JP5292054B2 - Thin film laminate and manufacturing method thereof, oxide superconducting conductor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film laminate making an intermediate layer thinner and also facilitating the manufacture thereof, while maintaining high crystal orientation properties. <P>SOLUTION: The thin film laminate is formed by laminating: an intermediate layer 12 made of a material capable of forming crystal orientation in a range where a half width (&Delta;&phiv;) of crystal axis dispersion in a direction within a plane formed by an ion beam assist method (IBAD method) on a metal base 11 is from 11&deg; to 13&deg;; and a cap layer 13 having a fluorite crystal structure or the equivalent crystal structure directly formed on the intermediate layer by a film forming method and crystal orientation properties showing a &Delta;&phiv; of 8&deg; or below in a film thickness of 100 nm or above, which is better than the crystal orientation properties of the intermediate layer, and a &Delta;&phiv; of 5&deg; or below in a film thickness of 300 nm or above. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a thin film laminate and a manufacturing method thereof, and an oxide superconducting conductor and a manufacturing method thereof. More specifically, the present invention maintains good crystal orientation even if the number of layers is reduced and the thickness of each layer is reduced. In addition, the present invention relates to a technique that can improve manufacturing efficiency.

The RE-123 oxide superconductor discovered recently (REBa ₂ Cu ₃ O _{7-X, where} RE is a rare earth element including Y) is extremely promising in practice because it exhibits superconductivity above liquid nitrogen temperature. There is a strong demand for processing this into a wire and using it as a conductor for power supply.
In order to obtain this kind of oxide superconductor, YSZ (yttria-stabilized zirconia) in which physical characteristic values such as thermal expansion coefficient and lattice constant are intermediate values between the substrate and the superconductor on the metal substrate. ), An intermediate layer (buffer layer) made of a material such as SrTiO ₃ or MgO is formed, and an oxide superconducting layer is formed on the intermediate layer.
However, in the intermediate layer obtained on the substrate by a general film forming method, when the a-axis, b-axis, and c-axis constituting the crystal are individually viewed, the c-axis is oriented perpendicular to the substrate surface. However, since the a-axis (or b-axis) is not aligned in the same direction in the substrate plane, the oxide superconducting layer formed thereon also has the a-axis (or b-axis) in the same direction. There was a problem that the in-plane orientation was not achieved, and as a result, the critical current density Jc was not improved.

Conventionally, as a method for controlling crystal orientation, a Rabits method (Rolling Assisted Biaxially textured substrate) and an ion beam assisted method (IBAD method: IBAD method) are known. Yes.
The ion beam assist method is a powerful technique for solving the problem of crystal orientation. Argon ions and oxygen ions generated from an ion gun are deposited when depositing constituent particles knocked out of a target by sputtering. Etc. are simultaneously deposited in an oblique direction (for example, 45 ° or 55 ° with respect to the substrate normal), and according to this method, a high c-axis orientation is formed with respect to the film formation surface on the substrate. And an intermediate layer having a-axis in-plane orientation can be obtained.
8 and 9 show an example in which a polycrystalline thin film forming an intermediate layer is formed on a substrate by the IBAD method. In FIG. 8, 100 is a plate-like substrate, and 110 is a substrate 100. The intermediate | middle layer formed in the upper surface is shown.
The intermediate layer 110 is an aggregate of fine crystal grains 120, and the c-axis of the crystal axis of each crystal grain 120 is oriented perpendicular to the upper surface (film formation surface) of the substrate 100. The crystal axes a-axis and b-axis are oriented in the same direction in the same direction. The orientations of the a-axes (or b-axes) of the crystal grains 120 are controlled so that the angle between them (the grain boundary tilt angle K shown in FIG. 7) is within 30 degrees.

The IBAD method is said to be a highly practical production method, such as excellent mechanical properties of the wire and easy to obtain stable high properties. Conventionally, an intermediate layer formed by the IBAD method (hereinafter, referred to as IBAD method) "IBAD intermediate layer") was said to have no good orientation without a film thickness of about 1000 nm. On the other hand, because the crystal orientation is controlled by ion beam bombardment on non-oriented metal tape, the IBAD method has a slow film formation speed of about 3 nm / min. there were.
As a method for solving these problems, an oxide having a fluorite crystal structure such as YSZ or Gd ₂ Zr ₂ O ₇ (hereinafter abbreviated as GZO) or an oxide having a rock salt crystal structure such as MgO is used. Development research is being actively pursued. Further, among these, oxides having a rock salt crystal structure are different from oxides having a fluorite crystal structure such as YSZ and GZO, and even a thin film structure in which a third layer is interposed is sufficient. Various research and developments have been made due to its orientation.

When an oxide having a fluorite crystal structure such as GZO is used, a laminated structure of IBAD-GZO layer / CeO ₂ layer / superconducting layer is studied. When an oxide having a rock salt crystal structure such as MgO is used, IBAD- Laminated structure of MgO layer / epitaxially grown MgO layer / LaMnO ₃ layer / superconducting layer, laminated structure of IBAD-MgO layer / LaMnO ₃ / superconducting layer, laminated structure of IBAD-MgO layer / LaMnO ₃ layer / CeO ₂ layer / superconducting layer It has been studied.
For example, Patent Document 1 discloses forming a CeO ₂ cap layer having a thickness of 50 nm or more after forming an intermediate layer having a thickness of 2000 nm or less on a metal substrate. Discloses a structure in which a GZO film and a CeO ₂ layer are stacked on a Hastelloy metal substrate.
Patent Document 2 discloses a structure in which an HfO layer or an HfO layer containing any one of CeO ₂ , Y ₂ O ₃ , LaO, ScO, CaO, and MgO is stacked on an IBAD-MgO layer / epitaxially grown MgO layer. ing.

