JP2003096563A - Method for forming polycrystalline thin film and oxide superconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining polycrystalline thin film which aligns c-axis of the crystal grain useful for the formation of oxide superconductor perpendicularly to the film forming surface of substrate, in addition, also aligns a-axis or b-axis of crystal axis of the crystal grain along the surface parallel to the film forming surface and is excellent in crystalline orientation. SOLUTION: This method forms the polycrystalline thin film of multiple oxide having a pyrochlore crystalline structure represented by composition formula of YZrO, GdZrO or EuZrO on the film forming surface of polycrystalline substrate. Therein, the temperature of the polycrystalline substrate is retained to a specified temperature of 90-300 deg.C and the thin film is formed by the ion beam assist method. In this polycrystalline thin film obtained by the method, a grain boundary oblique angle constituted by the same crystalline axis of respective crystal grains along the surface parallel to the film forming surface of the polycrystalline substrate is <=20 deg., Therein, EuZrO is useful, too.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a polycrystalline thin film having a pyrochlore type crystal structure with an aligned crystal orientation, which is useful for forming an oxide superconducting conductor having excellent superconducting properties. .

[0002]

2. Description of the Related Art Oxide superconductors discovered in recent years are excellent superconductors exhibiting a critical temperature exceeding liquid nitrogen temperature. Currently, oxide superconductors of this kind are used as practical superconductors. There are various problems to be solved for use. One of the problems is that the oxide superconductor has a low critical current density. The problem that the critical current density of the oxide superconductor is low is largely due to the existence of electrical anisotropy in the crystal itself of the oxide superconductor. It is known that electricity can easily flow in the a-axis direction and b-axis direction, but it is difficult to flow electricity in the c-axis direction. From such a viewpoint, in order to form an oxide superconductor on a substrate and use it as a superconducting conductor, an oxide superconductor in a good crystal orientation is formed on the substrate, and, Orient the a-axis or b-axis of the crystal of the oxide superconductor in the direction in which electricity is to flow, and the c-axis of the oxide superconductor in the other direction.
The axes need to be oriented.

Therefore, conventionally, on a base material such as a metal tape,
A sputtering apparatus is used to coat an intermediate layer having a good crystal orientation such as MgO or SrTiO ₃ and an oxide superconducting layer is formed on this intermediate layer. However, the oxide superconducting layer formed on the intermediate layer of this kind by a sputtering apparatus is an oxide superconducting layer (for example, a critical current density of several hundred thousand A) formed on a single crystal substrate made of these materials.
/ Cm ²⁾ much lower critical current density than (e.g., 1
000-10,000 A / cm ² ). This is considered to be due to the reason explained below.

FIG. 12 shows a polycrystalline substrate 1 such as a metal tape.
3 is a perspective view showing a structure of an oxide superconducting conductor in which an intermediate layer 5 of MgO, SrTiO ₃ or the like is formed on the intermediate layer 5 by a sputtering apparatus, and an oxide superconducting layer 3 is formed on the intermediate layer 5 by a sputtering apparatus. In the structure shown in FIG. 12, the oxide superconducting layer 3 is in a polycrystalline state, and a large number of crystal grains 4 are randomly bonded. These crystal grains 4
Looking at each of the above individually, although the c-axis of the crystal of each crystal grain 4 is oriented to be perpendicular to the substrate surface to some extent,
The axes and b-axis are thought to be oriented in random directions.

As described above, each crystal grain of the oxide superconducting layer has a
When the directions of the axis and the b-axis become disordered, the quantum coupling property of the superconducting state is lost at the grain boundaries where the crystal orientation is disordered, and as a result, the superconducting property, especially the critical current density, is considered to be lowered. Further, the oxide superconductor is a
The polycrystalline state which is not axially oriented or b-axis oriented is
Since the intermediate layer 5 formed thereunder is in a polycrystalline state without a-axis orientation or b-axis orientation, when the oxide superconducting layer 3 is formed, it should be aligned with the crystal of the intermediate layer 5. This is probably because the oxide superconducting layer 3 grows.

Therefore, the present inventors previously used a special method to improve the orientation of the a-axis and the b-axis on the polycrystalline substrate Y.
It is good if an intermediate layer of SZ (Yttrium Stabilized Zirconia: zirconium oxide stabilized by adding Y ₂ O ₃ ) is formed and an oxide superconducting layer is formed on this intermediate layer. It has been found that it is possible to manufacture an oxide superconducting conductor that exhibits a high critical current density (Japanese Patent Laid-Open Nos. 6-145977 and 9-120719).
Japanese Patent Application Laid-Open No. 10-112238, Japanese Patent Application Laid-Open No. 10-212238
(See JP-A-121239).

The techniques according to these patent applications, when forming a film on a polycrystalline substrate using a YSZ target, are in a direction of 50 to 60 oblique with respect to the normal to the film-forming surface of the polycrystalline substrate. The YSZ crystal with poor crystal orientation is selectively removed by performing the ion beam assist method in which an ion beam such as Ar ⁺ is simultaneously irradiated at an incident angle of 10 degrees, and a YSZ crystal with good crystal orientation is selected. It is a technique for forming an intermediate layer of YSZ which can be deposited in a desired manner and has excellent orientation. According to the technique previously filed by the inventors of the present application, a
It was possible to obtain a YSZ polycrystalline thin film in which the axis or the b axis was well oriented, and it was confirmed that the oxide superconductor layer formed on this polycrystalline thin film exhibited a good critical current density. Therefore, the inventors of the present application set about researching a technique for forming a more preferable polycrystalline thin film layer from another material.

As a result, the inventors of the present invention pursued a substance having a crystal structure with a good orientation on the base material of a metal tape and having a closest atomic spacing closer to that of an oxide superconductor than YSZ. By applying the ion beam assist method provided previously, a method for forming a polycrystalline thin film having good crystal orientation on a substrate was proposed (see Japanese Patent Application No. 2000-159249).

That is, the composition formula of either AZrO or AHfO (where A is
Y, Yb, Tm, Er, Ho, Dy, Eu, Gd, S
One kind selected from m, Nd, Pr, Ce and La is shown. ), Which is composed of crystal grains of a complex oxide having a pyrochlore type crystal structure, and has a grain boundary tilt angle of 30 which is formed by the same crystal axes of the crystal grains along a plane parallel to the film formation surface of the polycrystalline substrate. Is a method for forming a polycrystalline thin film having a degree of less than or equal to a degree on the deposition surface of a polycrystalline base material, and forming the constituent particles generated from the target of the constituent elements of the polycrystalline thin film by the sputtering method on the polycrystalline base material. When depositing on a polycrystalline substrate,
As the ion beam generated by the ion source when heated to a temperature of 00 ° C. or lower, an Ar ⁺ ion beam, a Kr ⁺ ion beam, a Xe ⁺ ion beam, or a mixed ion beam thereof is used. The beam energy is adjusted to be in the range of 150 eV or more and 300 eV or less, and the ion beam is irradiated at an incident angle of 50 ° or more and 60 ° or less with respect to the normal line of the film formation surface of the base material while It is a method of depositing on a material. By forming an oxide superconducting layer on such a polycrystalline thin film having a good crystal orientation, an oxide superconducting conductor having a high critical current density and excellent stability can be obtained.

