WO2010000685A1

WO2010000685A1 - Electrically conductive high-temperature superconductor layered structure and method for the production thereof

Info

Publication number: WO2010000685A1
Application number: PCT/EP2009/058090
Authority: WO
Inventors: Ruben HÜHNE; Konrad Güth; Rainer Kaltofen
Original assignee: Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V.
Priority date: 2008-07-02
Filing date: 2009-06-29
Publication date: 2010-01-07
Also published as: DE102008040087A1; DE102008040087B4

Abstract

The invention relates to the field of material sciences and to an electrically conductive high-temperature superconductor layered structure, used for example as a high-current bearing conductor. The aim of the invention is to provide an electrically conductive high-temperature superconductor layered structure, which in the event of an overload can be used to conduct current via the layered structure and the substrate. The aim is achieved by an electrically conductive high-temperature superconductor layered structure consisting of a substrate (1), at least one nucleic layer (2) situated on said substrate, a layer (3) which is applied to the nucleic layer by means of an IBAD process, a barrier layer (4) being in turn located on said layer and at least one high-temperature superconductor layer (5) being situated on said barrier layer. The aim is further achieved by a method for producing an electrically conductive high-temperature superconductor layered structure, according to which at least one nucleic layer is applied to the substrate, at least one layer is applied to said layer by means of an IBAD process, at least one barrier layer is applied thereto and at least one high-temperature superconductor layer is then applied to said barrier layer.

Description

Electrically conductive high-temperature superconductor layer structure and method for its production

The invention relates to the field of materials science and relates to an electrically conductive high-temperature superconductor layer structure, as it can be used for example as a high current-carrying conductor and a method for its preparation.

For the fabrication of high-current superconducting conductors based on the high-temperature superconductors REBa ₂ Cu ₃ θ _7-x (= REBCO), where RE can be both Y and a rare earth element, then layers with a biaxial texture over long lengths are required. This can be realized by an epitaxial growth of the REBCO on textured documents. In general, the conductor consists of a metallic carrier tape on which additionally one or more barrier layers and then the superconductor are applied. These are the so-called REBCO band conductors. The desired biaxial texture can be known either directly in the metallic carrier tape by strong deformation and subsequent heat treatment can be realized (so-called RABiTS - rolling assisted biaxially textured substrates, Goyal et al., Appl. Phys., Lett. 69 (1996) 1795) or alternatively in one of the barrier layers induced by a special deposition method.

One possibility for producing highly textured barrier layers on any desired substrates is ion beam-assisted deposition (IBA (Iijima et al., Appl. Phys. Lett. 60 (1992) 769) US Pat. No. 6,190,752 B1; US 2006/0142164 A1). In this method, an ion beam with a defined energy is directed onto the substrate surface at a defined angle to the substrate surface during layer growth. As materials for this IBAD process, various oxides are known to be known, such as Y-stabilized ZrO 2 (YSZ; iijima et al., Appl. Phys. Lett. 60 (1992) 769), MgO (Wang et al., Appl Lett. 71 (1997) 2955) or Gd ₂ Zr ₂ O ₇ (Iijima et al., Physica C 378 (2002) 960).

However, additional barrier layers are needed to achieve epitaxial REBCO layers with high current carrying capacity.

Furthermore, in the case of application, a REBCO-based high current carrying cable must be protected from the destruction of the superconductor by overload (e.g., caused by current spikes, local heating, etc.). In this case, the current must be dissipated via an electrical bridge to prevent destruction of the REBCO due to excessive heating during the sudden transition from the superconducting to the normal conducting state. In order to realize such an electrical bridge, thick metallic layers (e.g., Ag, Cu, etc.) are currently deposited on the superconductor capable of carrying the corresponding current in case of overload.

An alternative approach to this is the use of the metallic carrier tape for this purpose. In this case, however, electrically conductive barrier layers are necessary to make electrical contact between the carrier tape and the to realize superconducting layer. The buffer layers used as standard as Y2O3, YSZ, CeO _2, MgO, La ₂ Zr ₂ O _7, etc. are not suitable.

Electrically conductive barrier layer architectures have in the past been realized for REBCO band conductors on the basis of the RABiTS approach (US 2003/0211948 A1, US 2005/0239658 A1). Among others, noble metals (Ir, Pt) and conductive oxides (La ₀ 7Sr ₀ 3MnO ₃ , SrRuO ₃ , LaNiO ₃ , etc.) were used (Aytug et al., Appl. Phys. Lett., 76 (2000) 760; Aytug et al., Appl. Phys. Lett. 85 (2004) 2887).

