JPH06271392A - Production of oxide superconducting conductor and target for production of oxide superconducting conductor - Google Patents

Abstract

PURPOSE:To efficiently improve crystal orientability and superconducting characteristics by forming a polycrystalline thin film by irradiation with an ion beam simultaneously with laser vapor deposition on a base material and forming an oxide superconducting layer by a laser vapor deposition method on the resulted film. CONSTITUTION:The inside of a vapor deposition treatment chamber 23a contg. the base material 20 is evacuated to a reduced pressure by a vacuum evacuation device 26. A laser beam emitting device 32 and an ion gun 22 are then operated. A first target 25a consisting of MgO, etc., is irradiated with the laser beam from the device 32 and the splashed particulates are deposited on the base material 20. Simultaneously, the particulates successively deposited on the base material 20 are irradiated with the ion beam consisting of a mixture composed of Ar ions and O2 ions, from the ion gun 22 in such a manner that an incident angle theta attains 50 to 60 deg., by which the polycrystalline thin film is formed on the base material. A second target 25b contg. MgO, etc., is then irradiated with the laser beam and the oxide superconducting layer is formed on the surface of the polycrystalline thin film by the particulates splashed from the target 25b, by which the oxide superconducting conductor is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide superconducting conductor having an oxide superconducting layer having a uniform crystal orientation.

[0002]

2. Description of the Related Art The oxide superconductor discovered in recent years is an excellent superconductor exhibiting a critical temperature exceeding the liquid nitrogen temperature. At present, this type of oxide superconductor is a practical superconductor. There are various problems to be solved in order to be used as. 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 current easily flows in the a-axis direction and the b-axis direction of the crystal axis, but electricity hardly flows in the c-axis direction. From such a viewpoint, the oxide superconductor is formed on the substrate, and in order to use this as the superconductor, the oxide superconductor in a good crystal orientation is formed on the substrate, and , Orienting the a-direction or the b-axis direction of the crystal of the oxide superconductor in the direction in which electricity flows
It is necessary to orient the c-axis of the oxide superconductor in another direction.

Conventionally, various means have been tried to form an oxide superconducting layer having a good crystal orientation on a substrate such as a substrate or a metal tape. As one of the methods, MgO or Sr having a crystal structure similar to that of the oxide superconductor is used.
A method of forming an oxide superconducting layer on a single crystal substrate such as TO ₃ by a film forming method such as sputtering has been carried out.

When a film forming method such as sputtering is performed using a single crystal base material such as MgO or SrTiO ₃ , the crystal of the oxide superconducting layer grows on the basis of the crystal of the single crystal base material. It is possible to improve the crystal orientation, and the oxide superconducting layer formed on these single crystal substrates exhibits a sufficiently high critical current density of about several thousand to several tens of thousands A / cm ^2. It is known.

[0006]

In order to use an oxide superconductor as a conductor, an oxide superconductor layer having a good crystal orientation is formed on a long base material such as a tape. There is a need. However, when an oxide superconductor layer is directly formed on a base material such as a metal tape, the metal tape itself is a polycrystal and its crystal structure is significantly different from that of the oxide superconductor. The superconducting layer cannot be formed at all. In addition, the heat treatment performed when forming the oxide superconducting layer causes a diffusion reaction between the metal tape and the oxide superconducting layer, destroys the crystal structure of the oxide superconducting layer, and deteriorates the superconducting characteristics.

Therefore, conventionally, on a base material such as a metal tape,
It has been practiced to coat an intermediate layer such as MgO or SrTiO ₃ using a sputtering apparatus, and form an oxide superconducting layer on this intermediate layer. However, the oxide superconducting layer formed on the intermediate layer of this kind by a sputtering apparatus has a considerably lower electric field current density (for example, several thousand to 10,000 A / cm 2) than the oxide superconducting layer formed on the single crystal substrate. There was a problem that it only showed about ² ). This is considered to be due to the reason explained below.

FIG. 16 is a cross-sectional structure of an oxide superconducting conductor in which an intermediate layer 2 is formed on a base material 1 such as a metal tape by a sputtering device, and an oxide superconducting layer 3 is formed on the intermediate layer 2 by a sputtering device. Is shown. In the structure shown in FIG. 16, the oxide superconducting layer 3 is in a polycrystalline state,
A large number of crystal grains 4 are randomly bonded.
Looking at each of these crystal grains 4 individually, each crystal grain 4
Although the c-axis of the crystal is oriented perpendicular to the surface of the substrate, it is considered that the a-axis and the b-axis are oriented randomly.

[0009] As described above, each crystal grain of the oxide superconducting layer has a
When the directions of the axis and the b-axis are disordered, the quantum coupling property of the superconducting state is lost at the grain boundaries where the crystal orientation is disturbed, and as a result, the superconducting properties, especially the critical current density, may be lowered. The oxide superconductor is in a polycrystalline state in which the a-axis and the b-axis are not oriented because the intermediate layer 2 formed thereunder is in the polycrystalline state in which the a-axis and the b-axis are not oriented. In addition, it is considered that when the oxide superconducting layer 3 is formed, the oxide superconducting layer 3 grows so as to match the crystal of the intermediate layer 2.

