JP4809700B2 - YBCO high temperature superconductor film-forming substrate and YBCO high temperature superconductor film production method - Google Patents

Description

  The present invention relates to a YBCO-based high-temperature superconductor film-forming substrate, and particularly useful for producing products such as electronic devices and wires that apply the YBCO-based high-temperature superconductor in the form of a film. The present invention relates to an excellent base material for forming a high-temperature superconductor. The present invention also relates to a method for producing a YBCO-based high-temperature superconductor film, and more particularly to a method for producing a YBCO-based high-temperature superconductor film excellent in orientation using the above-described substrate for forming a high-temperature superconductor. It is.

  Superconductors have unique characteristics not found in other materials, such as 1) zero electrical resistance, 2) complete diamagnetism, 3) Josephson effect, etc. A wide range of applications such as fusion plasma confinement, magnetic levitation trains, magnetic shields, and high-speed computers are expected.

In 1986, Bednorz and Mueller discovered a copper oxide superconductor (La _1-x Ba _x ) ₂ CuO ₄ with a superconducting transition temperature T _c of about 30 K. Thereafter, YBa ₂ Cu ₃ O _7-δ (T _c = 90 K), Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _y (T _c = 110 K), Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _y (T _c = 125 K), copper oxides such as HgBa ₂ Ca ₂ Cu ₃ O _y (T _c = 135 K), etc., one after another, superconducting transition at high temperatures was reported.

Currently, many studies have been conducted on the production methods, physical properties, and applications of these substances. Above all, YBa ₂ Cu ₃ O _7-δ superconductor is 90K class even if Y is replaced with rare earth elements (La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu). It is known to exhibit superconductivity (see Non-Patent Document 1). In YBa ₂ Cu ₃ O _7-δ superconductor, all or part of Y is replaced with La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Y, A superconductor having a crystal structure similar to YBa ₂ Cu ₃ O _7-δ (hereinafter referred to as “YBCO series”), such as a superconductor in which a part of Ba is replaced with La, Nd, Sm, Eu, Sr, Ca. Superconductors ”) are the most promising materials for practical use in electronic devices and wires because they do not contain harmful elements such as Tl and Hg and are relatively low anisotropy.

  Here, when considering the practical application of YBCO-based superconductors, it is necessary to give the superconductor a shape according to the application. Development is essential. Various film forming methods can be used depending on the purpose, such as a method of depositing raw material powder on a substrate, a method of densely arranging chemical methods, and a method of growing pseudo single crystals by physical methods. (See Non-Patent Document 2).

  However, in order to realize application to highly reliable electronic devices and wires, advanced material control by a physical method such as sputtering or laser deposition is indispensable. The sputtering method and the laser vapor deposition method are film forming methods in which energy is applied by exposing a target material, which is a raw material, to plasma or laser, and the particles that have jumped out are deposited on a substrate. As the target material, it is common to use a ceramic material having a target composition. Then, conditions such as the atmospheric gas, the substrate temperature, the energy to be applied, and the target-substrate distance are changed to find a film forming condition for obtaining a desired film.

  Particularly important from the viewpoint of practical use is a technique for producing a c-axis oriented film having a uniform crystal orientation with good reproducibility. Usually, a substrate having a surface with a uniform crystal orientation is used as a base material for a superconducting film. A superconductor film oriented reflecting the crystal orientation of the surface grows on the surface of the base material. A single crystal is often used as the substrate. Further, in the case of a substrate in which a superconductor excellent in orientation is difficult to grow directly, a layer called a buffer layer or an intermediate layer suitable for ensuring orientation is formed on the surface of the substrate, A superconductor film is often formed on top (see Patent Documents 1 to 7).

  There are many factors that determine the orientation of the superconductor film deposited on the surface of the substrate, but it is clear that the crystal growth that occurs in the initial stage of film formation plays an extremely important role in whether the orientation is good or bad. ing. This is because, when a superconducting film is grown, if a part with a disordered crystal orientation is generated for some reason, a superconducting film with a disordered crystal orientation will grow on the part. . The disorder of crystal orientation in the superconductor film is likely to occur at the initial stage of film formation in which an interface between different substances is formed.

  Since the base material and the superconductor film deposited thereon are not the same material, if there is a portion with poor crystal matching at the interface, this portion will cause disturbance in the crystal orientation of the superconductor film. . In addition, defects on the surface of the base material, foreign matter, and the like are factors that disturb the crystal orientation of the superconductor film. The lack of single orientation that occurs in the superconductor film adversely affects the performance of products such as devices and wires.

  Furthermore, even if the film formation conditions are optimized so that the orientation is the best during film formation, the film formation conditions vary depending on the film formation environment such as target wear and gas release from the inner wall of the film formation chamber. Changes gradually. This subtle change in the film forming conditions also causes a lack of single orientation.

Until now, an effective coping method for avoiding the lack of orientation of the superconductor film has not been established, and the development of a method for effectively avoiding the lack of orientation of the superconductor film is expected among those skilled in the art. Is the actual situation.
JP-A-11-53967 JP 2000-86239 A JP 2001-110255 A JP 2002-150855 A JP 2003-36743 A Japanese Patent Laid-Open No. 2005-1935 Japanese Patent Laid-Open No. 2005-5089 JM Tarascon et al., Phys. Rev. B 36 (1987) 226. Naito, H., "High-Temperature Superconductors (above)-Materials and Physics" (JSAP Catalog Number: AP042312; Superconductivity Subcommittee School Text, 2004) p.101.

  Therefore, the present invention is based on the above circumstances. (I) YBCO-based high-temperature superconductor film having excellent orientation can be formed without depending on changes in film forming conditions, and YBCO having excellent orientation reproducibility. An object of the present invention is to provide a base material for forming a high-temperature superconductor film and to provide a method for producing a YBCO-based high-temperature superconductor film having excellent orientation.

  The present inventor is a group in which the crystal orientation is uniform and Zr or Zr oxide is present on the surface in the process of making a research on producing a c-axis oriented film of a YBCO high temperature superconductor by a physical technique. It was found that the reproducibility of the c-axis orientation of the YBCO-based high-temperature superconductor film was dramatically improved when the material was used. Here, the c-axis is the long axis direction of the crystal, and is the longest direction when the YBCO crystal is regarded as a rectangular parallelepiped.

That is, the YBCO-based high-temperature superconductor film-forming substrate of the present invention that solves the above problems (hereinafter sometimes referred to as “the substrate of the present invention”) has been made based on the above knowledge, and has a crystal orientation. a uniform crystalline phase, and Zr or Zr oxide which does not belong to its crystalline phase is characterized that you have exposed on the surface.