Using the IBAD method, it has heretofore been attempted to obtain an electrically conductive barrier layer architecture by the texture of indium tin oxide (ITO) (Thiele et al., J. Mater. Res. 18 (2003) 442).

As an alternative material for texturing using the IBAD process, the electrically conductive TiN is known (Huhne et al., Appl. Phys. Lett. 85 (2004) 2744).

Among others, Tai _-x Ni _x, _-x Tai Fe _x Co _x or _-x Tai known as temperature-stable, amorphous and electrically conductive barrier layers in microelectronics (Fang et al, J. Electr Mater 36 (2007) 614...; Fang et al., J. Electr. Mater. 35 (2006) 15).

The disadvantage of the prior art is that it has not yet been possible to produce a conductive layer structure on a metallic carrier tape by means of the IBAD method.

The object of the present invention is to specify an electrically conductive high-temperature superconductor layer structure in which, in the case of overload, the current can be dissipated via the layer structure and the metallic substrate and a simple and easily reproducible method for its production.

The object is achieved by the invention specified in the claims. Advantageous embodiments are the subject of the dependent claims.

The electrically conductive high-temperature superconductor layer structure according to the invention consists of an electrically conductive, metallic substrate, at least one electrically conductive seed layer having an amorphous and / or nanocrystalline structure thereon, on which at least one highly textured, electrically conductive layer applied by the IBAD method is present, on which in turn at least one highly textured, electrically conductive barrier layer and in turn at least one high temperature Superconductor layer are present.

Advantageously, the electrically conductive, metallic substrate consists of Ni, Ni-base alloys, stainless steel, Cu or copper alloys.

Also advantageously, the electrically conductive seed layer consists of an alloy containing at least Ta and / or Nb and / or Ni and / or Co and / or Fe, wherein advantageously still the electrically conductive seed layer of Tai _x Niχ, Tai _-x Cθχ, Tai _-x Fe _x , Nbi _-x Ni _x , Nbi _-x Co _x or Nbi _-x Fe _x , where x is in the range of 0.1 to 0.9.

Further advantageously, the highly textured, electrically conductive layer applied by means of the IBAD method consists of nitrides having a NaCl structure.

It is also advantageous if the layer consists of TiN, NbN, ZrN, HfN, CrN, VN or mixtures thereof.

It is also advantageous if the highly textured, electrically conductive barrier layer consists of Au, Ag, Pt, Ir, Rh, Mo, Nb, Pd or alloys thereof.

It is also advantageous if the high-temperature superconductor layer consists of YBa ₂ Cu ₃ O _7- X.

It is also advantageous if the high-temperature superconductor layer consists of REBa ₂ Cu ₃ O _7- X, where RE is Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb or mixtures thereof.

And it is also advantageous if under the high-temperature superconductor layer, an electrically conductive oxide cover layer is present, and it is even more advantageous is when the electrically conductive oxide cover layer consists of Nb- and / or La- and / or Au-doped SrTiO ₃ , SrRuO ₃ , LaNiO ₃ , (La ₁ Sr) MnO ₃ or mixtures thereof.

In the method according to the invention for producing an electrically conductive, high-temperature superconductor layer structure, at least one seed layer made of an electrically conductive material with an amorphous and / or nanocrystalline structure is applied to an electrically conductive, metallic substrate, and at least one high-output element is electrically applied thereto by means of the IBAD method conductive layer is applied to the following at least one highly textured, electrically conductive barrier layer and then at least one high-temperature superconductor layer is applied.

Advantageously, a seed layer made of an electrically conductive material having an amorphous and / or nanocrystalline structure by means of sputtering, evaporation, electrodeposition or laser ablation is applied to an electrically conductive, metallic substrate.

Also advantageously, the highly textured electrically conductive layer is deposited by ion bombardment using the IBAD method at an angle of 35 ° to 55 ° to the substrate normal and an ion energy of greater than 400 eV.

Further advantageously, the highly textured, electrically conductive barrier layer by the IBAD process or by sputtering, evaporation, chemical solution deposition, organometallic chemical

Applied vapor deposition or laser ablation.

And also advantageously, the highly textured high temperature superconductor layer is deposited by evaporation, chemical solution deposition, organometallic chemical vapor deposition, or laser ablation. With the method according to the invention, it becomes possible for the first time to realize a continuous electrically conductive high-temperature superconductor layer construction on the basis of the IBAD method, in which the highly textured structure of the layers is also continuously penetrated by the highly textured, electrically conductive layer which is produced by means of the IBAD method. Method has been applied (IBAD layer) is realized to at least the superconducting layer. The entire inventive electrically conductive high-temperature superconductor layer structure is shown schematically in FIG. The task of the individual layers is explained in more detail below.

