JPH0337104A - Production of oxide superconducting thin film and apparatus therefor - Google Patents

Abstract

PURPOSE:To enhance a pin fixing effect and retain high critical current density even in a state applying a magnetic field by introducing non-superconducting particles from a target arranged directly under a plasma in a process forming an oxide superconducting thin film. CONSTITUTION:Oxygen-argon mixed plasma 3 generated from arc discharge type plasma source 7 and anode 8 is introduced into a vessel. The plasma is formed into a cylindrical shape in a magnetic field generated from a pair of air-core coils 9. Raw materials of Y, Ba, Cu, etc., are heated in Knudsen cell 4 and formed into a film on a substrate while controlling to a prescribed deposition rate. Electricity is applied to an electromagnet of target 5 so as to carry out deposition of non-superconducting particles of Y2O3 and these particles are introduced into the thin film. The above-mentioned procedure is repeated. Thereby a superconducting thin film in which non-superconducting particles are dispersed is readily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method and apparatus for producing an oxide superconductor thin film.

[Prior Art] Conventionally, thin films of oxide superconductors containing copper and having a critical temperature higher than the liquid nitrogen temperature have been produced using various physical vapor deposition methods (sputtering, sputtering, etc.).
It has been manufactured using methods such as evaporation method, laser beam evaporation method, etc.), CVD method, etc. Regardless of the method, if the manufacturing conditions are selected appropriately, it can produce up to 1 million A at liquid nitrogen temperature and in an O magnetic field.
It is becoming possible to obtain thin films having critical current densities of 7 cm" or more.

[Problem to be solved by the invention] However, for applications such as superconducting magnets, materials that can flow a current of 100,000 A/Cm or more under a strong magnetic field of several Tesla or more are required, and the thin films obtained so far is under a magnetic field,
Particularly, when a magnetic field is applied perpendicularly to the Cu-0 plane, a problem arises in that a large current cannot flow. The cause of this is
Based on experimental results using single crystal oxide superconductors, it is thought that this is because the movement of magnetic flux due to the application of current under a magnetic field cannot be sufficiently suppressed.

In order to suppress the movement of magnetic flux under a magnetic field, it is necessary to introduce a suitable binning center into the superconductor. It is thought that fine particles of non-superconductors or small racks parallel to the current direction in thin films act as the binding center, but a method for forming a thin film with such a binding center has not yet been established. Not yet.

[Means for Solving the Problems] The present invention aims to obtain an oxide superconductor thin film in which fine particles of a non-superconductor having a bottling effect are dispersed. In the process of forming an oxide superconductor thin film on a substrate using oxygen-containing plasma, non-superconductor particles are transferred to the oxide superconductor from a non-superconductor target placed directly below the plasma to which a voltage or magnetic field can be applied. The present invention provides a method for producing an oxide superconductor thin film in which non-superconductor particles are dispersed, characterized in that the non-superconductor particles are introduced into the oxide superconductor thin film.

In the present invention, the non-superconductor material must be dispersed in the superconductor thin film in the form of fine particles. In order to obtain a high bottle-stopping effect, the particle size is preferably 100 to 500 Å. To do this, a DC voltage or a magnetic field is applied to the non-superconducting target, and plasma formed by the magnetic field is irradiated onto the target, under conditions such that particles of the above-mentioned size are ejected from the non-superconducting target. Sputtering is performed to disperse non-superconductor fine particles within the superconductor thin film. Moreover, the content of non-superconductor particles is preferably 10 to 50% by volume.

If the content is 10% by volume without grooves, it is not preferable because the bottle fixing effect may be insufficient. If the content exceeds 50% by volume, it is not preferable because the volume of the superconductor may decrease and the critical current density of the thin film may decrease.

In the present invention, in order to uniformly disperse the non-superconductor particles in the oxide superconductor thin film, it is preferable to adopt the following method. For example, the formation of the oxide superconductor thin film and the non-superconductor particles A method of simultaneously introducing oxide superconductor particles and dispersing non-superconductor particles into the thin film as the thin film grows is preferred because it is easier to obtain a homogeneous thin film, or a method in which the oxide superconductor thin film is formed in multiple steps is preferable. ,
A method of introducing non-superconductor particles during the formation of an oxide superconductor thin film can also be adopted. In this method, the growth of an oxide superconductor thin film is stopped midway, a non-superconductor is deposited in the form of particles on the thin film that is still growing, and then a superconductor thin film is formed on top of the thin film, or By further repeating this operation, a superconductor thin film in which non-superconductor particles are dispersed is obtained. At this time, it is necessary to select the deposition conditions so that the non-superconductor does not form a continuous film.

The non-superconducting substance is not particularly limited and various substances can be used, but compounds that do not react with superconductors, or
Compounds of elements constituting the superconductor that do not exhibit superconductivity at liquid nitrogen temperature are preferred. For example, silver, noble metals such as gold, yttrium oxide, oxides of lanthanum-based elements, oxides of alkaline earth metals, boron oxide, etc. are preferable.