In Patent Document 3, CeB ₂ , YSZ, SrTiO ₃ , SrRuO ₃ , LaMnO ₃ , Y ₂ O ₃ , Eu ₂ CuO ₄ , Nd ₂ CuO ₄ , Y ₂ CuO are formed on the IBAD-MgO layer / epitaxially grown MgO layer. ₄ , RE ₂ CuO _{4 and the} like are written in parallel.
Patent Document 4 discloses a laminated structure of IBAD-MgO layer / YSZ layer / CeO ₂ layer, and Patent Document 5 discloses a laminated structure of IBAD-MgO layer / SrRuO ₃ layer / CeO ₂ layer. Documents 6 and 7 disclose a laminated structure of IBAD-MgO layer / YSZ layer / CeO ₂ layer, and Patent Document 8 discloses a laminated structure of IBAD-MgO layer / Ln layer MnO ₃ layer / CeO ₂ layer. Has been.
Further, in Non-Patent Document 1, when a CeO ₂ layer is formed on a single crystal MgO, the crystallinity is better when a film such as BaSnO ₃ is interposed between the MgO and the CeO ₂ layer. Non-Patent Document 2 discloses a laminated structure of IBAD-MgO layer / LaMnO ₃ layer / CeO ₂ layer / superconducting layer.
Japanese Patent No. 3854551 US Pat. No. 7,258,927 US Pat. No. 6,921,741 US Pat. No. 6,843,898 US Pat. No. 6,800,701 US Pat. No. 6,716,545 US Pat. No. 6312819 M.Mukaida et al. “Hetero-Epitaxial Growth of CeO2 Film on MgO Substrates” JJAP vol.44 No.10 (2005) ppL318-321 Proceedings of the 2008 Spring Cryogenic Engineering Society pp.109-112

However, in the former technique using an oxide having a fluorite crystal structure, the laminated structure is simple, the film forming conditions are wide, and the lengthening has been advanced, but it is necessary to increase the thickness of the intermediate layer. In addition, the production rate is slow, and the internal stress of the film increases, causing the substrate to warp.
In addition, the latter method using an oxide having a rock salt crystal structure is expected to drastically solve the above-mentioned problem, but these methods are disclosed in the above-mentioned patent document, Because it is a method of laminating a number of very thin films of several tens of nanometers or less, it requires a lot of know-how to maintain the same narrow film formation conditions over a long length, resulting in poor production efficiency and high production costs. There was a problem.

The present invention has been devised in view of such conventional circumstances, and provides a thin film laminate that can be manufactured easily while reducing the thickness of the intermediate layer while maintaining good crystal orientation. This is one purpose.
In addition, the present invention provides an oxide that has a good crystal orientation, a thin intermediate layer, is easy to manufacture, is excellent in productivity, has a good crystal orientation, a high critical current density, and a good superconducting property. Another object is to provide a superconducting conductor.

In order to solve the above-mentioned problems, the present invention has a crystal orientation of 15 ° or less on a half-value width (Δφ) of crystal axis dispersion in an in-plane direction formed by an ion beam cyst method (IBAD method) on a metal substrate. An intermediate layer made of MgO having a film thickness of 50 nm or less, and a cap layer having a film thickness of 100 nm or more and 600 nm or less of a fluorite-based crystal structure formed directly on the intermediate layer by a film forming method. When the film thickness is less than that, the crystal orientation is Δφ = 8 ° or less , which is superior to the crystal orientation of the intermediate layer , and when the film thickness is 300 nm or more and 600 nm or less, Δφ = 5 ° or less. A cap layer made of CeO ₂ is laminated.

In the present invention, it may be characterized in that the thickness of the cap layer is formed by a [Delta] [phi = 5 ° or less in the 3 range of less than 00nm over 100 nm.
In the present invention, the intermediate layer may have a thickness of 5 to 10 nm.
In the present invention, the MgO (200) plane of the intermediate layer and the CeO ₂ (200) plane of the cap layer may be shared.
The oxide superconductor of the present invention has a RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-x : RE is Y, La, It is characterized in that an oxide superconducting layer made of Nd, Sm, Eu, or Gd) is laminated.

The method for producing a thin film laminate of the present invention is a thin film laminate in which an intermediate layer and a cap layer are laminated on a metal substrate, and an oxide superconducting layer is laminated on the cap layer to form an oxide superconducting conductor. In this manufacturing method, a metal substrate is made of MgO having a film thickness of 50 nm or less that is crystal-oriented to 15 ° or less in the half-value width (Δφ) of crystal axis dispersion in the in-plane direction by an ion beam assist method (IBAD method). An intermediate layer is formed, and thereafter, a cap layer having a fluorite-based crystal structure and having a thickness of 100 nm to 600 nm and having a thickness of 100 nm to less than 300 nm is superior to the crystal orientation of the intermediate layer. = 8 ° or less in crystal orientation becomes and the intermediate cap layer composed of CeO ₂ in a self-aligned so that the following crystalline orientation [Delta] [phi = 5 ° in the film thickness of at least 600nm or less 300nm And forming by directly film-forming method above.

