Ferroelectric radical thin film with good piezoelectric performance and preparation method and application thereof

Abstract

The application discloses a ferroelectric radical film with good force-electric performance, and comprises the following steps: sequentially growing a buffer layer, a bottom electrode layer and a ferroelectric functional layer on a substrate, and stripping the substrate after annealing to obtain the ferroelectric radical film; wherein, the growth is all carried out by using a pulse laser deposition technology; and the substrate and the buffer layer are cleaned by using a cavity atmosphere environment plasma surface cleaning technology before growth. The ferroelectric radical film is prepared based on the idea of co-regulation of the surface state of the substrate and the buffer layer and Van der Waals force, by using a mica substrate with high flexibility and chemical stability and special pretreatment, combining with an optimized cavity plasma treatment technology and a pulse laser deposition technology process, so that the prepared lead zirconate titanate radical film has excellent flexibility and ferroelectric performance.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, specifically to a ferroelectric free radical thin film with good electromechanical properties and its applications. Background Technology

[0002] The rapid development of industries such as the Internet of Things, aerospace, and artificial intelligence has placed higher demands on the functionality, wearability, and flexibility of functional thin-film materials and their flexible electronic devices. Ferroelectric materials have attracted much attention due to their spontaneous polarization characteristics that can be controlled by external fields. However, most inorganic ferroelectric materials are brittle ceramics grown on rigid substrates, making them difficult to bend significantly and repeatedly. While organic ferroelectric materials have better flexibility, their ferroelectric properties are poor. Organic-inorganic ferroelectric materials, on the other hand, suffer from instability and poor ferroelectric performance. Therefore, obtaining ferroelectric thin films that combine excellent ferroelectric properties and mechanical properties is a necessary prerequisite for the large-scale application of ferroelectric materials in flexible electronic devices.

[0003] Suitable substrates and optimized film growth parameters are crucial for obtaining high-performance ferroelectric thin film materials. Common organic substrates such as polyethylene terephthalate (PET) and polyimide (PI) have poor high-temperature resistance, resulting in films with low remanent polarization and high coercivity. Inorganic substrates such as strontium titanate are difficult to achieve good flexibility, and the strong clamping effect of the substrate restricts domain movement and leads to a decrease in ferroelectric performance. In recent years, researchers have developed two-dimensional layered substrates with weak van der Waals forces, such as graphene, hexagonal boron nitride, and molybdenum disulfide, to partially improve the performance of grown films by weakening the chemical bonding and strain at the film-substrate interface. However, the quality of film growth is affected by both the surface state of the substrate and van der Waals forces. The surface state and surface energy distribution of two-dimensional materials are often neglected, resulting in films with insufficient uniform epitaxial orientation, numerous internal defects, and whose flexibility and ferroelectric properties still need improvement.

[0004] Therefore, how to obtain ferroelectric free radical thin films with good functional properties, flexibility and ductility and their preparation methods are problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to propose a ferroelectric radical thin film with good electromechanical properties, its preparation method and application. Based on the idea of ​​co-regulation of the surface state of the substrate and buffer layer and van der Waals forces, this invention uses a mica substrate with high flexibility and chemical stability and has undergone special pretreatment, combined with optimized intracavity plasma treatment technology and pulsed laser deposition technology, to prepare a lead zirconate titanate radical thin film with excellent flexibility and ferroelectric properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a ferroelectric radical thin film with good electromechanical properties includes the following steps: sequentially growing a buffer layer, a bottom electrode layer and a ferroelectric functional layer on a substrate; after annealing, peeling off the substrate to obtain the ferroelectric radical thin film.

[0008] The growth process employs pulsed laser deposition technology.

[0009] The substrate and the buffer layer were cleaned using an intracavity atmosphere plasma surface cleaning technique before growth.

[0010] Preferably, the process parameters for the intracavity atmosphere plasma surface cleaning technology are as follows:

[0011] The substrate temperature is -60 to 220°C, and the vacuum degree is ≤5×10⁻⁶. -7 Pa, the atmosphere is at least one of argon, hydrogen, nitrogen, oxygen and helium, the partial pressure of the atmosphere is 1 to 100 mTorr, and the distance between the plasma electrode and the substrate is 10 to 60 mm.