Therefore, the inventors of the present application used an apparatus as shown in FIG. 15 to irradiate the constituent particles of the target 5 made of a polycrystalline body with the ion beam R and knock out the constituent particles from the target 15. Is simultaneously deposited on the base material A, and at the same time, a polycrystalline thin film is formed on the base material A by irradiating the ion beam R ′ with the ion gun 6 or the like.
Using a laser vapor deposition apparatus as shown in FIG. 14, the target 8 made of an oxide superconductor is irradiated with a laser beam from a laser emitting apparatus 9 to knock out constituent particles from the target 8 to form a particle on the base material A. On October 30, 1992, a patent application was filed for a method for producing an oxide superconducting conductor by depositing it on the polycrystalline thin film formed in 1. to form an oxide superconducting layer. According to this method, a polycrystalline thin film having good crystal orientation can be formed on the base material, and an oxide superconducting layer is epitaxially grown on the polycrystalline thin film having good crystal orientation as described above. By
It was possible to form an oxide superconducting layer having good crystal orientation and a high critical current density, and it was possible to manufacture an oxide superconducting conductor exhibiting extremely excellent superconducting properties.

However, the method for producing an oxide superconducting conductor by the above method has a problem that the film formation time of a polycrystalline thin film is very slow. Therefore, it is difficult to produce a long oxide superconducting conductor. However, there is a problem in that the film formation time is extremely long and a decrease in manufacturing efficiency is unavoidable.

The present invention has been made to solve the above-mentioned problems, and a polycrystalline thin film is formed on a substrate by laser beam deposition and ion beam irradiation simultaneously, and a laser deposition method is applied to the polycrystalline thin film. By forming an oxide superconducting layer by using, a polycrystalline thin film with good crystal orientation can be formed on the substrate in a short time, and the crystal orientation on the polycrystalline thin film is good, and the critical current density It is an object of the present invention to provide a method for producing an oxide superconducting conductor that exhibits excellent superconducting properties by forming the excellent oxide superconducting layer of 1.

[0013]

In order to solve the above-mentioned problems, the method for producing an oxide superconducting conductor according to claim 1
Fine particles scattered by irradiating laser light on the surface of the oxide superconductor or the target containing the raw material thereof are deposited on the surface of the polycrystalline thin film formed on the substrate deposition surface to form the oxide superconducting layer. In the method for manufacturing an oxide superconducting conductor, a first target containing a material forming a polycrystalline thin film is irradiated with laser light emitted from a laser light source, and fine particles scattered from the first target are used as a base film forming surface. A polycrystalline thin film is formed on the surface of the base material by irradiating the surface of the base material with an ion beam when it is deposited on the second target containing the oxide superconductor or its raw material. The oxide superconducting layer is formed by irradiating light and depositing fine particles scattered from the second target on the surface of the polycrystalline thin film.

In order to solve the above-mentioned problems, the method for producing an oxide superconducting conductor according to a second aspect is such that the ion beam according to the first aspect is obliquely or obliquely applied to the surface of the substrate on which the film is formed.
Irradiation is performed at an incident angle of 0 to 60 degrees to form a polycrystalline thin film or an oxide superconducting layer.

In order to solve the above-mentioned problems, the method for producing an oxide superconducting conductor according to claim 3 is the same as the method for producing an oxide superconducting conductor according to claim 1 or 2.
Inert gas ions for the ion beam ion source, or
It is characterized by using a mixed ion of an inert gas ion and an oxygen ion.

The method for producing an oxide superconducting conductor according to claim 4 is the method for producing an oxide superconducting conductor according to any one of claims 1 to 3, in order to solve the above problems. It is characterized in that a crystal of an oxide superconductor is epitaxially grown on a crystal of a polycrystalline thin film formed on the surface.

A target for producing an oxide superconducting conductor according to claim 5 is used in the method for producing an oxide superconducting conductor according to any one of claims 1 to 4, in order to solve the above problems. A target is characterized in that the target has a long shape.

In order to solve the above-mentioned problems, a method for producing an oxide superconducting conductor according to a sixth aspect of the present invention is to continuously or intermittently apply the target for producing an oxide superconducting conductor according to the fifth aspect at a predetermined speed. It is characterized in that the laser beam irradiation position is moved continuously or intermittently by moving in the longitudinal direction.

[0019]

As described above, in the method for manufacturing an oxide superconducting conductor of the present invention, the first target containing the material forming the polycrystalline thin film is irradiated with the laser light emitted from the laser light source, and the first target is irradiated. When depositing the fine particles scattered from the substrate on the substrate film formation surface, an ion beam is irradiated from the oblique direction of the substrate film formation surface to form a polycrystalline thin film on the substrate surface. A second target containing a body or its raw material is irradiated with laser light, and fine particles scattered from the second target are deposited on the surface of the polycrystalline thin film to form an oxide superconducting layer. Therefore, in the method of the present invention, since the ions are simultaneously irradiated from the oblique direction as described above, the constituent particles are efficiently activated. As a result, in addition to the c-axis direction with respect to the surface of the substrate, a
Axial orientation and b-axis orientation are also improved. As a result, even for a polycrystalline thin film having a large number of crystal grain boundaries, a
It is possible to obtain a polycrystalline thin film having good axial orientation, b-axis orientation and c-axis orientation.