A pyrochlore-type polycrystalline deposited film formed on a polycrystalline substrate is advantageous in the following points over a conventional YSZ polycrystalline thin film when an oxide-based superconducting layer is provided thereon. Is considered to be. That is, the lattice constant of ZrO _{2 which} is the main component in the YSZ crystal is 5.14Å,
In the face-centered cubic lattice of ZrO _{2, if} the distance between the atoms located at the center of the face and the atoms located at the corners of the face (closest interatomic distance) is 3.63Å, for example, S
The lattice constant of the m ₂ Zr ₂ O ₇ composite oxide crystal is 10.59Å
Considering that the closest interatomic distance is 3.74Å, whereas the closest interatomic distance of the oxide superconductor having a composition of Y ₁ Ba ₂ Cu ₃ O _7-x is 3.81Å. Then, it is considered that the polycrystalline thin film of the Sm ₂ Zr ₂ O ₇ composite oxide is more advantageous than the polycrystalline thin film of YSZ in terms of crystal matching.

That is, when the atoms of the polycrystalline thin film are deposited by performing the ion beam assist method, it is considered that the closer the distance between the closest atoms is, the easier the regular deposition of the atoms is. In addition, since Sm ₂ Zr ₂ O ₇ has a pyrochlore type crystal structure, another crystal lattice of Gd ₂ Zr ₂ similar to the pyrochlore type crystal structure is used.
O ₇ (closest interatomic distance 3.72Å), La ₂ Zr ₂ O
₇ (closest interatomic distance 3.81Å), Ce ₂ Zr ₂ O ₇ (closest interatomic distance 3.78Å), Pr ₂ Zr ₂ O ₇ (closest interatomic distance 3.78Å), Gd ₂ Hf ₂ One of O ₇ (closest interatomic distance 3.72Å), Sm ₂ Hf ₂ O ₇ (closest interatomic distance 3.74Å), La ₂ Hf ₂ O ₇ (closest interatomic distance 3.81Å) Those having a pyrochlore type crystal structure represented by the composition formula are also applicable.

As those having other pyrochlore type crystal structures, Y ₂ Zr ₂ O ₇ and Yb ₂ Zr are available.
₂ O ₇ , Tm ₂ Zr ₂ O ₇ , Er ₂ Zr ₂ O ₇ , Ho ₂ Zr
₂ O ₇ , Dy ₂ Zr ₂ O ₇ , Eu ₂ Zr ₂ O ₇ , Nd ₂ Zr
₂ O ₇ , Y ₂ Hf ₂ O ₇ , Yb ₂ Hf ₂ O ₇ , Tm ₂ Hf ₂ O ₇ ,
Er ₂ Hf ₂ O ₇ , Ho ₂ Hf ₂ O ₇ , Dy ₂ Hf ₂ O ₇ , Eu ₂
Hf ₂ O ₇ , Nd ₂ Hf ₂ O ₇ , Pr ₂ Hf ₂ O ₇ , Ce ₂ Hf ₂
A compound represented by any one of O ₇ and the composition formula may be adopted.
In addition, as another thing having a pyrochlore type crystal structure, the relative ratio of the rare earth element and zirconium (Zr) is not limited to 1: 1, but 0.1: 0.9 to 0.
Any relative ratio can be adopted within the range of 9: 0.1. In this case, the crystal structure does not necessarily have a pyrochlore type crystal structure, and may have a very similar structure called a defective fluorite type or a rare earth C type. It may also have a mixed crystal structure of pyrochlore and rare earth C type. Even in that case, if the cubic crystal is maintained, it has an effect as a base intermediate layer for the oxide superconductor layer.

[0013]

However, according to the technique previously filed by the inventors of the present invention, it is clear that the obtained polycrystalline thin film is oriented with good crystal orientation. However, judging from the pole figure by X-ray diffraction by the θ-2θ method using CuKα ray, the reached value of the full width at half maximum (FWHM) corresponding to the grain boundary tilt angle of the polycrystalline thin film is Sm ₂ Zr ₂ It remains at 17.1 degrees of the polycrystalline thin film of the composite oxide having the composition of O ₇ (see FIG. 13). In order to increase the critical current density of the oxide superconductor layer, further improvement of the orientation of the composite oxide polycrystalline thin film as the intermediate layer, that is, further reduction of the FWHM value is desired. The present invention aims at further improving the orientation of the composite oxide polycrystal thin film, and as a result of further detailed study aiming to significantly reduce the FWHM value of the composite oxide polycrystal thin film, the optimum crystal structure is obtained. It was found that the film forming conditions were different. Therefore, it is an object of the present invention to clarify the film forming conditions of a composite oxide containing various rare earth elements, particularly a Y ₂ Zr ₂ O ₇ composite oxide and a Gd ₂ Zr ₂ O ₇ composite oxide polycrystalline thin film.

By the way, in addition to the field of application of the oxide superconductor layer, techniques for forming various alignment films on a polycrystalline base material are used. For example, in the field of optical thin films,
In the fields of magneto-optical discs, wiring boards, high-frequency waveguides, high-frequency filters, and cavity resonators, any technology requires a polycrystalline thin film with stable film quality and good orientation. Forming is a challenge.
That is, if the crystal orientation of the polycrystalline thin film is good, the quality of the optical thin film, the magnetic thin film, the wiring thin film, etc. formed thereon will be improved, and the crystal orientation on the substrate will be improved. It is more preferable if a good optical thin film, magnetic thin film, wiring thin film and the like can be directly formed.

[0015]

In order to solve the above problems, the relationship between the substrate temperature and the orientation during the deposition of a YZrO-based, GdZrO-based or EuZrO-based composite oxide polycrystalline thin film was examined in detail. . As a result, in the present invention, crystal grains having a composition formula of YZrO type, GdZrO type or EuZrO type pyrochlore type, fluorite type, rare earth C type or a mixed type of pyrochlore and rare earth C type crystal grains. A method of forming a polycrystalline thin film having a grain boundary tilt angle of 30 degrees or less formed by the same crystal axis of the crystal grains along a plane parallel to the deposition surface of the polycrystalline substrate,
When depositing the constituent particles generated from the target of the constituent elements of the composition formula by the sputtering method on the film formation surface of the polycrystalline substrate, depending on the crystal composition of the intended polycrystalline thin film, the polycrystalline base As the ion beam generated by the ion source by heating the material to the optimum temperature range of 90 ° C to 300 ° C,
Using an Ar ⁺ ion beam, a Kr ⁺ ion beam, a Xe ⁺ ion beam, or a mixed ion beam thereof, the ion beam energy of the ion beam is set to 15
The ion beam is adjusted to a range of 0 eV to 300 eV, and the ion beam is 50 degrees or more and 60 degrees with respect to the normal line of the film formation surface of the substrate.
A method of forming a polycrystalline thin film, which is deposited while irradiating at an incident angle of less than 10 degrees, was adopted.

