Regeneration method of monocrystal strontium titanate substrate

Abstract

The invention provides a regeneration method of a single crystal strontium titanate substrate, which comprises the following steps: firstly depositing a strontium aluminate film on the single crystal strontium titanate substrate, and then carrying out epitaxy of a perovskite type film; placing the sample after epitaxy in water to dissolve the strontium aluminate thin film, and transferring the perovskite thin film to obtain a strontium titanate substrate; after the strontium titanate substrate is cleaned, an ammonium fluoride-hydrofluoric acid buffer solution is used for etching treatment, and then annealing treatment is carried out to regenerate the monocrystal strontium titanate substrate. According to the regeneration method provided by the invention, the single-crystal strontium titanate substrate with the single titanium-oxygen termination surface can be obtained, and the repeated utilization of the single-crystal strontium titanate substrate can be realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of semiconductor materials, and in particular, to a method for regenerating a single crystal strontium titanate substrate. Background Art

[0002] Single-crystalline perovskite oxide (ABO3 type) films have rich functionalities, such as ferroelectricity, ferromagnetism and metal-insulator phase transition properties, and can be used in advanced logic devices, high-speed non-volatile memory, special sensors, etc. At present, its structure, properties and regulation methods have been comprehensively studied. From the relevant technologies, it is known that a key bottleneck limiting the transformation of single-crystalline oxide films into practical device applications comes from the challenge of material integration: the incompatibility of oxide devices with complementary metal oxide semiconductor (CMOS) processes. These complex oxides usually require higher temperatures to crystallize, usually above 600°C. If they are directly epitaxially grown on semiconductor wafers, they will react with the semiconductor substrate, causing the quality of both and their interfaces to decline, affecting performance.

[0003] With the development of self-supporting oxide film technology, oxides can be directly transferred to semiconductor substrates at room temperature, making high-quality heterogeneous material integration possible. Self-supporting oxide films have been applied to microelectronic devices such as ferroelectric tunneling junctions and transistors. However, in the process of preparing self-supporting oxides, semiconductor substrates are required, resulting in a large amount of semiconductor substrate waste. Summary of the invention

[0004] In view of this, the present disclosure provides a method for regenerating a single crystal strontium titanate substrate to at least partially solve the above technical problems.

[0005] In order to solve the above technical problems, the technical solutions provided by the present disclosure are as follows:

[0006] According to an embodiment of the present disclosure, the present disclosure provides a method for regenerating a single crystal strontium titanate substrate, comprising:

[0007] First, a strontium aluminate film is deposited on a single crystal strontium titanate substrate, and then the epitaxy of the perovskite film is performed;

[0008] The epitaxially grown sample is placed in water to dissolve the strontium aluminate film, and the perovskite film is transferred to obtain a strontium titanate substrate;

[0009] After cleaning the strontium titanate substrate, an etching treatment is performed using an ammonium fluoride-hydrofluoric acid buffer solution, and then an annealing treatment is performed to regenerate the single crystal strontium titanate substrate.

[0010] According to an embodiment of the present disclosure, when cleaning the strontium titanate substrate, an acetone solution, an ethanol solution and deionized water are used in sequence for cleaning.

[0011] According to an embodiment of the present disclosure, the ammonium fluoride-hydrofluoric acid buffer solution is prepared by mixing ammonium fluoride and hydrofluoric acid.

[0012] According to an embodiment of the present disclosure, the molar ratio of ammonium fluoride to hydrofluoric acid in the ammonium fluoride-hydrofluoric acid buffer is 7:1.

[0013] According to an embodiment of the present disclosure, the etching process is performed at room temperature, and the etching process time is 40 to 55 seconds.

[0014] According to an embodiment of the present disclosure, the above regeneration method further includes: washing the strontium titanate substrate after the etching treatment with deionized water, drying it with nitrogen, and then performing annealing treatment.

[0015] According to an embodiment of the present disclosure, the annealing treatment is performed in an oxygen environment at a temperature of 950-1100° C. for a treatment time of not less than 30 minutes to obtain a single crystal strontium titanate substrate having an atomic-level step structure.

[0016] According to an embodiment of the present disclosure, a strontium aluminate film and an epitaxial perovskite film are deposited on a single crystal strontium titanate substrate using a pulsed laser deposition technique.

[0017] According to an embodiment of the present disclosure, the temperature during deposition of the strontium aluminate film is 700-750°C;

[0018] The temperature during epitaxial growth of perovskite thin films is 600 to 1000°C.