In the method for producing an oxide superconducting conductor according to the present invention, since the polycrystalline thin film is formed by laser vapor deposition, the film forming rate is significantly improved and the ion beam is irradiated from an oblique direction. By doing
A polycrystalline thin film having good crystal orientation can be formed. Then, by forming an oxide superconducting layer on such a polycrystalline thin film by a laser deposition method, it is possible to epitaxially grow the oxide superconducting layer, a high critical current density oxide superconducting layer with good crystal orientation. Can be formed.

Further, the irradiation angle of the ion beam is set to 50.
By setting it to -60 degrees, the crystal orientation can be adjusted more favorably, and a polycrystalline thin film having crystal orientation with a grain boundary tilt angle of 25 degrees or less can be obtained. In the polycrystalline thin film, diffraction peaks obtained by rotating the polycrystalline thin film appear every 90 degrees, so that the in-plane orientations of the crystal grains constituting the polycrystalline thin film in the a-axis and the b-axis are good, and Since the peak appears in the range of 0 to 30 degrees, it is also clear that the grain boundary tilt angle is 30 degrees.

Therefore, in the oxide superconducting conductor manufactured as described above, extremely excellent superconducting properties can be exhibited, and the polycrystalline thin film and the oxide superconducting layer constituting the oxide superconducting conductor are formed by laser. By using the vapor deposition method, the production efficiency of the oxide superconducting conductor can be remarkably improved.

The inventors of the present invention assume the following as a factor for adjusting the crystal orientation of the polycrystalline thin film. In the unit cell of the crystal of the cubic polycrystal thin film formed on the substrate, the substrate normal direction is the <100> axis, and the other <
Both the 010> axis and the <001> axis are directions orthogonal to the <100> axis. Considering an ion beam that is incident on these directions obliquely to the substrate normal direction, the diagonal direction of the unit lattice with respect to the origin of the unit lattice,
That is, in the case of incidence along <111>, 54.
The incident angle is 7 degrees.

Here, as described above, the good crystal orientation in the ion beam incident angle range of 50 to 60 degrees means that the ion beam incident angle coincides with the above-mentioned 54.7 degree. Seems to be related before and after,
Ion channeling occurs most effectively when these angles match or approximate to each other, and in the crystal deposited on the substrate, only the atoms that have a positional relationship that matches the angle on the upper surface of the substrate are , It becomes easier to remain selectively, and other disordered atomic arrangements are removed by being sputtered by the sputter effect generated by the obliquely incident ion beam. As a result, only crystals with well-oriented atoms are collected. Are selectively left and deposited, and it is presumed that the crystal orientation is adjusted due to this. The ions used as the ion beam are preferably inert gas ions or mixed ions of inert gas ions and oxygen gas.

If the oxide superconducting layer is epitaxially grown on the polycrystalline thin film having a good crystal orientation as described above, the oxide superconducting layer grows along the crystal of the polycrystalline thin film. The superconducting layer also has a-axis orientation and b
Good axial orientation and c-axis orientation can be obtained.

Further, elongated targets are used as the first target and the second target used in forming the polycrystalline thin film and the oxide superconducting layer, and the first target and the second target are indicated by arrows in the figure. By changing the irradiation position of the laser light for irradiating the target by translating in the direction, the local consumption of the target surface by the laser light is prevented and the energy density irradiated on the laser light irradiation surface of the target is changed. Can be kept constant,
As a result, stable release of target particles can be maintained for a long time, stable film formation is possible, and a film having a large area with stable quality can be obtained.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a laser vapor deposition apparatus for forming a polycrystalline thin film and an oxide superconducting layer on the upper surface of a substrate when forming the oxide superconducting conductor of the present invention. The laser vapor deposition apparatus shown in FIG. 1 has a configuration in which an ion gun for ion beam assist is provided in the laser vapor deposition apparatus.

Reference numeral 22 in the drawing is an ion beam assisting ion gun, and reference numeral 23 in the drawing is a processing container. A vapor deposition processing chamber 23a inside the processing container 23 is provided with a substrate holder 24 for placing the substrate 20 therein. Further, a first target 25a for forming a polycrystalline thin film and a second target 25b for forming an oxide superconducting layer are switchably attached.

The processing container 23 is connected to a vacuum exhaust device 26 through an exhaust hole 23b so that the inside of the processing container 23 can be vacuum exhausted. When a long metal tape (made of Hastelloy or stainless steel) is used as the base material 20, a metal tape feeding device 24a and a winding device 24b are provided inside the processing container 23. By continuously sending the base material 20 to the base material holder 24 and then winding it by the winding device 24b, a polycrystalline thin film and an oxide superconducting layer can be continuously formed on the tape-shaped base material 20. It is preferable to have such a configuration.

The substrate holder 24 has a heater inside so that the substrate 20 located on the substrate holder 24 can be heated to a desired temperature. An angle adjusting mechanism D is attached to the bottom of the base material holder 24. The angle adjusting mechanism D is configured such that the upper support plate 25a and the lower support plate 25b joined to the bottom of the base material holder 24 are rotatable with respect to each other via a pin coupling portion, and The horizontal angle can be adjusted. Although the angle adjusting mechanism D for adjusting the angle of the base material holder 24 is provided in this example, the angle adjusting mechanism D is attached to the ion gun 22 to adjust the inclination angle of the ion gun 22 and adjust the incident angle θ of the ion beam. It may be done. Further, the angle adjusting mechanism D is not limited to the configuration of this embodiment, and needless to say, various configurations can be adopted.