[0012] Preferably, the intracavity atmosphere plasma surface cleaning technology consists of three independent cleaning processes, with the following process parameters:

[0013] During the first surface treatment, the substrate temperature is -40 to -5°C, and the vacuum degree is ≤1×10⁻⁶. -6 Pa, the atmosphere is a mixture of argon and hydrogen, the partial pressure of the atmosphere is 10 to 80 mTorr, the distance between the plasma electrode and the substrate is 10 to 60 mm, and the processing time is 1 to 200 s;

[0014] During the second surface treatment, the substrate temperature is 20 to -150°C, and the vacuum degree is ≤1×10⁻⁶. -6 Pa, the atmosphere is helium and / or oxygen, the partial pressure of the atmosphere is 1 to 50 mTorr, the distance between the plasma electrode and the substrate is 10 to 40 mm, and the processing time is 1 to 100 s;

[0015] During the third surface treatment, the substrate temperature is 10–200°C, and the vacuum degree is ≤1×10⁻⁶. -6 Pa, the atmosphere is at least one of argon, hydrogen, nitrogen, oxygen and helium, the partial pressure of the atmosphere is 1 to 50 mTorr, the distance between the plasma electrode and the substrate is 10 to 60 mm, and the processing time is 1 to 100 s.

[0016] Preferably, the pulsed laser deposition parameters of the buffer layer are: deposition cavity vacuum degree ≤ 5 × 10⁻⁶. -7Pa; the substrate temperature is 590-620℃, the oxygen partial pressure is 80-100 mTorr; the laser energy is 350-390 mJ; the pulsed laser frequency is 6-10 Hz; the absolute value of the laser focal length is 0-20 mm; the absolute value of the target rotation speed is 15-18 o / min;

[0017] The pulsed laser deposition parameters for the bottom electrode layer are: deposition cavity vacuum degree ≤ 5 × 10⁻⁶. -7 Pa; the substrate temperature is 580–620℃; the oxygen partial pressure is 50–100 mTorr; the laser energy is 370–410 mJ; the pulsed laser frequency is 8–10 Hz; the absolute value of the laser focal length is 0–15 mm; and the absolute value of the target rotation speed is 12–16. o / min;

[0018] The pulsed laser deposition parameters for the ferroelectric functional layer are: deposition cavity vacuum degree ≤ 5 × 10⁻⁶. -6 Pa; the substrate temperature is 590~610℃; the oxygen partial pressure is 180~220mTorr; the laser energy is 310~370mJ; the pulsed laser frequency is 8~10Hz; the laser focal length is -15~+15mm; and the target rotation speed is ±10~±15o / min.

[0019] Preferably, the annealing process parameters are: cooling to room temperature at a cooling rate of 8-12°C / min under an oxygen partial pressure of 180-220 mTorr.

[0020] Preferably, the buffer layer is CoFeO4 or YSZ, with a thickness of 1 to 20 nm, and a preferred orientation of any one of (001), (101) and (111).

[0021] This invention selects a suitable buffer layer as the mixture of mica and Pb(Zr) x Ti 1-x The intermediate transition layer of O3 thin film enables the preferential growth of thin film grain orientation, thereby improving the growth quality of the thin film.

[0022] Preferably, the bottom electrode layer is SrRuO3 with a thickness of 15–40 nm.

[0023] Preferably, the ferroelectric functional layer is Pb(Zr) x Ti 1-x O3, where x = 0.1 to 0.5 and the thickness is 180 to 260 nm.

[0024] Preferably, the thickness of the buffer layer is less than the thickness of the bottom electrode layer, and the thickness of the bottom electrode layer is less than the thickness of the ferroelectric functional layer; the thickness of the ferroelectric functional layer accounts for 85% to 95% of the total thickness of the flexible lead zirconate titanate ferroelectric film.

[0025] Preferably, the substrate is a mica substrate.

[0026] Preferably, the substrate needs to undergo pretreatment, including: planarization, solvent cleaning, atmosphere drying, mechanical stripping, and atmosphere cleaning.

[0027] Preferably, the solvent is acetone, ethanol, or ultrapure water, and the atmosphere is nitrogen or oxygen.

