JP4523249B2 - In-plane rotating high critical current superconducting wiring of crystal axis - Google Patents

Description

  The present technology relates to increasing the critical current density of oxide superconducting films.

When a magnetic field higher than the lower critical magnetic field H _cl is applied to the superconductor, a quantized magnetic flux (φ ₀ = 2.07 × 10 ⁻¹⁵ Wb) is formed and enters the superconductor. It is known that the Lorentz force acts on this, and when these start moving, a voltage is generated and the superconducting state is broken.

Defects in a superconducting film made of a superconductor, for example, an oxide high-temperature superconductor LnBa ₂ Cu ₃ O _X (Ln represents a lanthanide element), for example, point defects such as oxygen vacancies and fine impurities, linear defects such as dislocations It is known that planar defects such as crystal grain boundaries act as a pinning center that restricts the movement of the quantized magnetic flux. In the LnBa ₂ Cu ₃ O _X film, the crystal defects are perpendicular to the film surface. That is, when the magnetic field is applied perpendicularly to the film surface when entering parallel to the c-axis of the LnBa ₂ Cu ₃ O _X crystal, the critical current density J _c is improved.

The density per unit area of dislocations naturally introduced by changing the film formation conditions during the film formation of LnBa ₂ Cu ₃ O _X was 10 / μm ^{2 to} 100 / μm ² , and the film was formed on the substrate. If fine precipitates are present during the growth process, the continuity of film growth is lost, crystal defects, dislocations, grain boundaries, and the like, and the critical current density J _{c of the} LnBa ₂ Cu ₃ O _X film is increased in the film. It has been reported that it increases with the dislocation density (see Non-Patent Document 1). This teaches that dislocations act as a pinning center for quantized magnetic flux, but it is extremely difficult to control the density of dislocations that are naturally introduced simply by changing the deposition conditions during deposition.

On the other hand, it is known that the grain boundary acts as a pinning center but also acts as a barrier for superconducting current. In a high-temperature superconducting film such as LnBa ₂ Cu ₃ O _X, J _{c at a} crystal grain boundary having a large tilt angle is very small, but since a large J _c is maintained at a crystal grain boundary having a small tilt angle, the low tilt grain boundary is regarded as a dislocation array. be able to. Since dislocations are insulators, there is a strong superconducting portion between the transitions at a small-angle grain boundary with a large dislocation spacing, and current flows.However, if the tilt of the grain boundary becomes large and the distortion of the transition overlaps, the current flows. It becomes difficult to flow. If these crystal grain interfaces are perpendicular to the surface of the superconducting film, it becomes a very effective pinning center. However, in general very difficult to control the J _c by controlling the inclination of the crystal grain boundaries because the crystal grain boundaries existing randomly.

The superconducting bulk _magnet by LnBa 2 _Cu 3 _{O X} a refractory material in which _Ln 2 BaCuO _X were mixed with finely ground _to, to produce a superconductor in conditions that do not melt the Ln ₂ BaCuO _X, LnBa 2 A pinning center is introduced into Cu ₃ O _X (see Non-Patent Document 2). On the other hand, when the LnBa ₂ Cu ₃ O _X film is formed by the vapor deposition method, the composition of only a part of the film is different, and the other part is a superconductor composition, and the Ln: Ba: Cu ratio is 1: 2: 3. It is extremely difficult to maintain. For example, when the composition of the film forming material is shifted from the superconducting YBCO composition so that Ln ₂ BaCuO _X which is a high melting point material is introduced into a part of the film, the composition of the entire film becomes Ln ₂ BaCuO in a part of the film. _X is not introduced, and the composition of the entire film deviates from the superconductor composition, degrading the superconducting properties.

D. Shi et al., Supercond. Sci. Technol., Vol.3, no.9, pp457-463, 1990 T. Mochida et al., Physica C, vol.366, no.4, pp229-237, 2002

  As described above, if a crystal grain interface perpendicular to the surface of the superconducting film exists along the direction of current flow in the superconducting film, it is considered to be most effective as a pinning center. However, when forming a superconducting film by vapor deposition, it is extremely difficult to control and introduce transition, crystal grain boundaries, and crystal defects that can act as a pinning center in the superconducting film. In particular, it is substantially impossible to disperse materials having completely different compositions in the film while maintaining the composition of the matrix portion of the superconducting film.

  Therefore, there is a need for a superconducting wiring in which an artificial pinning center existing along the direction of current flow is introduced in the superconducting film, and a method for forming the superconducting wiring.