In this specification, a YBCO-based high-temperature superconductor, a superconductor obtained by replacing all or a part of Y with La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu , Y and Ba are defined as superconductors having basically the same crystal structure as YBa ₂ Cu ₃ O _7-δ , such as superconductors in which a part of Y, Ba is replaced by La, Nd, Sm, Eu, Sr, Ca .

In one embodiment of the substrate of the present invention, the crystal phase is a single crystal.

In one embodiment of the substrate of the present invention, the crystal phase is composed of a substrate and a thin film on the substrate.

  In one embodiment of the substrate of the present invention, the thin film is an oxide composite containing Zr or a Zr oxide.

Further, in an embodiment of the present invention the substrate, on the surface of the crystal _{phase, MgO, SrTiO 3, LaAlO 3} , Sr 2 AlTaO 6, YSZ, LaGaO 3, NdGaO 3, PrGaO 3, YAlO 3, BaSnO 3, A composite oxide composed of one or more of BaZrO ₃ , Ba ₂ NdTaO ₆ , SrSnO ₃ , CaSnO ₃ , LaSrGaO ₄ , LaSrAlO ₄ and CeO ₂ is exposed.

In one embodiment of the substrate of the present invention, a complex oxide composed of one or more of BaSnO ₃ , BaZrO ₃ and Ba ₂ NdTaO ₆ is exposed on the surface of the crystal phase .

Furthermore, in the substrate of the present invention, the thin film is a composite of BaZrO ₃ and a Zr oxide and satisfies the following composition ratio.
0.65 ≤ Ba / Zr ≤ 0.98

  Next, the YBCO-based high-temperature superconductor film manufacturing method of the present invention that solves the above-mentioned problems (hereinafter referred to as “the present invention manufacturing method”) uses a base material of the present invention to manufacture a superconductor film. Features.

  Since the YBCO high temperature superconductor film produced using the substrate of the present invention has excellent orientation, it is a superconductor film suitable for manufacturing products such as electronic devices and wires.

  The present invention provides a substrate on which a YBCO-based high-temperature superconductor film excellent in orientation can be formed with good reproducibility. In the initial stage of the formation of the YBCO high-temperature superconductor film, Zr or Zr oxide intervenes in crystal growth, thereby promoting the growth of c-axis oriented particles. In addition, according to the present invention, lateral crystal growth along the substrate surface of oriented particles is also promoted, so that the high-temperature superconductor can be a convenient foundation for film growth in the vertical direction aligned with the crystal orientation of the substrate. Can form a crystal base.

  Therefore, according to the present invention, there is almost no mixture of a-axis oriented particles, and the YBCO-based high-temperature superconductor is composed of substantially c-axis oriented particles and has excellent orientation with a crystal orientation aligned with the crystal orientation of the substrate. A film can be produced with good reproducibility.

  In the present invention, since the above effect can be obtained by positively utilizing the reaction that occurs on the surface of the substrate due to the presence of Zr in the initial stage of film growth, the present invention provides a YBCO-based high-temperature superconductor. It can also be applied to a substrate made of a material with a somewhat poor crystal lattice matching. Furthermore, in the present invention, in the production of an actual YBCO-based high-temperature superconductor film, even if the film formation conditions are somewhat shifted, the reproducibility of the orientation can be maintained very well without being affected by the shift. Using various base materials, high quality YBCO high temperature superconductor film can be reliably manufactured.

  First, in order to make it easy to understand the characteristics of the present invention, the conventional film formation of a high-temperature superconductor film will be described with reference to a schematic diagram to clarify the problems.

  In general, in the deposition of YBCO-based high-temperature superconductors, the orientation of crystal grains can be qualitatively understood by a migration model (see H. Izumi et al., Jpn. J. Appl. Phys. 30 (1991) 1956.). ). The basic orientation is determined by whether the deposited particles have sufficient energy to move on the substrate surface.

  If the particles deposited on the substrate have sufficient kinetic energy and can move over a long distance on the surface of the substrate, the film is oriented more in the c-axis than in the a-axis oriented film in order to reduce the surface energy. Become a film. However, when the kinetic energy is insufficient, a-axis oriented particles that require a short moving distance are formed, so the film becomes an a-axis oriented film.

  Thus, although the length of the moving distance of the deposited particles greatly affects the orientation of the film, defects and disturbance of the underlying crystal can be cited as factors that hinder the movement of the deposited particles. In particular, in the initial stage of film growth, defects and disturbances in the underlying crystal greatly hinder the movement of accumulated particles and affect the orientation of the film. Therefore, the initial stage of film growth is a particularly important step in improving the orientation of the film.

  11A to 11E show growth modes of crystal grains when a superconductor film is formed on a conventional base material.

  FIG. 11A shows a single crystal base material 100 having a defect site 101 on the surface. When a film is formed on the surface of the single crystal base material 100, as shown in FIG. On the top, c-axis oriented particles 105 of a superconductor aligned with the crystal orientation of the surface are generated.

  However, as shown in FIGS. 11B to 11D, at the defect portion 101, the movement of the deposited particles is hindered by the defects, and crystal grains having different orientations are generated (see FIG. 11B), and the film formation is continued The crystal grains having different orientations continue to grow without changing the direction in the middle (see FIGS. 11C and 11D). As a result, as shown in FIG. 104 remains.

  High-temperature superconductors have strong anisotropy in electrical transport properties, and superconducting currents flow in a direction perpendicular to the c-axis to obtain good superconducting properties. If the above-mentioned outgrowth crystal grains remain, the superconducting critical current density decreases, and the superconducting characteristics deteriorate. This is recognized as a major problem by those skilled in the art in securing excellent superconducting properties in the high-temperature superconductor film.

  It is not only crystal defects that impair the movement (migration) of deposited particles on the substrate surface. For example, even if the crystal on the surface of the base material is perfect, the base material and the superconductor film deposited thereon are not the same substance, and therefore, there is a portion of poor crystal matching at the interface. It will occur. This mismatch may cause disturbance in the crystal orientation of the film.

  In actual high-temperature superconductor film formation, preliminary experiments are conducted first to find out the film formation conditions that provide the best orientation, and the film formation conditions are optimized. The film forming conditions gradually change due to changes in the film forming environment such as gas release from the gas. This subtle change in film forming conditions also causes a lack of single orientation of crystal grains.