[0028] By pretreating the mica substrate, a mica substrate with good flatness, surface cleanliness and good chemical stability can be obtained.

[0029] The ferroelectric radical thin film with good electromechanical properties is obtained by the preparation method described above.

[0030] Generally speaking, plasma cleaning is a common surface treatment technique. It typically uses radio frequency electrical excitation to generate plasma in air or a mixed atmosphere to clean the sample surface. However, this method has the following problems: ① The high energy of the plasma etches the sample surface while cleaning, inevitably increasing surface roughness; ② The vacuum level of the cleaning chamber is limited, resulting in residues after cleaning in various mixed atmospheres; ③ When the cleaned sample is transferred to the deposition chamber, it inevitably comes into prolonged contact with air, altering the surface energy distribution and cleanliness, thus making the surface van der Waals forces and surface state uncontrollable; ④ The effects of sample temperature, atmosphere combination and partial pressure, distance, processing time, and vacuum level on sample surface treatment are not comprehensively considered, especially the co-regulatory effect of temperature and plasma on the sample surface state; ⑤ In-situ surface treatment of films grown within the deposition chamber is not possible.

[0031] Unlike other methods, this invention employs an optimized intracavity plasma cleaning technique. By integrating and constructing a plasma cleaning system within a high-vacuum, high-cleanliness deposition cavity, and comprehensively considering the effects of sample temperature, atmosphere, plasma treatment, and treatment time on the sample surface state, optimized plasma treatment parameters are designed. This overcomes problems such as exposure to air environment before deposition, excessive etching of sample surface, and residual impurities. It can not only effectively control the surface state of the mica substrate, but also perform in-situ surface treatment of the deposited buffer layer within the cavity. This results in a mica substrate and buffer layer with high flatness, high cleanliness, suitable surface energy, and preferred epitaxial orientation along (111) or (101), providing a key prerequisite for obtaining high-quality epitaxial ferroelectric radical thin films.

[0032] The present invention provides a 20%–50% increase in remanent polarization intensity and a 100% increase in piezoelectric response intensity of the thin film compared to the prior art. Furthermore, because the present invention achieves strict control over the interfaces between the mica substrate and the buffer layer, and between the buffer layer and the bottom electrode layer, it also makes the ferroelectric thin film easier to radicalize, resulting in fewer defects and better mechanical properties, thus achieving a dual improvement in both the mechanical and ferroelectric properties of the thin film.

[0033] The above describes the application of ferroelectric radical thin films in the fabrication of flexible electronic devices.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention proposes a ferroelectric radical thin film with good electromechanical properties, its preparation method and application. Based on the idea of ​​co-regulation of the surface state of the substrate and buffer layer and van der Waals forces, this invention uses a mica substrate with high flexibility and chemical stability and has undergone special pretreatment, combined with optimized intracavity plasma treatment technology and pulsed laser deposition technology, to prepare a lead zirconate titanate radical thin film with excellent flexibility and ferroelectric properties. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0037] Figure 1 This is a schematic diagram of the flexible lead zirconate titanate ferroelectric thin film material prepared in Examples 1-3 of this invention;

[0038] Figure 2 This is a TEM image of the flexible lead zirconate titanate ferroelectric thin film material prepared in Example 1 of this invention;

[0039] Figure 3 The XRD patterns are of the lead zirconate titanate ferroelectric thin film materials prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0040] Figure 4 Comparison of surface morphology, in-plane and out-of-plane amplitude of PFM, and PFM piezoelectric response curve of lead zirconate titanate ferroelectric thin film materials prepared in Example 1 and Comparative Example 1 of this invention;

[0041] Figure 5 This is a PV comparison diagram of the lead zirconate titanate ferroelectric thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention;

[0042] Figure 6This is a comparison chart of the fatigue resistance test PV curve changes of the lead zirconate titanate ferroelectric thin film materials prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0043] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0044] Example 1

[0045] This invention provides a method for preparing a flexible lead zirconate titanate free radical thin film with high-speed electro-electric and high-voltage electro-electric properties, comprising the following steps:

[0046] (1) Select a smooth, crack-free, and impurity-free mica substrate as the flexible substrate layer, and perform a cleaning pretreatment on it. The cleaning steps are as follows:

[0047] S1. Perform chemical mechanical planarization on the muscovite substrate until the surface undulation is less than 10 nm.