In this case, the composition formula of the polycrystalline thin film is YZ.
In the case of rO and the ratio of ZrO ₂ and Y ₂ O ₃ is 2: 1, the heating temperature of the polycrystalline base material is 150 ° C. to 300 ° C.
C., more preferably 150 to 250.degree. By adopting such a forming method, it becomes possible to reduce the full width at half maximum FWHM value of the composite oxide polycrystalline thin film to 25 degrees or less, to at least about 15 degrees.

The composition formula of the polycrystalline thin film is GdZr.
When it is O and the ratio of ZrO ₂ and Gd ₂ O ₃ is 92: 8, the heating temperature of the polycrystalline base material is 90 ° C. to 250 ° C.
C., and more preferably 100 to 225.degree. Further, when the ratio of ZrO ₂ and Gd ₂ O ₃ is 2: 1, the heating temperature of the polycrystalline base material is 90 ° C to 300 ° C,
More preferably, the temperature is set to 120 ° C to 250 ° C.

Further, the ratio of ZrO ₂ and Gd ₂ O ₃ is 1:
In the case of 1, the heating temperature of the polycrystalline base material is 100 ° C to
It is better to set it to 290 ° C. Furthermore, ZrO ₂ and Gd ₂ O ₃
And the heating temperature of the polycrystalline base material is preferably 120 ° C to 250 ° C. By adopting such a forming method, the F of the composite oxide polycrystalline thin film is
It is possible to reduce the WHM value to 25 degrees or less, to at least about 12.5 degrees.

Further, even a polycrystalline thin film having a pyrochlore type crystal structure represented by the composition formula EuZrO can have a good crystal configuration. That is, the composition formula is EuZr.
Has a pyrochlore type crystal structure represented by O, and Z
A grain boundary tilt angle formed by crystal grains having a ratio of rO ₂ to Eu ₂ O ₃ of 2: 1 and having the same crystal axis of the crystal grains along a plane parallel to the film formation surface of the polycrystalline substrate is A method of forming a polycrystalline thin film having a temperature of 30 degrees or less, wherein constituent particles generated from a target of constituent elements of the composition formula by a sputtering method are deposited on a deposition surface of a polycrystalline substrate, The polycrystalline substrate is 100 ° C to 300 ° C, more preferably 150 to 2
As an ion beam generated by an ion source when heated to a temperature of 50 ° C., an Ar ⁺ ion beam, a Kr ⁺ ion beam, a Xe ⁺ ion beam, or a mixed ion beam thereof is used. A method was adopted in which energy was adjusted to a range of 150 eV or more and 300 eV or less, and the ion beam was deposited while irradiating the ion beam at an incident angle of 50 degrees or more and 60 degrees or less with respect to the normal line of the deposition surface of the substrate. Even if this method is adopted, FW
It is possible to form a polycrystalline thin film having an HM value of 13 to 11 degrees and good crystal orientation. The oxide superconductor formed on the polycrystalline thin film obtained as described above has a high critical current density.

[0020]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the polycrystalline thin film of the present invention is formed on a substrate.
1 is a tape-shaped polycrystalline substrate, 2 is a polycrystalline substrate 1
2 shows a polycrystalline thin film formed on the upper surface of the. As the polycrystalline base material 1, for example, various shapes such as a plate material, a wire material, and a tape material can be used.
A metal material such as a Ni alloy such as silver, platinum, stainless steel, copper, or Hastelloy, or a heat resistant material such as various kinds of glass or various kinds of ceramics can be used.

The polycrystalline thin film 2 of this embodiment is made of YZr.
Crystal grains 20 of an aggregate of fine crystals having a cubic pyrochlore type, a fluorite type, a rare earth C type, or a mixed type of a pyrochlore and a rare earth C type represented by a composition formula of O, GdZrO, or EuZrO 20. However, a large number of them are joined and integrated with each other through crystal grain boundaries, and the c-axis of the crystal axis of each crystal grain 20 is oriented perpendicularly to the upper surface (deposition surface) of the polycrystalline base material 1, A axes of crystal axes of the respective crystal grains 20 or b
The axes are oriented in the same direction and are in-plane oriented. Further, the c-axis of each crystal grain 20 is oriented perpendicular to the (upper surface) film formation surface of the polycrystalline base material 1. Then, the a-axis (or b-axis) of the respective crystal grains 20 are joined and integrated with each other within an angle (grain boundary inclination angle K shown in FIG. 2) formed by them within 30 degrees, for example, within a range of 15 to 25 degrees. There is.

The pyrochlore type composite oxide forming the crystal grains 20 is YZrO, GdZrO or Eu.
It is composed of a composite oxide represented by the composition formula of ZrO. YZ
Examples of the composite oxide having the rO composition include ZrO ₂ : Y
₂ O ₃ has a fluorite type (YSZ) of 92: 8 and a 2: 1 pyrochlore type Y ₂ Zr ₂ O ₇ (closest interatomic distance 3.67Å, lattice constant 5.19). Examples of the complex oxide having the composition of GdZrO include fluorite having 92: 8 of ZrO ₂ : Gd ₂ O ₃ and 2: 1 pyrochlore (Gd ₂ Zr ₂ O ₇ , closest interatomic distance 3.72Å, lattice There is a constant 10.52) pyrochlore + rare earth C type, and a 1: 1 pyrochlore + rare earth C type complex oxide.

Furthermore, as the one having the other pyrochlore type crystal structure, the relative ratio of the rare earth element and Zr is not limited to 1: 1, but 0.1: 0.9 to 0.9: 0.
Any relative ratio can be adopted within the range of 1. In this case, the crystal structure does not necessarily have a pyrochlore type crystal structure, and may have a very similar structure called a defective fluorite type or a rare earth C type. Even in that case, if the cubic crystal is maintained, it has an effect as a base intermediate layer for an oxide superconductor.

The crystal lattice of the pyrochlore type complex oxide is derived from a cubic CaF ₂ structure,
For example, the Gd ₂ Zr ₂ O ₇ crystal has eight unit cells having a face-centered cubic structure as shown in FIG. 3, which are located at the vertices of the unit cells when stacked in the vertical and horizontal directions and the depth direction.
Of the eight oxygen atoms O (existing at the position of the circle drawn by the chain line in FIG. 3) invading the lattice gap formed by the atoms of Zr and the atoms of Zr located at the face center of the unit cell Pyrochlore type is one in which only one is eliminated to generate an octant, I type octant and II type octant are generated according to the position where the oxygen atom is eliminated, and these I type octant and II type octant are regularly arranged. It is a crystal lattice of. Therefore, in the state of X-ray analysis, the unit cell is regarded as a unit cell in the state where eight unit cells are overlapped, so the lattice constant as the unit cell is 10.52, but the width of the lattice as the unit cell is 5.3Å. The closest interatomic distance is 3.72Å.

