Method for lossless transfer of large-area perovskite oxide film based on PPC supporting layer

Abstract

The invention relates to the technical field of flexible electronic device preparation, and particularly provides a method for lossless transfer of a large-area perovskite oxide film based on a PPC support layer, and the method comprises the steps: preparing a high-quality flexible perovskite oxide film through employing a water-soluble sacrificial layer strontium aluminate, preparing a PPC solution, and carrying out the spin coating of a flat PPC film with the thickness of 1-3 [mu] m through a spin coater, an acetone / ethanol solution is used for cleaning the PPC supporting layer, and the crystal structure and the physical property of the thin film are not damaged after transferring. The size of the oxide thin film transferred by the method reaches the millimeter level, the thin film keeps excellent single crystal characteristics, an atomic level flat surface and good ferroelectric performance, and the oxide thin film can be used as a flexible electronic material.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic device fabrication technology, specifically to a transfer method for perovskite oxide thin films, and more particularly to a highly efficient, non-destructive, large-area transfer technique based on a PPC support layer; applicable to the fabrication of high-quality flexible functional devices, including flexible memory, sensors, and energy conversion devices; PPC in this text refers to polypropylene carbonate. Background Technology

[0002] In recent years, perovskite oxide thin films have shown great promise in the field of flexible electronics due to their excellent ferroelectric, piezoelectric, and dielectric properties. However, how to completely transfer these high-performance oxide films from the growth substrate to a flexible substrate has always been a bottleneck problem restricting their practical application.

[0003] Traditional thin-film transfer technology faces three main challenges: first, the film is prone to cracking and defects during the transfer process; second, existing support layers struggle to balance good mechanical support and easy removal; and third, the transfer process is complex and inefficient. Especially for brittle materials like perovskite oxides, conventional PMMA or PDMS support layers often lead to film damage or contamination.

[0004] While some studies have attempted to address these issues using water-soluble sacrificial layers, most methods still suffer from drawbacks such as small transfer area, low success rate, and complex processes. For example, using PVA as a support layer requires high-temperature melting, which can easily damage the film; while using PVP results in poor film-forming properties. Therefore, developing a novel support layer material that can both protect the integrity of the film and is easy to remove has become a critical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned problems, this invention innovatively employs PPC as the support layer material and combines it with a water-soluble strontium aluminate sacrificial layer to establish a highly efficient and non-destructive perovskite oxide thin film transfer method, providing a new technical solution for the fabrication of flexible electronic devices.

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for the non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer. This method achieves complete transfer of large-area, high-quality perovskite oxide thin films by optimizing the support layer material and transfer process.

[0007] This invention provides a method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer, comprising the following steps: Step 1: Perform substrate pretreatment and grow a water-soluble sacrificial layer on the substrate; Step 2: Deposit an oxide film on the sacrificial layer; Step 3: Prepare the PPC solution and coat the support layer; Step 4: Peel the film off the substrate and transfer it to the target substrate; Step 5: Remove the support layer using an acetone / ethanol mixture solution; In step 1, a single crystal substrate is selected as the growth substrate and is ultrasonically cleaned for 5 minutes each with acetone, ethanol and deionized water in sequence. A 10-50 nm thick water-soluble sacrificial layer of strontium aluminate was grown on the substrate using pulsed laser deposition at a growth temperature of 850-950℃ and an oxygen pressure of 10. -4 Pa; In step 2, the thickness of the perovskite oxide film can be 5-200 nm, and the film can be a single-layer film or a multi-layer film. The material can be Pb(Zr) 1-x Ti x O3, BaTiO 3、 SrTiO3 or SrRuO3, etc.; In step 3, the mass fraction of the PPC solution is 20%, and the preparation process is as follows: PPC particles are dissolved in anisole solvent, placed in a brown bottle, and heated and stirred at 100°C for 6 hours. The PPC solution was spin-coated onto the surface of the oxide film at 3000-5000 rpm for 60 seconds. The PPC-coated film, along with the substrate, was placed on a heating stage and baked at 120°C for 5 minutes to obtain an oxide film with a PPC support layer.

[0008] In step 4, the sample is immersed in deionized water to dissolve the Sr3Al2O6 sacrificial layer for 4-12 hours.

[0009] The PPC / film is retrieved from the substrate and transferred to the target substrate (such as PDMS, Si, PI, etc.).

[0010] In step 5, the PPC-coated film is immersed in a mixed solution of acetone and ethanol with a volume ratio of 30%:70% for 10-30 minutes to remove the PPC support layer.