[0048] S2. Ultrasonically treat the muscovite substrate with acetone, ethanol and ultrapure water for 1-15 minutes respectively, and then dry it with nitrogen gas flow.

[0049] S3. Apply the polyimide tape to the work surface and keep the polyimide tape flat;

[0050] S4. Use tweezers to place a complete muscovite substrate on polyimide tape, and use tweezers to pick up and peel off the muscovite substrate layer by layer from one corner.

[0051] S5. Repeat step S2 until a 25µm thick, smooth, clean, and flat muscovite substrate is peeled off from the thick muscovite.

[0052] S6. The muscovite substrate obtained in S5 is ultrasonically treated with acetone, ethanol and ultrapure water for 1-15 minutes, and then dried with nitrogen gas.

[0053] (2) The muscovite substrate after cleaning and pretreatment in step (1) is bonded to the center of the substrate stage of the pulsed laser deposition system. Then the substrate stage is placed on the heating stage in the deposition cavity of the pulsed laser deposition system. At this time, the substrate is above the main target and the distance between the muscovite substrate and the target is 50 mm.

[0054] (3) The mica substrate surface is cleaned by intracavity atmosphere plasma cleaning, which is divided into three independent surface condition treatments:

[0055] During the first surface treatment, the substrate temperature was -30℃ and the vacuum degree was ≤1×10⁻⁶. -6Pa, the atmosphere is a mixture of argon (10%) and hydrogen (90%), the partial pressure of the atmosphere is 20mTorr, the distance between the plasma electrode and the substrate is 40mm, the processing time is 100s, the purpose of the first treatment is to bombard and remove organic impurities under low temperature protection, and uniformly etch the surface to further improve the flatness by less than 1nm.

[0056] During the second surface treatment, the substrate temperature was 110℃ and the vacuum degree was ≤1×10⁻⁶. -6 Pa, the atmosphere is a mixture of helium (50%) and oxygen (50%), the partial pressure of the atmosphere is 10 mTorr, the distance between the plasma electrode and the substrate is 30 mm, the treatment time is 20 s, the purpose of the second treatment is to bombard and remove organic and oxide impurities on the surface at a higher temperature, and to maintain the surface flatness.

[0057] During the third surface treatment, the substrate temperature is 120℃ and the vacuum degree is ≤1×10⁻⁶. -6 Pa, the atmosphere is nitrogen, the partial pressure of the atmosphere is 20 mTorr, the distance between the plasma electrode and the substrate is 30 mm, the treatment time is 20 s, the purpose of the third treatment is to make the mica surface have a suitable surface energy in the (111) or (101) orientation as much as possible, and to remove other unfavorable surface dangling bonds while maintaining the surface flatness.

[0058] (4) Using a pulsed laser deposition system, the CoFeO4 target is switched to the main target site to deposit a CoFeO4 thin film on a flexible mica substrate to obtain a buffer layer; the specific process parameters are: the vacuum degree of the deposition chamber is 5×10 -5 Pa; substrate temperature: 600℃; oxygen partial pressure: 80 mTorr; laser energy: 380 mJ; pulsed laser frequency: 10 Hz; laser focal length: 0 mm; target rotation speed: ±15° / min; deposition growth rate: 2 nm / min;

[0059] (5) The surface of the CoFeO4 buffer layer is cleaned by plasma in the cavity atmosphere. The parameters are the same as those of the mica substrate. The purpose is to make the surface of the buffer layer have a suitable surface energy in the (111) or (101) orientation and have good surface flatness.

