JPH01206675A - Superconductor - Google Patents

Abstract

PURPOSE:To enable the formation of a highly accurate superconductor at a low temperature by a method wherein a buffering film is formed on a substrate, and a quadruple compound film composed of Bi-Sr-Ca-Cu-O as a main component is made to adhere thereon to form the superconductor of a layered structure. CONSTITUTION:A quadruple compound film 12 of Bi-Sr-Ca-Cu-O is formed on a base body 11 through a method such as a sputtering method, and a buffer layer 15 is formed at a interface between the base body 11 and the compound film 12. If the quadruple compound film 12 is formed directly on the base body 11, a component element of the base body 11 of semiconductor is diffused into the quadruple compound film 12 to make the film 12 deteriorate in a superconductive property, therefore the buffer film 15 is provided to prevent the deterioration of the film 12. The quadruple compound film 12 is formed into a thin film by depositing a superconductive material on the base body after it is dissolved into supermicro particles such as to be in an atomic state, so that a formed superconductor is substantially uniform in composition and can be formed at a low temperature if it contains bismuth, and furthermore a very accurate superconductor can be obtained through the buffer layer 15. By these processes, an excellent superconductor can be formed into a thin film, so that the superconductor excellent in accuracy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to superconductors. In particular, it relates to compound thin film superconductors.

Conventional technology As high temperature superconductors, niobium nitride (NbN) and germanium niobium (Nb3.G) are used as A1'5 type binary compounds.
e), etc., but the superconducting transition temperature of these materials was at most 24°.

On the other hand, perovskite-based ternary compounds are expected to have an even higher transition temperature, with the Ba-La-Cu-0 system having a transition temperature of 9
0 class high temperature superconductors were proposed [J, (+,
Bendorz and K.A. Muller;
Zets Schrift Fair Physique
hrift f urphysikB)-Cc+nde
nsed Matter 64.189-193 (1
986) ].

Furthermore, B i -Sr-Ca-Cu-0 type material is 1
It has also been discovered that it exhibits a transition temperature above 0.00.

Although the details of the superconducting mechanism of this type of material are not clear,
The transition temperature can be higher than room temperature, and it is expected to have more promising properties as a high-temperature superconductor than conventional binary compounds.

Problems to be Solved by the Invention However, with the current technology, Bj-Sr-Cu-0 based materials can only be formed through the process of sintering, and therefore can only be obtained in the form of ceramic powder or blocks. On the other hand, when putting this type of material into practical use, there is a strong demand for thinning or linearization, but both are extremely difficult to achieve with conventional techniques.

The present inventors discovered that a thin film-like high-temperature superconductor can be formed by using a thin film technique such as sputtering for this kind of material, and based on this, invented a new superconductor structure. .

Means for Solving the Problems The superconductor of the present invention has a layered structure in which a buffer film is formed on a substrate, and a quaternary compound film whose main component is B1-Sr-Ca-Cu-O is adhered thereon. It is a feature.

Function The superconductor according to the present invention has a major feature in that the superconductor is formed as a thin film of the above compound. Thin film formation involves decomposing the superconductor material into ultrafine particles in the atomic state before depositing them on the substrate, so the composition of the formed superconductor is essentially homogeneous compared to conventional sintered bodies. With,
Including hismuth enables low-temperature formation, and furthermore, the present invention realizes a superconductor with very high precision using a buffer film.

Example The present invention will be explained with reference to the drawings.

In FIG. 1, 4 of B i -Sr-Ca-Cu-0
The original compound film 12 is formed on the substrate 11 by, for example, a sputtering method. In this case, the substrate 11 is 3
The purpose is to retain the original compound film 12. Furthermore, a major feature of the present invention is that a buffer layer 15 is provided at the interface between the substrate 11 and the compound coating 12. The superconductor of the invention therefore essentially consists of a layered structure.

When a semiconductor such as silicon, germanium, potassium arsenide, potassium nitride, potassium phosphide, indium phosphide, indium arsenide, zinc sulfide, zinc selenide, or cadmium sulfide is used as the substrate 11 in FIG. 1, superconducting and semiconductor functions can be integrated. A new functional element is formed. The present inventors discovered that when the quaternary compound film 12 is formed directly on the substrate 1O, these semiconductor constituent elements often diffuse into the quaternary compound film 12, degrading the superconducting properties of the quaternary compound film. did. Therefore, the present invention has discovered that a buffer film is formed in order to prevent deterioration of these characteristics.

Furthermore, it has been found that there is an optimal buffer film for forming a highly crystalline quaternary compound film 12 on the surface 13 of the substrate 11.

That is, the main components of the buffer film 15 are platinum, gold, silver,
The present inventors have confirmed that good superconducting properties can be obtained by using a film made of a metal such as rhodium or an alloy thereof.

Furthermore, the present inventors have used magnesium oxide, spinel, strontium titanate, zirconium oxide, or Ca such as BaF2, CaF2, SrF2, etc. as a buffer film.
F2 type material or ZnS, ZnO, Zn5e, Cd
ZnO type materials such as BaTio3. CaTi
It has been confirmed that good superconducting properties can be obtained even when using a crystalline thin film of a material having a berovskite structure such as Os, CaTiO2, PdZr○s, PbHfO3, etc.

Furthermore, when the buffer film is composed of porcelain such as alumina, magnesium oxide, zirconium oxide, steatite, forsterite, beryllia, or spinel, or quartz, high silicate glass, borosilicate glass, soda glass, aluminum oxide glass, The present inventors have confirmed that good superconducting properties can be obtained even when the film is formed on zirconia glass, silicon nitride glass, or silicon oxynitride glass.

