阅读说明：本技术 一种独立式高温超导薄膜的制备方法 (Preparation method of independent high-temperature superconducting film ) 是由 王莹 谢忠洲 李钟昊 逯浩 于 2021-09-30 设计创作，主要内容包括：本发明涉及一种独立式高温超导薄膜的制备方法,具体包括以下步骤：(1)取衬底,在衬底上采用Sr-(3)Al-(2)O-(6)陶瓷靶材沉积牺牲层,所述牺牲层的材质为Sr-(3)Al-(2)O-(6)；(2)采用GdBa-(2)Cu-(3)O-(7)陶瓷靶材继续在牺牲层上沉积高温超导薄膜,得到衬底/SAO/GBCO复合结构,所述高温超导薄膜的材质为GdBa-(2)Cu-(3)O-(7-x)；(3)沉积完成后,将步骤(2)得到的衬底/SAO/GBCO复合结构置于纯氧中进行吸氧处理,使高温超导薄膜充分吸氧；(4)吸氧完成后,取出衬底/SAO/GBCO复合结构浸入水中,待牺牲层溶解后高温超导薄膜从衬底上释放,即得到独立式高温超导薄膜。与现有技术相比,本发明制得的高温超导薄膜不仅为独立式且结构良好,有机会结合到各种复合材料结构中,拓展了应用范围,降低了应用成本。(The invention relates to a preparation method of a free-standing high-temperature superconducting film, which specifically comprises the following steps: (1) taking a substrate, and adopting Sr on the substrate 3 Al 2 O 6 Depositing a sacrificial layer on the ceramic target, wherein the material of the sacrificial layer is Sr 3 Al 2 O 6 (ii) a (2) Using GdBA 2 Cu 3 O 7 Continuously depositing a high-temperature superconducting thin film on the sacrificial layer by using the ceramic target to obtain a substrate/SAO/GBCO composite structure, wherein the high-temperature superconducting thin film is made of GdBA 2 Cu 3 O 7‑x (ii) a (3) After deposition is finished, placing the substrate/SAO/GBCO composite structure obtained in the step (2) in pure oxygen for oxygen absorption treatment, so that the high-temperature superconducting thin film fully absorbs oxygen; (4) and after oxygen absorption is finished, taking out the substrate/SAO/GBCO composite structure, immersing the substrate/SAO/GBCO composite structure into water, and releasing the high-temperature superconducting film from the substrate after the sacrificial layer is dissolved, thereby obtaining the independent high-temperature superconducting film. Compared with the prior art, the high-temperature superconducting film prepared by the invention is free-standing and has a good structure, and can be organically combined into various composite material structures, so that the application range is expandedThe application range is wide, and the application cost is reduced.)

1. A preparation method of a free-standing high-temperature superconducting thin film is characterized by comprising the following steps:

(1) taking a substrate, and adopting Sr on the substrate₃Al₂O₆Depositing a sacrificial layer on the ceramic target, wherein the material of the sacrificial layer is Sr₃Al₂O₆；

(2) Using GdBA₂Cu₃O₇The ceramic target material continues to beDepositing a high-temperature superconducting thin film on the sacrificial layer to obtain a substrate/SAO/GBCO composite structure, wherein the high-temperature superconducting thin film is made of GdBA₂Cu₃O_7-x；

(3) After deposition is finished, placing the substrate/SAO/GBCO composite structure obtained in the step (2) in pure oxygen for oxygen absorption treatment, so that the high-temperature superconducting thin film fully absorbs oxygen;

(4) and after oxygen absorption is finished, taking out the substrate/SAO/GBCO composite structure, immersing the substrate/SAO/GBCO composite structure into water, and releasing the high-temperature superconducting film from the substrate after the sacrificial layer is dissolved, thereby obtaining the independent high-temperature superconducting film.

2. The method according to claim 1, wherein in step (1), the substrate is LaAlO₃A substrate.

3. The method of claim 1, wherein in step (1), the deposition is performed by RF magnetron sputtering.

4. The method of claim 3, wherein the sacrificial layer is deposited under the following conditions in step (1): the sputtering gas is argon, the sputtering pressure is 1-1.4 Pa, the sputtering temperature is 650-750 ℃, the sputtering power is 90-130W, and the sputtering time is 0.5-1.5 h.