[0060] (6) Using a pulsed laser deposition system, the SrRuO3 target is switched to the main target position, and a SrRuO3 thin film is deposited on the buffer layer obtained in step (4) to obtain the bottom electrode layer; the specific process parameters are: the vacuum degree of the deposition chamber is 2×10 -5 Pa; substrate temperature: 600℃; oxygen partial pressure: 85 mTorr; laser energy: 390 mJ; pulsed laser frequency: 10 Hz; laser focal length: 5 mm; deposition rate: 2 nm / min; target rotation speed: ±17° / min;

[0061] (7) Using a pulsed laser deposition system, switch Pb(Zr) 0.1 Ti 0.9 The O3 target is located at the main target site, and Pb(Zr) is deposited on the bottom electrode layer obtained in step (6). 0.1 Ti 0.9 O3 thin film was used to obtain a ferroelectric functional layer; the specific process parameters were: the vacuum degree of the deposition chamber was 2×10⁻⁶. -6 Pa; substrate temperature: 600℃; oxygen partial pressure: 200 mTorr; laser energy: 340 mJ; pulsed laser frequency: 10 Hz; laser focal length: 10 mm; deposition rate: 2 nm / min; target rotation speed: ±12° / min;

[0062] (8) After the above ferroelectric functional layer is deposited, it is cooled to room temperature at a cooling rate of 10℃ / min in a deposition chamber environment with a substrate temperature of 600℃ and an oxygen partial pressure of 200mTorr to obtain a flexible lead zirconate titanate ferroelectric thin film. Then, the mica substrate and the ferroelectric thin film are peeled off to obtain a lead zirconate titanate free radical thin film.

[0063] Example 2

[0064] The difference from Example 1 is as follows:

[0065] In step (2), the distance between the muscovite substrate and the target is 10 mm.

[0066] In step (3), during the first surface treatment, the substrate temperature is -40℃ and the vacuum degree is ≤1×10⁻⁶. -6 The atmosphere was a mixture of argon (20%) and hydrogen (80%), with a partial pressure of 80 mTorr. The distance between the plasma electrode and the substrate was 60 mm, and the treatment time was 180 s. During the second surface treatment, the substrate temperature was 150 °C, and the vacuum degree was ≤1 × 10⁻⁶. -6 The atmosphere was a mixture of helium (60%) and oxygen (40%), with a partial pressure of 40 mTorr. The distance between the plasma electrode and the substrate was 40 mm, and the processing time was 100 s. During the third surface treatment, the substrate temperature was 80 °C, and the vacuum degree was ≤1 × 10⁻⁶. -6 Pa, nitrogen atmosphere, atmospheric partial pressure of 50 mTorr, distance between plasma electrode and substrate of 60 mm, processing time of 100 s;

[0067] The process parameters in step (4) are: the vacuum degree of the deposition chamber is 5×10 -5Pa; substrate temperature: 600℃; oxygen partial pressure: 75 mTorr; laser energy: 365 mJ; pulsed laser frequency: 8 Hz; laser focal length: 10 mm; target rotation speed: ±15° / min; deposition growth rate: 2 nm / min;

[0068] The process parameters in step (7) are: switching to Pb(Zr) 0.2 Ti 0.8 O3 target material, deposition chamber vacuum level 2×10 -5 Pa; substrate temperature: 600℃; oxygen partial pressure: 180 mTorr; laser energy: 345 mJ; pulsed laser frequency: 9 Hz; laser focal length: 10 mm; deposition rate: 1.8 nm / min; target rotation speed: ±12° / min;

[0069] The remaining steps and parameters are the same as in Example 1, to obtain Pb(Zr) 0.2 Ti 0.8 O3 free radical thin film.

[0070] Example 3

[0071] The difference from Example 1 is as follows:

[0072] In step (2), the distance between the muscovite substrate and the target is 60 mm.

[0073] In step (3), during the first surface treatment, the substrate temperature is -10℃ and the vacuum degree is ≤1×10⁻⁶. -6 The atmosphere was a mixture of argon (20%) and hydrogen (80%), with a partial pressure of 15 mTorr. The distance between the plasma electrode and the substrate was 20 mm, and the treatment time was 15 s. During the second surface treatment, the substrate temperature was 150 °C, and the vacuum degree was ≤1 × 10⁻⁶. -6 The atmosphere was a mixture of helium (60%) and oxygen (40%), with a partial pressure of 30 mTorr. The distance between the plasma electrode and the substrate was 15 mm, and the processing time was 15 s. During the third surface treatment, the substrate temperature was 60 °C, and the vacuum degree was ≤1 × 10⁻⁶. -6 Pa, nitrogen atmosphere, atmospheric partial pressure of 50 mTorr, distance between plasma electrode and substrate of 10 mm, processing time of 20 s;