The first target 25a is for forming a desired polycrystalline thin film, and has the same composition as or similar to that of the polycrystalline thin film having a desired composition. Specifically, as the first target 25a,
Zirconia stabilized with MgO or Y ₂ O ₃ (YS
Z), MgO, SrTiO ₃ or the like is used, but the present invention is not limited to this, and a target suitable for the polycrystalline thin film to be formed may be used. In addition, the second target 25
b is for forming a target oxide superconducting layer, and has a composition similar to or close to the target composition, or sintering of a composite oxide containing a large amount of components that easily escape during film formation. A body or a body formed from a bulk of an oxide superconductor is used. Specifically, as a currently known oxide superconductor having a high critical temperature, Y-Ba-C is specifically mentioned.
Since there are u-O type, Bi-Sr-Ca-Cu-O type, etc., those of these types can be used as the second target 25b. Note that, among the elements forming the oxide superconducting layer, the vapor pressure is high, and there are also elements that easily scatter during vapor deposition, so when using a target containing such an element, the element with a high vapor pressure should be used. It suffices to use a target containing more than a predetermined ratio.

The ion gun 22 is constructed so that an evaporation source is housed inside a container and an extraction electrode is provided near the evaporation source. Then, a part of atoms or molecules generated from the evaporation source is ionized, and the ionized particles are controlled by an electric field generated by an extraction electrode to irradiate as an ion beam. There are various methods for ionizing particles, such as a DC discharge method, a high frequency excitation method, a fermented method, and a cluster ion beam method. The ferment method is a method in which a tungsten ferrule is electrically heated to generate thermoelectrons, which are then collided with vaporized particles in a high vacuum to be ionized. The cluster ion beam method is a method of bombarding clusters of aggregate molecules that come out in a vacuum from a nozzle provided at an opening of a crucible containing a raw material, bombarded with thermal electrons, ionized, and radiated. In this embodiment,
The ion gun 22 having the internal structure shown in FIG. 2A is used. This ion gun 22 is inside a cylindrical container 27,
The extraction electrode 29, the filament 30, and the introduction tube 31 of Ar gas or the like are provided, and ions can be irradiated in parallel in a beam shape from the tip of the container 27.

As shown in FIG. 1, the ion gun 22 has its central axis S with respect to the upper surface (deposition surface) of the substrate 20 with an incident angle θ (a normal line (normal line) of the substrate 20 and a center line S). The angle is made by the angle) and the two are opposed to each other. The incident angle θ is preferably in the range of 50 to 60 degrees, but most preferably in the range of 55 to 60 degrees. Therefore, the ion gun 22 is arranged so that the ion beam can be incident on the upper surface of the base material 20 at an inclination angle θ. The ion beam applied to the substrate 20 by the ion gun 22 is H
An ion beam of a rare gas such as e ⁺ , Ne ⁺ , Ar ⁺ , Xe ⁺ , and Kr ⁺ , or a mixed ion beam of those and oxygen ions may be used. However, in order to arrange the crystal structure of the polycrystalline thin film, a certain amount of atomic weight is required, and considering that the effect becomes too thin with ions that are too light, Ar is considered.
It is preferable to use ions such as ⁺ and Kr ⁺ .

Next, a polycrystalline thin film made of YSZ is formed on the base material 20 by using the apparatus 21 having the above structure, and an oxide superconducting layer is formed on the polycrystalline thin film to form an oxide superconducting conductor. A method of manufacturing the will be described. To form a polycrystalline thin film on the substrate 20, the first target 2 made of YSZ is used.
5a is used and the angle adjusting mechanism D is adjusted so that the ion beam emitted from the ion gun 22 is applied to the substrate holder 2
4. Allow irradiation on the upper surface at an angle in the range of 50 to 60 degrees. Next, the vapor deposition processing chamber 23a containing the base material 20
The vacuum exhaust device 26 is operated to evacuate the interior to create a reduced pressure atmosphere. Then, the laser emitting device 32 and the ion gun 22 are operated.

From the laser emitting device 32 to the first target 2
When 5a is irradiated with laser light, the constituent particles of the first target 25a are knocked out and fly onto the base material 20. At the same time that the constituent particles knocked out from the first target 25a are deposited on the base material 20, a mixed ion beam of Ar ions and oxygen ions is applied from the ion gun 22 to the constituent particles being deposited on the base material 20. Irradiate. The incident angle θ of the ion beam when irradiating the ion beam is 5
The most preferred range is 0 to 60 degrees. Here, when θ is 90 degrees, the c-axis of the polycrystalline thin film 40 is oriented at right angles to the film forming surface of the base material 20, but (11
1) It is not preferable because the surface is raised. Further, when θ is 30 degrees, the polycrystalline thin film is not oriented even in the c-axis direction. If the ion beam irradiation is carried out at an angle within the above-mentioned preferable range, the (100) plane of the crystal of the polycrystalline thin film will stand.

Therefore, by performing laser deposition while performing ion beam irradiation at such an incident angle θ,
It is possible to orient the a-axis, the b-axis, and the c-axis of the crystal axes of the polycrystalline thin film made of YSZ formed on the substrate 20, which is suitable for the constituent particles being deposited. This is probably because the constituent particles knocked out by the laser beam were efficiently activated by the ion beam irradiation at various angles.