[0019] According to an embodiment of the present disclosure, polydimethylsiloxane is used as a support layer to transfer the perovskite type thin film.

[0020] According to the embodiment of the present disclosure, the present disclosure provides a method for regenerating a single crystal strontium titanate substrate, wherein water-soluble strontium aluminate is deposited on the single crystal strontium titanate substrate as a sacrificial layer, and the strontium aluminate film can be dissolved and removed with water, and the transfer of the perovskite film can be achieved. After that, the substrate is cleaned to remove the organic matter remaining on the surface of the substrate, and then the substrate is etched with ammonium fluoride-hydrofluoric acid buffer to directionally etch out a titanium-oxygen termination surface with a step structure, and an annealing treatment is performed to remove the water vapor and molecular impurities adsorbed on the surface of the strontium titanate substrate, and the strontium oxide on the surface is desorbed under high temperature conditions, and the remaining titanium oxide layer forms an orderly step arrangement at high temperature, and the single crystal strontium titanate substrate is regenerated, which is a single crystal strontium titanate (001) substrate with a single titanium oxide termination surface, and can be reused. The method is simple and effective, and effectively saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an atomic force microscope image of the single crystal strontium titanate substrate in Example 1 of the present disclosure;

[0022] Figure 2is a reflection high energy electron diffraction pattern of the single crystal strontium titanate substrate in Example 1 of the present disclosure;

[0023] Figure 3 is a rocking curve diagram of a barium hafnium titanate film prepared on a single crystal strontium titanate substrate in Example 1 of the present disclosure;

[0024] Figure 4 This is an atomic force microscope image of the regenerated single crystal strontium titanate substrate in Example 1 of the present disclosure;

[0025] Figure 5 is a reflection high energy electron diffraction pattern of the regenerated single crystal strontium titanate substrate in Example 1 of the present disclosure;

[0026] Figure 6 A rocking curve diagram of a barium hafnium titanate film prepared on a regenerated single crystal strontium titanate substrate in Example 1 of the present disclosure;

[0027] Figure 7 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 1 of the present disclosure;

[0028] Figure 8 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 2 of the present disclosure;

[0029] Fig. 9 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 3 of the present disclosure;

[0030] Fig.10 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 4 of the present disclosure;

[0031] Fig.11 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 5 of the present disclosure;

[0032] Fig.12 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 6 of the present disclosure;

[0033] Fig.13 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 7 of the present disclosure. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0036] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0037] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0038] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0039] In the process of realizing the present disclosure, it is found that the current method for preparing self-supporting oxide films mainly utilizes the strontium aluminate sacrificial layer etching method. The process is: epitaxially growing a sacrificial layer strontium aluminate film on a single crystal strontium titanate substrate, and then epitaxially growing other perovskite films, and finally dissolving the strontium aluminate layer by water to obtain a self-supporting oxide film. Therefore, the preparation of the self-supporting oxide film requires a large number of single crystal strontium titanate substrates, but the substrate is expensive, and the price of a single crystal strontium titanate substrate is about 600 yuan / square centimeter. In comparison, the price of single crystal silicon is about 1 yuan / square centimeter. In the process of preparing the self-supporting oxide film, a large amount of substrate is wasted, and the cost is relatively high.

[0040] In view of this, the present disclosure provides a method for regenerating a single crystal strontium titanate substrate. Specifically, according to an embodiment of the present disclosure, the regeneration method includes:

[0041] A strontium aluminate film is first deposited on a single crystal strontium titanate substrate, and then the epitaxial growth of a perovskite film is performed; the sample after the epitaxial growth is placed in water to dissolve the strontium aluminate film, and the perovskite film is transferred to obtain a strontium titanate substrate; after cleaning the strontium titanate substrate, it is etched with an ammonium fluoride-hydrofluoric acid buffer solution, and then annealed to regenerate the single crystal strontium titanate substrate.

[0042] According to the embodiment of the present disclosure, first, the polished strontium titanate substrate is cleaned with acetone, alcohol and deionized water in sequence, and then the cleaned strontium titanate substrate is treated with ammonium fluoride-hydrofluoric acid buffer, and then the strontium titanate substrate is subjected to high temperature annealing in an oxygen environment to obtain a single crystal strontium titanate substrate with atomic-level flatness and a step surface. After the target film is deposited according to the above method, the strontium titanate substrate is regenerated.

