JPH0337103A - Production of oxide superconducting thin film and apparatus therefor - Google Patents

Abstract

PURPOSE:To enhance pin fixing effect and retain high critical current density even in state applying a magnetic field by introducing non-superconducting particles from a cluster ion beam device in a process forming an oxide superconducting thin film. CONSTITUTION:A thin film having a prescribed thickness is formed on a substrate 2 by controlling deposition rate of Y, Ba, Cu, etc., which are raw materials from Knudsen cells so as to have prescribed composition. Shutters of Knudsen cells 4 are shut and a cluster of noble metal such as gold is irradiated using a cluster ion beam device 5 to introduce non-superconducting particles into a thin film. The procedure is repeated to afford prescribed film thickness. Thereby the 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 zero magnetic field.
It has become possible to obtain thin films having critical current densities greater than /cab''.

[Problems 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 The problem is that a large current cannot flow under a magnetic field, especially when a magnetic field is applied perpendicular to the Cu-0 plane.The reason for this is based on experimental results using a single crystal of an oxide superconductor. This is thought to be due to the inability to sufficiently suppress the movement of magnetic flux due to the application of current under a magnetic field.

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. A method for producing an oxide superconductor thin film in which non-superconductor particles are dispersed, the method comprising: introducing non-superconductor particles into the oxide superconductor thin film using a cluster ion beam device during the process of forming the oxide superconductor thin film on a substrate. This is what we provide.

In the present invention, when introducing a non-superconductor substance into an oxide superconductor thin film using a cluster ion beam device, it is necessary to deposit the non-superconductor substance in the form of particles. In order to obtain a high bottling effect, the diameter of the particles is 100
The number of non-superconductor particles is preferably 10 to 50% by volume. If the content is less than 10% by volume, it is not preferable because the bottle-stopping effect may become 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, it is preferable to employ the following method in order to uniformly disperse the non-superconductor particles in the oxide superconductor thin film. For example, a method in which the formation of an oxide superconductor thin film and the introduction of non-superconductor particles are performed simultaneously, and the non-superconductor particles are dispersed in the thin film as the thin film grows, is preferred because a homogeneous thin film is likely to be obtained. Alternatively, the oxide superconductor thin film is formed in multiple steps,
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 this thin film that is still growing, and a superconductor thin film is further formed on top of the non-superconductor, or By 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 it is preferable that it does not react with the superconductor. For example, noble metals such as silver and gold are preferably used.

The manufacturing method of the present invention can be carried out using an apparatus in which an evaporator for constituent elements of a superconductor and a cluster ion beam apparatus for a non-superconductor are installed in the same vacuum vessel. The device for evaporating constituent elements of the superconductor is not particularly limited, and various devices can be used, such as a Knudsen cell. The cluster ion beam device for non-superconductors is not particularly limited, and any known device can be used as appropriate.If the oxide superconductor thin film is formed in multiple steps, the constituent elements of the superconductor may be Preferably, each of the evaporator and the non-superconductor cluster ion beam device is provided with a shutter. As for the vacuum container, one in which the internal atmosphere can be controlled is preferable.

[Example] Three Knudsen cells 4 and one cluster ion beam device 5 are installed in a vacuum container, and the three Knudsen cells 4 are filled with Y, Ba, and Cu metals as raw materials, and gold is added to the cluster. It was used as a raw material for the ion beam device 5. The cluster ion beam device is provided with an accelerating electrode 6 and a thermionic beam generator 7, and gold clusters are ionized by thermionic electrons from the thermionic beam generator 7, which are then accelerated by the accelerating electrode 6. Attach it to the substrate. A MgO single crystal whose (Zoo) plane was mirror-polished was used as the substrate 2, and the substrate temperature was maintained at 700'C by the heater 1 to form a film.

During film formation, the oxygen pressure near the substrate is io-”
Oxygen was introduced through the nozzle 3 so that the temperature was about rr.

First, with the shutter of the cluster ion beam device 5 closed, Y:Ba:Cu=
The deposition rate was adjusted so that the composition was 1:2:3.
A thin film with a thickness of 0.000 was formed. Thereafter, the shutter of the Knudsen cell 4 was closed, and the cluster ion beam device 5 was used to irradiate the gold cluster for 30 seconds. The above procedure was repeated until the total film thickness 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 by TEM, it was found that about 30% by volume of particles with a diameter of about 300 particles were present in the film.

The obtained thin film was dry etched to a size of 0.3 mm in width and 50 μm in length, and the sample was immersed in liquid nitrogen and subjected to direct current
When the critical current and density were measured by the terminal method, a magnetic field of 2XlO'A/Clllt was applied parallel to the c-axis without applying a magnetic field]5. I
It was O' Arcs2.

[Comparative Example] A thin film was obtained by depositing only an oxide superconductor in the same manner as in the example except that the cluster ion beam device was not used using the same apparatus as in the example. As in Example A, 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 5×10′ A/cl11” without applying a magnetic field, and 1×lo′ A/c− with a magnetic field of 1 Tesla applied.

[Effects of the Invention] According to the method of the present invention, a superconductor thin film having a high bottle-stopping effect and a high critical current density even when a magnetic field is applied can be 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: Substrate 3: Nozzle 4: Knudsen cell 5: Cluster ion beam device 6: Accelerating electrode 7: Thermionic beam generator -5th! Kinuta

Claims (5)

[Claims] (1) In the process of forming an oxide superconductor thin film on a substrate,
A method for producing an oxide superconductor thin film in which non-superconductor particles are dispersed, the method comprising introducing non-superconductor particles into the oxide superconductor thin film using a cluster ion beam device. (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 manufacturing method according to any one of claims 1 to 3, wherein the non-superconducting particles are a noble metal. (5) An apparatus for producing an oxide superconductor thin film, comprising an evaporator for constituent elements of the oxide superconductor and a cluster ion beam apparatus for a non-superconductor in the same vacuum vessel.