Subsequently, the composition is similar to or close to that of the oxide superconducting layer to be formed on the polycrystalline thin film 40 formed on the base material 20, or contains a large amount of components that easily escape during film formation. The laser beam generated from the laser light emitting device 32 is focused on the second target 25b made of the sintered body of the complex oxide or the oxide superconductor, and is collected through the condenser lens 33 and the transparent window 34. Irradiate with light.
As a result, the constituent particles of the second target 25b are extracted or evaporated, and the particles are deposited on the polycrystalline thin film 40. Here, when the constituent particles are deposited, the polycrystalline thin film 4
Since 0 is preliminarily oriented along the c-axis and is also oriented along the a-axis and the b-axis, the c-axis, the a-axis, and the b-axis of the crystal of the oxide superconducting layer formed on the polycrystalline thin film 40 are also aligned with the polycrystalline thin film. It grows and crystallizes as it does. As a result, an oxide superconducting layer having good crystal orientation can be obtained.

The polycrystalline thin film 40 formed as described above
As shown in FIG. 3, they are joined and integrated through crystal grain boundaries, and the c-axis of the crystal axis of each crystal grain 35 ... Is the base material 20.
Oriented at right angles to the upper surface (deposition surface) of each crystal grain 3
The crystal axes a and b of 5 ... Are oriented in the same direction and are in-plane oriented. Further, the c-axis of each crystal grain 35 ... Is oriented at right angles to the (upper surface) film formation surface of the base material 20. And each crystal grain 35 ...
The a-axis (or the b-axis) of * are joined and integrated within an angle of 30 degrees.

The present inventors presume the following as a factor for adjusting the crystal orientation of the polycrystalline thin film 40. The unit cell of the crystal of the polycrystalline thin film 40 made of YSZ is a cubic crystal as shown in FIG. 2B, and in this crystal lattice, the substrate normal direction is the <100> axis and the other <010>. Both the> axis and the <001> axis are in the directions shown in FIG. Considering an ion beam that is incident obliquely to the normal to the substrate with respect to these directions, it is incident on the origin O of FIG. 2B along the diagonal direction of the unit lattice, that is, along the <111> axis. In that case, the incident angle is 54.7 degrees. Here, as described above, the incident angle is 50
A good crystal orientation in the range of up to 60 degrees means that ion channelig occurs most effectively when the incident angle of the ion beam coincides with or before or after 54.7 degrees, and In the crystal deposited on the material 20, only the atoms having the positional relationship matching the angle on the upper surface of the base material 20 are likely to remain selectively, and other disordered atomic arrangements are ion beam sputtered. It is presumed that, as a result of being sputtered and removed by the effect, only the crystals of the atoms with good orientation are selectively left and deposited.

In FIGS. 3 and 4 showing the film formation state of the polycrystalline thin film 40 formed on the substrate 20 by the above method, the crystal grains 35 ... Are composed of only one layer. However, it is a matter of course that the crystal grains 35 ... Have a multi-layer structure. Although only one target was used when the polycrystalline thin film 40 was formed, a plurality of targets for forming the polycrystalline thin film were provided, and different types of particles were punched out, and this was used as the base material 20. A polycrystalline film having a more complicated composition may be formed by depositing it on top.

Further, the oxide superconducting layer 50 obtained by the above method is coated on the polycrystalline thin film 40,
As shown in FIG. 3, the c-axis of the crystal grains 36 ... Is oriented at right angles to the upper surface of the polycrystalline thin film 40, and the a-axis and the b-axis of the crystal grains 36 ... Polycrystalline thin film 4
As in the case of 0, the grain boundary tilt angle K formed by the crystal grains 36 ..., which are in-plane oriented along the plane parallel to the upper surface of the substrate, is bonded and integrated within 30 degrees like the polycrystalline thin film. There is.

The oxide superconducting layer 50 formed on the polycrystalline thin film 40 is in a polycrystalline state, but in each of the crystal grains 36 ... As shown in FIG. 3, the c-axis in which a current hardly flows is oriented in the thickness direction of the base material 20, and the a-axis or the b-axis is oriented in the longitudinal direction of the base material 20. Therefore, the obtained oxide superconducting layer 50 is excellent in the quantum coupling property at the crystal grain boundaries and has little deterioration in the superconducting properties at the crystal grain boundaries. Excellent results are obtained.

Therefore, in the oxide superconducting conductor 60 manufactured as described above, the polycrystalline thin film 40 forming the oxide superconducting conductor 60 is formed by performing ion beam irradiation at the same time as laser deposition, thereby forming a film at a deposition rate. On the polycrystalline thin film 40 because the polycrystalline thin film 40 formed by such a method has a good crystal orientation. In addition, the oxide superconducting layer 50 formed by the laser deposition method can be formed by epitaxial growth, and the oxide superconducting conductor 60 having excellent crystal orientation and good critical current density can be manufactured. Further, the reduction of the film formation time of the polycrystalline thin film 40 is achieved by reducing the oxide superconducting conductor 60.
The manufacturing efficiency of can be remarkably improved.

Further, in the case of producing a long oxide superconducting conductor by the above method, a long target as shown in FIG. 5 is used, and this target is translated in the direction of the arrow shown in FIG. By irradiating the laser light generated from the light emitting device to a high region on the target, local consumption of the target surface by the laser light is prevented and the energy density irradiated to the laser light irradiation surface of the target is constant. Therefore, stable release of target particles can be maintained for a long time, stable film formation is possible, and a film having a large area with stable quality can be obtained. Even when the laser light emitting device is moved in translation while the target is fixed, the same effect as above can be obtained.