Method of manufacturing a thin film laminate of the present invention is characterized by the following [Delta] [phi = 5 ° in a range thickness of less than 3 00nm or 100nm of the cap layer.
The method for producing a thin film laminate of the present invention is characterized in that the thickness of the intermediate layer is 5 to 10 nm.
The method for producing a thin film laminate of the present invention is characterized in that the CeO ₂ cap layer is crystal-grown on the intermediate layer made of MgO while sharing the MgO (200) plane and the CeO ₂ (200) plane. To do.
In the method for producing an oxide superconductor of the present invention, a thin film laminate is produced by any one of the production methods described above, and then an RE-123 oxide superconductor (REBa) is formed on the cap layer of the thin film laminate. ₂ Cu ₃ O _7-x : RE is characterized by stacking an oxide superconducting layer made of a rare earth element of any one of Y, La, Nd, Sm, Eu, and Gd.

An intermediate layer made of MgO having a film thickness of 50 nm or less with an in-plane direction crystal axis dispersion half width Δφ of 15 ° or less by a IBAD method on a metal substrate, and 100 nm directly formed on the intermediate layer by a film forming method above 600nm a capping layer of less thickness, the film thickness of less than 100 nm 300nm is less and Do that crystal orientation [Delta] [phi = 8 °, and, [Delta] [phi = 5 DEG at 600nm following thickness above 300nm since it follows and the cap layer composed of CeO ₂ fluorite type crystal structure formed are laminated, and the intermediate layer due been provided conventionally IBAD method, an epitaxial growth MgO layer, a further cap layer via a LaMnO ₃ layer Compared to the thin film stack with a structure of three or more layers provided, the cap layer Δφ = 8 ° or less, or Δφ = 5 ° or less depending on the film thickness range in the two-layer structure of the intermediate layer and the cap layer A thin film laminate can be provided.
Moreover, when compared with the conventional structure of the layer structure of the IBAD-GZO layer / CeO ₂ layer, an intermediate layer consisting of thickness 50nm following MgO, 100 nm or more 600nm or less, or, in the film thickness range of 300nm or more 600nm or less [Delta] [phi = 8 ° or less, or, [Delta] [phi = the two-layer structure of a combination of 5 degrees comprising the following CeO ₂ cap layer, realizing a conventional structure a thinner laminated structure excellent crystal orientation of the thin film stack it can.

In addition, as described above, the RE-123 oxide superconducting layer (REBa ₂ Cu ₃ O _7-x : RE is Y, La, Nd, Sm, Eu, Gd on the cap layer of the thin film laminated body thinner than the conventional one. stacking one of rare earth elements) of a good crystal orientation, there is an effect that can be provided at low cost thin oxide superconductor having excellent superconducting properties.

<First embodiment>
FIG. 1 is a diagram schematically showing an embodiment of a thin film laminate 10 according to the present invention.
In this embodiment, a thin film laminate 10 is formed by sequentially laminating an intermediate layer 12 whose crystal orientation is controlled by an IBAD method and a cap layer 13 formed directly by a film forming method on a tape-like metal substrate 11. Configured. Then, an oxide superconducting conductor 16 is formed by laminating an oxide superconducting layer 15 on the cap layer 13 of the thin film laminate 10 having this structure as shown in FIG.

  In the thin film laminate 10, the metal substrate 11 is a tape-like material in the present embodiment, but is not limited to this, and for example, a metal substrate 11 having various shapes such as a plate material, a wire material, and a strip is used. Examples thereof include various metal materials such as silver, platinum, stainless steel, copper, nickel alloys such as Hastelloy, and various ceramic materials arranged on various metal materials.

Materials constituting the intermediate layer 12 that can be controlled in orientation by the IBAD method applied in the present embodiment are MgO, NiO, CoO, FeO, MnO, CdO, CaO, SrO, BaO, CrN, TiN, HfN, ZrN, YbN, One of DyN, CeN, LaN, SrN, SnO ₂ and TiO ₂ is preferable, and among these, MgO is preferable.
In the present embodiment, the material constituting the cap layer 13 having a fluorite system and a crystal structure conforming thereto is preferably CeO ₂ or PrO ₂ , and among these, CeO ₂ is preferable.