When the unit cell of the complex oxide is aligned in the direction of the a-axis or the b-axis and deposited by the ion beam assist method described later, the closest atomic distance is important, and this value is Y _1. It is desirable that the lattice constant of the oxide superconductor having a composition of Ba ₂ Cu ₃ O _7-x is close to 3.81. In this closest atomic distance, the difference in the closest atomic distance to the oxide superconductor layer having the composition of Y ₁ Ba ₂ Cu ₃ O _7-x is 4.5% because the closest atomic distance in YSZ is 3.63Å. Becomes In addition, Gd ₂ Zr ₂ O ₇ (closest interatomic distance 3.7
2) and Y ₂ Zr ₂ O ₇ (closest interatomic distance 3.67Å)
Of the closest atomic distance to the oxide superconductor layer of
They are 2.4% and 4.9%, respectively. Therefore, as the intermediate layer for forming the oxide superconductor, YZrO,
The composite oxide represented by the composition formula of GdZrO or EuZrO can also be expected to have the effect of improving the crystal orientation, which is equal to or higher than that of YSZ.

In addition, even if the closest interatomic distance in the composite oxide of each composition is slightly different from the closest interatomic distance of the oxide superconductor, other characteristics such as high-speed growth during film formation are obtained. Since there are some films that can be formed, it is needless to say that the complex oxides having various compositions described above can be appropriately selected and used for the purpose of the present invention.

Next, an apparatus and method for forming the polycrystalline thin film 2 will be described. FIG. 4 shows an example of an apparatus for forming the polycrystalline thin film 2, which has a structure in which a sputtering apparatus is provided with an ion source for ion beam assist. This apparatus supports a tape-shaped polycrystalline base material 1 and can heat the tape-shaped polycrystalline base material 1 to a desired temperature, and a base for feeding the tape-shaped polycrystalline base material 1 onto the base material holder 23. A material feeding bobbin 24, a base material winding bobbin 25 for winding the tape-shaped polycrystalline base material 1 on which a polycrystalline thin film is formed, and a diagonally upper portion of the base material holder 23, which are opposed to each other at a predetermined interval. Plate-shaped target 36
And a sputter beam irradiation device 38 disposed obliquely above the target 36 and directed toward the lower surface of the target 36. The sputter beam irradiation device 38 is opposed to the side of the base material holder 23 at a predetermined interval and separated from the target 36. The arranged ion source 39 and the ion source 39 are housed in a film forming processing container 40 that can be evacuated.

The base material holder 23 is provided with a heater inside so that the tape-shaped polycrystalline base material 1 delivered onto the base material holder 23 can be heated to a desired temperature as required. There is. The base material holder 23 is rotatably attached to the support body 23a by a pin or the like, and the tilt angle can be adjusted. The base material holder 23 as described above is arranged in the optimum irradiation region of the ion beam irradiated from the ion source 39 in the film formation processing container 40. In the polycrystalline thin film forming apparatus of this example, the tape-shaped polycrystalline base material 1 is continuously fed from the base material feeding bobbin 24 onto the base material holder 23 to form a polycrystal thin film in the optimum irradiation region. Bobbin 2 for winding base material
By winding the film at 5, it is possible to continuously form a film on the polycrystalline substrate 1. This base material winding bobbin 25
Are arranged outside the optimum irradiation area.

The target 36 is for forming a desired polycrystalline thin film, and has the same or similar composition as the polycrystalline thin film having a desired composition.
As the target 36, specifically, Y ₂ Zr ₂ O ₇ , Gd ₂
The target of the composite oxide represented by the composition formula of Zr ₂ O ₇ or Eu ₂ Zr ₂ O ₇ , or among these three individual constituent elements, a large amount of an element which is easily scattered when formed into a film is contained in advance. A composition target is used. Such a target 36 is attached to a target support 36a that is rotatably held by a pin or the like, and the tilt angle can be adjusted.

The sputter beam irradiation device (sputtering means) 38 is capable of irradiating the target 36 with an ion beam to knock out the constituent particles of the target 36 toward the polycrystalline base material 1. The ion source 39 has substantially the same configuration as the sputter beam irradiation device 38, and is configured to house an evaporation source inside the container and to provide a grid for applying an extraction voltage in the vicinity of the evaporation source. . Then, a part of the atoms or molecules generated from the evaporation source is ionized, and the ionized particles are controlled by an electric field generated by a grid and irradiated as an ion beam. There are various methods for ionizing particles, such as a DC discharge method, a high frequency excitation method, and a filament method. The filament type is a method in which a tungsten filament is electrically heated to generate thermoelectrons, which are then collided with vaporized particles in a high vacuum to be ionized.

In the polycrystalline thin film forming apparatus of this embodiment, the ion source 39 having the internal structure shown in FIG. 5 is used. The ion source 39 includes a grid 46, a filament 47, Ar gas, and K inside a cylindrical ion chamber 45.
An ion introducing tube 48 for r gas, Xe gas or the like is provided, and ions can be emitted in a beam shape substantially in parallel from a beam port 49 at the tip of the ion chamber 45.

As shown in FIG. 4, the ion source 39 has its central axis S on the upper surface (deposition surface) of the polycrystalline substrate 1.
With respect to each other, they are opposed to each other with an angle of incidence θ (an angle formed by a normal line (normal line) H of the film formation surface (upper surface) of the polycrystalline substrate 1 and the center line S). The incident angle θ is preferably in the range of 50 to 60 degrees, more preferably in the range of 55 to 60 degrees,
Most preferably, the angle is around 55 degrees. Therefore, the ion source 39 is arranged so as to be able to irradiate the ion beam at an incident angle θ with respect to the normal line H of the film-forming surface of the polycrystalline substrate 1. The incident angle of such an ion beam is related to the technique that the present inventors have previously applied for a patent.
The ion beam with which the polycrystalline substrate 1 is irradiated by the ion source 39 is an Ar gas ion beam, K
It is possible to use an ion beam of r gas, an ion beam of Xe gas, or a mixed ion beam of a combination of two or more of these Ar gas, Kr gas, and Xe gas, for example, a mixed ion beam of Ar gas and Kr gas. it can.

Returning to FIG. 4 again, the film forming container 40
Includes a rotary pump 51 and a cryopump 52 for bringing the inside of the container 40 into a low pressure state such as a vacuum,
Atmosphere gas supply sources (not shown) such as gas cylinders are connected to each other so that the inside of the film formation processing container 40 can be in a low pressure state such as vacuum and can be made to have an argon gas or other inert gas atmosphere. It has become. Further, the film forming processing container 40 includes the container 40
A current density measuring device 55 for measuring the current density of the ion beam inside and a pressure gauge 55 for measuring the pressure inside the container 40 are attached. In the polycrystalline thin film forming apparatus of this example, the tilt angle can be adjusted by rotatably attaching the base material holder 23 to the support body 23a with a pin or the like.
Attach the angle adjustment mechanism to the support part of the ion source 3
The incident angle of the ion beam may be adjusted by adjusting the tilt angle of 9 and the angle adjusting mechanism is not limited to this example, and it is needless to say that various structures can be adopted. Is.