The superconducting wiring of the first embodiment of the present invention is provided on a substrate and the substrate, and LnBa ₂ Cu ₃ O _x (wherein Ln is Y or a lanthanide element, the structure on the left is a superconductor) And a superconducting film that has a composition of 6.5 <x <7.1) and allows a current to flow. The superconducting film has a c-axis oriented perpendicular to the substrate surface. And a first orientation portion having a first in-plane orientation and a second orientation portion having a c-axis oriented perpendicular to the substrate surface and having a second in-plane orientation different from the first in-plane orientation. An alignment portion, wherein the second alignment portion is composed of a plurality of portions extending along a direction in which the current flows, and side surfaces of the plurality of portions are perpendicular to the substrate. And The difference between the in-plane orientation azimuth of the first orientation portion and the in-plane orientation azimuth of the second orientation portion is preferably 35 ° or more and 45 ° or less. In addition, a first buffer layer may be provided between the substrate and the second alignment portion of the superconducting film. The substrate may be MgO or a substrate in which an MgO layer is stacked on another substrate.

A superconducting wiring according to a second embodiment of the present invention includes a substrate, a second buffer layer composed of a plurality of portions provided on the substrate, and a first buffer layer that covers the substrate and the second buffer layer. 3. LnBa ₂ Cu ₃ O _x (wherein Ln represents an element in which the left structure is a superconductor in Y or a lanthanide element, provided on three buffer layers and the third buffer layer; 5 <x <7.1) and a superconducting film through which an electric current flows. The superconducting film has a c-axis oriented perpendicular to the substrate surface, and the first surface A first orientation portion having an in-plane orientation, and a second in-plane orientation that is located above the second buffer layer, the c-axis is oriented perpendicular to the substrate surface, and is different from the first in-plane orientation A second alignment portion having the second alignment portion along the direction of current flow Is composed of a plurality of portions standing, side portions of said plurality of characterized in that it is perpendicular to the substrate. The difference between the in-plane orientation azimuth of the first orientation portion and the in-plane orientation azimuth of the second orientation portion is preferably 35 ° or more and 45 ° or less. In addition, a first buffer layer may be provided between the substrate and the second alignment portion of the superconducting film. The substrate may be MgO; R-plane sapphire; A-plane sapphire; or a laminate of an MgO layer, R-plane sapphire layer, or A-plane sapphire layer on another substrate.

The superconducting wiring according to the third embodiment of the present invention includes a substrate, a fourth buffer layer provided so as to cover the substrate, and a second buffer layer comprising a plurality of portions provided on the fourth buffer layer. And provided on the second buffer layer and the fourth buffer layer, and LnBa ₂ Cu ₃ O _x (wherein Ln represents an element in which the left structure is a superconductor in Y or a lanthanide element, 6.5 <x <7.1), and a superconducting film through which a current flows. The superconducting film has a c-axis oriented perpendicular to the substrate surface, and the first A first orientation portion having an in-plane orientation, and a second surface located above the second buffer layer and having a c-axis oriented perpendicular to the substrate surface and different from the first in-plane orientation A second alignment portion having an inner alignment, and the second alignment portion is in a direction in which the current flows. What is composed of a plurality of portions extending, side portion of said plurality of characterized in that it is perpendicular to the substrate. The difference between the in-plane orientation azimuth of the first orientation portion and the in-plane orientation azimuth of the second orientation portion is preferably 35 ° or more and 45 ° or less. In addition, a first buffer layer may be provided between the substrate and the second alignment portion of the superconducting film. The substrate may be MgO; R-plane sapphire; A-plane sapphire; or a laminate of an MgO layer, R-plane sapphire layer, or A-plane sapphire layer on another substrate.

  In the superconducting wiring of the present invention, the superconducting film is composed of portions having different in-plane orientations, and an interface between the portions having different in-plane orientations is artificially introduced. To do. Since the interface is arranged along the direction of current flow, it functions as a pinning center that prevents the quantized magnetic flux from moving in the direction perpendicular to the current due to the Lorentz force generated when a current is passed. It is possible to flow a larger current than before without moving. That is, in other words, the superconducting wiring of the present invention has an effect that the current density that can flow with zero resistance can be improved as compared with the conventional case.

In the present invention, utilizing the anisotropy of the oxide superconductor, a pinning center is formed between the oxide superconductors having the same composition. That is, an interface that causes an abrupt change in the symmetry of the oxide superconductor is used for the pinning center by using the anisotropy that the symmetry of the oxide superconductor varies depending on the crystal orientation. Specifically, a change in symmetry in the ab-plane of the oxide superconductor is used. In the ab-plane of the oxide superconductor LnBa ₂ Cu ₃ O _x , the symmetry of superconductivity is d _x2 -y2, and there is a node in the direction of 45 °. Therefore, a 45 ° phase rotation is forced at the interface between the a- or b-axis direction of one superconductor and the <110> direction of another superconductor, and a large superconductor symmetry wall is formed at the interface. It is formed. The present invention provides a structure in which this symmetrical wall is a pinning center.