[0043] According to the embodiments of the present disclosure, when a single crystal strontium titanate substrate is used, a water-soluble strontium aluminate film is first deposited on the single crystal strontium titanate substrate, and then a perovskite film is epitaxially grown on the strontium aluminate film. The strontium aluminate film is used as a sacrificial layer, which can be dissolved and removed in water to separate the strontium titanate substrate from the perovskite film. Polydimethylsiloxane is used as a supporting layer to transfer the perovskite film, and the perovskite film is transferred to other substrates. The strontium titanate substrate remaining after the perovskite film is cleaned and transferred, and then etched with ammonium fluoride-hydrofluoric acid buffer. The titanium-oxygen end surface with a step structure is directionally etched through the etching treatment, and a suitable annealing treatment is performed to remove water vapor under high temperature conditions. The remaining titanium oxide layer forms an orderly step arrangement at high temperature to obtain a regenerated single crystal strontium titanate substrate.

[0044] According to the embodiments of the present disclosure, after etching and annealing with ammonium fluoride-hydrofluoric acid buffer, the single-crystal strontium titanate substrate can be directionally etched to form a titanium oxide end surface with a step structure, so that the surface presents a distinct step shape, and no corrosion holes appear on the entire step surface. Compared with single-crystal strontium titanate substrates processed by other methods, the substrate surface processed by this method has better surface quality, no holes appear at the center of the step, and low surface roughness, which is conducive to the deposition of the target film and enables the stable growth of high-quality functional films.

[0045] According to an embodiment of the present disclosure, when cleaning the strontium titanate substrate, an acetone solution, an ethanol solution and deionized water are used in sequence for cleaning.

[0046] According to the embodiment of the present disclosure, when regenerating a single crystal strontium titanate substrate, the untreated strontium titanate substrate after use is first cleaned. During the cleaning, the strontium titanate substrate is first cleaned with an acetone solution for about 10 minutes, and then cleaned with an ethanol solution for 15 minutes, and then ultrasonically cleaned with deionized water for 10 minutes to obtain a cleaned strontium titanate substrate, remove impurities on the surface of the substrate, and avoid affecting subsequent processing. The whole ultrasonic cleaning process can be selected according to actual conditions, and the temperature and time during the cleaning process can be adjusted.

[0047] According to an embodiment of the present disclosure, the ammonium fluoride-hydrofluoric acid buffer solution is prepared by mixing ammonium fluoride and hydrofluoric acid. The molar ratio of ammonium fluoride to hydrofluoric acid in the ammonium fluoride-hydrofluoric acid buffer solution is 7:1. At this ratio, the pH value of the ammonium fluoride-hydrofluoric acid buffer solution is about 5, and the pH value is suitable. The strontium titanate substrate can be directionally corroded without the formation of corrosion pits.

[0048] According to the embodiments of the present disclosure, the etching process is performed at room temperature, and the etching process time is 40 to 55 seconds, for example, it can be 40 seconds, 48 ​​seconds, 50 seconds, 52 seconds, etc., but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. If the etching process time is short, no steps will be formed on the surface of the strontium titanate substrate. If the etching process time is too long, holes may be corroded on the surface of the strontium titanate substrate, affecting the material properties, and the regeneration of the single crystal strontium titanate substrate cannot be effectively guaranteed.

[0049] According to an embodiment of the present disclosure, the above regeneration method further includes: washing the strontium titanate substrate after the etching treatment with deionized water, drying it with nitrogen, and then performing annealing treatment.

[0050] According to the embodiments of the present disclosure, after etching with ammonium fluoride-hydrofluoric acid buffer, free particles in the buffer solution will remain on the surface of the strontium titanate substrate. After etching, it is washed with deionized water for 1 to 5 minutes to effectively wash away the impurities remaining on the surface. After washing, it is blown dry with nitrogen to prevent the residual ions in the annealing process from reacting with the strontium titanate substrate and affecting the flatness of the surface steps of the single crystal strontium titanate substrate.

[0051] According to the embodiments of the present disclosure, the annealing treatment is performed in an oxygen environment at a temperature of 950-1100°C, for example, 950°C, 1000°C, 1050°C, 1100°C, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. Further, the oxygen environment of the annealing treatment is a low oxygen pressure condition, and the oxygen pressure is 10 -5 Under low oxygen pressure conditions and within this temperature range, the width of the steps formed on the surface of the strontium titanate substrate can be made more uniform and neat.