  The lack of single orientation of the superconducting film generated as described above causes a decrease in critical current density in the superconducting film, and as a result, adversely affects the performance of products such as devices and wires. Thus, the lack of single orientation of the superconducting film is a problem in the conventional high-temperature superconducting film, and in order to further improve the superconducting characteristics, a technique for eliminating the lack of the above single orientation. Need to develop.

  Next, the present invention that eliminates the lack of single orientation will be described in detail with reference to schematic diagrams.

  The present inventor has made a crystal as a base material on which a superconducting film is formed in the process of making a c-axis oriented film of a YBCO high temperature superconductor by a physical method such as sputtering or laser vapor deposition. It has been found that the reproducibility of the orientation of the superconductor film to be formed is dramatically improved by using a base material having a uniform orientation and having Zr or Zr oxide on the surface thereof.

  Specifically, the present inventor can promote the movement of particles that have accumulated in the initial stage of film formation when Zr or a Zr oxide is present on the surface of the substrate. It is possible to produce a YBCO-based high-temperature superconductor film that is stable and reproducible over a long period of time and is excellent in orientation without being sensitively affected by inconsistencies in the film formation, or even by deviations in film formation conditions. I found what I could do.

  That is, the present inventor can introduce a liquid phase generated by the presence of Zr or Zr oxide into the crystal grain growth process at the initial stage of the formation of the YBCO-based high-temperature superconductor film. It has been found that the orientation can be remarkably improved.

  The reason why the orientation of the superconductor film formed when the liquid phase produced by the presence of Zr or Zr oxide is introduced into the crystal grain growth process is not clear at present, is not clear at this time. Is guessed.

According to research using polycrystalline samples, when the temperature rises when the YBCO high-temperature superconductor is in contact with Zr or Zr oxide, a decomposition reaction occurs at a temperature lower than the melting point of the superconductor, CuO, Y ₂ Cu ₂ O ₅ , BaZrO _{3 and the} like are known to be produced (SW Filipzuk, Physica C 173 (1991) 1., T. Oka et al., Jpn. J. Appl. Phys. 31 (1992) 1760.) .

  This reaction does not complete with only a simple solid reaction, but proceeds as an intermediate product with a Ba—Cu—O 2 liquid phase. In general, mass transfer through the liquid phase proceeds very quickly. The Ba-Cu-O based liquid phase is also used as a flux for growing YBCO single crystals (Y. Hidaka et al., J. Cryst. Growth 85 (1987) 581.). In the present invention, it is presumed that the liquid phase generated by the presence of Zr or Zr oxide is actively used in the early stage of growth of the YBCO-based high-temperature superconductor film.

  FIG. 1A to FIG. 1E are schematic views for explaining a film formation process of a superconductor film using the substrate of the present invention. Hereinafter, the production method of the present invention will be described with reference to FIGS. 1A to 1E.

  First, Zr or Zr oxide 3 is attached to the surface of a single crystal substrate 2 having a defect site 1 on the surface to form a substrate 4 of an embodiment of the substrate of the present invention shown in FIG. 1A.

  Next, as shown in FIG. 1B, a superconductor film is formed on the surface 5 of the substrate 4 to which Zr or Zr oxide 3 is adhered. Specifically, first, c-axis oriented particles 8 of a superconductor aligned with the crystal orientation of the surface 5 are formed on the surface 5. Here, as shown in FIG. 1B, the superconducting phase decomposition reaction proceeds in the presence of Zr or Zr oxide 3 on the surface 5 due to the presence of Zr, and the Ba—Cu—O 2 -based liquid phase 10. Occurs.

  As shown in FIG. 1C, the liquid phase 10 comes into contact with the c-axis oriented particles 8 of the superconductor film that has grown in line with the crystal orientation of the surface 5 of the base material 4. It aids in the migration of particles that are successively deposited on the surface 5 and promotes the lateral growth of c-axis oriented particles, as shown in FIG. 1D.

  As a result, the flat c-axis oriented particles of the superconductor grow on the surface of the base material, and as shown in FIG. 1E, the superconductor film 11 having a very highly c-axis orientation can be formed on the surface of the base material. it can. Here, due to the effect of promoting migration by the liquid phase 10, it was confirmed that even if some defects 1 exist on the surface 5, the defects 1 do not cause generation of outgrowth crystal grains.

  FIG. 2 is a diagram schematically showing the surface texture of a superconductor film with an extremely high c-axis orientation. Specifically, FIG. 2A schematically shows a surface structure of a c-axis oriented superconductor film when a superconductor film is formed on a single crystal substrate on which Zr or Zr oxide is not present. It is. FIG. 2B shows the same film formation conditions as those for obtaining the surface structure shown in FIG. 2A on the single crystal substrate (the substrate of the present invention) having Zr or Zr oxide adhered on the surface. It is a figure which shows typically the surface texture of the c-axis oriented superconductor film when a superconductor film is formed under film conditions.

  In FIG. 2 (A), 21 indicates a superconductor crystal grain, and in FIG. 2 (B), 24 indicates a superconductor crystal grain. Note that FIG. 2 is created based on data in an example (investigation) described later (see FIG. 10).

  As shown in FIGS. 2 (A) and 2 (B), the surface texture in each case reflects the tetragonal crystal lattice of the YBCO high-temperature superconductor, and is a substantially square crystal with a uniform orientation. The surface structure is covered with grains. However, when both figures are compared in detail, (i) the particle size of the superconductor crystal grain 24 shown in FIG. 2 (B) is larger than the particle size of the superconductor crystal grain 21 shown in FIG. 2 (A), and (Ii) It is understood that the particle shape of the superconductor crystal grain 24 shown in FIG. 2 (B) is more angular than the particle shape of the superconductor crystal grain 21 shown in FIG. 2 (A).

  From the comparison between FIG. 2 (A) and FIG. 2 (B), the case where the substrate of the present invention shown in FIG. 2 (B) is used is due to the liquid phase generated by Zr or Zr oxide existing on the surface. It can be seen that crystal grain growth in the lateral direction (direction along the surface of the base material) is remarkably exhibited. From this, if a substrate on which Zr or Zr oxide is present on the surface is used, grain growth of the superconductor crystal in the lateral direction (direction along the substrate surface) can be promoted. It is possible to form a superconductor film having crystal grains having a substantially uniform size and having a very high c-axis orientation.