[0074] The process parameters in step (7) are: switching to Pb(Zr) 0.48 Ti 0.52 O3 target material, deposition chamber vacuum level 2×10 -5Pa; substrate temperature: 595℃; oxygen partial pressure: 210 mTorr; laser energy: 355 mJ; pulsed laser frequency: 10 Hz; laser focal length: 5 mm; deposition rate: 2.3 nm / min; target rotation speed: ±12° / min;

[0075] The remaining steps and parameters are the same as in Example 1, to obtain Pb(Zr) 0.48 Ti 0.52 O3 free radical thin film.

[0076] Comparative Example 1

[0077] The method for preparing a lead zirconate titanate ferroelectric thin film with a rigid (111)-SrTiO3 substrate in Comparative Example 1 includes the following steps:

[0078] (1) Select a substrate layer, select (111)-SrTiO3 substrate, clean it and bond it to the center of the substrate stage of the pulsed laser deposition system, and then place the substrate stage on the heating stage in the deposition cavity of the pulsed laser deposition system. At this time, the substrate is above the main target, and the distance between the SrTiO3 substrate and the target is 50mm.

[0079] (2) Using a pulsed laser deposition system, the SrRuO3 target is switched to the main target site to deposit a SrRuO3 thin film on the SrTiO3 substrate, thus obtaining the bottom electrode layer; the specific process parameters are: the vacuum degree of the deposition chamber is 2×10 -5 Pa; substrate temperature: 600℃; oxygen partial pressure: 85 mTorr; laser energy: 390 mJ; pulsed laser frequency: 10 Hz; laser focal length: 5 mm; deposition rate: 2 nm / min; target rotation speed: ±17° / min;

[0080] (3) Using a pulsed laser deposition system, switch Pb(Zr) 0.1 Ti 0.9 The O3 target is located at the main target site, and Pb(Zr) is deposited on the bottom electrode layer obtained in step (2). 0.1 Ti 0.9 O3 thin film was used to obtain a ferroelectric functional layer; the specific process parameters were: the vacuum degree of the deposition chamber was 2×10⁻⁶. -6 Pa; substrate temperature: 600℃; oxygen partial pressure: 200 mTorr; laser energy: 340 mJ; pulsed laser frequency: 10 Hz; laser focal length: 10 mm; deposition rate: 2 nm / min; target rotation speed: ±12° / min;

[0081] (4) Using a pulsed laser deposition system, the SrRuO3 target is switched to the main target position, and a SrRuO3 thin film is deposited on the ferroelectric functional layer obtained in step (3) to obtain the top electrode layer; the specific process parameters are: the vacuum degree of the deposition chamber is 2×10- 5 Pa; substrate temperature: 600℃; oxygen partial pressure: 85 mTorr; laser energy: 390 mJ; pulsed laser frequency: 10 Hz; laser focal length: 5 mm; deposition rate: 2 nm / min; target rotation speed: ±17° / min;

[0082] (5) After the above top electrode layer is deposited, it is cooled to room temperature at a cooling rate of 10℃ / min in a deposition chamber environment with a substrate temperature of 600℃ and an oxygen partial pressure of 200mTorr.

[0083] Regarding Example 2

[0084] The difference from Example 1 is that the substrate is the muscovite substrate of Example 1, and Pb(Zr) is prepared through other steps in Comparative Example 1. 0.2 Ti 0.8 The test results for the O3 ferroelectric thin film were roughly similar to those of Comparative Example 1.

[0085] Regarding Example 3

[0086] The difference from Example 1 is that the substrate is the muscovite substrate of Example 1, and a CoFeO4 buffer layer consistent with step (4) of Example 1 is added, and Pb(Zr) is prepared by the other steps in Comparative Example 1. 0.2 Ti 0.8 The test results for the O3 ferroelectric thin film were roughly similar to those of Comparative Example 1.

[0087] like Figure 1 The diagram shows the structure of the flexible lead zirconate titanate ferroelectric thin film prepared by the pulsed laser deposition system in this invention. A, B, C, and D in the diagram are schematic diagrams of the thin film components prepared by steps (2), (4), (6), and (7) in Examples 1-3 of this invention, respectively.