5. The method according to claim 1, wherein in step (2), the deposition is performed by rf magnetron sputtering.

6. The method of claim 5, wherein in step (2), the deposition conditions of the HTS film are as follows: sputtering gas 99.999% of high purity oxygen and high purity argon, O₂Ar is 1:3, the sputtering pressure is 20-60 Pa, the sputtering temperature is 800-880 ℃, the sputtering power is 90-130W, the negative bias is-40-20V, and the sputtering time is 1.5-2.5 h.

7. The method for preparing the free-standing high-temperature superconducting thin film according to claim 1, wherein in the step (3), the oxygen absorption treatment process specifically comprises the following steps: placing the deposited substrate/SAO/GBCO composite structure at 6.5 x 10⁴～8.5*10⁴Annealing for 25-35 min at 450-550 ℃ in an annealing atmosphere formed by Pa oxygen.

8. The method for preparing a free-standing high temperature superconducting thin film according to claim 1, wherein in the step (4), the substrate/SAO/GBCO composite structure is immersed in water at room temperature for 4-6 min to complete the dissolution of the sacrificial layer.

9. A method for preparing a free-standing high temperature superconducting thin film according to claim 1, wherein in the step (4), the high temperature superconducting thin film released from the substrate is transferred onto a flexible substrate.

10. The method of claim 9, wherein the flexible substrate is made of polyethylene terephthalate and the transfer is made of clean metal rings.

Technical Field

The invention relates to the technical field of preparation of high-temperature superconducting materials, in particular to a preparation method of a free-standing high-temperature superconducting film.

Background

Discovered from the phenomenon of superconductionThen, people never stop researching the superconducting material, and from low temperature to high temperature, from theory to practical application, people continuously make breakthrough in the superconducting field. Before 1960, the main direction of research was to find the cause of the occurrence of superconducting phenomenon, and after 1960, the research focus in the superconducting field was gradually changed from theory to practice, and attention was paid to the capability of superconducting materials in practical application. The critical current density of 0.45MA/cm under the magnetic field of 8.8T at the low temperature of 4.2K is manufactured in 1962²Low temperature superconductor Nb₃Sn, from which a great step has been taken to push superconducting materials to practical use. In 1986, researchers discovered a novel superconducting material lanthanum barium copper oxide (La-Ba-Cu-O) with a transition temperature of 38K, and since then, a new era of high-temperature superconductivity was opened.

At present, most of second-generation high-temperature superconducting layers researched internationally focus on Yttrium Barium Copper Oxide (YBCO) films, and at least 5 units of the second-generation high-temperature superconducting tapes prepare tapes with the lengths of more than 500m and the Ic of more than 300A. In particular, Superpower company in the United states has produced kilometer-sized long tapes of 1311m and Ic up to 300A, which is a great step forward in mass production. The second generation high temperature superconducting tape superconducting layer material selected in China is also YBCO superconducting film. The method for preparing the YBCO film mainly comprises the following steps: pulsed Laser Deposition (PLD), metal organic vapor deposition (MOCVD), chemical solution deposition (MOD), Evaporation (evaaporation), and the like. The methods can prepare YBCO strips with excellent performance, but the methods have different characteristics, for example, the evaporation and MOCVD methods have higher deposition rate in the methods; evaporation, MOCVD and MOD methods are easy to scale; in contrast, the raw material utilization of the PLD and MOD methods is high. These methods are currently widely used, and overall, MOD has the potential to reduce strip cost. At present, most of domestic patents on high-temperature superconducting materials are preparation methods of YBCO films.

Magnetron sputtering is generally considered to be a method for preparing a thin film with great potential, belongs to a physical vapor deposition method, and is widely applied to industrial production and experimental research due to strong coating function and high film-forming quality. In the process of preparing the GBCO superconducting film which is a material with complex components by a magnetron sputtering method, the phenomenon that the element ratio deviates due to the reverse sputtering of negative ions can occur. Moreover, the epitaxial growth of the superconducting thin film is too dependent on the lattice structure of the substrate, so that the application range of the superconducting thin film is narrow, the substrate cannot be reused, and the preparation cost is high.