[0052] According to the embodiments of the present disclosure, the annealing treatment time is not less than 30 minutes to obtain a single crystal strontium titanate substrate with an atomic-level step structure. The treatment time can be, for example, 30 minutes, 50 minutes, 80 minutes, 100 minutes, 150 minutes, etc. If the annealing treatment time is too short, the steps formed on the surface of the strontium titanate substrate will be uneven, affecting its flatness; the annealing treatment time is adjusted according to actual conditions, and the treatment time should also be avoided to be too long. If the annealing treatment time is too long, the surface of the single crystal strontium titanate substrate substrate will be over-reconstructed, and a structural surface of other shapes may be formed, which affects the formation of atomic-level steps on the surface of the single crystal strontium titanate.

[0053] According to the embodiments of the present disclosure, pulsed laser deposition technology is used to deposit strontium aluminate film and epitaxial perovskite film on a single crystal strontium titanate substrate. The temperature when depositing the strontium aluminate film is 700-750°C, for example, 700°C, 710°C, 720°C, 730°C, 740°C, etc.; the temperature when epitaxial perovskite film is 600-1000°C, for example, 600°C, 720°C, 850°C, 960°C, 1000°C, etc. However, it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] According to an embodiment of the present disclosure, a strontium titanate substrate treated with ammonium fluoride-hydrofluoric acid buffer is placed in a pulsed laser deposition (PLD) device, and a liquid of about 10 -5 After high-temperature annealing at 950°C in oxygen with a pressure of 10 torr, a strontium titanate substrate with a stepped titanium-oxygen termination surface with atomic-level flatness is obtained. The equipment temperature is then adjusted to deposit a strontium aluminate film on the strontium titanate substrate at 700°C, and then the temperature is adjusted to 750°C to epitaxially grow the target perovskite film on the surface deposited with strontium aluminate.

[0055] In order to make the purpose, technical solution and advantages of the present disclosure clearer and more specific, the technical solution and principle of the present disclosure are further explained below through specific embodiments combined with the accompanying drawings. It should be noted that the following specific embodiments are only used as examples, and the protection scope of the present disclosure is not limited thereto.

[0056] The test materials and reagents used in the following examples, unless otherwise specified, can be obtained from commercial sources. Specific techniques or conditions not specified in the examples are conventional methods and can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0057] Example 1

[0058] Simulation of preparation of strontium titanate substrate to be regenerated:

[0059] First, clean a brand new polished strontium titanate substrate, clean it with acetone solution for 10 minutes, clean it with ethanol solution for 10 minutes, and then ultrasonically clean it with deionized water for 10 minutes; prepare an ammonium fluoride-hydrofluoric acid buffer solution with a molar ratio of ammonium fluoride to hydrofluoric acid of 7:1, soak the cleaned strontium titanate substrate in the ammonium fluoride-hydrofluoric acid buffer solution at room temperature for 45 seconds, perform etching treatment, take it out after etching, clean it with deionized water for 1 minute, and then blow it dry with nitrogen.

[0060] Then, the etched SrTiO 4 substrate was placed in a vacuum chamber of a pulsed laser deposition (PLD) device and a 10 -5 Torr pressure oxygen, high temperature annealing treatment was carried out at 950℃ for 30min to obtain a single crystal strontium titanate substrate with atomic level flatness and stepped titanium-oxygen termination surface. Figure 1 As shown, the reflection high-energy electron diffraction is as follows Figure 2 As shown, Figure 1 This is an atomic force microscope image of the single crystal strontium titanate substrate in Example 1 of the present disclosure. Figure 2 This is a reflection high-energy electron diffraction pattern of the single crystal strontium titanate substrate in Example 1 of the present disclosure.

[0061] Afterwards, the temperature of the pulse laser deposition (PLD) equipment was adjusted to 700°C and the oxygen pressure to 10 -5 Torr conditions, an 8nm strontium aluminate film was deposited on a single crystal strontium titanate substrate as a sacrificial layer. The temperature was then raised to 750°C and the oxygen pressure was adjusted to 10 -4 Torr, under this condition, a 20nm barium hafnium titanate film was epitaxially grown on the strontium aluminate film.

