DE102008040087A1 - Electrically conductive high-temperature superconductor layer structure and method for its production - Google Patents

Abstract

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. 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 substrate. The object is achieved by an electrically conductive high-temperature superconductor layer structure consisting of a substrate, at least one seed layer thereon, on which at least one applied by the IBAD method layer is present on the turn at least one barrier layer and then again at least one High-temperature superconductor layer are present. The object is further achieved by a method for producing an electrically conductive high-temperature superconductor layer structure in which at least one seed layer is applied to a substrate, at least one layer thereon by means of the IBAD method, to which at least one barrier layer and subsequently at least one High-temperature superconductor layer is applied.

Description

The This invention relates to the field of materials science and relates to an electrically conductive high-temperature superconductor layer structure, as used for example as a high current carrying conductor for use can come and a process for its production.

For the fabrication of high-current superconducting conductors based on the high-temperature superconductors REBa ₂ Cu ₃ O _7-x (= REBCO), where RE can be both Y and a rare earth element, 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 it is induced in one of the barrier layers by a specific deposition method.

One possibility for producing highly textured barrier layers on any desired substrates is ion beam-assisted deposition (ion-beam assisted deposition - IBAD; Iijima et al., Appl. Phys. Lett. 60 (1992) 769 ) US 6,190,752 B1 ; US 2006/0142164 A1 ). In this method, an ion beam with a defined energy is directed at a defined angle to the substrate surface during the layer growth on this. As materials for this IBAD process, various oxides such as Y-stabilized ZrO ₂ (YSZ; Iijima et al., Appl. Phys. Lett. 60 (1992) 769 ), MgO ( Wang et al., Appl. Phys. Lett. 71 (1997) 2955 ) or Gd ₂ Zr ₂ O ₇ ( Iijima et al., Physica C 378 (2002) 960 ) used.

It However, more barrier layers are necessary to epitaxial REBCO layers with high current carrying capacity to achieve.

Farther must in case of application a high current carrying cable on the base by REBCO before the destruction of the superconductor by overload (eg caused by current peaks, local heating etc.) to be protected. In this case the current must be over An electric bridge will be derived to a destruction of the REBCO due to excessive warming during a sudden transition from the superconducting to the normal conducting state. To realize such an electrical bridge, be currently thick metallic layers (eg Ag, Cu, etc.) on the Superconductors are applied that are capable of overloading to carry the corresponding electricity.

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 realize an electrical contact between the carrier tape and the superconducting layer. The standard buffer layers used, such as Y ₂ O ₃ , YSZ, CeO ₂ , MgO, La ₂ Zr ₂ O ₇ , etc. are not suitable for this purpose.

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 ). Precious metals (Ir, Pt) as well as conductive oxides (La _0.7 Sr _0.3 MnO ₃ , SrRuO ₃ , LaNiO ₃ , etc.) were used for this purpose ( Aytug et al., Appl. Phys. Lett. 76 (2000) 760 ; Aytug et al., Appl. Phys. Lett. 85 (2004) 2887 ).

Using the IBAD method, it has hitherto been attempted to obtain an electrically conductive barrier layer architecture by texturing 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 ( Hühne et al., Appl. Phys. Lett. 85 (2004) 2744 ).

Among others, Ta _1-x Ni _x , Ta _1-x Fe _x or Ta _1-x Co _{x are 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 ).

Of the Disadvantage of the prior art is that it still has failed to establish a conductive layer structure a metallic carrier tape by the IBAD method manufacture.

The The object of the present invention is to specify an electrical conductive high-temperature superconductor layer structure, in case of overload the current over the Layer structure and the metallic substrate can be derived and a simple and well reproducible method for its production.

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

Of the inventive electrically conductive high-temperature superconductor layer structure consists of an electrically conductive, metallic Substrate, at least one electrically conductive thereon Seed layer with an amorphous and / or nanocrystalline structure, on at least one applied by the IBAD method highly textured, electrically conductive layer present is, on the turn, at least one highly textured, electric conductive barrier layer and then again at least a high-temperature superconductor layer are present.

advantageously, consists of the electrically conductive, metallic substrate made 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 Ta _1-x Ni _x , Ta _{1- x} Co _x , Ta _1-x Fe _x , Nb _1-x Ni _x , Nb _1-x Co _x or Nb _1-x Fe _x where x is in the range of 0.1 to 0.9.