  FIG. 3 is a diagram schematically showing a film cross-sectional structure when the c-axis oriented superconductor film shown in FIG. 2 is viewed from the lateral direction. Specifically, FIG. 3 (A) is a diagram schematically showing a film cross-sectional structure when the c-axis oriented superconductor film shown in FIG. 2 (A) is viewed from the lateral direction, and FIG. FIG. 3 is a diagram schematically showing a film cross-sectional structure when the c-axis oriented superconductor film shown in FIG. 2B is viewed from the lateral direction.

  In FIG. 3A, 30 indicates a base material, and in FIG. 3B, 31 indicates a base material. 3A and 3B, an arrow 9 indicates the c-axis direction of each crystal grain. The goodness or badness of the same direction of the arrow 9 is mainly affected by lattice mismatch or lattice defect at the interface between the base material and the superconductor film.

  In the production of the superconductor film, in order to realize and further reproduce the excellent c-axis orientation, in the crystal substrate that is formed in the vicinity of the interface between the base material and the superconductor film and serves as a foundation for crystal growth in the c-axis direction, It is necessary to alleviate the influence of non-crystal matching and lattice defects that disturb the c-axis orientation as much as possible. For this purpose, it is very advantageous to promote crystal growth in the lateral direction to form a crystal substrate. This will be described below.

  4 (A) and 4 (B), there are steps 41 and 42 at the atomic layer level in portions where the crystal orientations of the substrate surface are aligned, and these steps 41 and 42 are formed of superconductor crystal grains 43, FIG. 4 is a diagram schematically showing an aspect in the vicinity of the interface between superconductor films 47 and 48 and base materials 45 and 46 when the distance is larger than the atomic layer spacing of 44 in the c-axis direction.

  As shown in FIG. 4A, when the particle size of the superconductor crystal grain 43 is small, the portion where the superconductor crystal grain 43 is in contact with the step 41 at the atomic layer level in the substrate 45 is elongated in the vertical direction. On the other hand, the side surface that is not in contact with the level difference tends to maintain the original atomic layer spacing of the superconductor crystal grains 43. As a result, the c-axis direction of the superconductor crystal grains 43 is inclined from the normal line of the surface of the substrate 45.

  As shown in FIG. 4 (B), when the particle size of the superconductor crystal grains 44 is large, the portion where the superconductor crystal grains 44 are in contact with the step 42 at the atomic layer level of the base 46 is shown in FIG. However, as shown in FIG. 4B, in a portion sufficiently away from the step 42, the superconductor crystal is not affected by the step 42 of the base material 46, as shown in FIG. Since it has the original atomic layer spacing, the c-axis direction does not tilt from the normal of the surface of the substrate 46. The portion where the c-axis is not inclined serves to correct the inclination of the crystal grains caused by the distortion in the portion close to the step 42.

  Therefore, when the crystal base on which the crystal grains grow in the lateral direction (the direction along the surface of the base material) is formed on the surface of the base material, the c-axis of the superconductor film 48 is extremely highly aligned in one direction. The c-axis orientation of 48 is extremely excellent.

  As described above, the formation of the crystal base in the initial stage of the formation of the superconducting film is a major factor that determines the quality of the c-axis orientation of the finally obtained superconducting film. And the superconductor film excellent in c-axis orientation can be produced by accelerating the lateral growth of c-axis oriented superconductor crystal grains generated on the substrate surface.

  Zr or Zr oxide, which exists on the surface of a substrate with uniform crystal orientation and generates a liquid phase by reaction with the superconductor at the beginning of the formation of the superconductor film, forms a crystal base in the direction along the surface of the substrate. As a result, the c-axis is extremely highly oriented on the crystal substrate without being affected by lattice mismatch or lattice defect that disturbs the c-axis orientation of the superconductor film. It is possible to produce a superconductor film. The effect of this Zr or Zr oxide was first found by the present inventors.

  As described above, the base material of the present invention is characterized in that Zr or a Zr oxide partially exists on the surface of the base material with a uniform crystal orientation. In addition, the base material in which Zr or Zr oxide is partially attached to the surface of the single crystal base material shown in FIG. 1A is an embodiment of the present invention.

5A to 5D are cross-sectional views showing other embodiments of the substrate of the present invention.

  In the above embodiment, the substrate of the present invention is formed by attaching Zr or a Zr oxide to the surface of a single crystal substrate having a uniform crystal orientation on the surface. However, as shown in FIG. 5A, the base material of the present invention may be composed of a substrate 50 and a thin film 51 formed on the substrate 50 and having substantially the same crystal orientation. A substrate formed by attaching Zr or Zr oxide 52 to the surface of the thin film 51 is an embodiment of the present invention.

  As shown in FIG. 5B, the base material of the present invention may be composed of a substrate 53 and an oxide composite thin film 54 in which Zr or Zr oxide 55 formed on the substrate 53 is dispersed. Since the oxide composite thin film 54 contains Zr or Zr oxide 55 in a dispersed manner, a surface where Zr or Zr oxide is exposed on the surface can be obtained without intentionally attaching Zr or Zr oxide to the surface. The exposed Zr or Zr oxide functions to generate a liquid phase on the surface of the substrate and promote the formation of a crystal substrate at the initial stage of film formation of the YBCO-based superconductor.

  As shown in FIG. 5C, the base material of the present invention may be composed of a substrate 56 and an oxide composite thin film 58 having a grain boundary 57 on which Zr or Zr oxide formed on the substrate 56 is deposited. . Since the oxide composite thin film 58 includes the grain boundary 57 on which Zr or Zr oxide is deposited, the Zr or Zr oxide is exposed on the surface without intentionally attaching the Zr or Zr oxide to the surface. A morphology is obtained, and the exposed Zr or Zr oxide functions to generate a liquid phase on the surface of the substrate and promote the formation of a crystal substrate at the initial stage of film formation of the YBCO-based superconductor.

  Further, as shown in FIG. 5D, the base material of the present invention is formed on a substrate 59 made of a non-oriented material, an intermediate layer 60 having an orientation formed on the substrate 59, and an intermediate layer 60 having an orientation. The oxide composite thin film 61 may be used.

  As shown in FIG. 5D, the oxide composite thin film 61 formed on the intermediate layer 60 includes grain boundaries 62 on which Zr or Zr oxide is deposited, so that Zr or Zr oxide is intentionally attached to the surface. Without exposing the surface, Zr or Zr oxide is exposed on the surface, and the exposed Zr or Zr oxide forms a liquid phase on the surface of the substrate in the initial stage of film formation of the YBCO-based superconductor. It functions to promote the formation of the foundation.