Further, in the intermediate layer 12 made of MgO having a rock salt crystal structure formed by the IBAD method, the half-value width (Δφ) of crystal axis dispersion in the in-plane direction is 15 ° or less, for example, a range of 4 ° to 15 °. As an example, it is made of a material capable of crystal orientation in the range of 11 to 13 °. Here, when the a-axis, b-axis, and c-axis constituting the rock salt-based crystal structure of the intermediate layer 12 are individually viewed, the c-axis is oriented at right angles to the film formation surface of the substrate 11, and within the film formation surface. The a-axis (or b-axis) is oriented in-plane in substantially the same direction (in-plane direction crystal axis dispersion half width Δφ is 15 ° or less, for example, in the range of 11 to 13 °).
The film thickness of the intermediate layer 12 by this IBAD method is less than 100 nm, preferably 50 nm or less, more preferably 30 nm or less. This is because in the case of the MgO intermediate layer 12, the orientation starts to deteriorate when the film thickness exceeds 20 to 30 nm.
The cap layer 13 formed directly on the intermediate layer 12 and having a crystal structure according to the fluorite system has a film thickness of 100 nm or more and is superior to the crystal orientation of the intermediate layer by Δφ = 8 °. The crystal orientation is obtained as follows: Δφ = 5 ° or less, more preferably 4 ° or less, with a film thickness of 300 nm or more to 1300 nm.

When the oxide superconducting layer (for example, YBCO) 15 is formed on the cap layer 13 having a crystal orientation of Δφ = 8 ° or less or Δφ = 5 ° or less by a film forming method such as laser deposition, Good orientation and high characteristics can be obtained in the oxide superconducting layer 15, and a stable yield can be obtained.
When configuring the cap layer 13 in CeO ₂ layer, the CeO ₂ layer, all need not consist of CeO _2, Ce-M- some Ce has substituted with other metal atoms or metal ions An O-based oxide may be included. The CeO ₂ layer can be formed by a PLD method (pulse laser deposition method), a sputtering method, or the like, but it is desirable to use the PLD method from the viewpoint of obtaining a high film formation rate. As conditions for forming the CeO ₂ layer by the PLD method, a laser energy density of 1 to 5 J / cm ² can be performed in an oxygen gas atmosphere at a substrate temperature of about 500 to 900 ° C. and about 0.6 to 40 Pa. .

The film thickness of the CeO ₂ layer may be 50 nm or more, but is preferably 100 nm or more for obtaining sufficient orientation (for example, Δφ = 8 ° or less), more preferably 300 nm or more. If the film thickness is increased more than necessary, the film formation time will increase, so that the film thickness is preferably 600 nm or less.

As a material for the oxide superconducting layer 15, an RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-X : RE is a rare earth element such as Y, La, Nd, Sm, Eu, Gd) is used. it can. Preferred as the RE-123 oxide superconductor is Y123 (YBa ₂ Cu ₃ O _7-X : hereinafter referred to as “YBCO”) or Sm123 (SmBa ₂ Cu ₃ O _7-X) and hereinafter referred to as “SmBCO”. .)

Although the oxide superconducting layer 15 can be formed by a normal film forming method, from the viewpoint of productivity, the TFA-MOD method (organic metal deposition method using trifluoroacetate, coating pyrolysis method), PLD method or CVD method is preferably used.
The MOD method is a method in which a metal organic acid salt is applied and then thermally decomposed. After a solution in which a metal component organic compound is uniformly dissolved is applied on a substrate, the substrate is heated and thermally decomposed. This is a method of forming a thin film on top, and is suitable for the production of a long tape-shaped oxide superconducting conductor because it does not require a vacuum process and enables high-speed film formation at low cost.

  Here, as described above, when the oxide superconducting layer 15 is formed on the cap layer 13 having good orientation, the oxide superconducting layer 15 laminated on the cap layer 13 also has the crystal orientation of the cap layer 13. Crystallization is performed so as to exhibit a higher degree of crystal orientation by matching and self-alignment matching phenomenon. Therefore, the oxide superconducting layer 15 formed on the cap layer 13 is hardly disturbed in crystal orientation, and in each of the crystal grains constituting the oxide superconducting layer 15, The c-axis that hardly allows electricity to flow in the thickness direction is oriented, and the a-axis or the b-axis is oriented in the length direction of the metal substrate 11. Therefore, the obtained oxide superconducting layer 15 is excellent in quantum connectivity at the crystal grain boundary, and hardly deteriorates in the superconducting characteristics at the crystal grain boundary. A sufficiently high critical current density is obtained.

As described above, in the structure of the present embodiment, in the thin film stack 10, the Δφ indicating the degree of crystal orientation is set to 15 ° or less, for example, 11 to 13 ° by the film forming method on the intermediate layer 12 of the IBAD method. By laminating the cap layer 13 having a thickness of 100 nm or more and Δφ of 8 ° or less, the cap layer 13 having good orientation can be formed thinner.
Further, in contrast to the intermediate layer made of GZO having a fluorite structure that conventionally required a thickness of 1000 nm or more, the intermediate layer 12 having Δφ of 11 to 13 ° and the fluorite-based crystal structure have a thickness of 100 nm or more. By laminating the cap layer 13 having a thickness of Δφ8 ° or less, the thin film laminate 10 having good crystal orientation can be formed thinner, so that the internal stress of the film including the intermediate layer 12 and the cap layer 13 can be reduced. It can reduce, and the curvature of the metal base material 11 can be prevented.

As mentioned above, although the thin film laminated body and oxide superconducting conductor of this embodiment were demonstrated, this invention is not limited to this, It can change suitably as needed.
For example, in the present embodiment, the case where the thin film stack 10 is applied to the oxide superconductor 16 has been described. However, the present invention is not limited to this, and the thin film stack 10 of the present invention can be used as an optical thin film or a magnetic thin film of a magneto-optical disk. It can be applied to any of thin films for fine wiring for integrated circuits, dielectric thin films used for high-frequency waveguides, high-frequency filters, cavity resonators, and the like.