Disclosure of Invention

The invention aims to provide a preparation method of a free-standing high-temperature superconducting film, and the prepared free-standing high-temperature superconducting film has a good structure, is organically combined into various composite material structures, expands the application range and reduces the application cost.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a free-standing high-temperature superconducting thin film specifically comprises the following steps:

(1) preparing a sacrificial layer: taking a substrate, and adopting Sr on the substrate₃Al₂O₆Depositing a sacrificial layer on the ceramic target, wherein the material of the sacrificial layer is Sr₃Al₂O₆(expressed as SAO);

(2) preparing a substrate/SAO/GBCO composite structure: using GdBA₂Cu₃O₇Continuously depositing a high-temperature superconducting thin film on the sacrificial layer by using the ceramic target to obtain a substrate/SAO/GBCO composite structure, wherein the high-temperature superconducting thin film is made of GdBA₂Cu₃O_7-x(expressed as GBCO);

(3) oxygen absorption treatment: after deposition is finished, placing the substrate/SAO/GBCO composite structure obtained in the step (2) in pure oxygen for oxygen absorption treatment, so that the high-temperature superconducting thin film fully absorbs oxygen;

(4) GBCO film release: and after oxygen absorption is finished, taking out the substrate/SAO/GBCO composite structure, immersing the substrate/SAO/GBCO composite structure into water, and releasing the high-temperature superconducting film from the substrate after the sacrificial layer is dissolved, thereby obtaining the independent high-temperature superconducting film.

In the step (1), the substrate is LaAlO₃And the substrate SAO is directly grown on the LAO substrate and is tightly attached.

In the step (1), a radio frequency magnetron sputtering method is adopted for deposition.

In the step (1), the conditions for depositing the sacrificial layer are as follows: sputtering argon (Ar) gas, wherein the sputtering pressure is 1-1.4 Pa, the sputtering temperature is 650-750 ℃, the sputtering power is 90-130W, and the sputtering time is 0.5-1.5 h.

Preferably, the conditions for the deposition of the sacrificial layer are: the sputtering gas argon (Ar), the sputtering pressure 1.2Pa, the sputtering temperature 700 ℃, the sputtering power 110W and the sputtering time 1 h.

And (2) depositing by adopting a radio frequency magnetron sputtering method.

In the step (2), the deposition conditions of the high-temperature superconducting film are as follows: sputtering gas 99.999% of high purity oxygen and high purity argon, O₂Ar is 1:3 (i.e. the flow ratio in the process of introducing is 1:3), the sputtering pressure is 20-60 Pa, the sputtering temperature is 800-880 ℃, the sputtering power is 90-130W, the negative bias is-40-20V, and the sputtering time is 1.5-2.5 h.

Preferably, the conditions for the deposition of the high temperature superconducting thin film are: sputtering gas 99.999% of high purity oxygen and high purity argon, O₂Ar is 1:3, the sputtering pressure is 40Pa, the sputtering temperature is 840 ℃, the sputtering power is 110W, the negative bias is-30V, and the sputtering time is 2 h.

In the step (3), the oxygen absorption treatment process specifically comprises the following steps: placing the deposited substrate/SAO/GBCO composite structure at 6.5 x 10⁴～8.5*10⁴Annealing for 25-35 min at 450-550 ℃ in an annealing atmosphere formed by Pa oxygen.

Preferably, the oxygen absorption treatment process specifically comprises the following steps: placing the deposited substrate/SAO/GBCO composite structure at 7.5 x 10⁴Annealing at 500 ℃ for 30min in an annealing atmosphere of Pa oxygen.

In the step (4), the substrate/SAO/GBCO composite structure is soaked in water at room temperature for 4-6 min to complete the dissolution of the sacrificial layer.

Preferably, the substrate/SAO/GBCO composite structure is soaked in water at room temperature for 5min to complete the dissolution of the sacrificial layer.

In the step (4), the high-temperature superconducting thin film released from the substrate is transferred to a flexible substrate, and at this time, an independent superconducting thin film is obtained, and the flexible substrate is used as a carrier for supporting the released superconducting thin film.