[0088] like Figure 2 The image shown is a TEM image of the flexible lead zirconate titanate ferroelectric thin film material prepared in Example 1 of the present invention. The high-resolution TEM image shows that the actual thicknesses of the bottom electrode layer and the ferroelectric functional layer are 30 nm and 190 nm, respectively. The flexible substrate layer, buffer layer, bottom electrode layer and ferroelectric functional layer have clear boundaries, proving that the prepared film is layered.

[0089] like Figure 3 The image shows the XRD patterns of lead zirconate titanate ferroelectric thin film materials prepared in Examples 1-3 and Comparative Example 1 of this invention. It can be clearly seen from the XRD patterns that all the PZT films prepared are epitaxially grown with a high (111) orientation. In addition, no peaks related to impurities were observed, which proves that the PZT films are all single-phase crystals.

[0090] like Figure 4 As shown, the figures compare the surface morphology, in-plane and out-of-plane PFM amplitude, and PFM piezoelectric response curves of the lead zirconate titanate ferroelectric thin film materials prepared in Example 1 and Comparative Example 1 of this invention. AFM testing was performed on the thin film materials prepared in Example 1 and Comparative Example 1. Figures A and D show the morphology comparison of the thin films prepared in Example 1 and Comparative Example 1, respectively. Figure A shows the surface morphology of three structural variants, while Figure D shows obvious complex nanodomains. Figures B and E show the in-plane and out-of-plane PFM amplitude diagrams of the thin films prepared in Example 1 and Comparative Example 1, respectively. Figure F shows the PFM piezoelectric response diagram of the thin films prepared in Example 1 and Comparative Example 1, indicating that the Pb(Zr) on the mica substrate... 0.1 Ti 0.9 The piezoelectric response intensity of the SrTiO3 thin film is that of the Pb(Zr)O3 substrate. 0.1 Ti 0.9 Twice that of O3 thin film;

[0091] like Figure 5 The figures show a comparison of the polarization field (PV) of lead zirconate titanate (PZT) ferroelectric thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. PV tests were performed on the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3. Figure A compares Example 1 with Comparative Example 1, Figure B compares Example 2 with Comparative Example 2, and Figure C compares Example 3 with Comparative Example 4. From Figures A, B, and C, it can be seen that compared with the SrTiO3 substrate PZT thin film of the same composition, the mica substrate PZT thin film has a similar coercive field, but the ferroelectric polarization intensity is significantly increased. Figure D is a bar chart of the polarization intensity of Examples 1-3 and Comparative Examples 1-3. From Figure D, the Pb(Zr) polarization intensity of the mica substrate Pb(Zr) was calculated. 0.1 Ti 0.9 O3, Pb(Zr) 0.2 Ti 0.8 O3, Pb(Zr) 0.48 Ti 0.52 The remanent polarization intensity of the O3 film is ~50%, ~23%, and ~30% greater than that of the PZT film on the SrTiO3 substrate with the same composition, respectively.

[0092] like Figure 6 The figure shows a comparison of the PV curve changes of the lead zirconate titanate ferroelectric thin film materials prepared in Example 1 and Comparative Example 1. Figures A and B show the fatigue resistance tests of the thin film materials prepared in Example 1 and Comparative Example 1, respectively. After 13 cycles of testing, the Pb(Zr) on the mica substrate... 0.1 Ti 0.9 The ferroelectric properties of the O3 thin film were enhanced by 40%.

[0093] This invention combines optimized intracavity plasma cleaning technology and pulsed laser deposition technology to prepare flexible lead zirconate titanate ferroelectric thin films on chemically stable two-dimensional layered mica substrates. This not only significantly improves the fatigue resistance of the prepared ferroelectric thin film materials, but also greatly enhances the ferroelectric and piezoelectric properties of the flexible lead zirconate titanate ferroelectric thin film materials.