  Here, the intermediate layer 60 may be formed on a non-oriented material by, for example, an ion beam-assisted deposition method (Ion-Beam-Assisted Deposition Method) or the like. Further, when a substrate made of a non-oriented material is used, the oxide composite thin film 61 has grain boundaries where Zr or Zr oxide is precipitated, like the oxide composite thin film 58 shown in FIG. 5C. Similarly to the oxide composite thin film 54 shown in FIG. 5B, a form in which Zr or a Zr oxide is dispersed may be used in combination.

  The base material of the present invention is preferably one in which c-axis oriented superconductor crystals are easily formed at the initial stage of the formation of the superconductor film. In order to realize this, a material having a crystallographically similar structure and good lattice matching, for example, a composite oxide, is present on the substrate surface or exposed. desirable.

_{Specifically, MgO, SrTiO 3, LaAlO 3} , Sr 2 AlTaO 6, YSZ, LaGaO 3, NdGaO 3, PrGaO 3, YAlO 3, BaSnO 3, BaZrO 3, Ba 2 NdTaO 6, SrSnO 3, CaSnO 3, LaSrGaO ₄ , a composite oxide composed of one or more of LaSrAlO ₄ and CeO ₂ is preferably present or exposed on the surface of the substrate. In particular, BaSnO ₃ , BaZrO ₃ and Ba ₂ NdTaO ₆ have an atomic layer of Ba-O that can be shared at the interface with the YBCO-based oxide superconductor in the crystal. , Journal of the Japan Institute of Metals 67 (2003) 295.), it is preferable as a composite oxide used in combination with Zr or Zr oxide.

In the case of the base material of the present invention having a thin film, it is more preferable that the thin film is formed of a BaZrO ₃ —Zr oxide composite in terms of further improving the orientation of the superconductor film. When the BaZrO ₃ thin film is formed, the composition is Zr-excess composition slightly deviating from the stoichiometric composition, so that the BaZrO ₃ -Zr oxide composite thin film in which the Zr oxide is dispersed at the grain boundaries, etc. A film can be formed.

As a result of the present inventors investigating the orientation reproducibility of the base material of the present invention by varying the degree of Zr excess from the stoichiometric composition, Ba / Zr in the BaZrO ₃ —Zr oxide composite has the following composition ratio: It was found that the alignment reproducibility is remarkably improved when satisfying.
0.65 ≤ Ba / Zr ≤ 0.98

  In any case where Ba / Zr is less than 0.65 and Ba / Zr is more than 0.98, a liquid phase that promotes the formation of the crystal base is generated at the initial stage of film formation of the YBCO-based superconductor. If maintained within the range of the composition ratio, a liquid phase having an excellent c-axis orientation promoting function can be formed on the substrate surface. Therefore, Ba / Zr is preferably 0.65 or more and 0.98 or less.

The base material of the present invention provided with a thin film of BaZrO ₃ —Zr oxide composite does not require a step of partially attaching Zr or Zr oxide to the surface before superconductor film formation. The manufacturing process can be simplified and is industrially useful.

  The inventor investigated the effect of the substrate of the present invention on the orientation of the superconductor film and the quality of the reproducibility of the superconductor film. The results will be described below. The conditions employed in the method shown below are one condition employed for demonstrating the feasibility and reproducibility of the present invention, and the present invention is not limited by these conditions.

I. Investigation on the effect of the substrate of the present invention on the orientation of the superconductor film By laser vapor deposition, a La _0.3 Sr _1.7 AlTaO ₆ (LSAT) (100) single crystal substrate was formed into a Yb _0.9 La _{A 0.2} Ba _1.9 Cu ₃ O ₇ film is formed. Here, LSAT is a material in which LaAlO ₃ and Sr ₂ AlTaO ₆ are dissolved in 3: 7, and was developed as a base material for a high-temperature superconductor film (S.C. Tidrow et al. IEEE Trans. Appl. Supercond. 7 (1997) 1766).

A film forming apparatus having a plurality of target holders in the film forming chamber is used. In the target holder, a Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ sintered body and a Zr plate are installed as targets. The target holder has a rotation mechanism, and can be changed as necessary without opening the film forming chamber to the atmosphere.

  Laser light is appropriately scanned on the target by an optical system mirror driven by a motor, and at the same time, the target rotates. Therefore, the laser is not irradiated only on the same position on the target, and the laser can be irradiated on the target surface substantially uniformly.

While introducing oxygen into the film formation chamber, the displacement is controlled, the pressure in the chamber is set to 100 mTorr, the substrate temperature is increased to 650 ° C., the distance between the substrate and the target is set to 80 mm, and the Zr plate is used as the target material to energize the surface. Irradiate a KrF laser with a density of 1.5 J / cm ² at 1 Hz. The experiment was conducted by selecting three irradiations: 0 (no irradiation), 10 pulses, and 30 pulses.

Next, the target was changed to a Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ sintered body, the substrate-target distance was set to 50 mm, and the laser was irradiated at 5 Hz for 2 hours. After the film formation, the heater was turned off, and oxygen was introduced to 300 Torr and quenched.

Here, as a preliminary experiment, after 30 pulses of laser light were irradiated using a Zr plate as a target, the heater was turned off without forming a Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film, Oxygen was introduced to 300 Torr to prepare a rapidly cooled sample. When the surface structure of the obtained sample was examined by reflection high-energy electron diffraction without taking it into the atmosphere, a strong diffraction pattern indicating the structure of LSAT was observed. This indicates that LSAT having a uniform crystal orientation is exposed on the substrate surface.

Further, when the sample was taken out into the atmosphere and the surface was observed with an optical microscope, a large number of uniformly dispersed island-like grains were observed on the flat substrate. These grains are Zr or Zr oxide. In this way, before the formation of the Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film, a substrate obtained by irradiating 10 or 30 pulses of laser light using the Zr plate as a target material is obtained. Further, it was confirmed that the substrate was such that Zr or Zr oxide was partially present on the surface of the substrate having the same crystal orientation.

  The thickness of the obtained superconductor film was 180 nm for all samples. When the orientation was examined by X-ray diffraction (2θ-θ scan using Cu-Kα rays; XRD), in addition to the peak from the LSAT of the substrate, the 00L reflection of the YBCO-based superconductor exhibiting c-axis orientation A strong peak could be confirmed.

  However, in the sample to which Zr or Zr oxide was not attached, peaks of 200 and 300 showing a slight mixture of a-axis oriented particles were also observed. These peaks disappeared when the number of pulses of the laser for depositing Zr or Zr oxide, that is, the amount of deposition increased. From this, it is understood that when Zr or Zr oxide is attached to the surface of the substrate, a YBCO superconductor film having excellent c-axis orientation can be produced.