That is, if these thin films are formed on the thin film laminate 10 having good crystal orientation by a film forming method such as sputtering, laser vapor deposition, vacuum vapor deposition, CVD (chemical vapor deposition), etc., the thin film laminate 10 is good. Because these thin films are deposited or grown with consistency, the orientation is good.
These thin films provide high-quality thin films with good orientation, so optical films are excellent in optical characteristics, magnetic films are excellent in magnetic characteristics, and wiring thin films are free from migration. Can provide a thin film with good dielectric properties.

First, a film forming apparatus for carrying out the IBAD method used in this embodiment will be described.
FIG. 3 shows an example of an apparatus for manufacturing a thin film laminate by performing the IBAD method. The apparatus of this example has a configuration in which an ion gun for ion beam assist is provided in a sputtering apparatus. .
The film forming apparatus includes a base material holder 51 that holds the base material A horizontally, a plate-like target 52 that is disposed diagonally above the base material holder 51 at a predetermined interval, and an oblique position of the base material holder 51. It is mainly configured by an ion gun 53 that is opposed to the upper side at a predetermined interval and is spaced apart from the target 52, and a sputter beam irradiation device 54 that is disposed below the target 52 and toward the lower surface of the target 52. Yes. Reference numeral 55 in the drawing denotes a target holder that holds the target 52.
The apparatus is housed in a vacuum container (not shown) so that the periphery of the substrate A can be maintained in a vacuum atmosphere. Further, an atmospheric gas supply source such as a gas cylinder is connected to the vacuum container, the inside of the vacuum container is in a low pressure state such as a vacuum, and an inert gas containing argon gas or other inert gas atmosphere or oxygen The atmosphere can be changed.

When a long metal tape is used as the base material A, a metal tape feeding device and a winding device are provided inside the vacuum container, and the base material A is continuously fed from the feeding device to the base material holder 51. Subsequently, it is preferable that the polycrystalline thin film be continuously formed on the tape-shaped substrate by winding with a winding device.
The base material holder 51 includes a heater inside, and the base material A positioned on the base material holder 51 can be heated to a desired temperature. In addition, an angle adjustment mechanism that can adjust the horizontal angle of the substrate holder 51 is attached to the bottom of the substrate holder 51. An angle adjustment mechanism may be attached to the ion gun 53 to adjust the tilt angle of the ion gun 53 to adjust the ion irradiation angle.

The target 52 is used to form the target thin film stack 10, and has the same composition as the intermediate layer 12 or the cap layer 13 of the target thin film stack 10 or a similar composition. Specifically, when the MgO intermediate layer 12 is formed as the target 52, MgO, Mg, or the like is used. However, the present invention is not limited to this, and a target corresponding to the intermediate layer 12 to be formed may be used. Also, when forming a CeO ₂ layer as a cap layer 13 using a CeO ₂ or Ce, the oxygen gas may be deposited by supplying a deposition atmosphere as required.
The ion gun 53 is configured such that a gas to be ionized is introduced into a container and a lead electrode is provided on the front surface. And it is an apparatus which ionizes one part of the atom or molecule | numerator of gas, and irradiates the ionized particle | grain as an ion beam controlled by the electric field generated with the extraction electrode. There are various types of ionization of gas, such as a high frequency excitation method and a filament type. The filament type is a method in which a tungsten filament is energized and heated to generate thermoelectrons and collide with gas molecules in a high vacuum to be ionized. The high-frequency excitation method ionizes gas molecules in a high vacuum by polarization with a high-frequency electric field.
In this embodiment, for example, an ion gun 53 having an internal structure shown in FIG. 4 is used. The ion gun 53 includes an extraction electrode 57, a filament 58, and an introduction tube 59 for Ar gas or the like inside a cylindrical container 56, and can irradiate ions in parallel in a beam shape from the tip of the container 56. It is.

As shown in FIG. 3, the ion gun 53 is opposed to the upper surface (film formation surface) of the substrate A with an inclination angle θ. The inclination angle θ is preferably in the range of 30 to 60 degrees, but in the case of MgO, around 45 degrees is particularly preferable. Accordingly, the ion gun 53 is arranged so as to irradiate ions with an inclination angle θ with respect to the upper surface of the substrate A. The ions irradiated onto the substrate A by the ion gun 53 may be ions of rare gases such as He ⁺ , Ne ⁺ , Ar ⁺ , Xe ⁺ , Kr ⁺ , or mixed ions of these and oxygen ions.
The sputter beam irradiation device 54 has the same configuration as that of the ion gun 53, and can irradiate ions on the target 52 to knock out the constituent particles of the target 52. In the device of the present invention, since it is important that the constituent particles of the target 53 can be knocked out, a voltage is applied to the target 52 with a high frequency coil or the like so that the constituent particles of the target 52 can be knocked out. The sputter beam irradiation device 54 may be omitted.