[0094] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a ferroelectric free radical thin film with good electromechanical properties, characterized in that, The process includes the following steps: sequentially growing a buffer layer, a bottom electrode layer, and a ferroelectric functional layer on a substrate; after annealing, peeling off the substrate yields a ferroelectric free radical thin film. The growth process employs pulsed laser deposition technology. The substrate is cleaned using an intracavity atmosphere plasma surface cleaning technique before the growth of the buffer layer and before the growth of the bottom electrode layer in the buffer layer. The intracavity atmosphere plasma surface cleaning technology consists of three independent cleaning processes, with the following parameters: During the first surface treatment, the substrate temperature is -40~-5℃, and the vacuum degree is ≤1×10⁻⁶. -6 Pa, the atmosphere is a mixture of argon and hydrogen, the partial pressure of the atmosphere is 10~80 mTorr, the distance between the plasma electrode and the substrate is 10~60 mm, and the processing time is 1~200 s; During the second surface treatment, the substrate temperature is 20~150℃, and the vacuum degree is ≤1×10⁻⁶. -6 Pa, atmosphere is helium and / or oxygen, atmosphere partial pressure is 1~50 mTorr, distance between plasma electrode and substrate is 10~40 mm, processing time is 1~100 s; During the third surface treatment, the substrate temperature is 60~200℃, and the vacuum degree is ≤1×10⁻⁶. -6 Pa, the atmosphere is at least one of argon, hydrogen, nitrogen, oxygen and helium, the partial pressure of the atmosphere is 1~50mTorr, the distance between the plasma electrode and the substrate is 10~60mm, and the processing time is 1~100s. The buffer layer is CoFe2O4 or YSZ, the bottom electrode layer is SrRuO3, and the ferroelectric functional layer is Pb(Zr) x Ti 1-x O3, where x = 0.1~0.5, and the substrate is a mica substrate.

2. The method for preparing a ferroelectric free radical thin film with good electromechanical properties according to claim 1, characterized in that, The pulsed laser deposition parameters for the buffer layer are: deposition cavity vacuum degree ≤ 5 × 10⁻⁶. -7 Pa; the substrate temperature is 590~620℃, the oxygen partial pressure is 80~100 mTorr; the laser energy is 350~390 mJ; the pulsed laser frequency is 6~10 Hz; the absolute value of the laser focal length is 0~20 mm; the absolute value of the target rotation speed is 15~18 o / min; The pulsed laser deposition parameters for the bottom electrode layer are: deposition cavity vacuum degree ≤ 5 × 10⁻⁶. -7 Pa; the substrate temperature is 580~620℃; the oxygen partial pressure is 50~100 mTorr; the laser energy is 370~410 mJ; the pulsed laser frequency is 8~10 Hz; the absolute value of the laser focal length is 0~15 mm; and the absolute value of the target rotation speed is 12~16. o / min; The pulsed laser deposition parameters for the ferroelectric functional layer are: deposition cavity vacuum degree ≤ 5 × 10⁻⁶. -6 Pa; the substrate temperature is 590~610℃; the oxygen partial pressure is 180~220 mTorr; the laser energy is 310~370 mJ; the pulsed laser frequency is 8~10 Hz; the laser focal length is -15~+15 mm; and the absolute value of the target rotation speed is 10~15. o / min.

3. The method for preparing a ferroelectric free radical thin film with good electromechanical properties according to claim 1, characterized in that, The annealing process parameters are as follows: under an oxygen partial pressure of 180–220 mTorr, the temperature is cooled to room temperature at a rate of 8–12 °C / min.

4. The method for preparing a ferroelectric free radical thin film with good electromechanical properties according to claim 1, characterized in that, The thickness of the buffer layer is 1~20nm, and the preferred orientation is any one of (001), (101) and (111); The thickness of the bottom electrode layer is 15~40nm; The thickness of the ferroelectric functional layer is 180~260nm.

5. The method for preparing a ferroelectric free radical thin film with good electromechanical properties according to claim 4, characterized in that, The substrate needs to undergo pretreatment, including: planarization, solvent cleaning, atmosphere drying, mechanical stripping, and atmosphere cleaning.

6. The ferroelectric free radical thin film with good electromechanical properties obtained by the preparation method according to any one of claims 1-5.

7. The application of the ferroelectric radical thin film as described in claim 6 in the fabrication of flexible electronic devices.

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