Next, the polycrystalline substrate 1 is prepared by using the apparatus having the above-mentioned structure.
A case where the pyrochlore type polycrystalline thin film 2 having the above-described composition such as Gd ₂ Zr ₂ O ₇ is formed thereon will be described. In order to form a polycrystalline thin film on the tape-shaped polycrystalline substrate 1, the target 36 made of the complex oxide described above is used, and the inside of the film forming processing container 40 accommodating the polycrystalline substrate 1 is vacuumed. The polycrystalline substrate 1 is sent from the substrate sending bobbin 24 to the substrate holder 23 at a predetermined speed, and the ion source 39 and the sputter beam irradiation device 38 are operated. When the target 36 is irradiated with an ion beam from the sputter beam irradiation device 38, the constituent particles of the target 36 are knocked out and fly onto the polycrystalline base material 1. Then, the constituent particles beaten from the target 36 are deposited on the polycrystalline base material 1 sent to the base material holder 23, and at the same time, from the ion source 39, for example, Ar
⁺ Ion beam, Kr ⁺ ion beam,
Ion beam of Xe ⁺ ions, or Kr ⁺ and Xe ⁺
A polycrystalline ion thin film having a desired thickness is formed by irradiating a mixed ion beam of ions, and the tape-shaped polycrystalline substrate 1 after film formation is wound on a substrate winding bobbin 25.

Here, the incident angle θ when irradiating the ion beam is preferably in the range of 50 degrees or more and 60 degrees or less, and most preferably 55 degrees. Here, when θ is 90 degrees, the c-axis of the above-mentioned polycrystalline thin film of the composite oxide is not oriented. Further, when θ is 30 degrees, the polycrystalline thin film of the complex oxide described above does not even have c-axis orientation. If the ion beam irradiation is performed at an incident angle within the above-mentioned preferable range, the c-axis of the crystal of the above-mentioned polycrystal thin film of the complex oxide stands. By performing sputtering while irradiating the ion beam at such an incident angle, the a-axes and the b-axes of the crystal axes of the polycrystalline thin film of the complex oxide formed on the polycrystalline substrate 1 are in the same direction. The in-plane orientation can be achieved along the plane parallel to the upper surface (deposition surface) of the polycrystalline substrate 1 facing to.

Further, when forming the polycrystalline thin film 2 of the complex oxide, the ion beam energy of the assist ion beam is set within a prescribed range in addition to the irradiation angle of the assist ion beam, and the polycrystalline It is preferable to keep the temperature of the base material 1 at an optimum level. The ion beam energy is 150 eV or more, 30 or more in order to make the grain boundary tilt angle 30 degrees or less.
0 eV or less is preferable, but in order to make the grain boundary tilt angle 20 degrees or less, a range of 175 ° C. or higher and 225 ° C. or lower is preferable, and 200 eV is most preferable.

The temperature of the polycrystalline base material 1 is preferably heated to a suitable temperature of 300 ° C. or lower to form a film. Further, from the results of Examples described later, the grain boundary tilt angle is set to 25 ° or less. Is preferably 90 ° C. or higher and 300 ° C. or lower, and in order to ensure that the grain boundary tilt angle is 20 ° or less within this range, the temperature is controlled to an appropriate temperature according to the composition of the polycrystalline thin film 2 of the composite oxide to be obtained. Then, it is necessary to form a film. Here, the temperature of 90 ° C. is the temperature at which the base material is naturally heated by the ion beam irradiating the base material, the residual heat of the equipment, and the like, even if the base material is not specially heated and the equipment installation environment is room temperature. Is.

That is, the composition formula of the polycrystalline thin film is YZ.
In the case of rO and the ratio of ZrO ₂ and Y ₂ O ₃ is 92: 8, the heating temperature of the polycrystalline base material is 90 ° C. to 300 ° C.
C., more preferably 90 to 150.degree. By adopting such a forming method, it becomes possible to lower the FWHM value of the composite oxide polycrystalline thin film to 25 or less, to at least about 15. Furthermore, ZrO ₂ and Y ₂ O ₃
And the heating temperature of the polycrystalline base material is 150 ° C to 300 ° C, more preferably 150 ° C to 2
Set to 50 ° C.

The composition of the polycrystalline thin film is expressed by Gd.
ZrO, and ZrO₂And Y₂O ₃Ratio with 92:
In the case of 8, the heating temperature of the polycrystalline base material is 90 ° C to 2
50 degreeC, More preferably, it is 100 degreeC-225 degreeC. It
ZrO₂And Y₂O₃When the ratio with is 2: 1
Is a heating temperature of the polycrystalline base material of 90 ° C. to 300 ° C., more preferably
More preferably, the temperature is 120 ° C to 250 ° C. further,
ZrO₂And Y₂O₃If the ratio with is 1: 1
The heating temperature of the crystal substrate is 100 ° C to 290 ° C. Furthermore
To ZrO₂And Y₂O₃And the ratio is 1: 2,
The heating temperature of the polycrystalline base material is 120 ° C to 250 ° C. This
By adopting a forming method such as
FWHM value of crystalline thin film is 25 degrees or less, at least about 12.5 degrees
It is possible to lower it all the time.

When the composition formula is EuZrO, the temperature of the polycrystalline substrate is 100 ° C. to 300 ° C., preferably about 2 ° C.
It is necessary to heat to a temperature of 00 ° C. Even if EuZrO is used, the same effect as GdZrO can be obtained.

Under the conditions of polycrystalline substrate temperature, ion beam energy and ion beam incident angle in these ranges,
By the ion assist method, a polycrystalline thin film 2 of pyrochlore type or the like can be formed on the polycrystalline substrate 1 with good orientation. 1 and 2 show a polycrystalline thin film 2 of the aforementioned complex oxide, such as Gd ₂ Zr ₂ O ₇ , deposited on a polycrystalline substrate 1 by the method described above. Although FIG. 1 shows a state in which only one layer of crystal grains 20 is formed, it goes without saying that the crystal grains 20 may have a multilayer structure.

The inventors of the present invention assume the following as a factor for adjusting the crystal orientation of the polycrystalline thin film 2.
The unit cell of the crystal of the polycrystalline thin film 2 of Gd ₂ Zr ₂ O ₇ has an equiaxed face-centered cubic pyrochlore structure as shown in FIG. 6, and in this crystal lattice, the base material method is used. The line direction is the <100> axis and <001> with the other <010> axes.
The axes are all in the directions shown in FIG. Considering an ion beam that is incident obliquely to the normal to the base material with respect to these directions, when incident along the diagonal direction of the unit lattice, that is, along the <111> axis with respect to the origin O in FIG. Is 5
The incident angle is 4.7 degrees. Here, as described above, exhibiting good crystal orientation in the incident angle range of 50 to 60 degrees means that the ion channeling is performed when the incident angle of the ion beam coincides with or before and after the 54.7 degree. Occurs most effectively, and in the crystal deposited on the polycrystalline base material 1, only the stable atoms are likely to remain selectively due to the arrangement relationship on the upper surface of the polycrystalline base material 1 that matches the angle. , Other unstable atomic arrangements that are unstable are removed by being sputtered by the ion beam sputtering effect, and as a result, only crystals in which atoms with good orientation are aggregated selectively remain and are deposited. Is estimated.