  The superconducting wiring of the first embodiment of the present invention is shown in FIG. 1 includes a plurality of first buffer layers 2 extending along a current-carrying direction 8 on a substrate 1, and a first oriented portion 7 in which the superconducting film is in contact with the substrate 1. And a second orientation portion 6 provided on the first buffer layer 2. In both the first orientation portion 7 and the second orientation portion 6, the c-axis of the superconductor is oriented perpendicular to the surface of the substrate 1. However, the first orientation portion 7 and the second orientation portion 6 have a first in-plane orientation and a second in-plane orientation, respectively, and are different planes from the first in-plane orientation and the second in-plane orientation. It has an inner orientation orientation. The in-plane orientation direction in this specification means the <110> direction of the superconductor. The orientation directions of the first in-plane orientation and the second in-plane orientation have a difference of 35 ° to 45 °, preferably 40 ° to 45 °.

A superconductor material that can be used to form the superconducting film of the present invention is an oxide superconductor having the chemical formula LnBa ₂ Cu ₃ O _x , where Ln is Y or superconducting the chemical formula. Represents a lanthanide element as a body, and 6.5 <x <7.1. A preferred oxide superconductor is YBa ₂ Cu ₃ O _x . _{Further, (such} as _{Bi 2 Sr 2 Ca n-1} Cu n O x) LnBa 2 Cu 3 O x other than Bi system, Tl system _{(TlSr 2 Ca 2 Cu 3 O} x, TlSr 2 Ca n-1 Cu n O x Etc.) and Hg-based (HgSr ₂ Cann _-1 Cu _n O _x ) oxide superconductors have the same effect if there is a buffer layer that rotates the in-plane orientation by 35 ° or more and 45 ° or less. It goes without saying that it can be obtained.

  The substrate 1 is formed of a material that can orient the c-axis of the superconductor material perpendicular to the substrate surface and the <110> axis in a specific direction (first in-plane orientation). . A preferred substrate material is MgO. Alternatively, other substrates (oxide substrates, nitride substrates, semiconductor substrates, Ni-based alloy substrates such as pure Ni, Ni—Cr, and Ni—W, Cu-based alloy substrates such as pure Cu and Cu—Ni, or Fe) A substrate in which an MgO layer is laminated on a Fe-based alloy substrate such as Si or stainless steel may be used as the substrate 1.

When the first buffer layer 2 is formed on the substrate 1, the c-axis of the superconductor material is oriented perpendicular to the substrate surface, and the <110> axis is different from the first in-plane orientation. It is formed from a material that can be oriented in a specific direction (second in-plane orientation), that is, the in-plane orientation can be rotated. The material that can be used as the first buffer layer 2 includes a material having a fluorite structure such as CeO ₂ , ZrO ₂ or the like, or a material having a pyrochlore structure such as Gd ₂ Zr ₂ O ₇ or the like. When the first buffer layer 2 has a film thickness of 0.4 nm or more, preferably 10 nm, the in-plane orientation of the superconducting film formed thereon can be controlled.

In this embodiment, the substrate 1 and the first buffer layer 2 have an in-plane orientation of the superconductor material oriented thereon of 35 ° to 45 °, preferably 40 ° to 45 °. It is important to use a combination that can be controlled to have an orientation difference. A preferable combination of the substrate 1 and the first buffer layer 2 includes MgO / CeO ₂ and MgO / ZrO ₂ .

The first buffer layer 2 is made of PLD (pulse laser deposition), vapor deposition, sputtering, CVD (chemical vapor deposition), MBE (molecular beam epitaxy), or metal organic matter deposition (MOD). Can be formed by epitaxial growth on the substrate. In order to divide the first buffer layer 2 into a plurality of portions extending along the current-carrying direction 8, a nanolithography method, a method using a mask during stacking, a lift-off method, or the like can be used. The width of each of the plurality of divided portions of the first buffer layer (the dimension in the direction perpendicular to the direction of current application 8) is the quantized magnetic flux lattice constant a _f (a _f = 1) at the magnetic flux density B of the applied magnetic field. 0.07 × (φ ₀ / B) ^1/2 ) (desired). The width of each of the divided portions of the first buffer layer 2 is usually 100 nm or less, preferably 5 nm to 50 nm. Furthermore, the distance between two adjacent portions of the first buffer layer may also be desirable in the magnetic flux density B of the magnetic field applied is less than the quantization flux lattice constant a _f. The distance between two adjacent portions of the first buffer layer is usually 100 nm or less, preferably 5 nm to 50 nm.