FIG. 6 is a diagram showing XRD patterns of the _three Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ films produced, and is a diagram showing XRD patterns obtained by enlarging the 006 and 200 peak portions. .

As shown in FIG. 6, the 006 peak of the Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film partially overlaps the 400 peak of LSAT. On the other hand, the 200 peak can be detected without overlapping in the three curves. As shown in FIG. 6, there are 200 peaks when the number of pulses is zero and ten. On the other hand, in the case of 30 pulses, 200 peaks disappear.

  From this, it is possible to produce a highly highly c-axis oriented superconductor film by using the base material of the present invention in which Zr or Zr oxide is partially adhered to the surface of the LSAT base material with uniform crystal orientation. I understand.

FIG. 7 is a diagram showing the temperature dependence of the electrical resistivity of the _three Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ films produced. When a-axis oriented crystal grains are mixed in c-axis oriented crystal grains, the flow of the superconducting current is disturbed and the critical current density is lowered. As shown in FIG. 7, the critical temperature _Tc seen in the temperature dependence of the electrical resistivity measured by applying the same current decreases as the number of a-axis oriented particles increases.

This indicates that the critical current density decreases in the temperature region slightly lower than _Tc as the sample contains more a-axis oriented particles. Incidentally, the measurement to examine the temperature dependence of the electrical resistivity was performed by a four-terminal method, the critical temperature T _c, was determined by flowing a current of 0.1mA in the superconducting film of 3mm wide.

II. Investigation 1 regarding the relationship between the substrate of the present invention and the reproducibility of superconductor film orientation
Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film is formed on a substrate made of LSAT (100) single crystal by laser vapor deposition using the same apparatus as used in the above investigation. To do. The substrate temperature is raised to 690 ° C. without attaching Zr or Zr oxide to the surface of the LSAT substrate. The chamber is oxygen 100 mTorr, the substrate-target distance is 50 mm, laser irradiation (energy density 1.5 J / cm ² on the target) is 2 Hz at 5 Hz, and a 180 nm thick superconductor film is formed. Form.

XRD confirms that it is a c-axis oriented film. Next, a Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film is continuously formed over several weeks under the same film forming conditions. From the 20th film formation, a mixture of a-axis oriented particles was observed. This lack of orientation reproducibility is presumed to be caused by the fact that the film formation conditions change little by little as the number of film formation increases. Possible causes of the lack of orientation reproducibility include wear and deterioration of the target surface and contamination of the laser introduction window.

Next, from the 31st film formation, before the Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film was formed, an operation of attaching Zr or Zr oxide to the substrate surface was performed. . The conditions for adhesion are the same as those for 30 pulses in the above investigation. The obtained superconducting film was a c-axis oriented film, and a mixture of a-axis oriented particles was not observed. From this, if the operation of attaching Zr or Zr oxide to the surface of the base material before the formation of the superconductor film, it is possible to form a superconductor film with extremely excellent orientation reproducibility on the base material. I understand.

III. Investigation on the relationship between the substrate of the present invention and the orientation reproducibility of the superconducting film 2)
Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film is formed on a substrate made of LSAT (100) single crystal by laser vapor deposition using the same equipment used in the above survey. To do. The substrate temperature was 650 ° C., the inside of the chamber was oxygen 100 mTorr, the substrate-target distance was 50 mm, and laser irradiation (energy density on the target 1.5 J / cm ² ) was 5 Hz for 2 hours.

In addition, before the film formation of Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film, Zr or Zr oxide was formed on the substrate surface under the same conditions as in the case of 30 pulses performed in Survey I. The operation of adhering was performed.

  The superconductor film obtained as described above was a c-axis oriented film, and a mixture of a-axis oriented particles was not observed.

A Yb _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film was continuously produced over several weeks under the same film forming conditions. Even after the 20th film formation, mixing of a-axis oriented particles was not recognized. The mixture of a-axis oriented particles started to be recognized around the 50th film formation, and the orientation reproducibility was very good.

IV. Investigation on orientation reproducibility of superconductor film when single crystal substrate and oxide composite thin film formed thereon are used as the base material of the present invention
A substrate is prepared by forming a composite film of BaZrO ₃ (hereinafter referred to as BZO) and Zr oxide on the MgO (100) single crystal as a substrate by sputtering, and then producing SmBa ₂ Cu ₃ O. _Seven films are formed.

As the film forming apparatus, an off-axis sputtering apparatus in which the normal of the substrate surface and the normal of the sputtering target surface are orthogonal to each other is used. As a sputtering target, a BaZrO ₃ sintered body and a SmBa ₂ Cu ₃ O ₇ sintered body are used. As the film forming apparatus, one having a plurality of sputter cathodes in the film forming chamber is used. In such an apparatus, the sputtering target is appropriately opened without opening the film forming chamber to the atmosphere as necessary. Alternatively, a film can be formed.

  First, an oxide composite thin film of BZO and Zr oxide is formed. Specifically, while introducing a gas in which argon and oxygen are mixed at a ratio of 9: 1, the displacement is controlled, the pressure in the chamber is set to 70 mTorr, the substrate temperature is set to 780 ° C., and 100 W is set. A high frequency plasma is generated near the target surface.

  In addition, the positional relationship between the base material holder and the sputter cathode was systematically changed, and the conditions under which Ba and Zr adhered to the base material at a desired ratio to form a thin film were studied. And Ba / Zr was controlled from 1.10 to 0.55, and the film-forming conditions which can produce a thin film were calculated | required. At this time, the peaks of MgO and BZO can be confirmed from the XRD measurement.

  Regarding BZO, it was confirmed from φ scan measurement of X-ray diffraction that it was aligned with the orientation of MgO substrate. BZO is a chemically very stable substance and has no non-stoichiometry of constituent elements. Therefore, when the composition of the film deviates from the stoichiometry (Ba / Zr = 1), a thin film in which an oxide of Ba or Zr is present at a crystal grain boundary or the like in the film is obtained. In this case, the XRD peak of the Ba or Zr oxide can hardly be detected because the crystallinity of the Ba or Zr oxide is very poor or the particles are fine and non-oriented.

  In this way, three types of Ba—Zr—O thin films with Ba / Zr of 1.00, 0.90, and 0.75 were deposited to a thickness of 10 nm.