Under the above conditions, Gd ₂ Zr ₂ O ₇
Even if the polycrystalline thin film 2 is formed, if the temperature of the polycrystalline substrate 1 at the time of film formation and the energy of the ion beam at the time of ion beam assist are not set within the above-specified range, sufficient ion Beam channeling effect cannot be obtained. Therefore, it is important that the three conditions of the ion beam assist angle, the temperature of the polycrystalline substrate 1 and the ion beam energy described above are all aligned within the prescribed preferable range.

Next, FIGS. 7 and 8 show an embodiment of an oxide superconductor utilizing the present invention. The oxide superconductor 22 is a tape-shaped polycrystalline substrate 1 and this polycrystalline superconductor. It is composed of a polycrystalline thin film 2 formed on the upper surface of the base material 1 and an oxide superconducting layer 3 formed on the upper surface of the polycrystalline thin film 2.
The polycrystalline base material 1 and the polycrystalline thin film 2 are made of the same materials as those described above, and the crystal grains 20 of the polycrystalline thin film 2 are included.
Are oriented so that the grain boundary tilt angle is within 25 degrees, preferably 17 to 20 degrees.

Next, the oxide superconducting layer 3 is deposited on the upper surface of the polycrystalline thin film 2, and the c-axis of the crystal grain 21 is perpendicular to the upper surface of the polycrystalline thin film 2 as shown in FIG. And the a-axis and the b-axis of the crystal grain 21 are in-plane oriented along a plane parallel to the upper surface of the base material, and the grain boundary tilt angle K ′ formed by the crystal grains 21 is within 30 degrees. There is. The oxide superconductor forming the oxide superconducting layer is Y ₁ Ba ₂ Cu ₃ O.
_7-x , Y ₂ Ba ₄ Cu ₈ O _x , Y ₃ Ba ₃ Cu ₆ O _x , or (Bi, Pb) ₂ Ca ₂ Sr ₂ Cu ₃ O _x , (Bi, P
b) ₂ Ca ₂ Sr ₃ Cu ₄ O _x composition or Ti ₂ B
a ₂ Ca ₂ Cu ₃ O _x , Ti ₁ Ba ₂ Ca ₂ Cu ₃ O _x , Ti ₁ B
The oxide superconductor has a high critical temperature represented by a composition such as a ₂ Ca ₃ Cu ₄ O _x , but it goes without saying that other oxide superconductors of these examples may be used. .

The oxide superconducting layer 3 is formed, for example, on the above-mentioned polycrystalline thin film 2 by a well-known film forming method such as sputtering or laser vapor deposition.
The oxide superconducting layer laminated on the upper layer is also made of Y ₂ Zr ₂ O ₇ or Gd ₂
Polycrystalline thin film of Zr ₂ O ₇ pyrochlore type complex oxide 2
The polycrystalline thin film 2 is deposited so as to match the orientation of
The oxide superconducting layer formed on the top has excellent quantum bondability at the crystal grain boundaries and hardly deteriorates the superconducting properties at the crystal grain boundaries. Therefore, it becomes easy to pass electricity in the length direction of the polycrystalline base material 1. A sufficiently high critical current density can be obtained.

[0047]

EXAMPLE A polycrystalline thin film forming apparatus having the structure shown in FIG. 4 was used, and the inside of the film forming processing container of this forming apparatus was evacuated by a rotary pump and a cryopump to obtain 3.0 × 10 5.
^The pressure was reduced to ⁻⁴ Torr (399.9 × 10 ⁻⁴ Pa). As the tape-shaped substrate, Hastelloy C276 having a width of 10 mm, a thickness of 0.5 mm and a length of 100 cm and having a surface mirror-polished.
Tape was used. Also, the target is Gd ₂ Zr ₂ O
A composite oxide having a composition of ₇ , Y ₂ Zr ₂ O ₇ and Eu ₂ Zr ₂ O ₇ and different ratios of rare earth elements and Zr was used. Sputtering voltage is 1000 V, sputtering current is 100 m
A, the incident angle of the Ar ⁺ ion beam generated from the ion source is set to 55 degrees with respect to the normal to the film-forming surface of the substrate, the ion beam transport distance is set to 40 cm, and the assist voltage of the ion source is set. Is set to 200 eV, the temperature of the base tape is changed between 90 and 300 ° C., and oxygen of 133.3 × 10 ⁻⁴ Pa (1 × 10 ⁻⁴ Torr) is caused to flow in the atmosphere to apply the base tape onto the base. The constituent particles of the target were deposited and simultaneously irradiated with an ion beam to form a film-shaped composite oxide polycrystalline thin film having a thickness of 1.0 μm.

The obtained composite oxide polycrystalline thin film was subjected to X-ray diffraction by the θ-2θ method using CuKα rays, and from the pole figure obtained, the composite oxide polycrystalline thin film of each composition was excellent. It was clarified that they were oriented with various orientations. The full width at half maximum corresponding to the grain boundary tilt angle of each polycrystalline thin film obtained from the pole figure is shown in FIGS. 9 to 11.

FIG. 9 is a diagram showing the relationship between the plate temperature and the full width at half maximum of the polycrystalline substrate during the formation of various polycrystalline thin films. The horizontal axis represents the substrate temperature during film formation, and the vertical axis represents the crystal orientation, and the full width at half maximum (FWHM) corresponding to the grain boundary tilt angle. The curve (a) in the figure is a GdZrO-based crystal, and ZrO
_In the case of fluorite with ₂ : ₂ Gd ₂ O ₃ of 92: 8, the curve (b) is Y
In the case of a ZrO-based crystal in which ZrO ₂ : Y ₂ O ₃ is 92: 8 fluorite-type YSZ, the curve (c) is a YZrO-based crystal.
When ZrO ₂ : Y ₂ O ₃ is a 2: 1 pyrochlore type, the curve (d) is a GdZrO type crystal, and ZrO ₂ : Gd ₂ O ₃
Shows the case of 2: 1 pyrochlore.