The flexible substrate is made of polyethylene terephthalate and is transferred by a clean metal ring. This is a common and simple way of transferring.

Two-dimensional materials are generally one of the independent materials with isolated structures, have remarkable electronic properties, and show great practical application potential. Wherein, Sr₃Al₂O₆Is a water-soluble material applicable to almost all perovskites and heterostructures thereof, is an oxide similar to the perovskites, and has a cubic structure and a lattice constantCan be bonded with most representative perovskite substrateIs closely matched with the four units of the same, and directly adopts Sr₃Al₂O₆The ceramic target material can successfully prepare independent films with various perovskite structures. Sr₃Al₂O₆The water solubility of (A) is a prerequisite for the transferability of the high-temperature superconducting thin film, and Sr is used simultaneously₃Al₂O₆The structure of the film is also the premise for preparing the high-temperature superconducting film with good structure. The growth of the high temperature superconducting thin film generally requires lattice matching with the substrate, while the superconducting thin film of the present invention is grown on the SAO, and also requires lattice matching with the SAO, which are related to the structure.

The invention utilizes the water solubility of the SAO film, firstly deposits the SAO film on the substrate as a sacrificial layer, then deposits the high-temperature superconducting film on the SAO film to obtain a substrate/SAO/GBCO composite structure, and puts the whole deposited composite structure into water to dissolve the SAO film so as to release the high-temperature superconducting film from the substrate, thus obtaining the independent GBCO superconducting film, and then selectively transfers the independent GBCO superconducting film to the flexible substrate.

Compared with the prior art, the invention has the technical advantages that:

1. the invention provides a preparation route of an independent film, and the method for obtaining the independent superconducting film by etching a sacrificial layer reduces the dependence degree of the superconducting film on a substrate, obtains the independent GBCO superconducting film, enables the superconducting film to be combined into various composite material structures after synthesis, and widens the application field of the superconducting film.

2. The phenomenon that the element ratio of the superconducting thin film is deviated by applying negative bias is adjusted, and the GBCO thin film with good performance is prepared.

3. According to the invention, through the technical means of etching the sacrificial layer, the independent superconducting thin film is obtained, meanwhile, the used substrate is recovered, the recovered substrate can be used for multiple times, and the preparation cost of the thin film is reduced, so that the method has important significance for widening the application range of the superconducting material and reducing the application cost.

4. The invention can release the superconducting film from the substrate after the preparation and combine the superconducting film into other composite structures, thereby providing more application potential, and the substrate can be reused, thereby reducing the cost.

Drawings

FIG. 1 is an X-ray diffraction pattern (a) of a SAO/GBCO two-layer composite structure prepared in example 1 and an X-ray diffraction pattern (b) of a GBCO single-layer thin film prepared in comparative example 1;

FIG. 2 is a scanning electron micrograph of a GBCO thin film prepared in example 1 before and after transfer (a is before transfer, b is after transfer, and the scale bar is 1 μm);

FIG. 3 is a graph of EDS after transfer of a GBCO thin film prepared in example 1;

FIG. 4 is an SEM of a GBCO single-layer thin film obtained in comparative example 2 (scale bar of SEM image is 1 μm);

fig. 5 is an EDS diagram of a GBCO monolayer film prepared in comparative example 2.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

A preparation method of a free-standing high-temperature superconducting thin film specifically comprises the following steps:

(1) preparing a sacrificial layer: taking LaAlO₃A substrate deposited on the substrate by radio frequency magnetron sputtering method and adopting Sr₃Al₂O₆Depositing a sacrificial layer on a ceramic target, the method comprisingThe material of the sacrificial layer is Sr₃Al₂O₆Wherein, the conditions for depositing the sacrificial layer are as follows: sputtering argon (Ar) gas, wherein the sputtering pressure is 1-1.4 Pa, the sputtering temperature is 650-750 ℃, the sputtering power is 90-130W, and the sputtering time is 0.5-1.5 h;