Next, an SmBa ₂ Cu ₃ O ₇ film was formed to a thickness of 200 nm. Specifically, the argon-oxygen ratio is set to 11: 1, the pressure in the chamber is set to 120 mTorr, the substrate temperature is set to 750 ° C., and a voltage is applied between the target and a shield material of earth potential installed around the target. DC plasma was generated near the target surface. The values of current and voltage were 0.70 A and 140 V, respectively. After the film formation, the heater was turned off, and oxygen was introduced to 300 Torr for rapid cooling.

FIG. 8 is a diagram showing XRD patterns of the _three SmBa ₂ Cu ₃ O ₇ films produced. As shown in FIG. 8, in the case of the stoichiometric composition (Ba / Zr = 1.00), a strong k00 reflection peak is observed, and it can be seen that the a-axis oriented particles grow dominantly. On the other hand, when the composition is excessive in Zr, the appearance changes dramatically, and c-axis oriented particles are dominant. When Ba / Zr = 0.75, the film is completely a c-axis alignment film. From this, when Ba / Zr = 0.75 is set, the superconductor film can be a desired c-axis alignment film.

FIG. 9 is a diagram showing the temperature dependence of the electrical resistivity of the three produced SmBa ₂ Cu ₃ O ₇ films. Mixing of a-axis oriented particles detracts from the flow of the superconducting current, and thus reduces the critical current density. Therefore, _Tc seen in the temperature dependence of the electrical resistivity measured by applying the same current is low in the a-axis alignment film. On the other hand, _Tc is high in the c-axis alignment film. When investigating the electrical temperature dependence, the measurement was carried out by the four-terminal method, and a current of 0.1 mA was passed through a 3 mm wide superconducting film.

When a similar SmBa ₂ Cu ₃ O ₇ film was formed by changing the thickness of Ba / Zr = 0.75 to 100, 10, 3 nm, the XRD pattern of the obtained superconductor film was No difference was found. This is a manifestation that the amount of Zr oxide exposed on the surface is substantially constant regardless of the film thickness of the Ba—Zr—O film. From this, it is considered that the Zr oxide is uniformly distributed in the thickness direction of the film in the Ba—Zr—O film. As a form capable of realizing this, for example, the case where the Zr oxide is uniformly dispersed in the film or is precipitated at the BZO grain boundary can be considered.

V. Investigation on c-axis orientation of superconductor film formed on substrate of the present invention
MgO (100) single crystal as a substrate, thereon by sputtering, after forming the base material by forming a complex film of BZO thin film or BZO and Zr oxides, onto the substrate, Y _{0 A .9} La _0.2 Ba _1.9 Cu ₃ O ₇ film was deposited. The same off-axis sputtering apparatus as used in Survey IV was used as the film forming apparatus. As the sputtering target, BaZrO ₃ sintered body and Y _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ sintered body were used. Then, two types of base materials having a composition ratio Ba / Zr of 1.00 and 0.75 of the Ba—Zr—O thin film deposited on the substrate were produced.

After depositing a Ba—Zr—O thin film having the above composition ratio to 10 nm, a Y _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film was formed to a thickness of 200 nm. The argon-oxygen ratio was 12: 1 and the pressure in the chamber was 120 mTorr. Further, the substrate temperature was set to 730 ° C., and the target material was sputtered by direct current plasma to form a film. As values of current and voltage, 0.70 A and 125 V were used, respectively. After the film formation, the heater was turned off and oxygen was introduced to 300 Torr, followed by rapid cooling.

  It was found that all superconductor films prepared by XRD diffraction were c-axis oriented films. When the half width of the rocking curve of the 005 diffraction peak was measured, the samples of Ba / Zr = 1.00 and 0.75 were 0.830 ° and 0.261 °, respectively. This result shows that the latter is a superconducting film composed of crystal grains having a more uniform c-axis direction.

FIG. 10 is a diagram showing an atomic force microscope image of the surface of the superconductor film of the two Y _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ films, and was obtained for a region having a side of 2 μm. It is a figure which shows an image.

  As shown in FIG. 10, both have a structure in which square crystal grains reflecting the tetragonal crystal system of the superconductor are arranged. In addition, the size of the superconductor crystal grains is larger in the Ba / Zr = 0.75 sample than in the Ba / Zr = 1.00 sample. This is because in the sample with Ba / Zr = 0.75, the liquid phase was generated by the action of the Zr oxide existing on the surface of the base material, so that the lateral crystal growth on the base material was promoted. it is conceivable that.

In the initial stage of crystal growth of superconductor grains, the lateral grain growth along the substrate surface is promoted, which is advantageous for the longitudinal growth of grains with a more uniform c-axis direction. Encourage formation. As a result, an improvement in orientation as seen in the half width of the rocking curve can be obtained.

When the temperature dependence of the resistivity of these two samples was measured, both _Tc were 88K. The critical current density J _{c at} 77K is 6.0 × 10 ⁴ A / cm ² and 2.2 × 10 for the samples with Ba / Zr = 1.00 and Ba / Zr = 0.75, respectively. ^The latter, which is a superconductor film composed of crystal grains with ⁵ A / cm ² and more aligned in the c-axis direction, showed a higher value.

With Ba / Zr = 1.00 or Ba / Zr = 0.75, using the same sputter target, Y _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film was continuously applied for 3 months. Produced. In the case of Ba / Zr = 1.00, a-axis-oriented particles were mixed from the 13th film formation. This lack of orientation reproducibility is considered to be caused by the fact that the film formation conditions gradually change as the number of film formation increases. As a factor that causes a change in the film forming conditions, firstly, wear and deterioration of the target surface are considered. On the other hand, when Ba / Zr = 0.75, a c-axis alignment film with good alignment reproducibility is obtained even after the 20th time.

Table 1 below shows the superconducting film obtained when a Y _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film is continuously produced over 3 months using the same sputter target. It is the result of investigating the orientation. Although depending on the frequency of use, in the experimental cycle that the present inventor routinely performs, the film quality of the superconductor film suddenly deteriorates in about 3 months, and the target is exchanged.

In the first, fifth, and tenth weeks after starting to use a new sputter target, the composition of the Ba-Zr-O film was changed, and Y _0.9 La _0.2 Ba _1.9 Cu ₃ O ₇ film ( A film thickness of 100 nm) was formed, and the intensity ratio of the 200 and 006 peaks of the XRD pattern was examined.