The manufacturing method of the present invention includes an evaporator for constituent elements of an oxide superconductor, an oxygen-containing plasma formed by a magnetic field between a substrate and the evaporation source, and a voltage or magnetic field placed directly below the plasma. This can be carried out using an apparatus in which a target of a non-superconductor to which the voltage can be applied is installed in the same vacuum container. The evaporation device for the constituent elements of the superconductor is not particularly limited, and various devices can be used; for example, a Knudsen cell can be used61! The non-superconducting target to which a voltage or magnetic field can be applied is preferably one that can apply a larger voltage or magnetic field than a normal sputtering device so as to generate particles of a size that is effective for binding. When forming the oxide superconductor thin film in multiple steps, it is preferable that the evaporator for the constituent elements of the superconductor be provided with a shutter. As for the vacuum container, one in which the internal atmosphere can be controlled is preferable.

In the present invention, the plasma needs to contain oxygen, and a higher ion density is preferable because it increases the reactivity of the constituent elements of the oxide superconductor with oxygen and increases the oxygen content in the superconducting thin film. Although various types of plasma sources can be used, an arc discharge type plasma source having a composite 1aBs cathode provided with an auxiliary cathode is preferred for the reasons mentioned above.

[Example] A composite type LaB in which three Knudsen cells 4 and an electromagnet 6 provided directly below the yttrium oxide magnet 5 are arranged as shown in Figure 1 in a vacuum container 10, and an auxiliary cathode is installed.
Oxygen/argon mixed plasma 3 generated by an arc discharge type plasma source 7 having 5 cathodes and an anode 8 is introduced into the container, and the substrate is heated by a magnetic field generated by a pair of air-core coils 9 installed outside the vacuum container. , a cylindrical plasma was formed between the deposition sources. Y, Ba, and Cu metals are used as raw materials and heated in three Knudsen cells to produce Y:Ba,:
The deposition rate was adjusted so that the composition of Cu was 1:2:3. Substrate 2 is made of Mg whose (100) plane is mirror-polished.
Using an O single crystal, the substrate temperature was set to 700°C using a heater -1.
The film was formed while being kept at ℃. The oxygen partial pressure near the substrate is 5 x 1
0 ”'Torr, argon partial pressure is 3 X l O-'
It was Torr.

When the thickness of the superconductor reaches 1000 people,
The shutter of the Knudsen cell was closed, and the electromagnet of the yttrium oxide target was energized for 1 minute to deposit yttrium oxide particles. The above procedure was repeated until the overall film thickness of 5 was 1 μm. Using an X-ray diffraction apparatus, it was confirmed that the C-axis of the obtained thin film was perpendicular to the substrate surface. When this thin film was observed using a TEM, it was found that there was a diameter of approximately 3 mm inside the film.
Approximately 30% by volume of 0.00 particles were present.

The obtained thin film was dry etched to a size of 0.3 mm in width and 50 μm in length, and the critical current density was measured by the DC 4-terminal method with the sample immersed in liquid nitrogen. ×10 'A/c+a'', 1 x 10 with a 1 Tesla magnetic field applied parallel to the C axis
'A/cm''.

[Comparative Example] Using the same apparatus as in the example, only the oxide superconductor was vaporized to obtain a thin film. As in the Examples, the C-axis of the obtained thin film was perpendicular to the substrate surface. When the critical current density was measured in the same manner as in the example, it was found that 5X I
O'A/cm'', and lXl0'A/c- with a 1 Tesla magnetic field applied.

[Effects of the Invention] According to the method of the present invention, a superconductor having a high bottle-stopping effect and a high critical current density even when a magnetic field is applied.
A thin film is obtained.

According to the apparatus of the present invention, a superconductor thin film in which non-superconductor particles are dispersed can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a thin film manufacturing apparatus used in an example of the present invention. 1: Heater 2 2 substrates 3: Ar・0□ mixed plasma 4: Knudsen cell 5: Target 6: Electromagnet 7: Plasma generator 8 near node 9: Air core coil 10: Vacuum vessel substitute Shigebe Tsugamura and 1 other person - 21

Claims (6)

[Claims] (1) In the process of forming an oxide superconductor thin film on a substrate using oxygen-containing plasma formed by a magnetic field, a non-superconducting target is A method for producing an oxide superconductor thin film in which non-superconductor particles are dispersed, the method comprising introducing superconductor particles into the oxide superconductor thin film. (2) The manufacturing method according to claim 1, wherein the non-superconductor particles are introduced simultaneously with the formation of the oxide superconductor thin film. (3) The manufacturing method according to claim 1, wherein the oxide superconductor thin film is formed in multiple steps, and the non-superconductor particles are introduced during the oxide superconductor thin film formation. (4) The non-superconductor particles are noble metals, yttrium oxide,
4. The method according to claim 1, wherein the oxide is one or more selected from the group consisting of lanthanum-based element oxides, alkaline earth metal oxides, and boron oxides. (5) An evaporator for constituent elements of an oxide superconductor, an oxygen-containing plasma formed by a magnetic field between the substrate and the evaporation source, and a non-superconductor placed directly below the plasma to which a voltage or magnetic field can be applied. 1. An apparatus for producing an oxide superconductor thin film, characterized in that it has a target in the same vacuum container. (6) The manufacturing apparatus according to claim 5, wherein the plasma is an oxygen-containing plasma generated by an arc discharge type plasma source using a composite type LaB_■ cathode provided with an auxiliary cathode.