Next, the case where a polycrystalline thin film is formed on the base material A using the apparatus having the above configuration will be described.
In order to form a polycrystalline thin film on the substrate A, a predetermined target is used, and the angle adjustment mechanism is adjusted to irradiate the upper surface of the substrate holder 51 with ions irradiated from the ion gun 53 at an angle of about 45 degrees. It can be so. Next, the inside of the container containing the substrate is evacuated to form a reduced pressure atmosphere. Then, the ion gun 53 and the sputter beam irradiation device 54 are operated.

  When the target 52 is irradiated with ions from the sputter beam irradiation device 54, the constituent particles of the target 52 are knocked out and fly onto the substrate A. Then, the constituent particles knocked out from the target 52 are deposited on the substrate A, and at the same time, a mixed ion of Ar ions and oxygen ions is irradiated from the ion gun 53. For example, when forming MgO, the irradiation angle θ at the time of ion irradiation is preferably about 45 °.

"Production Example 1"
As the metal substrate, a 10 mm wide Hastelloy tape whose surface was polished was used. On this metal substrate, an MgO film (about 5 to 10 nm) was formed as an intermediate layer by the IBAD method.
At this time, the MgO film was produced while performing ion beam assist with a rare gas ion beam of Ar or the like at a substrate temperature of 200 ° C. or lower.
Furthermore, a CeO ₂ film (film thickness: 600 nm) was laminated on the MgO film by the PLD method (pulse laser deposition method). The half width (Δφ) of crystal axis dispersion in the in-plane direction was measured for the MgO film and CeO ₂ film thus obtained. The results are shown in Table 1 below.
Next, for comparison, a thin film stack sample in which a LaMnO ₃ film (film thickness 100 nm) is formed on an MgO film formed on a metal substrate under the same conditions as described above is manufactured. A thin film stack sample in which a CeO ₂ film (600 nm in thickness) is formed on a body sample is manufactured, and the in-plane direction crystal axis dispersion half width Δφ of the MgO film and the in-plane direction crystal of the LaMnO ₃ film in each sample The axial dispersion half-value width Δφ and the in-plane crystal axis dispersion half-value width Δφ of the CeO ₂ film were measured. The results are summarized in Table 1 below.

"Table 1"
Sample IBAD-MgO (Δφ) LaMnO ₃ film (Δφ) CeO ₂ film (Δφ)
1 11.3 to 12.7 12.6 to 12.7-
2 11.3 to 12.7 12.6 to 12.7 4.9
3 11.3 to 12.7-4.6

As shown in Table 1, in the structure of Sample 1, when the LaMnO ₃ film was formed, only a crystal orientation in a substantially equivalent range according to the crystal orientation of IBAD-MgO was obtained. Therefore, it can be seen that in this laminated structure, it is impossible to improve the orientation of the LaMnO ₃ film unless the crystal orientation of IBAD-MgO itself is improved.
In the structure of Sample 2, it is clear that the CeO ₂ film on the LaMnO ₃ film exhibits a self-alignment effect, and the in-plane orientation is better than the underlying LaMnO ₃ film.
For these, the structure of the sample 3, without forming a LaMnO ₃ film, comparable to the case of forming a CeO ₂ film is LaMnO ₃ film, or more superior plane oriented crystal orientation It can be seen that the self-orientation effect is expressed. The structure of Sample 3 has a great merit in terms of manufacturing cost because the LaMnO ₃ film forming step is eliminated.
In order to obtain an oxide superconducting layer having high characteristics in critical current characteristics, etc., in the crystal orientation of the cap layer, the c-axis of the superconducting layer is oriented perpendicular to the substrate, and the half width of the in-plane crystal axis Must be within 10 degrees.

"Production Example 2"
For comparison, a plurality of substrates were prepared by depositing Gd ₂ Zr ₂ O ₇ films (GZO films) with various film thicknesses on the Hastelloy tape equivalent to the previous example by the IBAD method. On top of this, a CeO ₂ layer was deposited by a thickness of 500 nm by the PLD method. The CeO ₂ layer was deposited by the PLD method in an O ₂ gas atmosphere at a temperature of about 650 ° C. and a pressure of about 4 Pa under the conditions of a laser density of 3 J / cm ² and a laser frequency of 17 Hz. First, a 3 cm diameter pellet of CeO ₂ was attached to a vacuum chamber, which was evacuated, and then the O ₂ gas was flowed to adjust the pressure. A KrF excimer laser was irradiated onto the pellet, thereby depositing a CeO ₂ layer on the IBAD substrate placed opposite the pellet. The YBCO superconductor film was formed with a thickness of 250 nm by the TFA-MOD method (organic metal deposition method using trifluoroacetate, coating pyrolysis method).

FIG. 5 shows the value of ΔΦ of each CeO ₂ film with respect to the thicknesses of 20 types, 50 nm, 100 nm, 300 nm, 600 nm, 1000 nm, 300 nm, 5000 nm, and 7000 nm of nine types of CeO ₂ films. The smaller the value of ΔΦ is, the better the crystal orientation is. However, according to the result shown in FIG. 5, the crystal orientation becomes slightly worse at 7000 nm (that is, exceeding 5000 nm). In the thickness range of 100 to 5000 nm, ΔΦ is smaller than 10 degrees. A YBCO of the superconducting layer was formed on this sample by the TFA-MOD method in the same manner as in Example 1 and the critical current was measured. At 77 K and 0 T, the CeO ₂ film thickness was 50 nm to 7000 nm and 1 MA / cm. ² or more Jc is obtained, especially in between 100nm~5000nm obtained 2 MA / cm ² or more Jc, high critical current density 3 MA / cm ² at maximum was obtained.
As can be seen from the results shown in FIG. 5, when a CeO ₂ film is laminated on a GZO film to form an intermediate layer and a cap layer, the orientation is good according to the film thickness of the CeO ₂ film.