Farther Advantageously, the applied by means of the IBAD method highly textured, electrically conductive layer of nitrides with a NaCl structure.

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

Farther It is advantageous if the hochtexturierte, electrically conductive Barrier layer of Au, Ag, Pt, Ir, Rh, Mo, Nb, Pd or alloys of which consists.

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 of Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb or mixtures thereof.

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

at the process according to the invention for the preparation an electrically conductive high-temperature superconductor layer structure becomes an electrically conductive, metallic substrate at least one seed layer of an electrically conductive material applied with an amorphous and / or nanocrystalline structure and then by means of the IBAD method at least one highly textured electrically conductive layer applied to the following at least a highly textured, electrically conductive barrier layer and subsequently at least one high-temperature superconductor layer is applied.

advantageously, becomes an electrically conductive, metallic substrate a seed layer of an electrically conductive material with an amorphous and / or nanocrystalline structure by means of sputtering, Evaporation, electrode position or laser ablation applied.

Also Advantageously, the highly textured electrically conductive Layer using the IBAD method for ion bombardment at an angle from 35 ° to 55 ° to the substrate normal and one Ion energy of more than 400 eV applied.

Farther Advantageously, the highly textured, electrically conductive Barrier layer by the IBAD process or by sputtering, Evaporation, chemical solution separation, organometallic chemical vapor deposition or laser ablation applied.

And Also advantageously, the highly textured high temperature superconductor layer is through vaporizing, chemical solution separation, metalorganic chemical vapor deposition or laser ablation applied.

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 1 shown. The task of the individual layers is explained in more detail below.

So far, 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. To realize the desired highly textured structure or the biaxial texture during the IBAD process in materials having a NaCl structure, is erfindungs according to an amorphous and / or nanocrystalline seed layer ( 2 ), which is stable in structure up to temperatures of 500 ° C. The amorphous and / or nanocrystalline seed layer ( 2 ) can be applied with a variety of deposition methods, such as sputtering, evaporation, electrode position or laser ablation, on the electrically conductive, metallic substrate. In order to ensure 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 succeeded in using an electrically conductive seed layer an amorphous and / or nanocrystalline structure on a substrate specify and apply on which then the highly textured, growing conductive layer by the IBAD method can.

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 a high-temperature superconductor layer ( 6 ) on the highly textured conductive IBAD layer is the presence of at least one highly textured, 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 a high oxygen pressure, proves to be a conductive, oxidic cover layer ( 5 ) on the high-temperature superconductor layer as helpful to prevent oxidation of the underlying metallic layers.

Finally, the high-temperature superconductor layer ( 6 ) are 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.

following The invention will be closer to an embodiment explained.

there shows:

1 FIG. 2: a schematic sketch of the high-temperature superconductor layer structure, FIG.

2 Figure 4: The RHEED images during the growth of an electrically conductive barrier layer architecture on electropolished Hastelloy: (a) amorphous Ta _0.75 Ni _0.25 seed layer; (b) highly textured IBAD-TiN; (c) epitaxial TiN; (d) Au; (e) Ir

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

example 1

On an electro-polished substrate made of 57% Ni, 16% Mo, 15.5% Cr, 5.5% Fe, 4% W, 2.5% Co, 1% Mn (Hastelloy ^® C-276) is deposited by sputtering at room temperature an amorphous, electrically conductive Ta _0.75 Ni _{0.25 applied} as electrically conductive seed layer with a thickness of 50 nm. Subsequently, the substrate with the seed layer is heated to 350 ° C. in a high-vacuum chamber, the amorphous structure of the Ta _0.75 Ni _0.25 seed layer being retained. In the next step, at this temperature, the biaxially textured TiN (IBAD) layer is laser-deposited from a Ti target in a nitrogen atmosphere with ion bombardment (IBAD) with argon and nitrogen ions at 800 eV energy at an angle of 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 ° 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 at a temperature of 600 ° C. 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 ( 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 O _7-x (= YBaCuO) is produced by means of 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 ° ( 3 ) and showed a superconducting transition temperature of 88 K. For all layers a good electrical conductivity was determined.

Example 2

On a electropolished non-magnetic stainless steel with an amorphous seed layer of Ta _0.5 Co _0.5 , a biaxially textured, electrically conductive TiN layer is produced by the IBAD process. For this purpose, a reactive deposition means 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 ° 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 ° 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 SrRuO 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 (GdBa ₂ Cu ₃ O _7-x ) is produced by means of pulsed laser deposition at a temperature of 800 ° C. and an oxygen pressure of 300 Pa. All layers have a good electrical conductivity after deposition.