Until now, it has not been possible to apply a highly textured conductive layer to an electrically conductive metallic substrate (1) by means of the IBAD method without using non-electrically conductive intermediate layers. In order to realize the desired highly textured structure or the biaxial texture during the IBAD process in materials having a NaCl structure, an amorphous and / or nanocrystalline seed layer (2) is necessary according to the invention, the structure of which is stable up to temperatures of 500 ^° C. is. The amorphous and / or nanocrystalline seed layer (2) can be applied to the electrically conductive, metallic substrate by a wide variety of deposition methods, such as sputtering, evaporation, electrodeposition or laser ablation. In order to realize an electrical contact between the electrically conductive, metallic substrate (1) and the highly textured, electrically conductive IBAD layer (3), the amorphous and / or nanocrystalline seed layer must also be electrically conductive.

According to the invention, it has been possible to specify and apply an electrically conductive seed layer having an amorphous and / or nanocrystalline structure on a substrate, on which the highly textured, conductive layer can then be grown by means of the IBAD method.

In this case, advantageously, the thickness of the highly textured conductive layer produced by the IBAD process can be further increased by the epitaxial growth. To apply a high-temperature superconductor layer (6) to the highly textured conductive IBAD layer is the presence at least one hochtextuherten, electrically conductive barrier layer (4) necessary.

Such barrier layers may for example consist of Au, Ag, Ir, Pt, Rh, Mo, Nb or Pd or their alloys. Since the high-temperature superconductor layer (6) is produced at temperatures above 650 ^° C. under high oxygen pressure, a conductive, oxidic cover layer (5) on the high-temperature superconductor layer proves to be helpful for oxidation of the underlying metallic layer Prevent layers.

Finally, the high-temperature superconductor layer (6) is applied to the completely electrically conductive layer structure by a deposition method such as evaporation, chemical solution deposition, organometallic chemical vapor deposition or laser ablation.

The invention will be explained in more detail using an exemplary embodiment.

Showing:

1 is a schematic sketch of the high-temperature superconductor layer structure,

2 shows the RHEED images during the growth of an electrically conductive barrier layer architecture on electropolished Hastelloy: (a) amorphous Tao 7sNi _O 25 seed layer; (b) highly textured IBAD-TiN; (c) epitaxial TiN; (d) Au; (e) Ir

FIG. 3: biaxially textured YBCO layer on IBAD-TiN with electrically conductive barrier layers

example 1

On an electropolished substrate of 57% Ni, 16% Mo, 15.5% Cr, 5.5% Fe, 4% W, 2.5% Co, 1% Mn (Hastelloy® C-276) becomes sputtered at room temperature amorphous, electrically conductive Tao 7sNi _O 25 applied as an electrically conductive seed layer with a thickness of 50 nm. Subsequently, the substrate with the seed layer in a high vacuum chamber is heated to 350 ⁰ C, whereby the amorphous structure of the Tao ₇₅ Ni _{O 25} -Keimschicht is maintained. In the next step, at this temperature, the biaxially textured TiN (IBAD) layer is annealed by reactive laser deposition from a Ti target in a nitrogen atmosphere with simultaneous ion bombardment (IBAD) with argon and nitrogen ions at 800 eV energy 45 ° to the substrate normal. At a layer thickness between 5 to 10 nm, the ion bombardment is turned off and the further growth of the TiN layer by means of continuous reactive laser deposition at a temperature of 700 ⁰ C to a thickness of 40 nm. Subsequently, as a barrier layers, a 10 nm thick gold layer and a 20 nm thick iridium layer by means of pulsed laser deposition at a temperature of 600 ⁰ C epitaxially applied to the TiN layer. Throughout the deposition, surface growth was observed with high energy electron diffraction (RHEED). Thus, both the amorphous structure of the seed layer and the highly textured growth of all other layers could be detected (FIG. 2). Furthermore, a 120 nm thick Nb-doped SrTiO ₃ cover layer with pulsed laser deposition is deposited at a temperature of 550 ° C. In the final step, a 300 nm thick high-temperature superconductor layer YBa ₂ Cu ₃ θ _7-x (= YBaCuO) is produced by pulsed laser deposition at a temperature of 810 ° C and an oxygen pressure of 300 Pa. The YBCO layer had an inplane half-width of 7.2 ° (FIG. 3) and exhibited a superconducting transition temperature of 88 K. Good electrical conductivity was determined for all layers.