"Production Example 3"
Instead of the plurality of base materials on which the GZO film was formed, a plurality of base materials using the MgO film used in the previous Production Example 1 were used, and a CeO ₂ film was formed on the base material by a PLD method to a thickness of 300 nm. FIG. 6 shows the result of measuring the in-plane orientation Δφ of the MgO film by preparing a plurality of thin film laminates formed at 600 nm, 900 nm, and 1300 nm, respectively. FIG. 6 shows comparison with the in-plane orientation of the CeO ₂ film on the GZO film shown in FIG.
Further, FIG. 7 shows the results of measuring the in-plane orientation of the CeO ₂ film on the MgO film according to the thickness of the film. In addition, since it is difficult to accurately obtain the surface information of the CeO ₂ film in the X-ray measurement at an extremely thin film thickness, a GdBCO film (thickness 1000 nm) is formed on the CeO ₂ film, and the in-plane orientation state thereof By measuring the orientation of the surface of the CeO ₂ film.

From the results shown in FIGS. 6 and 7, it can be seen from the data of CeO ₂ film / MgO that the orientation of the CeO ₂ film is not completed with a film thickness of about 200 nm, but the GdBCO film formed on the CeO ₂ film When the orientation state is observed, it can be seen that the crystal orientation of the CeO ₂ film has already been completed at a film thickness of about 100 nm.
Thereby, compared with the data of the previous manufacturing example 2, that is, compared with the case where the CeO ₂ film is laminated on the GZO film to form the intermediate layer and the cap layer, the CeO ₂ film is laminated on the MgO film. In the case of using the intermediate layer and the cap layer, it is clear that the crystal orientation has been completed with a thinner film thickness, and a structure in which the CeO ₂ film is directly laminated on the MgO film constitutes the cap layer. The advantage of is clear.

  As described above, it was confirmed that the polycrystalline thin film produced in Production Examples 1 and 3 can achieve a level of Δψ superior to the conventional one with a laminated structure of an intermediate layer and a cap layer thinner than the conventional one. That is, according to the configuration of the present invention, the intermediate layer and the cap layer forming the thin film stack can be thinned, so that the internal stress of the film is reduced and the conventional problem of the substrate warping is solved. can do. Furthermore, since the film thickness of the intermediate layer and the cap layer is reduced, the manufacturing speed can be dramatically increased, and the manufacturing cost can be reduced.

Further, a GdBCO superconducting layer was formed to a thickness of 1000 nm by the PLD method on the CeO ₂ film having a thickness of 400 nm. This GdBCO superconducting layer is heat-treated in an oxygen atmosphere at 500 ° C. for 5 hours after film formation. As a result of evaluating the characteristics, it was confirmed that high characteristics of critical current density Jc = 3.6 MA / cm ² and critical current Ic = 360 A were obtained at the liquid nitrogen temperature.

Next, when various MgO substrates having different Δφ are prepared and a CeO ₂ film (film thickness of 300 nm) is formed on the substrates by the PLD method, the value of Δφ obtained according to the orientation degree Δφ of the MgO substrate is It is shown in Table 2 below.
"Table 2"
Δφ (MgO substrate) Δφ (CeO ₂ film)
Sample A -20 ° -7 °
Sample B ~ 15 ° ~ 5 °
Sample C -10 ° to 4 °
Sample D-8 °-3 °
Sample E-6 °-2 °
Sample F -4 ° -1 °
As a result shown in Table 2, it is possible to adopt a value of 15 ° or less as a guide when a CeO ₂ film is formed on an MgO substrate. One object of the present invention is to obtain an excellent oxide superconducting conductor. In that case, an excellent oxide superconducting layer can be formed when the Δφ of the CeO ₂ film as the base is about 5 ° or less. Therefore, in that case, it is considered that Δφ of the MgO film is preferably 15 ° or less.

In addition, considering the contrast between the laminated structure of the IBAD method MgO film + CeO ₂ film used in the present invention and the conventionally known IBAD method GZO film + CeO ₂ film, the GZO (222) plane is related to GZO and CeO _2. The crystal growth is carried out sharing the CeO ₂ (111) plane, and the lattice constant mismatch is about 3.1%. On the other hand, as a result of the analysis of the above-mentioned sample, regarding MgO and CeO ₂ , crystal growth sharing the MgO (200) plane and CeO ₂ (200) plane is observed, and the lattice constant is very far from 28.5%. Yes. This seems to be the reason why CeO ₂ on MgO grows by a different mechanism as compared with CeO ₂ on GZO and shows high orientation as a thin film. Thus, when a CeO ₂ film was formed directly on a thin MgO film by the IBAD method, it was found for the first time by this test that CeO ₂ self-mixed and showed a Δψ of 10 ° or less. The result is that a thin CeO ₂ film is laminated on a thin MgO film, and an oxide superconducting layer is laminated thereon, so that an excellent oxide superconducting conductor can be obtained. In the technical field of superconducting conductors that have problems to be solved, it is possible to obtain extremely excellent effects.