Therefore, a production example of the oxide superconducting conductor produced by the above method will be described below. (Production Example) Using the apparatus having the configuration shown in FIG. 1, the inside of the vapor deposition processing chamber 23a is evacuated by a vacuum pump 26 to 1 × 10 ^−4.
The pressure was reduced to Torr. As the base material 20, a Hastelloy tape having a width of 10 mm, a thickness of 0.1 mm and a length of 1 m was used.
Then, the first target 25a was made of YSZ (stabilized zirconia), and a Kr-F excimer laser having a wavelength of 248 nm was used as a laser for vapor deposition of the first target. Then, the incidence angle of the beam of the ion source is set to 55 degrees, the assist voltage of the ion source is set to 300 V, and the current density of the ion beam is set to 500 μA / cm ² , respectively, and laser deposition is performed on the substrate 20 at the same time as ion deposition. Irradiation was performed to form a film-like YSZ layer having a thickness of 0.5 μm. Here, the current density of the ion beam is measured by a current density measuring device grounded near the sample.

In the above apparatus, the polycrystalline thin film composed of the YSZ layer formed on the base material 20 is formed at a film forming rate of 5 μm in 1 hour, which is significantly higher than the conventional method for producing a polycrystalline thin film. The film forming speed has been improved. Conventionally, the film forming rate when a polycrystalline thin film is manufactured by performing ion irradiation simultaneously with sputtering is as follows: the film forming conditions are the same as above, the beam incident angle of the ion source is 55 degrees, and the assist voltage of the ion source is Was 300 V and the current density of the ion beam was 100 μA / cm ² , it was 0.1 μm / hour.

Further, an X-ray diffraction test by the θ-2θ method using CuKα rays was conducted on the polycrystalline thin film samples of each YSZ produced by changing the ion beam current density by the above method. FIG. 6 is a diagram showing the diffraction intensity of a sample measured with an ion beam current density of 40 μm / cm ² at an ion source incident angle of 55 ° and an ion beam voltage of 300 V. From the results shown in FIG. 6, in the sample in which the current density of the ion beam was set to 40 μA / cm ² , the YSZ
It can be presumed that the (200) plane or the (400) plane peak of YSZ is observed, and the (100) plane of the YSZ polycrystalline thin film is oriented along a plane parallel to the substrate surface. It was found that the polycrystalline thin film of 1 was formed with its c-axis oriented perpendicular to the upper surface of the substrate.

Subsequently, FIG. 7 shows a pole figure of the above sample. As is clear from this figure, the sample having an ion beam current density of 40 μA / cm ² gave results similar to those shown in FIG. 7.

FIG. 8 is a diagram showing the diffraction intensity of the sample measured with a beam voltage of 300 V and a beam current of 40 μm / A at an incident angle of 90 degrees to the ion source. From the results shown in FIG. 8, the YSZ (200) peak and (400) peak can be recognized even when the incident angle of the ion source is set to 90 °, and sufficient c-axis orientation is recognized. It was

Next, it was measured whether or not the a-axis or the b-axis of the YSZ polycrystalline thin film was oriented in each of the samples oriented in the c-axis as described above. For the measurement, as shown in FIG. 9, the X-ray polycrystalline thin film formed on the base material 20 is irradiated with X-rays at an angle θ, and <incident X-rays are included in a vertical plane including the incident X-rays. For 2θ (58.7
The X-ray counter 25 is installed at a position of (degrees), and the diffraction intensity obtained by rotating the X-ray counter 25 by a horizontal angle φ with respect to the vertical plane including the incident X-rays is measured to measure the a-axis of the polycrystalline thin film B or The orientation of the b-axes was measured. The results are shown in FIGS. 10 and 11.

As shown in FIG. 10, in the case of the sample manufactured by setting the incident angle of the ion beam at 55 degrees, no diffraction peak appears and φ is set to 90 degrees and 0 degrees, that is, the rotation angle. The YSZ (311) plane peak appears every 90 degrees with respect to φ. This corresponds to the (011) peak of YSZ in the substrate plane, and it was revealed that the a-axis or the b-axis of the YSZ polycrystalline thin film was oriented. On the other hand, as shown in FIG. 11, in the case of the sample manufactured with the ion beam incident angle set to 90 degrees, no special beak is observed and the directions of the a-axis and the b-axis are disordered. There was found.

From the above results, it has been clarified that the polycrystalline thin film of the sample manufactured by the above-mentioned apparatus has not only the c-axis orientation but also the a-axis and the b-axis orientations.
Therefore, it was revealed that a polycrystalline thin film such as YSZ having excellent orientation can be manufactured.

On the other hand, FIG. 12 shows the result of testing the crystal orientation in each crystal grain of the polycrystalline layer of this sample using the sample of the YSZ polycrystalline thin film used in FIG. In this test, when X-ray diffraction is performed by the method described with reference to FIG. 19, the diffraction peak is measured when the angle of φ is set to a value in steps of 5 degrees from −10 degrees to 45 degrees. . From the results shown in FIG. 12, it is clear that the diffraction peak of the obtained YSZ polycrystalline thin film appears within the grain boundary tilt angle of 30 degrees, but disappears at 45 degrees. Therefore, it was found that the grain boundary tilt angle of the crystal grains of the obtained polycrystalline thin film was within 30 degrees, and it was revealed that the polycrystalline thin film had a good orientation.