[0062] Finally, polydimethylsiloxane (PDMS) was used as a support layer to cover the surface of the barium titanate film on the substrate, and then immersed in deionized water for 12 hours to fully dissolve and remove the strontium aluminate film. The barium titanate film was transferred to other substrates using polydimethylsiloxane. Figure 3 The rocking curve of the barium hafnium titanate film prepared on the single crystal strontium titanate substrate in Example 1 of the present disclosure is shown in FIG. After the transfer, the strontium titanate substrate to be processed is obtained.

[0063] The strontium titanate substrate to be treated obtained above is subjected to regeneration treatment:

[0064] First, the strontium titanate substrate was cleaned with acetone solution for 10 minutes, then with ethanol solution for 10 minutes, and then ultrasonically cleaned with deionized water for 10 minutes; an ammonium fluoride-hydrofluoric acid buffer solution with a molar ratio of ammonium fluoride to hydrofluoric acid of 7:1 was prepared, and the cleaned strontium titanate substrate was immersed in the ammonium fluoride-hydrofluoric acid buffer solution at room temperature for 45 seconds, and then taken out after etching, and washed with deionized water for 1 minute, and then dried with nitrogen. Then, the strontium titanate substrate after etching was placed in the vacuum chamber of the pulsed laser deposition (PLD) equipment, and 10 -5 The substrate is subjected to high temperature annealing at 950°C for 30 minutes in oxygen with a torr pressure, thereby obtaining a regenerated single crystal strontium titanate substrate with a stepped titanium-oxygen termination surface with atomic-level flatness, which can be reused to prepare a self-supporting oxide film.

[0065] The surface of the regenerated single crystal strontium titanate substrate is as follows Figure 4 As shown, the reflection high-energy electron diffraction is as follows Figure 5 As shown, Figure 4 is an atomic force microscope image of the regenerated single crystal strontium titanate substrate in Example 1 of the present disclosure, Figure 5 This is a reflection high energy electron diffraction pattern of the regenerated single crystal strontium titanate substrate in Example 1 of the present disclosure.

[0066] Depend on Figure 1 and Figure 3 By comparison, it can be seen that the method for regenerating a single crystal strontium titanate substrate provided by the present disclosure can obtain the same surface quality as a new single crystal strontium titanate substrate through a simple wet treatment, with atomic-level flatness, relatively neat steps and uniform width. Figure 2 and Figure 4 The point-like diffraction spots in the image also indicate that both the new single-crystal strontium titanate substrate and the regenerated single-crystal strontium titanate substrate have atomically flat two-dimensional surfaces, and the regenerated single-crystal strontium titanate substrate can be reused.

[0067] A strontium aluminate film and a barium hafnium titanate film are deposited on the surface of a regenerated single crystal strontium titanate substrate to prepare a self-supporting barium hafnium titanate film. Figure 6 The rocking curve of the barium hafnium titanate film prepared on the regenerated single crystal strontium titanate substrate in Example 1 of the present disclosure is shown in FIG. Figure 3 and Figure 6 It can be seen that the half-width of the rocking curves of the barium titanate film prepared on the single crystal strontium titanate substrate before and after regeneration is similar, indicating that the barium titanate film prepared on the regenerated single crystal strontium titanate substrate is of similar quality to the barium titanate film prepared on the new single crystal strontium titanate, the regenerated single crystal strontium titanate substrate can be reused, the single crystal strontium titanate substrate is of high quality, and can also grow high-quality perovskite oxide films.

[0068] Comparative Example 1

[0069] The same treatment method as in Example 1 is used, the only difference being that the regeneration treatment method is changed to: no treatment is performed on the strontium titanate substrate to be treated.

[0070] Figure 7 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 1 of the present disclosure, as shown in FIG. Figure 7 As shown, there are no atomic-level steps on the surface of the strontium titanate substrate, and there are products of strontium aluminate dissolution on the surface.

[0071] Comparative Example 2

[0072] The same treatment method as in Example 1 was used, except that the regeneration treatment method was changed to: the strontium titanate substrate to be treated was placed in hot water at 90° C. and soaked for 30 minutes.

[0073] Figure 8 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 2 of the present disclosure, as shown Figure 8 As shown, there are no atomic-level steps on the surface of the strontium titanate substrate, and the product of the dissolution of strontium aluminate still exists on the surface.

[0074] Comparative Example 3

[0075] The same treatment method as in Example 1 is used, the only difference being that the regeneration treatment method is changed to: the strontium titanate substrate to be treated is placed in a concentrated hydrochloric acid solution and immersed for 10 minutes.