  Then, a superconductor material is laminated on the substrate 1 on which the first buffer layer 2 divided into a plurality of portions is formed by using PLD, vapor deposition method, sputtering method, CVD, MBE or MOD. A superconductor film composed of the first orientation portion 7 and the second orientation portion 6 is formed. In the present embodiment, since the second alignment portion 6 is provided on the first buffer layer composed of a plurality of portions extending along the current supply direction 8, the first alignment portion 7 is also arranged in the current supply direction 8. Divided into a plurality of parts extending along (see FIG. 2). Therefore, the interface 9 between the first orientation portion 7 and the second orientation portion is parallel to the current conduction direction 8. In the present invention, if the interface 9 is not perpendicular to the direction of current flow, the structure can function as a superconducting wiring. In the present invention, the in-plane orientation directions of the first orientation portion 7 and the second orientation portion 6 may be any direction on the condition that the in-plane orientation orientation difference is as described above.

  Each of the first alignment portion 7 and the second alignment portion 6 of the superconducting film has its c-axis aligned perpendicularly to the substrate surface, and is parallel to the substrate surface in the ab-plane (so-called superconducting surface Is). Accordingly, the current flowing along the direction 8 can flow in the ab− plane of the first alignment portion 7 and the second alignment portion 6, so that the current density can be improved. And in the interface 9, the in-plane orientation differs greatly and the big difference has arisen in the symmetry of a wave function. Therefore, even if the quantized magnetic flux in the superconducting film receives a Lorentz force in a direction perpendicular to the current supply direction 8 during current application, it cannot move beyond the interface 9. That is, the interface 9 functions as an effective pinning center for the movement of the quantized magnetic flux, and allows the critical current density Jc to be increased.

  The superconducting wiring of the second embodiment of the present invention is shown in FIG. The superconducting wiring of FIG. 3 includes a second buffer layer 3 composed of a plurality of portions extending along the current-carrying direction 8 on the substrate 1, and a third buffer existing over the substrate 1 and the second buffer layer. The layer 4 and a superconducting film provided on the third buffer layer 4 are included. The superconducting film is located above the second buffer layer 3 and above the second alignment portion 6 having the second in-plane alignment and the portion where the substrate 1 and the third buffer layer 4 are in direct contact. And a first alignment portion 7 having a first in-plane alignment. Also in this embodiment, the difference between the orientation orientation of the first in-plane orientation and the orientation orientation of the second in-plane orientation is 35 ° or more and 45 ° or less, preferably 40 ° or more and 45 ° or less. desirable.

  As a material for the substrate 1, MgO, R-plane sapphire, and A-plane sapphire can be used. Alternatively, other substrates (oxide substrates, nitride substrates, semiconductor substrates, Ni-based alloy substrates such as pure Ni, Ni—Cr, and Ni—W, Cu-based alloy substrates such as pure Cu and Cu—Ni, or Fe) The substrate 1 may be a laminate of an MgO layer, an R-plane sapphire layer, or an A-plane sapphire layer on a Fe-based alloy substrate such as Si or stainless steel.

When the third buffer layer 4 is formed on the second buffer layer 3, the c-axis of the superconductor material is oriented perpendicular to the substrate surface, and the <110> axis is in a specific direction. It is formed from a material that can be oriented (second in-plane orientation), that is, the in-plane orientation can be rotated. Materials that can be used as the second buffer layer 3 include BaSnO ₃ , BaZrO ₃ , SrSnO ₃ , SrTiO ₃ , SrZrO ₃ , and BaTiO ₃ having a II-IV group perovskite structure. When the second buffer layer 3 has a thickness of 0.4 nm or more, preferably 10 nm, the in-plane orientation of the superconducting film formed thereon can be controlled.

The second buffer layer 3 is formed by laminating a material on the substrate 1 using PLD (pulse laser deposition), vapor deposition, sputtering, CVD (chemical vapor deposition) or MBE (molecular beam epitaxy). Can be formed. In order to divide the second buffer layer 3 into a plurality of portions extending along the current supply direction 8, a nanolithography method, a method using a mask at the time of stacking, a lift-off method, or the like can be used. The width of each of the plurality of divided portions of second buffer layer (the dimension in the direction perpendicular to the current flowing direction 8) is not more than the quantization flux lattice constant a _f of the magnetic flux density B of an applied magnetic field desirable. The width of each of the divided portions of the second buffer layer 3 is usually 100 nm or less, preferably 5 nm to 50 nm. Furthermore, the distance between two adjacent portions of the second buffer layer may also be desirable in the magnetic flux density B of the magnetic field applied is less than the quantization flux lattice constant a _f. The interval between two adjacent portions of the second buffer layer is usually 100 nm or less, preferably 5 nm to 50 nm.

The third buffer layer 4 does not cause mutual diffusion with the superconductor material forming the superconductor film, and the c-axis of the superconductor material constituting the superconductor film is perpendicular to the substrate surface. From a material that can be oriented and can change the in-plane orientation direction of the superconducting film material formed thereon depending on whether the substrate 1 or the second buffer layer 3 is present thereunder. It is formed. In the portion where the substrate 1 and the third buffer layer 4 are in direct contact, the <110> axis of the superconductor material is oriented in a specific direction (first in-plane orientation). By providing the third buffer layer 4, mutual diffusion between the material of the substrate 1 and a superconductor material such as LnBa ₂ Cu ₃ O _x can be prevented. The third buffer layer 4 is uniformly formed on the front surface so as to cover the substrate 1 and the second buffer layer 3. The material that can be used as the third buffer layer 4 includes a material having a fluorite structure such as CeO ₂ , ZrO ₂ or the like, or a material having a pyrochlore structure such as Gd ₂ Zr ₂ O ₇ or the like. Since the third buffer layer 4 has a thickness of 0.4 nm or more, preferably 10 nm, the in-plane orientation of the superconducting film formed thereon can be controlled depending on the type of the underlying layer. Become.

In the present embodiment, the substrate 1, the second buffer layer 3, and the third buffer layer 4 have an in-plane orientation of the superconductor oriented thereon of 35 ° to 45 °, preferably 40 ° to 45 °. It is important to use a combination that can be controlled to have an in-plane orientation azimuth difference of less than or equal to. Preferred combinations of the second buffer layer 3 / second buffer layer 4 are BaSnO ₃ / CeO ₂ , BaZrO ₃ / CeO ₂ , SrSnO ₃ / CeO ₂ , SrTiO ₃ / CeO ₂ , SrZrO ₃ / CeO ₂ , BaTiO ₃ / ZrO _{3 2} is included.

  Then, a superconductor material is laminated on the third buffer layer 4 using PLD, vapor deposition, sputtering, CVD, MBE or MOB, thereby constituting the first alignment portion 7 and the second alignment portion 6. A superconductor film is formed. In the present embodiment, since the second alignment portion 6 is provided above the second buffer layer composed of a plurality of portions extending along the current supply direction 8, the first alignment portion 7 also has the current supply direction 8. Is divided into a plurality of parts extending along. Therefore, the superconducting film of this embodiment has the same shape as the superconducting film of the first embodiment (see FIG. 2). Also in the present embodiment, the in-plane orientation directions of the first orientation portion 7 and the second orientation portion 6 may be any direction on the condition that the in-plane orientation orientation difference is provided.

  Also in the present embodiment, the current flowing along the current conduction direction 8 can flow in the ab− plane of the first alignment portion 7 and the second alignment portion 6, so that the current density can be improved. it can. Then, the interface 9 between the first alignment portion 7 and the second alignment portion 6 functions as an effective pinning center for the movement of the quantized magnetic flux, and can increase the critical current density Jc.

  The superconducting wiring of the third embodiment of the present invention is shown in FIG. The superconducting wiring of FIG. 4 is formed on the substrate 1 with a second buffer layer 3 consisting of a plurality of parts extending along the current conduction direction 8 and a plurality of parts extending along the current conduction direction 8. It has a third buffer layer 4 and a superconducting film provided on the third buffer layer 4 and the second buffer layer 3. In the present embodiment, the third buffer layer 4 is not provided so as to cover the entire surface of the substrate 1 and the second buffer layer 3, but is provided only between two adjacent portions of the second buffer layer 3. This is different from the second embodiment. Therefore, in the present embodiment, the third buffer layer 4 is composed of a plurality of portions, and each of the portions is sandwiched between two adjacent portions of the second buffer layer 3. The superconducting film is composed of a second alignment portion 6 having a second in-plane alignment on the second buffer layer 3 and a first alignment portion 7 having a first in-plane alignment on the third buffer layer 4. Is done. Also in this embodiment, the difference between the orientation orientation of the first in-plane orientation and the orientation orientation of the second in-plane orientation is 35 ° or more and 45 ° or less, preferably 40 ° or more and 45 ° or less. desirable.

  As a material for the substrate 1, MgO, R-plane sapphire, and A-plane sapphire can be used as in the second embodiment. Alternatively, other substrates (oxide substrates, nitride substrates, semiconductor substrates, Ni-based alloy substrates such as pure Ni, Ni—Cr, and Ni—W, Cu-based alloy substrates such as pure Cu and Cu—Ni, or Fe) The substrate 1 may be a laminate of an MgO layer, an R-plane sapphire layer, or an A-plane sapphire layer on a Fe-based alloy substrate such as Si or stainless steel.

The second buffer layer 3 of the present embodiment is similar to the second buffer layer of the present embodiment in that the BaSnO ₃ , BaZrO ₃ , SrSnO ₃ , SrTiO ₃ , SrZrO ₃ , BaTiO having a perovskite structure is the same as the second embodiment. _{3 is} formed. The second buffer layer 3 is composed of a plurality of portions extending along the current conduction direction 8. Two adjacent portions of the second buffer layer 3 are separated by the constituent portions of the third buffer layer 4. Each of the plurality of portions constituting the second buffer layer 3, it is desirable in the magnetic flux density B of the magnetic field applied is less than the quantization flux lattice constant a _f. The width of each part is usually 100 nm or less, preferably 5 nm to 50 nm. Further, the interval between two adjacent portions of the second buffer layer 3 (ie, corresponding to the width of each portion constituting the third buffer layer 4) is also the quantized magnetic flux lattice at the magnetic flux density B of the applied magnetic field. It is desirable that the constant _af or less. The interval between two adjacent portions of the second buffer layer is usually 100 nm or less, preferably 5 nm to 50 nm.

The third buffer layer 4 does not cause mutual diffusion with the superconductor material such as LnBa ₂ Cu ₃ O _x forming the superconductor film, and the c-axis of the superconductor material formed on the third buffer layer 4 It is formed from a material that can be oriented in a direction perpendicular to the substrate surface and that can be oriented in the first in-plane orientation orientation. The third buffer layer 4 is composed of a plurality of portions extending along the current conducting direction 8, and two adjacent portions of the third buffer layer 4 are separated by one of the constituent portions of the second buffer layer 3. Is done. As mentioned above that the spacing of the respective width and the two adjacent portions of the plurality of portions constituting the second buffer layer 3, the magnetic flux density B of the magnetic field applied is less than the quantization flux lattice constant a _f Is desirable. The width of each part is usually 100 nm or less, preferably 5 nm to 50 nm. The distance between two adjacent portions of the third buffer layer 4 is usually 100 nm or less, preferably 5 nm to 50 nm. The material that can be used as the third buffer layer 4 includes a material having a fluorite structure such as CeO ₂ , ZrO ₂ or the like, or a material having a pyrochlore structure such as Gd ₂ Zr ₂ O ₇ or the like. When the third buffer layer 4 has a thickness of 0.4 nm or more, preferably 10 nm, the in-plane orientation of the superconducting film formed thereon can be controlled.

In the present embodiment, the second buffer layer 3 and the third buffer layer 4 have an in-plane orientation of the superconductor oriented thereon of 35 ° to 45 °, preferably 40 ° to 45 °. It is important to use a combination that can be controlled so as to have an in-plane orientation difference. Preferred combinations of the second buffer layer 3 / second buffer layer 4 are BaSnO ₃ / CeO ₂ , BaZrO ₃ / CeO ₂ , SrSnO ₃ / CeO ₂ , SrTiO ₃ / CeO ₂ , SrZrO ₃ / CeO ₂ , BaTiO ₃ / ZrO _{3 2} is included.

  The second buffer layer 3 and the third buffer layer 4 in the present embodiment can be formed as follows, for example. First, the third buffer layer 4 is formed on the entire surface of the substrate 1. Next, a photoresist is applied, exposure and development are performed so as to give the third buffer layer 4 having a desired shape, and an etching mask is formed. Then, using the etching mask, the third buffer layer 4 is etched to expose the surface of the substrate 1. Next, the second buffer layer 3 is formed using the above-described etching mask as a lift-off resist. Finally, by removing the etching mask and the second buffer layer 3 formed thereon, the second buffer layer 3 and the third buffer layer 4 each having a plurality of portions and alternately arranged are obtained. . If applicable processing conditions exist, the second buffer layer 3 may be deposited first, and then the third buffer layer 4 may be lifted off. Here, the etching can be performed using any means known in the art, such as wet etching, RIE, and plasma etching.

  Then, by superposing a superconductor material on the second buffer layer 3 and the third buffer layer 4 by using PLD, vapor deposition method, sputtering method, CVD, MBE or MOB, the first alignment portion 7 and the first buffer portion 3 A superconductor film composed of two oriented portions 6 is formed. In the present embodiment, since the second alignment portion 6 is provided above the second buffer layer 3 composed of a plurality of portions extending along the current supply direction 8, the first alignment portion 7 also has the current supply direction. 8 is divided into a plurality of parts extending along the line 8. Therefore, the superconducting film of this embodiment has the same shape as the superconducting film of the first embodiment (see FIG. 2). Also in the present embodiment, the in-plane orientation directions of the first orientation portion 7 and the second orientation portion 6 may be any direction on the condition that the in-plane orientation orientation difference is provided.

  Also in the present embodiment, the current flowing along the current conduction direction 8 can flow in the ab− plane of the first alignment portion 7 and the second alignment portion 6, so that the current density can be improved. it can. Then, the interface 9 between the first alignment portion 7 and the second alignment portion 6 functions as an effective pinning center for the movement of the quantized magnetic flux, and can increase the critical current density Jc.

In the first to third embodiments described above, the example in which the second alignment portion 6 of the superconducting film is continuous in the current conduction direction 8 has been described. However, as shown in FIG. It may be discontinuous. In this case, the distance between the two second alignment portion adjacent the current supply direction 8, it is preferable in the magnetic flux density B of the magnetic field applied is less than the quantization flux lattice constant a _f. In a normal case, the distance between two second alignment portions adjacent in the current application direction 8 is 500 nm or less, preferably 15 nm to 300 nm, more preferably 20 nm to 200 nm. By setting such an interval, it is possible to prevent the quantized magnetic flux from moving through the discontinuous portion and improve the critical current density Jc.

  In order to form such a discontinuous second alignment portion 6, the first buffer layer 2 may be formed in a shape corresponding to a desired discontinuous shape in the first embodiment. In the second embodiment, the second buffer layer 3 may be formed in a shape corresponding to a desired discontinuous shape. In the third embodiment, the buffer layer to be stacked first may be formed in a shape corresponding to a desired discontinuous shape.

  Further, in the first to third embodiments, the example in which the superconducting film is formed on the front surface of the substrate 1 has been described. However, the superconducting film having the first alignment portion and the second alignment portion is formed on a part of the substrate. The superconducting wiring may be formed by forming only in the above. Furthermore, as shown in FIG. 6, a superconducting wiring bent at a right angle can be formed, and as shown in FIG. 7, a superconducting wiring bent in a curve can be formed. Even in these bent wirings, the superconducting film has the first and second orientation portions composed of a plurality of portions arranged along the current-carrying direction, so that the critical current density is not lowered.

CeO ₂ was deposited on the MgO substrate 1 at a temperature of 750 ° C., and a first buffer layer 2 having a thickness of 10 nm was formed on the entire surface of the substrate. Next, a resist was applied to form a pattern composed of a plurality of portions having a width of 100 nm extending in one direction. The interval between two adjacent portions was 100 nm. Then, etching was performed using the resist composed of the plurality of portions as a mask, and the portion of the first buffer layer 2 not covered with the resist was removed. After removing the resist, ErBa ₂ Cu ₃ O _x was vapor-deposited at a temperature of 700 ° C. to form a superconducting film having a thickness of 500 nm, and the superconducting wiring shown in FIG. 1 was obtained. The superconducting film formed in direct contact with the substrate 1 is deposited along the lattice of the substrate to become the first alignment portion 7, and the superconducting film located on the first buffer layer 2 has different in-plane alignment. It became the 2nd orientation part 6 which has. The in-plane alignment azimuth difference between the first alignment portion 7 and the second alignment portion 6 was 45 °.

BaSnO ₃ was deposited on the R-plane sapphire substrate 1 at a temperature of 750 ° C. to form a second buffer layer 3 having a thickness of 10 nm on the entire surface of the substrate. Next, a resist was applied to form a pattern composed of a plurality of portions having a width of 100 nm extending in one direction. The interval between two adjacent portions was 100 nm. Then, etching was performed using the resist composed of the plurality of portions as a mask, and the second buffer layer 3 in a portion not covered with the resist was removed. After removing the resist, CeO ₂ was deposited at a temperature of 750 ° C., and a third buffer layer 4 having a thickness of 10 nm was formed so as to cover the substrate 1 and the second buffer layer 3. Next, ErBa ₂ Cu ₃ O _x was vapor-deposited at a temperature of 700 ° C. to form a superconducting film having a thickness of 500 nm, and the superconducting wiring shown in FIG. 2 was obtained. The superconducting film formed in the portion having the laminated structure of the substrate 1 / third buffer layer 4 becomes the first orientation portion 7, and in the portion having the laminated structure of substrate 1, second buffer layer 3 / third buffer layer 4. The formed superconducting film became the second alignment portion 6 having different in-plane alignment. The in-plane alignment azimuth difference between the first alignment portion 7 and the second alignment portion 6 was 45 °.

CeO ₂ was deposited on the R-plane sapphire substrate 1 at a temperature of 750 ° C. to form a third buffer layer 4 having a thickness of 10 nm on the entire surface of the substrate. Next, a resist was applied to form a pattern composed of a plurality of portions having a width of 100 nm extending in one direction. The interval between two adjacent portions was 100 nm. Then, etching was performed using the resist composed of the plurality of portions as a mask, and the portion of the fourth buffer layer 4 not covered with the resist was removed. Next, BaSnO ₃ having a thickness of 10 nm was deposited at a temperature of 750 ° C. Finally, the resist and the BaSnO ₃ film formed on the resist were removed to form a second buffer layer 3 composed of a plurality of portions. The second buffer layer 3 and the third buffer layer 4 were alternately arranged, and their respective portions had a width of 100 nm.