Next, the ion beam voltage was set to 300 V, the ion beam current density was set to 40 μA / cm ^{2, the} ion beam energy was set to 300 eV, and the incident angle of the ion beam was changed from 0 ° to 65 °. 3 shows the relationship between the incident angle and the full width at half maximum in the distribution of the crystals of the obtained polycrystalline thin film in the (111) direction.
The above full width at half maximum is shown in FIG.
Fig. 7 is obtained from the center of this pole figure.
When the auxiliary lines e and f as shown in (3) are drawn, the angle is determined by half the angle α formed by these auxiliary lines e and f, that is, the peak ratio. From the results shown in FIG. 13, it has been clarified that the crystal orientation becomes good when the incident angle of the ion beam is in the range of 50 to 60 degrees. Further, in particular, by setting the incident angle of the ion beam to 55 to 60 degrees, the grain boundary tilt angle becomes 2
It was also revealed that the minimum value can be set to about 5 degrees.

Then, the focus of the laser light generated from the laser emitting device is adjusted to the second target 25b having the composition of Y _0.7 Ba _1.7 Cu _3.0 O _7-X, and the pressure inside the vapor deposition processing chamber 23a is adjusted to 200 mmTorr. Then, laser deposition was performed at 700 ° C. An Ar-F excimer laser having a wavelength of 193 nm was used as a laser for vapor deposition of the second target. As a result, an oxide superconducting layer having a thickness of 1.0 μm was formed.

The oxide superconducting conductor produced as described above was cooled, and the critical temperature and the critical current density were measured. As a result, the critical temperature = 90K and the critical current density = 500,000A.
/ Cm ^2, and it was confirmed that extremely excellent superconducting properties were exhibited.

The first target 25a and the second target 25b used in forming the polycrystalline thin film and the oxide superconducting material have long shapes as shown in FIG. 25a and the second target 25b are moved in translation in the direction of the arrow in the figure to change the irradiation position of the laser light for irradiating the target, thereby preventing local consumption of the target surface by the laser light and laser of the target. The energy density applied to the light irradiation surface can be kept constant, which allows stable release of target particles for a long time, stable film formation, and stable film quality over a large area. Obtainable.

[0058]

As described above, according to the method for producing an oxide superconducting conductor of the present invention, the first target containing the material forming the polycrystalline thin film is irradiated with the laser light emitted from the laser light source, and the first target is irradiated with the laser light. When depositing the fine particles scattered from one target on the base material film formation surface, by irradiating an ion beam from the oblique direction of the base material film formation surface, a polycrystalline thin film is formed on the base material surface and then oxidized. The second target containing the superconductor or its raw material is irradiated with laser light, and the fine particles scattered from the second target are deposited on the surface of the polycrystalline thin film to form the oxide superconducting layer. Therefore, in the method of the present invention, since the ions are simultaneously irradiated from the oblique direction as described above, the constituent particles are efficiently activated, resulting in the a-axis orientation in addition to the c-axis direction with respect to the surface of the substrate. Property and b-axis orientation are also improved. as a result,
Even with a polycrystalline thin film having a large number of crystal grain boundaries, it is possible to obtain a polycrystalline thin film having good a-axis orientation, b-axis orientation and c-axis orientation for each crystal grain.

In the method for producing an oxide superconducting conductor according to the present invention, since the polycrystalline thin film is formed by laser vapor deposition, the film forming rate is significantly improved and the ion beam is obliquely irradiated. By doing
A polycrystalline thin film having good crystal orientation can be formed. Then, by forming an oxide superconducting layer on such a polycrystalline thin film by a laser deposition method, it is possible to epitaxially grow the oxide superconducting layer, a high critical current density oxide superconducting layer with good crystal orientation. Can be formed.

Further, the irradiation angle of the ion beam is set to 50.
By setting it to -60 degrees, the crystal orientation can be adjusted more favorably, and a polycrystalline thin film having crystal orientation with a grain boundary tilt angle of 25 degrees or less can be obtained. In the polycrystalline thin film, diffraction peaks obtained by rotating the polycrystalline thin film appear every 90 degrees, so that the in-plane orientations of the crystal grains constituting the polycrystalline thin film in the a-axis and the b-axis are good, and Since the peak appears in the range of 0 to 30 degrees, it is also clear that the grain boundary tilt angle is 30 degrees.

Therefore, in the oxide superconducting conductor manufactured as described above, extremely excellent superconducting properties can be exhibited, and the polycrystalline thin film and the oxide superconducting layer constituting the oxide superconducting conductor are formed by laser. By using the vapor deposition method, the production efficiency of the oxide superconducting conductor can be remarkably improved. If the oxide superconducting layer is epitaxially grown on the polycrystalline thin film having good crystal orientation as described above, the oxide superconducting layer grows along the crystal of the polycrystalline thin film, and as a result, the oxide superconducting layer is also formed. Good a-axis orientation, b-axis orientation and c-axis orientation are obtained.

Further, elongated targets are used as the first target and the second target used in forming the polycrystalline thin film and the oxide superconducting layer, and the first target and the second target are indicated by arrows in the figure. By changing the irradiation position of the laser light for irradiating the target by translating in the direction, the local consumption of the target surface by the laser light is prevented and the energy density irradiated on the laser light irradiation surface of the target is changed. Can be kept constant,
As a result, stable release of target particles can be maintained for a long time, stable film formation is possible, and a film having a large area with stable quality can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus used for an embodiment method in the present invention.