As is clear from the figure, Zr of the curve (a)
In the case of fluorite with O ₂ : Gd ₂ O ₃ of 92: 8, the base material temperature is 9
The FWHM value becomes 24 degrees or less between 0 ° C and 250 ° C,
The FWHM value becomes 20 degrees or less between 100 ° C and 225 ° C. When ZrO ₂ : Y ₂ O _{3 of} the curve (b) is fluorite-type YSZ of 92: 8, the FWHM value becomes 24 ° C. or less when the base material temperature is 90 ° C. to 300 ° C., and the FWHM value is 90 ° C. 150 ° C
The FWHM value becomes 16 degrees or less between. Further, in the case of the pyrochlore type in which the ZrO ₂ : Y ₂ O _{3 of} the curve (c) is 2: 1, the FWHM value becomes 18 degrees or less when the substrate temperature is 150 ° C. to 300 ° C., and the FWHM value is 150 ° C. to 250 ° C. The FWHM value becomes 15 degrees or less. In addition, ZrO ₂ : G of the curve (d)
In the case of pyrochlore with d ₂ O ₃ of 2: 1, the substrate temperature is 90
FWHM value is below 16 degrees between 1 ℃ and 300 ℃
The FWHM value becomes 13 degrees or less between 20 ° C and 250 ° C.

FIG. 10 shows a GdZrO system crystal.
ZrO _2: is a diagram illustrating the relation between the board temperature and the full width at half maximum of the polycrystalline group during the deposition in the case of changing the ratio of Gd ₂ O _3.
As in FIG. 9, the horizontal axis represents the substrate temperature during film formation, the vertical axis represents the crystal orientation, and the full width at half maximum (FWHM) corresponding to the grain boundary tilt angle.
Indicates the value of. As is clear from the figure, the curve (a)
When the ratio of ZrO ₂ : Gd ₂ O ₃ is 92: 8, the FWHM value is 24 degrees or less when the substrate temperature is 90 ° C. to 250 ° C., and the FWHM value is 20 degrees between 100 ° C. and 225 ° C. It becomes the following. When the ratio of ZrO ₂ : Gd ₂ O _{3 in} the curve (b) is 1: 2, the substrate temperature is 90 ° C. to 300 ° C. and the FW is
HM value is 23 degrees or less and FW at 120 ° C to 250 ° C
The HM value becomes 19 to 15 degrees. Furthermore, Z of the curve (c)
When the ratio of rO ₂ : Gd ₂ O ₃ is 1: 1, the substrate temperature is 100 ° C. to 300 ° C. and the FWHM value is 16 to 12 degrees. Moreover, when the ratio of ZrO ₂ : Gd ₂ O _{3 in} the curve (d) is 2: 1, the substrate temperature is 120 ° C. to 250 ° C. and the FW
The HM value is 12 to 13 degrees.

FIG. 11 shows the type of polycrystalline thin film as RE ₂
Zr ₂ O ₇ and Yb, E as RE (rare earth element)
r, Ho, Y, Dy, Gd, Eu, Sm, Nd and Pr
Using the same film forming conditions as described above, that is, the substrate temperature 2
The FWHM values in the case of forming a film at 00 ° C., using Ar ⁺ ion beam, ion beam energy of 200 eV, and ion beam incident angle of 55 degrees are arranged in order from the smallest ionic radius. As shown in the figure, when a pyrochlore polycrystalline thin film represented by the composition formula of RE ₂ Zr ₂ O ₇ is formed under the film forming conditions of the present invention, the FWHM value is oriented with good orientation of 18 degrees or less. It became clear. In particular, when Gd and Eu are adopted as RE (rare earth element), the FWHM value becomes 12, and a pyrochlore polycrystalline thin film having extremely excellent orientation can be formed.

Further, an oxide superconductor layer having a composition of Y ₁ Ba ₂ Cu ₃ O _7-x is formed on the polycrystalline thin film formed under the respective film forming conditions as described above by a laser deposition method and is oxidized. As a superconducting conductor. The method for forming the oxide superconductor layer is as follows.
It was kept and vapor deposited. The obtained oxide superconducting conductor was immersed in liquid nitrogen, and the central portion was 10 mm wide and 1 length long by the 4-terminal method.
The critical current density was measured for the 0 mm portion.

As a result, the curve (a) in FIG. 9 (= FIG. 10)
ZrO shown in the curve (a))₂ : Gd ₂O₃Is based on 92: 8
The FWHM value formed with the material temperature of 150 ° C is 17 degrees.
Critical current density of oxide superconductor using polycrystalline thin film
Is 0.5 MA / cm² , ZrO shown in the curve (c) of FIG.
₂ : Y₂O₃Is 2: 1 and the substrate temperature is 200 ° C.
With FWHM value of 13 degrees
The critical current density of the conductive conductor is 1.0 MA / cm² ,Also,
Zr shown in the curve (d) of FIG. 9 (= curve (d) of FIG. 10)
O₂ : Gd₂O₃Is 2: 1 and the substrate temperature is 200 ° C.
Oxidation using a polycrystalline thin film with a FWHM value of 12 degrees
Superconducting conductor has a critical current density of 1.2 MA / cm² And
It was.

Further, ZrO shown in the curve (b) of FIG.
₂ : Gd ₂ O ₃ is 1: 2, the critical current density of the oxide superconducting conductor is 0.7 MA / cm ² using the polycrystalline thin film formed with the substrate temperature of 200 ° C. and the FWHM value of 15 degrees. , The criticality of an oxide superconducting conductor using a polycrystalline thin film having a FWHM value of 12 degrees formed by setting ZrO ₂ : Gd ₂ O ₃ at a ratio of 1: 1 and a substrate temperature of 200 ° C. shown in a curve (c) of FIG. The current density was 0.9 MA / cm ² . Also, FIG.
ZrO ₂ : Eu ₂ O ₃ shown in 1 is 2: 1 and the substrate temperature is 20.
The critical current density of an oxide superconducting conductor using a polycrystalline thin film having a FWHM value of 11.5 degrees formed at 0 ° C is 1.2.
It was MA / cm ² .

As described in detail above, the optimum base material temperature is selected according to the type of the polycrystalline thin film, and then the ion beam of Ar ⁺ , Kr ⁺ ion beam, Xe ⁺ ion is used as the ion beam. Beam or a mixed ion beam of these beams, the ion beam energy of the ion beam is adjusted to a range of 150 eV or more and 300 eV or less, and the ion beam is 50 ° or more and 60 ° or more with respect to the normal to the surface of the substrate on which the film is formed. A pyrochlore polycrystalline thin film having excellent orientation can be formed by forming the film under the film forming condition of depositing while irradiating at an incident angle of not more than 40 degrees. Further, when the oxide superconductor layer is formed by using the pyrochlore polycrystalline thin film having excellent orientation as described above as an underlayer, an oxide superconductor having a high critical current density can be obtained.

[0057]

As described above, according to the method for forming a polycrystalline thin film of the present invention, a polycrystalline thin film composed of pyrochlore type crystal grains having a grain boundary tilt angle of 25 degrees or less and excellent crystal orientation is polycrystalline. It becomes possible to form it on a base material. In addition, since the film can be formed at a growth rate about twice that of the conventional YSZ,
The process time can be shortened. Further, the superconducting conductor formed on the pyrochlore-type polycrystalline thin film excellent in such crystal orientation has a high critical current density,
It has superconducting characteristics with excellent stability.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a complex oxide polycrystalline thin film formed by the method of the present invention.

