film with high C-axis orientation can be obtained.

[Effect]

Re I M e 2 Cu 307 with Perobus type structure
A superconducting film with a large critical current can be obtained by aligning the plane consisting of the a-axis and b-axis, which contribute to the electrical conduction of -X, parallel to the substrate surface. When a film formed by a sputtering method or a vapor deposition method is gradually heated in an oxidizing atmosphere gas in a range of 10° C./h to 300° C./h, the oxide superconductor becomes strongly c-axis oriented with respect to the substrate. At this time, if a substrate is selected in which the lattice constant of the substrate surface matches the lattice constants of the a-axis and b-axis of the superconductor thin film by an integer, the tendency for C-axis orientation will be further strengthened.

(Example〕 Hereinafter, the effects of the present invention will be explained in detail in Examples.

Example I Preparation of Y1Ba2Cu3O7,4 thin film using Y as a target
The process was carried out using a magnetron sputtering device using a sintered body of 1Ba2Cu30. The gas was a mixed gas of Ar+10%0□, and the introduced gas pressure was 4×10 Pa. The substrate is 5rTr03, which has a lattice constant similar to Y1Ba2Cu30g4.
The fruit was used. The plane orientation of the substrate was (100), and the substrate temperature was room temperature. The prepared film had a thickness of 1.0 μm,
According to X@ diffraction, it is amorphous. Crystallization temperature is 900
℃×2h. Temperature increase rate is 50℃/h, 100℃/h
, 200c/h, 300℃/h
X-ray diffraction was performed on the CuK line, the line diffraction pattern is shown in 2nd@. Here, a) is the standard pattern of powder X-ray diffraction, b) is 50℃/h to 300℃/h, C) is 30℃/h
This is the case when the temperature is 0°C/h or more. 50℃/h to 300℃/
At a heating rate of h, the (OOx) plane is strongly oriented. On the other hand, when the heating rate is 300℃ or higher, YIBa2Cu30-1
The diffraction pattern is similar to the standard diffraction pattern of -X powder. Therefore, at a slow temperature increase rate of 300° C./h or less, the Y1Ba2Cu3O7-x thin film has a property of being strongly c-axis oriented on the substrate.

FIG. 2 shows the influence of the heating rate on the critical current density Jo at the liquid nitrogen temperature. It can be seen that the smaller the heating rate is, the larger the critical current density is. Therefore, from the results shown in FIGS. 1 and 2, it can be seen that the film oriented perpendicularly to the substrate has a higher critical current.

From this, it is desirable that the temperature increase rate be 300° C./h or less, but 10° C./h takes too much time to raise the temperature and is not practical.

Example 2 The same experiment as described in Example 1 was conducted using a YiBa2cu307-x thin film, using Sc and a rare earth element other than Y for Re, and using an alkaline earth metal element other than Ba for Me. As a result, a thin film with strong orientation toward the substrate was obtained, and a high critical current value was also obtained.

Example 3 The effect of Example 1 is that RAM cs2Cu3o, -, instead of sputtering, each metal of Re, Me, and Cu is vapor deposited by resistance heating method and then oxidized in coordination gas. It was also confirmed during the process.

Example 4 The thin films described in Examples 1 to 3 were heat-treated at temperatures other than 900°C and 8°C.
The experiment was also carried out at 00°C and 1000°C, and the same results as in Example 1 were obtained. However, at temperatures lower than 800°C, an orthorhombic superelectric phase is not formed.

At temperatures higher than 1000° C., there was a problem that it would react with the substrate.

Example 5 The effect of Example 1 is that the substrate is replaced with SrTiO3 crystal, a = b = 3.90, which is almost equal to the lattice constant of the superconductor film,
(1
00) surface wafer, a = b = c = about 3 times that of the superconductor film
(100) of Y3AlaOx* with 12 lattice constants
It was also confirmed on surface wafers. Therefore, if a substrate is selected that does not react with the superconductor material and can be aligned with the a- and b-axes of the superconductor material, a film with strong C-axis orientation can be obtained.

〔Effect of the invention〕

By forming a film with strong C-axis orientation according to the present invention, a high value of critical current of 1000 A/am'' or more can be obtained.

[Brief explanation of drawings]

Figure 1 shows the X-ray diffraction pattern of the fabricated film, Figure 2
The figure shows the influence of temperature increase rate on critical current density J0 at liquid nitrogen temperature. 7th 21 11 4
11 II 2nd station quick farming (ζυ

Claims (1)

[Claims] 1. Re_1Me_2Cu_3O_ with high critical temperature
7_-_x thin film (Re; Y, Sc, rare earth element, Me;
High-temperature oxidation of alkaline earth metal elements) characterized by an orientation in which the c-axis of the orthorhombic structure is perpendicular to the substrate, and the a-axis and b-axis are parallel to the substrate. Physical superconductor thin film. 2. In claim 1, the film formed by sputtering or vapor deposition is
A high-temperature oxide superconductor thin film characterized in that it is a c-axis oriented film formed by heating at a rate of 0°C/h and reacting between 800°C and 1000°C. 3. In claim 1, a material whose lattice constant on the substrate surface matches the lattice constants of the a-axis and b-axis of the superconductor thin film in an integer ratio is selected, and the high temperature is used to form a c-axis oriented film. Oxide superconductor thin film.