Here, as the substrate 11 forming these buffer films, silicon, germanium, gallium arsenide, gallium nitride,
Good results were obtained using single crystals of gallium phosphide, indium phosphide, indium arsenide, zinc sulfide, zinc selenide, or cadmium sulfide, but when a crystalline thin film is formed on these single crystal substrates 11, crystallinity Good buffer layer 15
The inventors confirmed that this can be obtained.

Further, the present inventors formed a buffer layer 15 in which at least layers A and B were sequentially laminated as shown in FIG. 2, and covered the substrate surface 13 with this multilayer buffer layer. It has been confirmed that an even better superconducting material can be obtained by using a substrate 11 of , gallium arsenide, gallium nitride, gallium phosphide, indium phosphide, indium arsenide, zinc sulfide, zinc selenide, cadmium sulfide, or the like. Here, the A layer and B layer are glass layers such as quartz, silicon oxide, high silicate glass, and borosilicate glass, CaFz type crystal layers such as calcium fluoride, barium fluoride, and strontium fluoride, platinum, gold, It is obtained by a combination of two of a metal layer such as silver, and a dielectric layer such as zirconium oxide, aluminum oxide, magnesium oxide, etc.

In order to provide a deeper understanding of the content of the present invention, more specific examples will be presented below.

(Specific Example 1) Using a gallium arsenide single crystal plane as the substrate 11, a buffer layer 15 made of a platinum thin film with a thickness of 0.1 μm was provided by high-frequency planar magnetron sputtering, and a Bi-(S)
r/Ca)2-Cu2-0 coating 12 was deposited to form layered structure 10. In this case, the pressure of Ar gas is 0.5P
a, sputtering power IL'50 W, sputtering time 10 hours, film thickness 6 μm, substrate temperature 500'
There was C. The formed layered structure is further heated in air for 80 minutes.
Heat treatment was performed at 0°C for 1 hour.

The room temperature resistivity of the film is 100 μΩcm, and the superconducting transition temperature is 8.
It was 0.

(Specific Example 2) Using a gallium arsenide single crystal plane as the substrate 11, a 1 μm thick quartz thin film and a 0.1 μm thick platinum thin film were sequentially formed by high frequency planar magnetron sputtering to form the buffer layer 1.
5 A layer and B layer are provided, and Bi (Sr/Ca)
2 A Cu20 coating 12 was deposited to form a layered structure 10. In this case, the Ar gas pressure is Q, 5 Pa, sputtering power 150 W, sputtering time 10 hours,
The film thickness of the film was 6 μm, and the substrate temperature was 500°C. The formed layered structure was further heat-treated in air at 800° C. for 1 hour.

The room temperature resistivity of the film is 100 μΩam, superconducting transition a)
The details of changes in superconducting properties due to changes in the composition ratio of the constituent elements of 2 Cu20 are not clear.

However, even if the ratios of B i, S r/Ca, and 02 are changed, C
As long as a is included, the essential characteristics of the layered structure of the invention will not change, even if the superconducting transition temperature changes.

In particular, the superconductor according to the present invention has a great feature in that a high-quality superconductor can be formed into a thin film at low temperatures. In other words, conventional high-temperature superconducting materials require a temperature of 600°C to
A substrate temperature of 900°C was required. However, Bi-containing materials can inherently be cooled compared to conventional sintered bodies.

Furthermore, as already explained (using the features of low-temperature synthesis of the present invention, it is possible to integrate devices such as Si or GaAs), and it can also be used as an elemental material for various superconducting devices such as Josephson elements. In particular, the transition temperature of this type of compound superconductor may be room temperature, so the range of conventional practical use is wide (and the industrial value of the present invention is high).

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing the structure of a superconductor substrate according to an embodiment of the present invention. 11...Substrate, 12...Ternary compound coating. 15...Buffer layer. Name of agent: Patent attorney Toshio Nakao and one other person Written amendment 1 Indication of the case 1988 Patent Application No. 32240 2 Name of the invention Superconductor 3 Person making the amendment Relationship with the case Patent application
Address 1006 Oaza Kadoma, Kadoma City, Osaka Name (582) Matsushita Electric Industrial Co., Ltd. Representative Tani
Akio I 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 5 Subject of Amendment 2, Claims (1) Said buffering of a substrate having at least one surface covered with a buffering film On the film, the main component is B1-Sr-Ca-Cu-0
A superconductor characterized by having a film attached to it. (2) Any of silicon, germanium, gallium arsenide, gallium nitride, gallium phosphide, indium phosphide, indium arsenide, zinc sulfide, and cadmium sulfide, the surface of which is coated with a multilayer film in which at least first and second buffer films are sequentially laminated. 2. The superconductor according to claim 1, characterized in that the superconductor uses a substrate made of .

Claims (2)

[Claims] (1) On the buffer film of the substrate whose at least one surface is covered with a buffer film, the main portion is Ba-Sr-Ca-Cu-O.
A superconductor characterized by having a film attached to it. (2) Any of silicon, germanium, gallium arsenide, gallium nitride, gallium phosphide, indium phosphide, indium arsenide, zinc sulfide, and cadmium sulfide, the surface of which is coated with a multilayer film in which at least first and second buffer films are sequentially laminated. 2. The superconductor according to claim 1, characterized in that the superconductor uses a substrate made of .