FIG. 2 is a diagram showing crystal grains of the polycrystalline thin film shown in FIG. 1, crystal grain directions thereof and grain boundary tilt angles.

FIG. 3 is a conceptual diagram showing a crystal lattice of a pyrochlore type polycrystalline thin film having a composition of Gd ₂ Zr ₂ O ₇ .

FIG. 4 is a configuration diagram showing an example of an apparatus used for forming a polycrystalline thin film of the present invention.

5 is a configuration diagram showing an example of an ion source of the apparatus shown in FIG.

FIG. 6 is a diagram illustrating an ion beam incident angle.

FIG. 7 is a perspective view showing an oxide superconducting layer formed on a polycrystalline thin film.

8 is a diagram showing crystal grains, crystal axis directions, and grain tilt angles of the oxide superconducting layer shown in FIG.

FIG. 9 is a diagram showing a relationship between a substrate temperature and a full width at half maximum of a polycrystalline thin film.

FIG. 10 is a diagram showing the relationship between the composition of a polycrystalline thin film and the full width at half maximum of the polycrystalline thin film.

FIG. 11 is a diagram showing a relationship between an ionic radius of various complex oxides and a full width at half maximum of a polycrystalline thin film.

FIG. 12 is a perspective view showing a complex oxide polycrystalline thin film formed by a conventional method.

FIG. 13 is a diagram showing a relationship between a base material temperature and a full width at half maximum of a polycrystalline thin film having a composition of Sm ₂ Zr ₂ O ₇ formed by a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polycrystalline base material, 2 ... Polycrystalline thin film, 3 ... Oxide superconducting layer, 4 ... Crystal grains, 5 ... Intermediate layer, H ... Normal line, K ... Grain boundary tilt angle, R ... Crystal grain boundary, θ ... Incident angle, 20 ... Crystal grain, 21 ... Crystal grain, 22 ... Oxide superconducting conductor, 36 ...
-Target, 39 ... Ion source.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 39/24 H01L 39/24 B (72) Inventor Kazumoto Kazuomi 1-5-1 Kiba, Koto-ku, Tokyo No. Stock Company Fujikura F-term (reference) 4G047 JA04 JB02 JC02 KE02 4G077 AA03 AA07 BC60 DA11 EA02 SB02 4K029 AA02 AA25 BA50 BB08 BC04 CA05 CA15 DC37 EA08 EA09 4M113 AD35 AD68 BA01 BA04 CA27 CA21 CA21 CA04 CA36 5

Claims (12)

[Claims] 1. A polycrystalline substrate comprising crystal grains having a pyrochlore type, a fluorite type, a rare earth C type or a mixed type of pyrochlore and rare earth C type having a composition formula represented by either GdZrO or YZrO. Is a method for forming a polycrystalline thin film having a grain boundary tilt angle of 30 degrees or less formed by the same crystal axis of the crystal grains along a plane parallel to the film-forming surface, which is a constituent element of the composition formula by a sputtering method. When depositing the constituent particles generated from the target of 1) on the film formation surface of the polycrystalline base material, the polycrystalline base material is heated to a temperature of 90 ° C. to 300 ° C., and as an ion beam generated by the ion source, Ar ⁺ ion beam, Kr ⁺ ion beam, Xe
^Using an ion beam of ⁺ or a mixed ion beam thereof, the ion beam energy of the ion beam is adjusted to a range of 150 eV or more and 300 eV or less, and the ion beam is adjusted to 50 with respect to the normal line to the film formation surface of the substrate. A method of forming a polycrystalline thin film, which comprises depositing while irradiating at an incident angle of not less than 60 degrees and not more than 60 degrees. 2. The composition formula of the polycrystalline thin film is YZrO, the ratio of ZrO ₂ and Y ₂ O ₃ is 2: 1, and the heating temperature of the polycrystalline substrate is 150 ° C. to 300 ° C. The method for forming a polycrystalline thin film according to claim 1, wherein: 3. The heating temperature of the polycrystalline base material is 150.degree.
The method for forming a polycrystalline thin film according to claim 2, wherein the temperature is 250 ° C. 4. The composition formula of the polycrystalline thin film is GdZrO, the ratio of ZrO ₂ to Gd ₂ O ₃ is 92: 8, and the heating temperature of the polycrystalline substrate is 90 ° C. to 250 ° C. The method for forming a polycrystalline thin film according to claim 1, wherein: 5. The heating temperature of the polycrystalline base material is 100.degree.
The method for forming a polycrystalline thin film according to claim 4, wherein the temperature is 225 ° C. 6. The composition formula of the polycrystalline thin film is GdZrO, the ratio of ZrO ₂ and Gd ₂ O ₃ is 2: 1, and the heating temperature of the polycrystalline substrate is 90 ° C. to 300 ° C. The method for forming a polycrystalline thin film according to claim 1, wherein: 7. The heating temperature of the polycrystalline base material is 120.degree.
The method for forming a polycrystalline thin film according to claim 6, wherein the temperature is 250 ° C. 8. The composition formula of the polycrystalline thin film is GdZrO, the ratio of ZrO ₂ and Gd ₂ O ₃ is 1: 1, and the heating temperature of the polycrystalline substrate is 100 ° C. to 290 ° C. The method for forming a polycrystalline thin film according to claim 1, wherein: 9. The composition formula of the polycrystalline thin film is GdZrO, the ratio of ZrO ₂ and Gd ₂ O ₃ is 1: 2, and the heating temperature of the polycrystalline substrate is 120 ° C. to 250 ° C. The method for forming a polycrystalline thin film according to claim 1, wherein: 10. A polycrystal substrate having a pyrochlore type crystal structure represented by EuZrO and a crystal grain having a ratio of ZrO ₂ and Eu ₂ O ₃ of 2: 1. A method for forming a polycrystalline thin film having a grain boundary tilt angle of 30 degrees or less formed by the same crystal axis of the crystal grains along a plane parallel to the film surface, which is obtained by sputtering a target of the constituent elements of the composition formula. When depositing the generated constituent particles on the film formation surface of the polycrystalline base material, the polycrystalline base material is heated to 100 ° C. to 30 ° C.
As an ion beam generated by an ion source when heated to a temperature of 0 ° C., an Ar ⁺ ion beam, a Kr ⁺ ion beam, a Xe ⁺ ion beam, or a mixed ion beam thereof is used. Energy is adjusted to a range of 150 eV or more and 300 eV or less, and deposition is performed while irradiating the ion beam at an incident angle of 50 degrees or more and 60 degrees or less with respect to a normal line of the film formation surface of the base material. Method for forming crystalline thin film. 11. The heating temperature of the polycrystalline base material is 150 ° C.
The method for forming a polycrystalline thin film according to claim 10, wherein the temperature is set to ˜250 ° C. 11. 12. The method according to any one of claims 1 to 11.
An oxide superconductor comprising an oxide superconductor layer formed on the polycrystalline thin film obtained by the method described in the item 1.