FIG. 2 is a diagram showing an example of the ion source shown in FIG.

FIG. 3 is a diagram showing an oxide superconducting conductor formed of a polycrystalline thin film and an oxide superconducting layer formed by the method according to the embodiment of the present invention.

4 is an enlarged plan view showing crystal grains of the oxide superconducting layer shown in FIG. 3, the crystal axis direction thereof, and a grain boundary tilt angle.

FIG. 5 is a schematic configuration diagram showing an example of an apparatus used in the method of the embodiment of the present invention when a target having a long shape is used.

FIG. 6 shows an ion beam incident angle of 55 degrees, an ion beam voltage of 300 V, and an ion beam current density of 40 μA /
is a chart showing the X-ray diffraction pattern of the polycrystalline thin film produced in cm ^2.

FIG. 7 shows an ion beam incident angle of 55 degrees, an ion beam voltage of 300 V, and an ion beam current density of 40 μm /
It is a pole figure of a polycrystalline thin film produced in cm ^2.

FIG. 18 shows an ion beam incident angle of 90 degrees, an ion beam voltage of 700 V, and an ion beam current of 40 μm / c.
X-ray diffraction results of the polycrystalline thin film produced in m ² and 20 [mu] m / cm ² is a graph showing a.

FIG. 9 is a configuration diagram for explaining a test performed for examining the a-axis and b-axis orientation of a polycrystalline thin film.

FIG. 10 shows (31) of the produced polycrystalline thin film.
It is a graph which shows the diffraction peak of 1) surface.

FIG. 11 shows (31) of the manufactured polycrystalline thin film.
It is a graph which shows the diffraction peak of 1) surface.

FIG. 12 is a rotation angle 5 of the obtained polycrystalline thin film.
It is a graph which shows a diffraction peak for every degree.

FIG. 13 is a graph showing the relationship between the ion beam incident angle and the full width at half maximum of the obtained polycrystalline thin film.

FIG. 14 is a schematic configuration diagram showing a laser vapor deposition apparatus.

FIG. 15 is a schematic configuration diagram showing an apparatus for forming a polycrystalline thin film having good crystal orientation by irradiating the constituent particles punched from the turret by sputtering on the base material with an ion beam. is there.

FIG. 16 is a configuration diagram showing a polycrystalline thin film manufactured by a conventional apparatus.

[Explanation of symbols]

20 ... Substrate, 22 ... Ion gun, 24 ... Substrate holder, 2
5a ... first target, 25b ... second target, 32
... laser emitting device, 35 ... crystal grain, 36 ... crystal grain, 40
… Polycrystalline thin film, 50… Oxide superconducting layer, K, K ′… Grain boundary tilt angle, θ… Incident angle, φ… Rotation angle

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical indication location C30B 29/22 501 M 8216-4G (72) Inventor Kazunori Onabe 1-5-1 Kiba, Koto-ku, Tokyo Stocks Company Fujikura (72) Inventor Naohiro Futaki 1-5-1, Kiba, Koto-ku, Tokyo Stock Company Fujikura (72) Inventor Nobuyuki Tekata 1-5-1, Kiba, Koto-ku, Tokyo Stock Company Fujikura

Claims (6)

[Claims] 1. A surface of a target containing an oxide superconductor or a raw material thereof is irradiated with laser light to be scattered, and fine particles are deposited on the surface of a polycrystalline thin film formed on a base material film-forming surface to be oxidized. In the method for manufacturing an oxide superconducting conductor to form a superconducting layer, a first target containing a material forming a polycrystalline thin film is irradiated with laser light emitted from a laser light source, and fine particles scattered from the first target are scattered. When depositing on the base material film formation surface, a polycrystalline thin film is formed on the base material surface by irradiating an ion beam from an oblique direction of the base material film formation surface, and then an oxide superconductor or its raw material is included. A second target is irradiated with laser light, and fine particles scattered from the second target are deposited on the surface of the polycrystalline thin film to form an oxide superconducting layer. Manufacturing method. 2. A polycrystalline thin film or an oxide superconducting layer is formed by irradiating the surface of a substrate on which a film is formed with the ion beam according to claim 1 at an incident angle of 50 to 60 degrees from an oblique direction. A method of manufacturing an oxide superconducting conductor, comprising: 3. The method for producing an oxide superconducting conductor according to claim 1 or 2, wherein an inert gas ion or a mixed ion of an inert gas ion and an oxygen ion is used as an ion beam ion source. A method for producing a characteristic oxide superconducting conductor. 4. The method for producing an oxide superconductor according to claim 1, wherein a crystal of the oxide superconductor is epitaxially grown on a crystal of the polycrystalline thin film formed on the surface of the base material. A method for producing an oxide superconducting conductor, comprising: 5. A target used in the method for producing an oxide superconducting conductor according to claim 1, wherein the target has an elongated shape. Target for conductor production. 6. The target for producing an oxide superconducting conductor according to claim 5, is moved continuously or intermittently at a predetermined speed in its longitudinal direction, and the laser light irradiation position is moved continuously or intermittently. A method for producing an oxide superconducting conductor, comprising: