JP6638949B2 - Method for producing Bi-based oxide superconducting thin film and Bi-based oxide superconducting thin film structure - Google Patents

Description

  The present invention relates to a method for producing a non-c-axis oriented Bi-based oxide superconducting thin film and a Bi-based oxide superconducting thin film structure.

  An oxide superconductor has a structure in which superconducting layers and insulating layers are alternately laminated in a unit crystal thereof, and it is known that the intrinsic Josephson effect is exhibited by this laminated structure. Above all, Bi-based oxide superconductors are a group of substances that exhibit this effect strongly. In the case of manufacturing a Josephson device using the intrinsic Josephson effect of a Bi-based oxide superconductor, conventionally, a c-axis oriented body of a Bi-based oxide superconductor (bulk single crystal or single crystal thin film) is generally used. Has been used for In order to apply a c-axis oriented Bi-based oxide superconductor to a Josephson device, it is necessary to form a mesa structure. However, in the mesa structure, the length in the c-axis direction is limited by the thickness of the c-axis oriented body, so that the number of superconducting layers / insulating layers cannot be sufficiently increased, and the mesa structure itself is not manufactured. There are difficulties such as the need for complicated processing.

From such a point, research on a non-c-axis oriented film of a Bi-based oxide superconductor has been advanced. For example, Patent Documents 1 to 3 disclose that, on a single crystal substrate such as LaSrAlO ₄ or LaSrGaO ₄ , the c-axis of a Bi-based oxide superconductor crystal is parallel to the substrate surface, and the a-axis or b-axis is the substrate surface. It is described that a Bi-based oxide superconducting thin film oriented perpendicularly to a thin film is formed. According to the Bi-based oxide superconducting thin film in which the a-axis or the b-axis is oriented perpendicular to the substrate surface, a planar structure that is easy to manufacture can be applied, and the length of the c-axis direction is the surface of the thin film. The number of superconducting layers / insulating layers can be sufficiently increased. However, since the c-axis is parallel to the substrate surface, it is difficult to install electrodes constituting the Josephson element.

  According to the Bi-based oxide superconducting thin film in which the c-axis of the Bi-based oxide superconductor crystal is grown in a direction oblique to the substrate surface, the Bi-based oxide in which the c-axis is grown in parallel to the substrate surface is provided. As in the case of the superconducting thin film, a planar structure can be applied, and the increase in the number of superconducting layers / insulating layers and the ease of installation of the electrodes can both be achieved. However, in the conventional method for producing a Bi-based oxide superconducting thin film, an obliquely oriented Bi-based oxide superconducting thin film having excellent practicality has not been obtained. For example, by selecting the crystal plane of a single crystal substrate on which a Bi-based oxide superconductor crystal is grown, the c-axis can be oriented obliquely with respect to the substrate surface of the single crystal substrate. The growth direction cannot be limited to one direction. In this case, the Josephson effect does not appear, and a Josephson element cannot be realized.

Japanese Patent No. 4448934 Japanese Patent No. 4452805 Japanese Patent No. 4572386

  The problem to be solved by the present invention is to provide a Bi-based oxide superconducting thin film having excellent reproducibility, which is capable of obtaining a Bi-based oxide superconducting thin film having excellent practicability and having a c-axis obliquely oriented. An object of the present invention is to provide a Bi-based oxide superconducting thin film structure.

  The method for producing a Bi-based oxide superconducting thin film of the present invention has a surface inclined at an angle of 3 ° or more and 25 ° or less from a two-fold symmetric crystal plane of a perovskite crystal, a pseudo perovskite crystal, or a rock salt crystal. Preparing a perovskite-type, pseudo-perovskite-type, or rock salt-type oxide single-crystal substrate; and growing a Bi-based oxide superconductor crystal on the surface of the oxide single-crystal substrate to form a Bi-based oxide superconductor. A step of forming a conductive thin film, wherein the c-axis of the Bi-based oxide superconductor crystal is inclined at a predetermined angle from the crystal plane, and based on an inclination angle of the surface from the crystal plane. The Bi-based oxide superconducting thin film is grown by growing the Bi-based oxide superconducting thin film only in one direction.

  The Bi-based oxide superconducting thin film structure of the present invention has a perovskite surface having a surface inclined at an angle of 3 ° or more and 25 ° or less from a two-fold symmetric crystal plane of a perovskite crystal, a pseudo perovskite crystal, or a rock salt crystal. And a pseudo perovskite-type or rock-salt-type oxide single-crystal substrate, and a Bi-based oxide superconducting thin film formed on the surface of the oxide single-crystal substrate, wherein the Bi-based oxide superconductor crystal Is characterized by having a Bi-based oxide superconducting thin film grown obliquely at a predetermined angle from the crystal plane and in only one direction.

  According to the manufacturing method of the present invention, a Bi-based oxide superconducting thin film in which the c-axis of the Bi-based oxide superconductor crystal is grown obliquely to the substrate surface and in only one direction can be obtained with good reproducibility. be able to. Accordingly, it is possible to provide a Bi-based oxide superconducting thin film having excellent practicality and a structure using the same.

It is a figure showing a manufacturing process of a Bi system oxide superconducting thin film of an embodiment. SrTiO ₃ is a diagram schematically showing a growth state of a (115) oriented film of the single crystal substrate _{(110) Bi 2 Sr 2 Cu} 1 O 6 + δ on the plane (Bi-2201). FIG. 3 is a diagram schematically showing an initial growth state of a Bi-based oxide superconductor crystal on a single crystal substrate having a surface parallel to a (110) plane of SrTiO ₃ . FIG. 4 is a diagram schematically illustrating a Bi-based oxide superconducting thin film based on the Bi-based oxide superconductor crystal illustrated in FIG. 3. FIG. 3 is a diagram schematically illustrating an initial growth state of a Bi-based oxide superconductor crystal on a single crystal substrate whose surface is inclined with respect to the (110) plane of SrTiO ₃ . FIG. 6 is a diagram schematically illustrating a Bi-based oxide superconducting thin film based on the Bi-based oxide superconductor crystal illustrated in FIG. 5. FIG. 7 is a diagram showing an X-ray diffraction result of a Bi-2212 superconducting thin film of Comparative Example 1 by a φ-ψ biaxial scanning method. FIG. 3 is a diagram showing an X-ray diffraction result of a Bi-2212 superconducting thin film of Example 1 by a φ-ψ biaxial scanning method. FIG. 8 is a diagram showing an X-ray diffraction result of a Bi-2212 superconducting thin film of Example 2 by a φ-ψ biaxial scanning method. FIG. 9 is a view showing an X-ray diffraction result of a Bi-2212 superconducting thin film of Example 3 by a φ-ψ biaxial scanning method. Is a diagram showing a measurement state of the X-ray diffraction schematically by SrTiO 3 ₍₁₁₀₎ Bi system were then deposited onto the parallel single-crystal substrate with respect to surface oxide superconducting thin film phi-.psi.2 axial scanning method surface . Is a diagram showing a measurement state of the X-ray diffraction schematically by SrTiO 3 ₍₁₁₀₎ Bi-based film was formed on a single crystal substrate which is inclined with respect to surface oxide ultrafine conductive thin phi-.psi.2 axial scanning method surface .

  Hereinafter, a method for manufacturing a Bi-based oxide superconducting thin film and a Bi-based oxide superconducting thin film structure according to an embodiment will be described with reference to the drawings.

FIG. 1 is a view showing a manufacturing process of a Bi-based oxide superconducting thin film of an embodiment. First, as shown in FIG. 1A, a single crystal substrate 1 made of a perovskite oxide, a pseudo perovskite oxide, or a rock salt oxide is prepared. The single crystal substrate 1 for growing a Bi-based oxide superconducting thin _{film, SrTiO 3 (STO), LaAlO} 3 (LAO), NdGaO 3 (NGO), NdAlO 3, (LaAlO 3) 0.3 - (SrAl 0. General formula ABO ₃ such as ₅ Ta _0.5 O ₃ ) _0.7 (LSAT) (A is a cation having a large radius such as Ca, Sr or La, and B is a cation smaller than A such as Ti or Al). has a composition represented by, oxides having a perovskite crystal structure single _crystal, LaSrAlO 4, oxide single crystal, or an oxide having a rock-salt crystal structure such as MgO having a pseudo-perovskite type crystal structure of LaSrGaO ₄ such It is preferable to use a single crystal.

In the case of a perovskite oxide crystal, the single crystal substrate 1 has a physical surface (substrate surface) SS inclined at an angle (β) of 3 ° or more and 25 ° or less with respect to a two-fold symmetric crystal plane CF. A two-fold symmetric crystal plane is a crystal plane having a shape overlapping the original shape when rotated by 180 °. For example, as shown in FIG. 2, on the (110) plane of SrTiO ₃ , the axis length of the unit cell in the [11 (bar) 0] direction is 5.523 °, and the axis length in the [001] direction is 3.095 °. It can be seen that it is a two-fold symmetric crystal plane. Here, the (110) plane of SrTiO ₃ has been described, but the same applies to the (110) plane of LaAlO ₃ . The surface of the single crystal body is processed so that the surface (hereinafter also referred to as an inclined surface) SS is inclined at an angle β of 3 to 25 ° from a specific crystal plane CF of such a perovskite oxide crystal. The substrate 1 is manufactured. The same applies to the case where a single crystal substrate 1 made of a perovskite oxide other than SrTiO ₃ or LaAlO ₃ or a pseudo perovskite oxide or a rock salt oxide is used.

Next, as shown in FIG. 1B, a Bi-based oxide superconductor crystal is grown on a single-crystal substrate 1 having a specific inclined surface SS to form a Bi-based oxide superconducting thin film 2. . As the Bi-based oxide superconducting thin film 2, a Bi-based oxide superconductor having a composition represented by the following formula (1), (2), or (3) is used.
(Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Cu ₁ O _{6 + δ} (1)
(Where A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1. .)
(Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Ca ₁ Cu ₂ O _{8 + δ} (2)
(Where A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1. .)
(Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Ca ₂ Cu ₃ O _{10 + δ} (3)
(Where A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1. .)
In the above formulas (1) to (3), the element A is represented by Pb, but Hg, Al and the like are also exemplified, and the element B is exemplified by Ba and lanthanoid.

For example, when a thin film of a Bi-based oxide superconductor (Bi-2201) having a composition represented by the formula (1) is formed on a (110) plane of a SrTiO ₃ single crystal substrate, the Bi-2201 based on the lattice matching or the like of the (110) plane of the conductor crystals and SrTiO _3, (115) plane of the Bi-2201 superconductor crystal is grown on the (110) plane of SrTiO ₃ as shown in FIG. 2 . As a result, the Bi-2201 superconductor crystal grows such that the c-axis ([001] f) forms an angle (α1) of 38.5 ° with respect to the (110) plane of SrTiO ₃ . The angle α1 is the angle of the c-axis of the Bi-2201 superconductor crystal from the (110) plane of SrTiO ₃ . Angle α2 is the inclination angle of the c-axis of the Bi-2201 superconductor crystal with respect to the normal direction of the (110) plane of SrTiO ₃ , and in this case, is 51.5 °.

A thin film of a Bi-based oxide superconductor (Bi-2212) having a composition represented by the formula (2) or a Bi-based oxide superconductor (Bi-2223) having a composition represented by the formula (3) In the case where the thin film is formed on the (110) plane of the SrTiO ₃ single crystal substrate, although the specific angles (α1, α2) and the like are different, as in the case of the Bi-2201 superconductor crystal, Bi- The 2212 superconductor crystal and Bi-2223 superconductor crystal grow so that their c-axis is oriented obliquely from the (110) plane of SrTiO ₃ . When the (110) plane of LaAlO ₃ is used instead of the (110) plane of SrTiO _3, the (110) plane of another perovskite-type oxide crystal, pseudo perovskite-type oxide crystal, and rock salt-type oxide crystal is further changed. Similarly, when used, a thin film of a Bi-based oxide superconductor crystal grows such that the c-axis is oriented in an oblique direction.

In the Bi-2212 superconductor crystal, the (117) plane grows on the (110) plane of SrTiO ₃ . As a result, the Bi-2212 superconductor crystal grows so that the angle (α1) of the c-axis with respect to the (110) plane of SrTiO ₃ is 41.6 °. In this case, the angle α2 is 48.4 °. In the Bi-2223 superconductor crystal, the (119) plane grows on the (110) plane of SrTiO ₃ . As a result, the Bi-2223 superconductor crystal grows such that the angle (α1) of the c-axis with respect to the (110) plane of SrTiO ₃ is 47.3 °. In this case, the angle α2 is 42.7 °.

As described above, by utilizing lattice matching between the Bi-based oxide superconductor crystal and a specific crystal plane CF of an oxide crystal such as SrTiO ₃ or LaAlO ₃ , the Bi-based oxide superconductor crystal can be used. The c-axis can be grown obliquely at a predetermined angle α1 with respect to a specific crystal plane CF of the oxide crystal. When SrTiO ₃ or LaAlO ₃ is used as the perovskite oxide, the angle α1 between the c-axis of the Bi-based oxide superconductor crystal and the crystal plane CF of the perovskite oxide crystal is about 38 to 48 as described above. °. Here, the relationship between the Bi-based oxide superconductor crystal and the specific crystal plane CF of SrTiO ₃ or LaAlO ₃ has been described, but the present invention is not limited to this. Oblique orientation of c-axis of Bi-based oxide superconductor crystal thin film using perovskite-type oxide crystal other than SrTiO ₃ or LaAlO ₃ , pseudo-perovskite-type oxide crystal, rock salt-type oxide crystal, and Bi-type For the oblique orientation of the c-axis of the oxide superconductor crystal thin film other than the above, lattice matching between the oxide superconductor crystal and the oxide crystal can be used. The specific angle varies depending on the type and orientation plane of the oxide superconductor.

  When a Bi-based oxide superconductor crystal is grown on a single-crystal substrate such as a perovskite-type oxide, a single-crystal substrate 1X whose physical surface SS substantially matches the crystal plane CF as shown in FIG. When used, the Bi-based oxide superconductor crystal 2A grows in two directions because the crystal plane CF is a two-fold symmetry plane. FIG. 4 shows that the c-axis of the Bi-based oxide superconductor crystal is obliquely oriented at a predetermined angle α1 with respect to a specific crystal plane CF of the oxide crystal, but the c-axis is oriented in two directions. This shows a Bi-based oxide superconducting thin film 2X. When an electrode is attached to the surface of such a Bi-based oxide superconducting thin film 2X to produce a planar intrinsic Josephson device, the electrodes are connected by the c-plane of the thin film crystal. No voltage can be applied in the stacking direction, and the intrinsic Josephson effect does not appear.

  Therefore, in the manufacturing method of the embodiment, a single crystal substrate 1 such as a perovskite oxide having a surface SS inclined at an angle β of 3 to 25 ° from a specific crystal plane CF is used. In the single crystal substrate 1 having the inclined surface SS, steps 1S are formed on the surface SS at the atomic layer level, as shown in FIG. When a Bi-based oxide superconducting thin film is formed on the surface SS having the step 1S, the superconductor crystal 2B in the initial stage of film formation grows from the lower part of the step surface 1R in the step 1S. Superconductor crystal 2B grows only in one direction in which step surface 1R faces, and growth in the other direction is blocked by step surface 1R. Accordingly, as shown in FIG. 6, the Bi-based oxide superconducting thin film 2 in which the c-axis of the Bi-based oxide superconductor crystal is grown obliquely at a predetermined angle α1 from the crystal plane CF and in only one direction is obtained. Obtainable.

For example, using a SrTiO ₃ single crystal substrate 1, β the angle of inclination of the (110) plane of SrTiO ₃ having a surface SS of 10 °, when growing the Bi-2201 superconductor crystals, Bi-2201 superconducting The c-axis of the body crystal is obliquely oriented at an angle α1 of 38.5 ° with respect to the (110) plane of SrTiO ₃ and at an angle (α1 + β) of 48.5 ° with respect to the surface SS of the single crystal substrate 1. As a result, a Bi-based oxide superconducting thin film 2 in which the orientation of the c-axis of the Bi-2201 superconductor crystal is limited to only one direction is obtained. Even when the LaAlO ₃ single crystal substrate 1 is used, a similar Bi-based oxide superconducting thin film 2 can be obtained. Even when a Bi-2212 superconductor crystal or Bi-2223 superconductor crystal is used, a similar Bi-based oxide superconducting thin film 2 can be obtained although the c-axis orientation angle is slightly different.

  The method for forming the Bi-based oxide superconducting thin film 2 is not particularly limited, but is a metal organic chemical vapor deposition (MOCVD) method using an organic metal or a gas thereof as a raw material, a sputtering method, or a pulse laser deposition. A general film formation method such as a method (PLD method) and a reactive evaporation method can be applied. Among these, it is preferable to apply the MOCVD method that can obtain a high-quality Bi-based oxide superconducting thin film 2 because the film forming rate is close to the thermodynamic equilibrium condition and the film forming rate is low. When forming the Bi-based oxide superconducting thin film 2 by applying the MOCVD method, the film forming conditions are not particularly limited, but typical manufacturing conditions include a substrate temperature of about 600 ° C. and a total pressure of about 6 kPa. Preferably, the oxygen partial pressure is about 3 kPa, and the film forming rate is about 10 ° per hour.

  As described above, according to the manufacturing method of the embodiment, the Bi-based oxide superconductor crystal has the c-axis grown from the specific crystal plane CF obliquely at a predetermined angle α1 and in only one direction. The oxide superconducting thin film 2 can be obtained with good reproducibility. According to the Bi-based oxide superconducting thin film 2 of the embodiment, for example, when manufacturing a Josephson element, a planar structure that can be formed by a two-dimensional lithography technique such as a general lift-off method can be applied. Since the length in the c-axis direction is in the plane direction of the thin film, the number of stacked superconducting layers / insulating layers can be sufficiently increased. Further, since the c-axis direction is oblique to the substrate surface, the installation of the electrodes is facilitated. Therefore, it becomes possible to provide a Bi-based oxide superconducting thin film structure having excellent practicality.

  Next, examples and evaluation results thereof will be described.

(Comparative Example 1)
A LaAlO ₃ single crystal substrate was prepared. The LaAlO ₃ single crystal substrate has a surface (β = 0 °) parallel to the (110) plane. Bi-2212 superconductor crystals were grown on the surface ((110) plane) of such a LaAlO ₃ single crystal substrate by MOCVD. The deposition conditions were a substrate temperature of 600 ° C., a total pressure of 6 kPa, an oxygen partial pressure of 3 kPa, and a deposition rate of 10 ° per hour.

  The thus obtained Bi-2212 superconducting thin film was subjected to X-ray diffraction measurement by a φ-ψ biaxial scanning method. FIG. 7 shows the measurement results. FIG. 7 shows the results of measuring the X-ray diffraction peak by scanning the surface of the superconducting thin film in two directions, the φ-axis direction and the ψ-axis direction, by flattening the results based on the φ-axis angle and the ψ-axis angle. It is something. FIG. 7 shows four peaks (circled portions). This is because two peaks appear from one plane (c-plane) based on symmetry. In FIG. 7, the upper right and lower left peaks and the lower right and upper left peaks are respectively the same c-axis viewed from the opposite side. The presence of four peaks means that the c-axis exists in two directions, and it can be seen that the c-axis grows in two directions. The X-ray diffraction measurement by the φ-ψ two-axis scanning method will be described later in detail.

(Example 1)
A LaAlO ₃ single crystal substrate was prepared. The LaAlO ₃ single crystal substrate has a surface (β = 10 °) inclined by 10 degrees with respect to the (110) plane. Bi-2212 superconductor crystals were grown on the surface of such a LaAlO ₃ single crystal substrate by MOCVD. The film forming conditions were the same as in Comparative Example 1. The thus obtained Bi-2212 superconducting thin film was subjected to X-ray diffraction measurement by a φ-ψ biaxial scanning method. FIG. 8 shows the measurement results.

  FIG. 8 shows a measurement result of the X-ray diffraction peak similar to FIG. In FIG. 8, only two peaks (circled portions), that is, the lower right and upper left peaks appear, and the upper right and lower left peaks have disappeared. The presence of only two peaks means that the c-axis exists only in one direction, and it can be seen that the c-axis grows in one direction.

(Example 2)
A LaAlO ₃ single crystal substrate was prepared. The LaAlO ₃ single crystal substrate has a surface (β = 20 °) inclined by 20 degrees with respect to the (110) plane. Bi-2212 superconductor crystals were grown on the surface of such a LaAlO ₃ single crystal substrate by MOCVD. The film forming conditions were the same as in Comparative Example 1. The thus obtained Bi-2212 superconducting thin film was subjected to X-ray diffraction measurement by a φ-ψ biaxial scanning method. FIG. 9 shows the measurement results.

  FIG. 9 shows the measurement result of the X-ray diffraction peak similar to FIG. In FIG. 9, only two peaks (circled portions), that is, the lower right and upper left peaks appear, and the upper right and lower left peaks have disappeared. The presence of only two peaks means that the c-axis exists only in one direction, and it can be seen that the c-axis grows in one direction.

(Example 3)
An SrTiO ₃ single crystal substrate was prepared. The SrTiO ₃ single crystal substrate has a surface (β = 10 °) inclined by 10 degrees with respect to the (110) plane. Bi-2212 superconductor crystal was grown on the surface of such a SrTiO ₃ single crystal substrate by MOCVD. The film forming conditions were the same as in Comparative Example 1. The thus obtained Bi-2212 superconducting thin film was subjected to X-ray diffraction measurement by a φ-ψ biaxial scanning method. FIG. 10 shows the measurement results.

  FIG. 10 shows a measurement result of the X-ray diffraction peak similar to FIG. In FIG. 10, only two peaks (circled portions), that is, the lower right and upper left peaks appear, and the upper right and lower left peaks have disappeared. The presence of only two peaks means that the c-axis exists only in one direction, and it can be seen that the c-axis grows in one direction.

As in Example 1 to 3, LaAlO ₃ single crystal substrate having a 10-degree inclined surface with respect to (110) plane, LaAlO ₃ single crystal substrate having a 20-degree inclined surface with respect to (110) plane A Bi-2201 superconductor crystal or a Bi-2223 superconductor crystal was grown by MOCVD on a SrTiO ₃ single crystal substrate having a surface inclined by 10 degrees with respect to the (110) plane. It was confirmed that the same results as in Nos. To 3 were obtained.

  The X-ray diffraction measurement by the above-described φ-ψ two-axis scanning method will be described in detail below. Evaluation of a thin film using an ordinary θ-2θ type powder X-ray diffractometer (biaxial diffractometer) is generally performed. When the orientation of a thin film is evaluated using a normal biaxial diffractometer, diffraction in a direction perpendicular to the substrate is observed. A general Bi-based oxide superconducting thin film is c-axis oriented (c-axis is perpendicular to the substrate surface), and diffraction (002n) in the direction perpendicular to the substrate can be observed with a biaxial diffractometer. It is possible. The Bi-based oxide superconducting thin film formed on the (110) plane of the perovskite-type oxide single crystal substrate has a non-c-axis orientation (eg, 117 orientation). 117) Diffraction by the plane is observed. However, since the (117) plane is parallel to the (110) plane of the substrate, observation of the (117) peak cannot distinguish between one-way growth and two-way growth.

  From such a viewpoint, it is desirable to measure the direction of the c-axis in order to directly evaluate the growth direction. Furthermore, in the case where a substrate whose crystal plane is greatly inclined with respect to the mechanical surface of the substrate is used, in order to observe the c-axis, the inclination angle (α2) of the c-axis with respect to the normal of the crystal plane and the crystal plane with respect to the normal It is necessary to evaluate (α2 + β) and (α2-β) with respect to the mechanical substrate surface in consideration of the inclination angle (β) of the substrate surface. In order to know the orientation of such a sample in which the c-axis is inclined with respect to the substrate surface, it is necessary to give an offset (axis offset) to the angle of the ω-axis. This method is very effective for samples with a small slope. However, in a method in which the tilt of the substrate (substrate offset) is large and the axis offset is further provided, the diffraction X-rays become a shadow of the sample itself, and the measurement becomes impossible. Therefore, it is not possible to directly observe the direction of the c-axis of the non-c-axis alignment film.

  When a multi-axis X-ray diffractometer is used, a pole figure method is often used. In the φ-ψ two-axis scanning method shown in the above-described embodiment, the scan axis is the same as the pole projection, but the scanning range is widened on the plus and minus sides of the ψ axis and displayed in orthogonal coordinates. Thus, the biaxially-oriented growth mode on the substrate having a large inclination angle can be directly visualized. This means that the ψ axis uses the inclination of the crystal plane instead of the offset of the ω axis when the two-axis diffractometer is used. Further, by measuring each of the crystal of the substrate and the crystal of the film, the orientation relationship can also be directly evaluated. FIG. 10 schematically shows a measurement state of two-way growth, and FIG. 11 schematically shows a measurement state of one-way growth. In both the two-way growth and the one-way growth, the measurement result is determined based on a set of peaks at the lower right and upper left and a set of peaks at the upper right and lower left due to symmetry. If only one set of peaks appears, it is confirmed that the c-axis is growing in one direction.

  DESCRIPTION OF SYMBOLS 1 ... Single crystal substrate, 1S ... Step of substrate surface, 1R ... Step surface of step, 2 ... Bi-based oxide superconducting thin film, 2A, 2B ... Bi-based oxide superconductor crystal in early growth, CF ... Perovskite type Crystal plane of oxide, SS: Surface of single crystal substrate, SF: Surface of Bi-based oxide superconducting thin film, α1: Angle of c-axis of Bi-based oxide superconductor crystal with respect to crystal plane of single crystal substrate, α2 ... The angle of the c-axis of the Bi-based oxide superconductor crystal with respect to the direction of the normal to the crystal plane of the single crystal substrate. Β. The angle of the substrate surface with respect to the crystal plane of the perovskite oxide substrate.

Claims (7)

A step of preparing an SrTiO ₃ single crystal substrate or a LaAlO ₃ single crystal substrate having a surface inclined at an angle of 3 ° or more and 25 ° or less from a (110) plane of SrTiO ₃ or LaAlO ₃ ;
On the surface of the SrTiO ₃ single crystal substrate or the LaAlO ₃ single crystal substrate , (Bi _1−a A _a ) ₂ (Sr _1−b B _b ) ₂ Cu ₁ O _{6 + δ} (A and B are cations and a Is a number that satisfies 0 ≦ a <1, b is a number that satisfies 0 ≦ b <1, and δ is a number that satisfies 0 ≦ δ <1.) A step of growing a conductor crystal and forming a Bi-based oxide superconducting thin film,
The (115) plane of the Bi-based oxide superconductor crystal, said SrTiO ₃ or LaAlO ₃ of (110) is grown on the surface, the c-axis of the Bi-based oxide superconductor crystals, the (110) obliquely at an angle of 38.5 ° to the plane, or one 1 grown only in the direction, of the Bi-based oxide superconducting thin film characterized by depositing the Bi-based oxide superconducting thin film Production method. SrTiO ₃ Or LaAlO ₃ Having a surface inclined at an angle of 3 ° or more and 25 ° or less from the (110) plane of SrTiO 3 ₃ Single crystal substrate or LaAlO ₃ Preparing a single crystal substrate;
The SrTiO ₃ Single crystal substrate or LaAlO ₃ On the surface of the single crystal substrate, (Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Ca ₁ Cu ₂ O _{8 + δ} (A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1.) A step of growing a Bi-based oxide superconductor crystal having the composition represented to form a Bi-based oxide superconducting thin film,
The (117) plane of the Bi-based oxide superconductor crystal was ₃ Or LaAlO ₃ And the c-axis of the Bi-based oxide superconductor crystal is grown obliquely at an angle of 41.6 ° with respect to the (110) plane and in only one direction. And forming the Bi-based oxide superconducting thin film. SrTiO ₃ Or LaAlO ₃ Having a surface inclined at an angle of 3 ° or more and 25 ° or less from the (110) plane of SrTiO 3 ₃ Single crystal substrate or LaAlO ₃ Preparing a single crystal substrate;
The SrTiO ₃ Single crystal substrate or LaAlO ₃ On the surface of the single crystal substrate, (Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Ca ₂ Cu ₃ O _{10 + δ} (A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1.) A step of growing a Bi-based oxide superconductor crystal having the composition represented to form a Bi-based oxide superconducting thin film,
The (119) plane of the Bi-based oxide superconductor crystal was replaced with the SrTiO ₃ Or LaAlO ₃ And the c-axis of the Bi-based oxide superconductor crystal is grown obliquely at an angle of 47.3 ° with respect to the (110) plane and in only one direction. And forming the Bi-based oxide superconducting thin film. X-ray diffraction measurement of the Bi-based oxide superconducting thin film was performed by the φ-ψ biaxial scanning method, and the c-axis of the Bi-based oxide superconductor crystal grew in only one direction from the obtained X-ray diffraction result. The method for producing a Bi-based oxide superconducting thin film according to any one of claims 1 to 3 , wherein the method confirms that the above-mentioned process is performed. An SrTiO ₃ single crystal substrate or a LaAlO ₃ single crystal substrate having a surface inclined at an angle of 3 ° or more and 25 ° or less from a (110) plane of SrTiO ₃ or LaAlO ₃ ;
A film is formed on the surface of the SrTiO ₃ single crystal substrate or the LaAlO ₃ single crystal substrate , and (Bi _1−a A _a ) ₂ (Sr _1−b B _b ) ₂ Cu ₁ O _{6 + δ} (A and B are cations) A is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1.) An oxide superconducting thin film, wherein the (115) plane of the Bi-based oxide superconductor crystal grows on the (110) plane of the SrTiO ₃ or LaAlO ₃ , and the Bi-based oxide superconductor crystal And a Bi-based oxide superconducting thin film grown in only one direction at an angle of 38.5 ° with respect to the (110) plane of SrTiO ₃ or LaAlO _3. A Bi-based oxide superconducting thin film structure. SrTiO ₃ Or LaAlO ₃ Having a surface inclined at an angle of 3 ° or more and 25 ° or less from the (110) plane of SrTiO 3 ₃ Single crystal substrate or LaAlO ₃ A single crystal substrate;
The SrTiO ₃ Single crystal substrate or LaAlO ₃ A film is formed on the surface of the single crystal substrate, and (Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Ca ₁ Cu ₂ O _{8 + δ} (A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1.) A Bi-based oxide superconducting thin film having the composition shown, wherein the (117) plane of the Bi-based oxide superconductor crystal is the SrTiO ₃ Or LaAlO ₃ Of the Bi-based oxide superconductor crystal grown on the (110) plane of ₃ Or LaAlO ₃ A Bi-based oxide superconducting thin film grown obliquely at an angle of 41.6 ° with respect to the (110) plane and in only one direction.
A Bi-based oxide superconducting thin-film structure comprising: SrTiO ₃ Or LaAlO ₃ Having a surface inclined at an angle of 3 ° or more and 25 ° or less from the (110) plane of SrTiO 3 ₃ Single crystal substrate or LaAlO ₃ A single crystal substrate;
The SrTiO ₃ Single crystal substrate or LaAlO ₃ A film is formed on the surface of the single crystal substrate, and (Bi _1-a A _a ) ₂ (Sr _1-b B _b ) ₂ Ca ₂ Cu ₃ O _{10 + δ} (A and B are cations, a is a number satisfying 0 ≦ a <1, b is a number satisfying 0 ≦ b <1, and δ is a number satisfying 0 ≦ δ <1.) A Bi-based oxide superconducting thin film having the composition shown, wherein the (119) plane of the Bi-based oxide superconductor crystal has the SrTiO 2 ₃ Or LaAlO ₃ Of the Bi-based oxide superconductor crystal grown on the (110) plane of ₃ Or LaAlO ₃ A Bi-based oxide superconducting thin film grown obliquely at an angle of 47.3 ° with respect to the (110) plane and in only one direction.
A Bi-based oxide superconducting thin-film structure comprising:

Images