[0076] Fig. 9 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 3 of the present disclosure, as shown in FIG. Fig. 9 As shown, there are no atomic-level steps on the surface of the strontium titanate substrate, the surface roughness is high, and there are many impurities.

[0077] Comparative Example 4

[0078] The same treatment method as in Example 1 was used, except that the regeneration method was changed to: the strontium titanate substrate to be treated was immersed in a concentrated hydrochloric acid solution for 10 minutes, and then immersed in an ammonium fluoride-hydrofluoric acid buffer solution for 55 seconds.

[0079] Fig.10 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 4 of the present disclosure, as shown in FIG. Fig.10 As shown, there are atomic-level steps on the surface of the strontium titanate substrate, but etching pits appear on the surface.

[0080] Comparative Example 5

[0081] The same treatment method as in Example 1 is used, with the only difference being that the regeneration treatment method is changed to: the strontium titanate substrate to be treated is immersed in a concentrated hydrochloric acid solution for 10 minutes, then immersed in an ammonium fluoride-hydrofluoric acid buffer solution for 55 seconds, and then subjected to the same high-temperature annealing treatment as in Example 1.

[0082] Fig.11 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 5 of the present disclosure, as shown Fig.11 As shown, there are no atomic-level steps on the surface of the strontium titanate substrate after high-temperature annealing, and etching pits still exist on its surface.

[0083] Comparative Example 6

[0084] The same treatment method as in Example 1 is used, the only difference being that the regeneration treatment method is changed to: the strontium titanate substrate to be treated is placed in a dilute hydrochloric acid solution and immersed for 1 hour.

[0085] Fig.12 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 6 of the present disclosure, as shown Fig.12 As shown, fuzzy step boundaries appear on the surface of the strontium titanate substrate and a small amount of impurities exist.

[0086] Comparative Example 7

[0087] The same treatment method as in Example 1 is used, the only difference being that the regeneration treatment method is changed to: the strontium titanate substrate to be treated is placed in a dilute hydrochloric acid solution and immersed for 20 hours.

[0088] Fig.13 This is an atomic force microscope image of the regenerated strontium titanate substrate in Comparative Example 7 of the present disclosure, as shown Fig.13 As shown, holes are etched on the surface of the strontium titanate substrate and the surface is rough.

[0089] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for regenerating a single crystal strontium titanate substrate, comprising: First, a strontium aluminate film is deposited on a single crystal strontium titanate substrate, and then the epitaxy of the perovskite film is performed; Placing the epitaxially grown sample in water to dissolve the strontium aluminate film, and transferring the perovskite film to obtain a strontium titanate substrate; After cleaning the strontium titanate substrate, an etching treatment is performed using an ammonium fluoride-hydrofluoric acid buffer solution, and then an annealing treatment is performed to regenerate the single crystal strontium titanate substrate.

2. The regeneration method according to claim 1, wherein: When cleaning the strontium titanate substrate, acetone solution, ethanol solution and deionized water are used in sequence for cleaning.

3. The regeneration method according to claim 1, wherein: The ammonium fluoride-hydrofluoric acid buffer solution is prepared by mixing ammonium fluoride and hydrofluoric acid.

4. The regeneration method according to claim 3, wherein: The molar ratio of ammonium fluoride to hydrofluoric acid in the ammonium fluoride-hydrofluoric acid buffer is 7:

1.

5. The regeneration method according to claim 1, wherein: The etching process is performed at room temperature, and the etching process time is 40 to 55 seconds.

6. The regeneration method according to claim 1, further comprising: The strontium titanate substrate after the etching treatment is washed with deionized water, blown dry with nitrogen, and then subjected to the annealing treatment.

7. The regeneration method according to claim 1, wherein: The annealing treatment is carried out in an oxygen environment at a temperature of 950-1100° C. for a treatment time of not less than 30 minutes to obtain a single crystal strontium titanate substrate with an atomic-level step structure.

8. The regeneration method according to claim 1, wherein: The pulse laser deposition technology is used to deposit the epitaxy of the strontium aluminate film and the perovskite film on the single crystal strontium titanate substrate.

9. The regeneration method according to claim 8, wherein: The temperature when depositing the strontium aluminate film is 700-750° C.; The temperature during epitaxial growth of the perovskite film is 600-1000°C.

10. The regeneration method according to claim 1, wherein: The perovskite film was transferred using polydimethylsiloxane as a support layer.

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