Next, ErBa ₂ Cu ₃ O _x was vapor-deposited at a temperature of 700 ° C. to form a 500 nm-thick superconducting film, and the superconducting wiring shown in FIG. 3 was obtained. The superconducting film formed in the portion having the laminated structure of the substrate 1 / third buffer layer 4 becomes the first orientation portion 7, and the superconducting film formed in the portion having the laminated structure of the substrate 1 / second buffer layer 3 Became the second orientation portion 6 having a different in-plane orientation. The in-plane alignment azimuth difference between the first alignment portion 7 and the second alignment portion 6 was 45 °.

It is a perspective sectional view showing superconducting wiring of a 1st embodiment of the present invention. It is a top view which shows the superconducting wiring of the 1st Embodiment of this invention. It is a perspective sectional view showing the superconducting wiring of the 2nd embodiment of the present invention. It is a perspective sectional view showing superconducting wiring of a 3rd embodiment of the present invention. It is a top view which shows the superconducting wiring containing a discontinuous 2nd orientation part. It is a top view which shows the superconducting wiring bent at right angle. It is a top view which shows the superconducting wiring bent along the curve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 1st buffer layer 3 2nd buffer layer 4 3rd buffer layer 6 2nd orientation part of superconducting film 7 1st orientation part of superconducting film 8 Current supply direction 9 1st orientation part and 2nd orientation part Interface

Claims (10)

A substrate,
LnBa ₂ Cu ₃ O _x provided on the substrate (wherein Ln represents an element in which the left structure is a superconductor among Y or lanthanide elements, and 6.5 <x <7.1) A superconducting film that has a composition and allows current to flow,
The superconducting film has a c-axis oriented perpendicular to the substrate surface and a first orientation portion having a first in-plane orientation, a c-axis oriented perpendicular to the substrate surface, and the first A second orientation portion having a second in-plane orientation different from the in-plane orientation of
The superconducting wiring, wherein the second orientation portion is composed of a plurality of portions extending along a direction in which the current flows, and side surfaces of the plurality of portions are perpendicular to the substrate.   2. The superconducting wiring according to claim 1, wherein a difference between an in-plane orientation azimuth of the first orientation portion and an in-plane orientation azimuth of the second orientation portion is not less than 35 ° and not more than 45 °.   The superconducting wiring according to claim 1, wherein a first buffer layer is provided between the substrate and the second orientation portion of the superconducting film.   2. The superconducting wiring according to claim 1, wherein the substrate is selected from the group consisting of MgO and another substrate in which an MgO layer is stacked. A substrate,
A second buffer layer comprising a plurality of portions provided on the substrate;
A third buffer layer provided over the substrate and the second buffer layer; and provided on the third buffer layer; and LnBa ₂ Cu ₃ O _x (where Ln is Y or a lanthanide element) A superconducting film having a composition in which the structure on the left represents an element that becomes a superconductor and 6.5 <x <7.1.
The superconducting film has a c-axis oriented perpendicular to the substrate surface and is positioned above the first alignment portion having the first in-plane orientation and the second buffer layer, and the c-axis is located on the substrate surface. And a second orientation portion having a second in-plane orientation different from the first in-plane orientation,
The superconducting wiring, wherein the second orientation portion is composed of a plurality of portions extending along a direction in which the current flows, and side surfaces of the plurality of portions are perpendicular to the substrate.   6. The superconducting wiring according to claim 5, wherein a difference between an in-plane orientation direction of the first orientation portion and an in-plane orientation direction of the second orientation portion is not less than 35 ° and not more than 45 °.   6. The substrate is selected from the group consisting of MgO; R-plane sapphire; A-plane sapphire; and another substrate in which an MgO layer, R-plane sapphire layer, or A-plane sapphire layer is laminated. Superconducting wiring as described in 1. A substrate,
A fourth buffer layer provided to cover the substrate; a second buffer layer comprising a plurality of portions provided on the fourth buffer layer;
5. Provided on the second buffer layer and the fourth buffer layer, and LnBa ₂ Cu ₃ O _x (wherein Ln represents an element of which Y or lanthanide element has the left structure as a superconductor; 5 <x <7.1), and a superconducting film that allows current to flow therethrough,
The superconducting film has a c-axis oriented perpendicular to the substrate surface and is positioned above the first alignment portion having the first in-plane orientation and the second buffer layer, and the c-axis is located on the substrate surface. And a second orientation portion having a second in-plane orientation different from the first in-plane orientation,
The superconducting wiring, wherein the second orientation portion is composed of a plurality of portions extending along a direction in which the current flows, and side surfaces of the plurality of portions are perpendicular to the substrate.   The superconducting wiring according to claim 8, wherein a difference between an in-plane orientation direction of the first orientation portion and an in-plane orientation direction of the second orientation portion is not less than 35 ° and not more than 45 °. 9. The substrate is selected from the group consisting of MgO; R-plane sapphire; A-plane sapphire; and another substrate in which an MgO layer, R-plane sapphire layer, or A-plane sapphire layer is laminated. Superconducting wiring as described in 1.

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