(2) preparing a substrate/SAO/GBCO composite structure: taking GdBA₂Cu₃O₇Depositing the ceramic target material by adopting a radio frequency magnetron sputtering method to continuously deposit a high-temperature superconducting thin film on the sacrificial layer to obtain a substrate/SAO/GBCO composite structure, wherein the material of the high-temperature superconducting thin film is GdBA₂Cu₃O_7-xWherein, the deposition conditions of the high-temperature superconducting film are as follows: sputtering gas 99.999% of high purity oxygen and high purity argon, O₂Ar is 1:3, the sputtering pressure is 20-60 Pa, the sputtering temperature is 800-880 ℃, the sputtering power is 90-130W, the negative bias is-40-20V, and the sputtering time is 1.5-2.5 h;

(3) oxygen absorption treatment: after the deposition is finished, placing the substrate/SAO/GBCO composite structure obtained in the step (2) in pure oxygen for oxygen absorption treatment to ensure that the high-temperature superconducting thin film fully absorbs oxygen, wherein the oxygen absorption treatment process specifically comprises the following steps: placing the deposited substrate/SAO/GBCO composite structure at 6.5 x 10⁴～8.5*10⁴Annealing for 25-35 min at 450-550 ℃ in an annealing atmosphere formed by Pa oxygen;

(4) GBCO film release: and after oxygen absorption is finished, taking out the substrate/SAO/GBCO composite structure, immersing the substrate/SAO/GBCO composite structure in water, soaking the substrate/SAO/GBCO composite structure in water at room temperature for 4-6 min, releasing the high-temperature superconducting film from the substrate after the sacrificial layer is dissolved to obtain an independent high-temperature superconducting film, and transferring the high-temperature superconducting film released from the substrate to a polyethylene glycol terephthalate flexible substrate by using a clean metal ring.

Example 1

The embodiment provides a preparation method of a free-standing high-temperature superconducting thin film, which comprises the following specific steps:

(1) preparation of Sr₃Al₂O₆(SAO) film: get Sr₃Al₂O₆The ceramic target material is prepared by adopting a radio frequency magnetron sputtering method on LaAlO₃Depositing an SAO film on a substrate as a sacrificial layer, wherein the deposition conditions are as follows: sputtering pressure 1.2Pa, sputteringThe emission temperature is 700 ℃, the sputtering power is 110W, and the sputtering time is 1 h.

(2) Preparing a substrate/SAO/GBCO composite structure: after the SAO film deposition in the step (1) is finished, taking GdBA₂Cu₃O₇The GBCO superconducting thin film is continuously deposited on the SAO thin film by adopting a radio frequency magnetron sputtering method, and the deposition conditions are as follows: sputtering pressure of 40Pa, sputtering temperature of 840 ℃ and sputtering power of 110W, O₂When Ar is 1:3, negative bias is-30V, sputtering time is 2h, and crystallization phenomenon occurs in the sputtered film.

(3) Oxygen absorption treatment: after the step (2) is completed, performing oxygen absorption treatment on the high-temperature crystallized GBCO film, specifically: placing the substrate/SAO/GBCO composite structure at 7.5 x 10⁴Annealing at 500 deg.C for 30min in annealing atmosphere of Pa oxygen to absorb oxygen fully from GBCO film. An X-ray diffraction pattern of the substrate/SAO/GBCO composite structure prepared by the above step is shown in fig. 1 (a), in the curve, a characteristic peak of 22 ° to 23 ° corresponds to a SAO (004) crystal plane, a characteristic peak of 46 ° to 48 ° corresponds to a SAO (008) crystal plane, a characteristic peak of 7.5 ° corresponds to a GBCO (001) crystal plane, a characteristic peak of about 27.5 ° corresponds to a GBCO (102) crystal plane, a characteristic peak of about 38 ° corresponds to a GBCO (005) crystal plane, and a characteristic peak of about 54.7 ° corresponds to a GBCO (007) crystal plane. At this time, the substrate/SAO/GBCO composite structure is scanned, and a scanning electron micrograph of the GBCO thin film in the composite structure is shown in fig. 2 (a).