1

electrical conductive substrate

2

electrical conductive germ layer

3

highly-textured electrically conductive IBAD layer

4

highly-textured electrically conductive barrier layer

5

oxide topcoat

6

High temperature superconductor layer

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 6190752 B1 [0004]
• US 2006/0142164 A1 [0004]
• US 2003/0211948 A1 [0008]
• US 2005/0239658 A1 [0008]

Cited non-patent literature

• Goyal et al. Appl. Phys. Lett. 69 (1996) 1795 [0003]
• Iijima et al., Appl. Phys. Lett. 60 (1992) 769 [0004]
• Iijima et al., Appl. Phys. Lett. 60 (1992) 769 [0004]
• Wang et al., Appl. Phys. Lett. 71 (1997) 2955 [0004]
• - Iijima et al., Physica C 378 (2002) 960 [0004]
• Aytug et al., Appl. Phys. Lett. 76 (2000) 760 [0008]
• Aytug et al., Appl. Phys. Lett. 85 (2004) 2887 [0008]
• Thiele et al. J. Mater. Res. 18 (2003) 442 [0009]
• Hühne et al., Appl. Phys. Lett. 85 (2004) 2744 [0010]
• Fang et al., J. Electr. Mater. 36 (2007) 614 [0011]
• Fang et al., J. Electr. Mater. 35 (2006) 15 [0011]

Claims (16)

Electrically conductive high-temperature superconductor layer structure consisting of an electrically conductive, metallic Substrate, at least one electrically conductive thereon Seed layer with an amorphous and / or nanocrystalline structure, on at least one applied by the IBAD method highly textured, electrically conductive layer present is, on the turn, at least one highly textured, electric conductive barrier layer and then again at least a high-temperature superconductor layer are present. Electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the electrically conductive, metallic Substrate made of Ni, Ni-based alloys, stainless steel, Cu or copper alloys consists. 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 contains. The electrically conductive high-temperature superconductor layer structure according to claim 3, wherein the electrically conductive seed layer is Ta _1-x Ni _x , Ta _1-x Co _x , Ta _1-x Fe _x , Nb _1-x Ni _x , Nb _1-x Co _x or Nb _1-x Fe _x , where x is in the range of 0.1 to 0.9. 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 with a NaCl structure. Electrically conductive high-temperature superconductor layer structure according to claim 4, wherein the layer of TiN, NbN, ZrN, HfN, CrN, VN or mixtures thereof. Electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the highly textured, electrically conductive Barrier layer of Au, Ag, Pt, Ir, Rh, Mo, Nb, Pd or alloys thereof consists. An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the high-temperature superconductor layer consists of YBa ₂ Cu ₃ O _7-x . An electrically conductive high-temperature superconductor layer structure according to claim 1, wherein the high-temperature superconductor layer consists of REBa ₂ Cu ₃ O _7-x , wherein RE is selected from Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb or mixtures thereof. Electrically conductive high-temperature superconductor layer structure according to claim 1, wherein below the high-temperature superconductor layer an electrically conductive oxide cover layer present is. 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, Sr) MnO ₃ or mixtures of which consists. Process for producing an electrically conductive High-temperature superconductor layer construction, in which on an electric conductive, metallic substrate at least one seed layer made of an electrically conductive material with an amorphous and / or nanocrystalline structure is applied and then by means of the IBAD method at least one highly textured electrically conductive Layer is applied, followed by at least one highly textured, electrically conductive barrier layer and subsequently at least a high-temperature superconductor layer is applied. The method of claim 12, wherein an electric conductive, metallic substrate from a seed layer an electrically conductive material with an amorphous and / or nanocrystalline structure by means of sputtering, evaporation, Electrode position or laser ablation is applied. The method of claim 12, wherein the highly textured electrically conductive layer by means of the IBAD method for ion bombardment at an angle of 35 ° to 55 ° to Substrate standards and an ionic energy of more than 400 eV is applied. The method of claim 12, wherein the highly textured, electrically conductive barrier layer through the IBAD process or by sputtering, evaporation, chemical solution separation, metalorganic chemical vapor deposition or laser ablation is applied. The method of claim 12, wherein the highly textured High-temperature superconductor layer by evaporation, the chemical Solution separation, the metal-organic chemical vapor deposition or the laser ablation is applied.