[0011] The advantages of this invention are: The PPC support layer exhibits excellent film-forming properties and mechanical strength, effectively protecting the film from damage during transfer. PPC is highly soluble in organic solvents, ensuring thorough removal without residual contamination. Using Sr3Al2O6 film as a sacrificial layer results in rapid dissolution, and deionized water does not damage the oxide film. The entire transfer process can be completed at low temperatures, avoiding the impact of high temperatures on film performance. The method is simple, efficient, suitable for transferring large-area films, and boasts a high success rate. Attached Figure Description

[0012] Figure 1A schematic diagram of the process flow of the method of the present invention; Figure 2 Schematic diagram of the PPC solution preparation process; Figure 3 XRD of SrTiO3 thin film before and after transfer. The diffraction peaks of SrTiO3 and Sr3Al2O6 are marked as

[001] in the figure. The data in parentheses represent the characteristic crystal planes of SrTiO3, such as SrTiO3 (001) representing the (001) crystal plane of SrTiO3. Figure 4 Optical microscope image after transfer; Figure 5 XRD of BaTiO3 thin film before and after transfer. The diffraction peaks of BaTiO3 and Sr3Al2O6 are marked as

[001] . The data in parentheses represent the characteristic crystal planes of BaTiO3, such as BaTiO3 (001) representing the (001) crystal plane of BaTiO3. Figure 6 Optical microscope image after transfer; Figure 7 Atomic force microscopy displays a roughness map; Figure 8 BiFeO3 / La before and after transfer 0.67 Sr 0.33 XRD of MnO3 thin film, the diffraction peaks of

[001] BiFeO3 and Sr3Al2O6 are marked in the figure. The data in parentheses represent the characteristic crystal planes of BiFeO3, such as BiFeO3(001) representing the (001) crystal plane of BiFeO3; where La 0.67 Sr 0.33 The MnO3 film is relatively thin, and the diffraction peaks are relatively weak. Figure 9 Optical microscope image after transfer; Figure 10 Performance comparison chart before and after the transfer. Detailed Implementation

[0013] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto. Figure 1 This is a schematic diagram of the process flow of the method of the present invention, which focuses on exploring the preparation of the PPC support layer to obtain a uniform and elastic PPC film; and invented a solution for cleaning PPC films, which can remove PPC without damaging the single crystal structure and properties of the oxide film. Figure 2 The preparation process of the PPC solution was shown, and the solvent, solution temperature, and solubility of PPC were explored. Finally, it was confirmed that anisole was used as the solvent, and dissolution at 100°C resulted in a system concentration of 10 wt%.

[0014] Example 1 Preparation and transfer of single perovskite oxide thin films; A single-crystal SrTiO3 substrate was used, and the substrate was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 10 minutes each. A 30 nm thick Sr3Al2O6 layer was grown as a sacrificial layer using a pulsed laser deposition system, with the Sr3Al2O6 target being a dense ceramic target. The growth temperature was 950 °C, and the oxygen pressure was 10. -4 Pa, frequency 6 Hz; 10-100 nm dielectric oxide SrTiO3 and ferroelectric oxide BaTiO3 epitaxial films were deposited on the sacrificial layer; growth temperature was 800℃, oxygen pressure was 1 Pa, frequency 6 Hz; PPC solution was prepared: 4 g of PPC particles were dissolved in 16 ml of anisole and heated and stirred at 100 °C for 6 hours. The PPC solution was spin-coated onto the surface of SrTiO3 and BaTiO3 films at 5000 rpm for 60 seconds. The samples were immersed in deionized water for 4 hours to dissolve the sacrificial layer Sr3Al2O6 and to peel off the PPC / STO and PPC / BTO films. The films were retrieved and transferred to a Si substrate and soaked in a 3:7 acetone:ethanol mixture for 20 minutes to remove PPC, thus obtaining flexible STO and BTO films.

[0015] Figure 3 and Figure 5 The X-ray diffraction patterns of the prepared SrTiO3, BaTiO3 films and the transferred films are shown respectively. The peaks marked are the characteristic crystal plane diffraction peaks of the substrate and the film, showing that the films before and after the transfer have excellent single-crystal properties.

[0016] Figure 4 and Figure 6 An optical microscope image of the film surface after transfer, showing a large area of ​​the film.