(4) GBCO film release: and (4) after the step (3) is completed, the taken-out substrate/SAO/GBCO composite structure is immersed into deionized water at room temperature, and the GBCO film is released from the substrate after the sacrificial layer of the SAO film is dissolved. When the SAO film with a good structure is soaked in deionized water, the dissolving process of the SAO film in water needs about 5 minutes, and the GBCO film is transferred out of the substrate as soon as possible to avoid long-time contact with water.

(5) After the high-temperature superconducting film falls off from the substrate and is released, a polyethylene terephthalate (PET) flexible substrate is used as a carrier of the superconducting film, and the superconducting film is transferred to the PET flexible substrate by using a clean metal ring. The scanning electron micrograph of the GBCO thin film at this time is shown in FIG. 2 (b). With the optimized preparation parameters of the superconducting thin film in this example, the obtained thin film does not have the problem of element ratio deviation (as shown in fig. 3).

The free-standing high temperature superconducting thin film prepared in this example had no cracks on the surface, good superconducting properties and surface morphology, and the reason for the slight difference between the morphology of the thin film in fig. 2(b) and the film in fig. 2(a) is that: the grain size slightly increases and the surface of the film slightly sags due to the effect of water on the GBCO grains. The independent GBCO thin film is tested by PPMS equipment, and the critical current density reaches 0.4MA/cm under the self-field of 77K²It shows that the film has good superconducting performance.

Comparative example 1

The existing preparation method of the conventional dependent high-temperature superconducting film comprises the following specific steps:

(1) taking the component as GdBA₂Cu₃O₇The ceramic target material is prepared by adopting a radio frequency magnetron sputtering method on LaAlO₃Depositing the GBCO superconducting thin film on a substrate, wherein the deposition conditions are as follows: sputtering pressure of 40Pa, sputtering temperature of 840 ℃ and sputtering power of 110W, O₂When Ar is 1:3, negative bias is-30V, sputtering time is 2h, and crystallization phenomenon occurs in the sputtered film.

(2) Oxygen absorption treatment: after the step (1) is completed, performing oxygen absorption treatment on the high-temperature crystallized GBCO film, specifically: placing the substrate/GBCO composite structure at 7.5 x 10⁴Annealing at 500 deg.C for 30min in annealing atmosphere of Pa oxygen to absorb oxygen fully from GBCO film. The X-ray diffraction pattern of the GBCO monolayer film obtained by this procedure is shown in fig. 1 (b). The GBCO superconducting thin film prepared by this method in this comparative example, in combination with the substrate, does not have the ability to be incorporated into other composite structures, and the preparation cost is extremely high since the substrate can be used only once.

Comparing the two curves in fig. 1, the following conclusions can be drawn: according to the invention, the SAO sacrificial layer prepared firstly grows in a c-axis mode, the microstructure is good, and the growth of the GBCO superconducting film is not influenced by the SAO sacrificial layer.

Comparative example 2

The existing preparation method of a conventional non-independent non-negative bias high-temperature superconducting film comprises the following specific steps:

(1) taking the component as GdBA₂Cu₃O₇The ceramic target material is prepared by adopting a radio frequency magnetron sputtering method on LaAlO₃Depositing the GBCO superconducting thin film on a substrate, wherein the deposition conditions are as follows: sputtering pressure of 40Pa, sputtering temperature of 840 ℃ and sputtering power of 110W, O₂When Ar is 1:3, the negative bias is 0V, and the sputtering time is 2 hours, the thin film obtained by sputtering is crystallized.

(2) Oxygen absorption treatment: after the step (1) is completed, performing oxygen absorption treatment on the high-temperature crystallized GBCO film, specifically: placing the substrate/GBCO composite structure at 7.5 x 10⁴Annealing at 500 deg.C for 30min in annealing atmosphere of Pa oxygen to absorb oxygen fully from GBCO film. SEM and EDS of the GBCO single-layer thin film obtained by this procedure are shown in FIGS. 4 and 5. The GBCO superconducting thin film prepared by the method has the advantages that the element ratio deviates from the normal ratio, the superconducting performance is poor, the GBCO superconducting thin film does not have the capacity of being combined into other composite structures, and the substrate can be used only once. In comparison with example 1, it is shown that a negative bias can affect and adjust the elemental ratio in the film.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.