[Table 1]

  As shown in Table 1, when the Ba / Zr value is in the range of 0.65 ≦ Ba / Zr ≦ 0.98, a 200 peak indicating a mixture of a-axis oriented particles is observed even after the 10th week. Was not. Therefore, when the value of Ba / Zr is set to 0.65 ≦ Ba / Zr ≦ 0.98, a superconductor film having an extremely excellent c-axis orientation can be produced.

  As described above, according to the present invention, there is almost no mixture of a-axis oriented particles, only a substantially c-axis oriented particle, and a YBCO system excellent in orientation having a crystal orientation aligned with the crystal orientation of the substrate. A high-temperature superconductor film can be produced with good reproducibility. The present invention can also be applied to a substrate made of a material with slightly poor matching between the YBCO high temperature superconductor and the crystal lattice. Furthermore, in the present invention, a high-quality YBCO-based high-temperature superconductor film can be reliably manufactured using a wide variety of base materials. Therefore, the present invention has great applicability in industries using superconducting films.

It is a schematic diagram explaining the film-forming process using the base material for YBCO type | system | group high temperature superconductor film-forming excellent in the orientation reproducibility of one Embodiment of this invention. It is a schematic diagram explaining the film-forming process using the base material for YBCO type | system | group high temperature superconductor film-forming excellent in the orientation reproducibility of one Embodiment of this invention. It is a schematic diagram explaining the film-forming process using the base material for YBCO type | system | group high temperature superconductor film-forming excellent in the orientation reproducibility of one Embodiment of this invention. It is a schematic diagram explaining the film-forming process using the base material for YBCO type | system | group high temperature superconductor film-forming excellent in the orientation reproducibility of one Embodiment of this invention. It is a schematic diagram explaining the film-forming process using the base material for YBCO type | system | group high temperature superconductor film-forming excellent in the orientation reproducibility of one Embodiment of this invention. It is a schematic diagram of the surface structure of a superconductor c-axis alignment film. FIG. 3 is a schematic cross-sectional view of the structure of the superconductor c-axis alignment film shown in FIG. 2 viewed from the lateral direction. Schematic showing the vicinity of the interface between the superconductor film and the substrate when there is a step at the atomic layer level in the portion where the crystal orientation is aligned on the surface of the substrate, and the step is larger than the atomic layer spacing in the c-axis direction of the superconductor. FIG. FIG. 6 is a cross-sectional view showing another embodiment of a YBCO-based high-temperature superconductor film-forming substrate excellent in orientation reproducibility of the present invention. FIG. 6 is a cross-sectional view showing another embodiment of a YBCO-based high-temperature superconductor film-forming substrate excellent in orientation reproducibility of the present invention. FIG. 6 is a cross-sectional view showing another embodiment of a YBCO-based high-temperature superconductor film-forming substrate excellent in orientation reproducibility of the present invention. FIG. 6 is a cross-sectional view showing another embodiment of a YBCO-based high-temperature superconductor film-forming substrate excellent in orientation reproducibility of the present invention. Is a diagram showing three _{Yb 0.9 La 0.2 Ba 1.9 Cu 3} O 7 film XRD pattern is a view showing an XRD pattern of an enlarged portion of the 006 and 200 peaks. It is a graph showing the temperature dependence of the three _{Yb 0.9 La 0.2 Ba 1.9 Cu 3} O 7 film electrical resistivity. It is a diagram showing three SmBa ₂ Cu ₃ O ₇ film XRD pattern. It is a graph showing the temperature dependence of the three SmBa ₂ Cu ₃ O ₇ film electrical resistivity. It is a figure which shows the atomic force microscope image of the superconductor film | membrane surface of two samples, and is a figure which shows the image acquired about the area | region whose one side is 2 micrometers. It is a schematic diagram explaining the film-forming method and problem of the conventional superconductor film | membrane. It is a schematic diagram explaining the film-forming method and problem of the conventional superconductor film | membrane. It is a schematic diagram explaining the film-forming method and problem of the conventional superconductor film | membrane. It is a schematic diagram explaining the film-forming method and problem of the conventional superconductor film | membrane. It is a schematic diagram explaining the film-forming method and problem of the conventional superconductor film | membrane.

DESCRIPTION OF SYMBOLS 1 Defect site 2 Single crystal base material 3, 52, 55 Zr or Zr oxide 4, 30, 31, 45, 46 Base material 5 Surface 8, 105 c-axis oriented particle 9 c-axis direction 10 Liquid phase 11, 47, 48 Superconductor film 21, 24, 43, 44 Superconductor crystal grain 41, 42 Steps at atomic layer level 50, 53, 56, 59 Substrate 51 Thin film 54, 58, 61 Oxide composite thin film 57, 62 Grain boundary 60 Intermediate layer 100 Single crystal base material 101 Defect site 104 Outgrowth crystal grain

Claims (8)

And a uniform crystal orientation crystal phase, the crystalline phase do not belong Zr or Zr oxide, YBCO system characterized that you have exposed on the surface high-temperature superconductor film-forming substrate. 2. The YBCO-based high-temperature superconductor film-forming substrate according to claim 1, wherein the crystal phase is a single crystal. 2. The YBCO-based high-temperature superconductor film-forming substrate according to claim 1, wherein the crystal phase is composed of a substrate and a thin film on the substrate.   4. The YBCO-based high-temperature superconductor film-forming substrate according to claim 3, wherein the thin film is an oxide composite containing Zr or a Zr oxide. MgO in the crystalline _{phase, SrTiO 3, LaAlO 3, Sr} 2 AlTaO 6, YSZ, LaGaO 3, NdGaO 3, PrGaO 3, YAlO 3, BaSnO 3, BaZrO 3, Ba 2 NdTaO 6, SrSnO 3, CaSnO 3, LaSrGaO 4 5. The YBCO-based high-temperature superconductor composition according to claim 1, 2, 3, or 4, wherein a composite oxide composed of one or more of LaSrAlO ₄ and CeO ₂ is exposed on the surface. Membrane substrate. The composite oxide comprising any one or more of BaSnO ₃ , BaZrO ₃ and Ba ₂ NdTaO ₆ is exposed on the surface in the crystal phase . The base material for YBCO type high temperature superconductor film formation as described. 5. The YBCO-based high-temperature superconductor film-forming substrate according to claim 3, wherein the thin film on the substrate is a composite of BaZrO ₃ and a Zr oxide and satisfies the following composition ratio.
0.65 ≤ Ba / Zr ≤ 0.98   A method for producing a YBCO-based high-temperature superconductor film, comprising producing a superconductor film using the YBCO-based high-temperature superconductor film-forming substrate according to any one of claims 1 to 7.