It is a figure which shows typically an example of the thin film laminated body which concerns on this invention. It is a figure which shows typically an example of the oxide superconducting conductor which concerns on this invention. It is a figure which shows typically the film-forming apparatus by IBAD method. It is a figure which shows typically the ion gun with which the film-forming apparatus shown in FIG. 3 is provided. Is a diagram showing an in-plane orientation in accordance with the thickness of the IBAD method GZO film of CeO ₂ film produced in Production Example. Figure comparatively showing fabricated IBAD method MgO film of CeO ₂ plane orientation in accordance with the thickness of film and IBAD method GZO film thickness in-plane orientation in accordance with the CeO ₂ film on the film in the manufacturing example It is. A plane orientation according to the thickness of the CeO ₂ layer on the IBAD method MgO film produced in Production Example, the plane corresponding to the film thickness at GdBCO film when laminated further GdBCO film on the CeO ₂ film It is a figure which compares and shows orientation. It is explanatory drawing which shows the crystal orientation of an intermediate | middle layer at the time of forming an intermediate | middle layer into a film by the IBAD method on a base material. It is explanatory drawing which shows the grain boundary inclination | tilt angle of the parameter | index of in-plane orientation in the intermediate | middle layer shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Thin-film laminated body, 11 ... Metal base material, 12 ... Intermediate | middle layer, 13 ... Cap layer, 15 ... Oxide superconductor layer, 16 ... Oxide superconductor, A ... Base material, 52 ... Target, 53 ... Ion gun, 54 ... Sputter beam irradiation device, 55 ... Target holder.

Claims (10)

An intermediate layer made of MgO having a film thickness of 50 nm or less and having a crystal orientation of 15 ° or less at a half-value width (Δφ) of crystal axis dispersion in the in-plane direction formed by an ion beam cyst method (IBAD method) on a metal substrate And a cap layer having a thickness of 100 nm to 600 nm of a fluorite-based crystal structure formed directly on the intermediate layer by a film forming method, and a crystal orientation of the intermediate layer at a thickness of 100 nm to less than 300 nm The crystal orientation is such that Δφ = 8 ° or less , which is superior to the crystallinity, and in the film thickness of 300 nm or more and 600 nm or less, the crystal orientation is such that Δφ = 5 ° or less which is superior to the crystal orientation of the intermediate layer . And a cap layer made of CeO ₂ . Film laminate according to claim 1, wherein a thickness of the cap layer is formed by a [Delta] [phi = 5 ° or less in the 3 range of less than 00nm over 100 nm.   The thin film laminate according to claim 1 or 2, wherein the intermediate layer has a thickness of 5 to 10 nm. Thin film lamination according to any one of claims 1 to 3, characterized in that said CeO 2 ₍₂₀₀₎ of the MgO intermediate layer (200) plane and the cap layer surface is shared. An RE-123-based oxide superconductor (REBa ₂ Cu ₃ O _7-x : RE is Y, La, Nd, Sm, Eu) on the cap layer of the thin film laminate according to claim 1. And an oxide superconducting layer made of a rare earth element of Gd). In the method for producing a thin film laminate in which an intermediate layer and a cap layer are laminated on a metal substrate, and an oxide superconducting layer is laminated on the cap layer to form an oxide superconducting conductor,
An intermediate layer made of MgO having a film thickness of 50 nm or less is formed on a metal substrate by ion beam assist method (IBAD method) and crystallized to 15 ° or less in the half-value width (Δφ) of crystal axis dispersion in the in-plane direction. Thereafter, a cap layer having a fluorite crystal structure and a thickness of 100 nm to 600 nm and having a thickness of 100 nm to less than 300 nm is superior to the crystal orientation of the intermediate layer, and Δφ = 8 ° or less . crystal orientation becomes and the cap layer composed of CeO ₂ in a self-aligned such that the superior [Delta] [phi = 5 ° or less of crystalline orientation than the crystalline orientation of the intermediate layer is a thickness of more than 600nm or less 300nm A method for producing a thin film laminate, which is formed directly on the intermediate layer by a film forming method. Method of manufacturing a thin film laminate according to claim 6, characterized in that at most [Delta] [phi = 5 ° in a range thickness of less than 3 00nm or 100nm of the cap layer.   The method of manufacturing a thin film laminate according to claim 6 or 7, wherein the thickness of the intermediate layer is 5 to 10 nm. 9. The crystal growth of the cap layer made of CeO ₂ on the intermediate layer made of MgO is performed by sharing the MgO (200) plane and the CeO ₂ (200) plane. Method for manufacturing a thin film laminate. After producing the thin film stack by the production method according to any one of claims 6-9, on the cap layer of the thin film stack, RE-123-based oxide superconductor _{(REBa 2 Cu 3 O 7-} x: RE is a method for producing an oxide superconducting conductor comprising stacking an oxide superconducting layer made of RE, a rare earth element of any one of Y, La, Nd, Sm, Eu, and Gd.

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