Example 2

An electro-polished nonmagnetic stainless steel with an amorphous seed layer of TaosCoo s is used to produce a biaxially textured, electrically conductive TiN layer by the IBAD process. For this purpose, a reactive deposition by means of pulsed laser deposition of a Ti target in a nitrogen atmosphere with simultaneous ion bombardment (argon and nitrogen ions with an energy of 800 eV) at an angle of 45 ° to the substrate normal at a temperature of 400 ⁰ C. At a layer thickness between 5 to 10 nm, the ion beam is turned off and the further growth of the TiN layer by means of continuous reactive laser deposition at a temperature of 700 ⁰ C to a thickness of 40 nm. Subsequently, as a barrier layers, a 10 nm thick gold layer and a 20 nm thick iridium layer is epitaxially deposited on the TiN layer by pulsed laser deposition.

Furthermore, a 200 nm thick SrRuOs cover layer with pulsed laser deposition is deposited at a temperature of 550 ° C. In the final step, a 300 nm thick high temperature superconductor layer (GdBa2Cu3θ _7-x) by pulsed laser deposition at a temperature of 800 ⁰ C and an oxygen pressure of 300 Pa is established. All layers have a good electrical conductivity after deposition.

LIST OF REFERENCE NUMBERS

1 electrically conductive substrate

2 electrically conductive seed layer

3 highly textured electrically conductive IBAD layer

4 highly textured electrically conductive barrier layer

5 oxidic cover layer

6 high-temperature superconductor layer

Claims

claims

1. Electrically conductive high-temperature superconductor layer structure consisting of an electrically conductive, metallic substrate, at least one thereon electrically conductive seed layer having an amorphous and / or nanocrystalline structure, on which at least one applied by the IBAD method highly textured, electrically conductive layer is, on which in turn at least one hochtexturierte, electrically conductive barrier layer and in turn at least one high-temperature superconductor layer are present.

2. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the electrically conductive, metallic substrate consists of Ni, Ni-base alloys, stainless steel, Cu or copper alloys.

3. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the electrically conductive seed layer consists of an alloy containing at least Ta and / or Nb and / or Ni and / or Co and / or Fe.

4. An electrically conductive high-temperature superconductor layer structure according to claim 3, wherein the electrically conductive seed layer of Tai _-x Ni _x , Tai _-x Cθχ, Tai _-x Fe _x , Nbi _-x Ni _x , Nbi _-x Co _x or Nbi _-x Fe _x , where x is in the range of 0.1 to 0.9.

5. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the applied by the IBAD method highly textured, electrically conductive layer of nitrides having a NaCl structure.

6. The electrically conductive high-temperature superconductor layer structure according to claim 4, wherein the layer consists of TiN, NbN, ZrN, HfN, CrN, VN or mixtures thereof.

7. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the highly textured, electrically conductive barrier layer consists of Au, Ag, Pt, Ir, Rh, Mo, Nb, Pd or alloys thereof.

8. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the high-temperature superconductor layer of YBa ₂ Cu ₃ O _7- X consists.

9. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the high-temperature superconductor layer consists of REBa ₂ Cu ₃ 0 _7-x , wherein RE of Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb or Mixtures of these are.

10. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein below the high-temperature superconductor layer, an electrically conductive oxide cover layer is present.

11. An electrically conductive high-temperature superconductor layer structure according to claim 10, wherein the electrically conductive oxide cover layer of Nb and / or La and / or Au-doped SrTiO ₃ , SrRuO ₃ , LaNiO ₃ , (La ₁ Sr) MnO ₃ or mixtures thereof.

12. A method for producing an electrically conductive high-temperature superconductor layer structure, wherein at least one seed layer of an electrically conductive material having an amorphous and / or nanocrystalline structure is applied to an electrically conductive, metallic substrate and thereon by means of the IBAD method at least one hochtexturierte electrically conductive layer is applied to the following at least one highly textured, electrically conductive barrier layer and subsequently at least one high-temperature superconductor layer is applied.

13. The method of claim 12, wherein on a electrically conductive, metallic substrate, a seed layer of an electrically conductive Material with an amorphous and / or nanocrystalline structure by sputtering, evaporation, electrode position or laser ablation is applied.

14. The method of claim 12, wherein the highly textured electrically conductive layer is deposited by ion bombardment using the IBAD method at an angle of 35 ° to 55 ° to the substrate normal and an ion energy of greater than 400 eV.

15. The method of claim 12, wherein the hochtextuherte, electrically conductive barrier layer by the IBAD process or by sputtering, evaporation, chemical solution deposition, metal-organic chemical vapor deposition or laser ablation is applied.

16. The method of claim 12, wherein the high-texture high-temperature superconductor layer by the evaporation, the chemical solution deposition, the metal-organic chemical vapor deposition or laser ablation is applied.