[0017] Example 2 Preparation and transfer of composite perovskite oxide heterojunction thin films; Using a SrTiO3 single-crystal substrate, the substrate was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 10 minutes each. A 30 nm thick Sr3Al2O6 layer was grown as a sacrificial layer in a pulsed laser deposition system, and a 10 nm thick La was deposited on the sacrificial layer. 0.67 Sr 0.33 MnO3 (LSMO) thin film was used as the bottom electrode, with a growth temperature of 850℃ and an oxygen pressure of 13.3 Pa. After the bottom electrode was grown, the substrate temperature was lowered to 800℃, and a 10-100 nm thick BiFeO3 (BFO) thin film was deposited on the bottom electrode with an oxygen pressure of 10 Pa. Prepare a PPC solution and spin-coat it onto the surface of a BiFeO3 film at 5000 rpm for 60 seconds. Immerse the sample in deionized water for 4 hours to dissolve the sacrificial layer and peel off the PPC / BFO / LSMO film. The film was retrieved and transferred to a Si substrate, and then immersed in a 3:7 acetone:ethanol mixture for 20 minutes to remove PPC, thus obtaining a flexible BFO / LSMO film.

[0018] Figure 8 Indicator of BiFeO3 / La before and after transfer 0.67 Sr 0.33 MnO3 thin film XRD and Figure 9 The image shows an optical microscope image after transfer. The results indicate that the perovskite oxide film transferred using the method of this invention has a large area of ​​integrity, maintains good crystal quality, and has a transfer success rate exceeding 95%. Figure 10 The transferred film retains excellent ferroelectric properties, fully meeting the application requirements of flexible electronic devices.

[0019] Matters not covered in this invention are common knowledge.

[0020] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer, characterized in that: The method for non-destructive transfer of large-area perovskite oxide films based on a PPC support layer utilizes a water-soluble sacrificial layer and PPC spin-coating technology, followed by removal of the PPC using an acetone / ethanol solution to obtain various high-quality self-supporting single-crystal perovskite oxide films. The specific steps are as follows: Step 1: Perform substrate pretreatment and grow a water-soluble sacrificial layer on the substrate; Step 2: Deposit an oxide film on the sacrificial layer; Step 3: Prepare the PPC solution and coat the support layer; Step 4: Peel the film off the substrate and transfer it to the target substrate; Step 5: Remove the support layer using an acetone / ethanol mixture solution.

2. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: In step 1, a single crystal substrate is selected as the growth substrate, and it is ultrasonically cleaned with acetone, ethanol and deionized water for 5 minutes each in sequence. A 10-50 nm thick water-soluble sacrificial layer of strontium aluminate is grown on the substrate using pulsed laser deposition at a growth temperature of 850-950℃ and an oxygen pressure of 10-4 Pa.

3. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: In step 2, the thickness of the perovskite oxide film can be 5-200 nm, and the film can be a single-layer film or a multi-layer film. The material can be Pb(Zr1-xTix)O3, BaTiO3, SrTiO3 or SrRuO3.

4. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: In step 3, the mass fraction of the PPC solution is 20%, and the preparation process is as follows: PPC particles are dissolved in anisole solvent, placed in a brown bottle, and heated and stirred at 100°C for 6 hours; the PPC solution is spin-coated onto the surface of the oxide film at a speed of 3000-5000 rpm for 60 seconds. The PPC-coated film, along with the substrate, was placed on a heating stage and baked at 120°C for 5 minutes to obtain an oxide film with a PPC support layer.

5. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: In step 4, the sample is immersed in deionized water to dissolve the Sr3Al2O6 sacrificial layer for 4-12 hours; the PPC / film is then retrieved from the substrate and transferred to the target substrate, including PDMS, Si, and PI.

6. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: In step 5, the PPC-coated film is immersed in a mixed solution of acetone and ethanol with a volume ratio of 30%:70% for 10-30 minutes to remove the PPC support layer.

7. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: The support layer is PPC with a Young's modulus of 0.5-1.5 GPa, and the thickness of the PPC is determined by the solution concentration and spin coating speed, ranging from 1 to 3 μm.

8. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: The sacrificial layer is a strontium aluminate compound, including monocrystalline / polycrystalline / amorphous Sr3Al2O6 and Sr4Al2O7, which can be removed with pure water without damaging the oxide film.

9. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: The removal efficiency of the acetone / ethanol solution is determined by the ratio of acetone to ethanol, with a ratio of 1:3 showing the optimal removal efficiency, effectively removing PPC without damaging the oxide film.

10. The method for non-destructive transfer of large-area perovskite oxide thin films based on a PPC support layer according to claim 1, characterized in that: The oxide film has a single-crystal structure and a thickness of 2-200 nm; the self-supporting oxide film has a size on the millimeter scale, maintains a single-crystal structure, and has an atomically smooth surface; the self-supporting oxide film maintains excellent ferroelectric properties, and therefore can be used as a flexible electronic material.

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