A method for preparing flexible self-supporting silver niobate thin films
Flexible self-supporting silver niobate films were successfully prepared by wet etching technology using water-soluble strontium aluminate as a sacrificial layer and pulsed laser deposition. This solved the problem that silver niobate films are difficult to apply to flexible devices in traditional methods, and achieved high-quality polarization and electrical properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI UNIVERSITY
- Filing Date
- 2026-04-23
- Publication Date
- 2026-05-26
AI Technical Summary
Traditional silver niobate films are prepared on rigid substrates, making them difficult to apply directly to flexible devices. Furthermore, conventional peeling methods can easily damage the films, limiting their application in flexible electronic devices.
Using water-soluble strontium aluminate oxide as a sacrificial layer, silver niobate film was separated from strontium titanate substrate by wet etching, and flexible self-supporting silver niobate film was prepared by pulsed laser deposition technology.
The non-destructive exfoliation of silver niobate films was achieved, and self-supporting films with good polarization properties and electrical stability were prepared, which are suitable for flexible electronic devices.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of flexible self-supporting silver niobate thin film preparation, including the preparation structure, experimental equipment, specific experimental conditions, and experimental operation methods. Background Technology
[0002] With the rapid development of flexible electronic devices in wearable devices, smart sensors, and flexible energy storage, there is an urgent need for functional thin film materials that combine excellent electrical properties with good flexibility. Silver niobate (AgNbO3), as a typical antiferroelectric material, possesses unique polarization behavior and a high dielectric constant, showing broad application prospects in microelectronic devices, energy storage, and conversion. However, traditional silver niobate films are mostly prepared on rigid substrates, making direct application in flexible devices difficult. Furthermore, conventional peeling methods easily damage the film, limiting its further application in flexible electronic devices.
[0003] Currently, the main technologies for the stripping and transfer of functional thin films include chemical etching, mechanical stripping, and sacrificial layer-based stripping methods. Among these, the method of using water-soluble materials as sacrificial layers to separate the functional layer from the substrate through wet etching has attracted widespread attention due to its simplicity, minimal interface damage, and applicability to various material systems. Existing sacrificial layer materials, such as water-soluble strontium aluminate oxide (Sr3Al2O6), have shown good performance in the stripping and transfer of perovskite-based oxide thin films, enabling complete stripping and structural preservation.
[0004] Based on this, developing a process-controllable, structurally sound, and electrically superior method for preparing flexible self-supporting silver niobate thin films is of great significance for expanding the application of silver niobate materials in flexible electronic devices. Summary of the Invention
[0005] The main objective of this invention is to provide a method for preparing flexible self-supporting silver niobate thin films, which can effectively solve the problems mentioned in the background art.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a flexible self-supporting silver niobate thin film, characterized by comprising the following steps: S1: Pretreatment of the strontium titanate substrate; S2: Place the strontium titanate substrate into a vacuum chamber, evacuate, heat up, inject oxygen, pre-sputter with a strontium aluminate target for 10 min, then perform formal sputtering for 10 min, and deposit for 10 min to form a strontium aluminate sacrificial layer on the strontium titanate substrate. Then sputter with a silver niobate target for 60 min and deposit for 10 min to form a silver niobate functional layer on the strontium aluminate sacrificial layer. S3: Polydimethylsiloxane is attached to the surface of the silver niobate functional layer, and then the supporting layer is immersed in deionized water at ambient temperature. The strontium aluminate sacrificial layer is dissolved to obtain a self-supporting silver niobate film.
[0007] Preferably, the pretreatment in step S1 involves first immersing the strontium titanate substrate in an acetone solution for ultrasonic cleaning for 10 minutes to remove surface contaminants, then immersing it in an alcohol solution for ultrasonic cleaning for 10 minutes, and finally drying it with high-purity nitrogen gas for later use.
[0008] Preferably, after step S1, the insert valve is closed, the molecular pump is turned off, the rotation speed is reduced to 0, the forestage valve is closed, the mechanical pump is turned off, and nitrogen gas is introduced into the cavity, thus forming an STO / SAO / ANO thin film structure on the substrate.
[0009] Preferably, the specific operation of step S2 is as follows: S21: Place the strontium titanate substrate into the vacuum chamber, close the chamber's sealing door, turn on the mechanical pump, and then slowly open the bypass valve. Once the pressure inside the chamber drops below 5 Pa, close the bypass valve. S22: Turn on the molecular pump start switch, then slowly open the fore-stage valve and gate valve until the pressure reaches 2×10⁻⁶. - 4 Pa; S23: Start heating, adjust the gate valve to the slightly open state, inject oxygen at a flow rate of 50 sccm into the chamber, and adjust the gate valve to stabilize the pressure in the chamber at 5 Pa. S24: Wait for the temperature to rise to 750℃ in preparation for sputtering. In order to remove contaminants on the target surface, a 10-minute pre-sputtering is performed before the formal deposition of the strontium aluminate film. The formal sputtering of the strontium aluminate film is performed for 10 minutes, followed by a 10-minute deposition to form a strontium aluminate sacrificial layer on the strontium titanate substrate. Then, the temperature is adjusted to 550℃ and the pressure is adjusted to 7.6 Pa to begin the deposition of the silver niobate film. The sputtering is performed for 60 minutes, followed by a 10-minute deposition to form a silver niobate functional layer on the strontium aluminate sacrificial layer.
[0010] Preferably, prior to step S3 and before peeling, we attach the surface of the ANO / SAO heterostructure to a 0.5 mm thick polydimethylsiloxane film. Then, we immerse the entire sample in deionized water at room temperature. This process continues until the Sr3Al2O6 layer is completely dissolved, allowing the AgNbO3 film to separate from the substrate.
[0011] Preferably, in step S2, the thickness of the strontium aluminate sacrificial layer is about 40 nm, and the sputtering time is 10 min.
[0012] Preferably, the thickness of the silver niobate functional layer in step S3 is 250 nm.
[0013] Preferably, the VO2 thin film 1 is directly deposited on a natural mica substrate using pulsed laser deposition, wherein the target material used is a VO2 ceramic target, the laser used is a KrF excimer laser (λ=248nm), and the laser energy density is set to 1J / cm². 2 .
[0014] Preferably, during the deposition process, in order to select the optimal growth conditions, a series of VO2 films were grown under a range of different deposition oxygen pressures (1-4 Pa) and different deposition temperatures (500-600 °C). Furthermore, to eliminate the influence of film thickness on its growth quality, the film thickness under all different conditions was controlled to be approximately 40 nm.
[0015] Preferably, based on the weak interfacial forces of van der Waals epitaxy, a simple wet process (immersion in deionized water) successfully peeled millimeter-sized VO2 films completely from mica substrates, yielding entirely independent films. However, this technique is limited by the mica substrate, restricting its ability to prepare self-supporting perovskite-based oxide single-crystal films, and the size of the peeled and transferred films is relatively small. Therefore, the peeling and transfer technique using water-soluble strontium aluminate (Sr3Al2O6) as a sacrificial layer is applicable to various perovskite-based oxides, enabling the preparation of high-quality self-supporting films with excellent crystal structures and electrical properties.
[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention selects a classic antiferroelectric material—a freestanding single-crystal AgNbO3 film—as a prototype and employs a non-destructive exfoliation process to prepare a flexible self-supporting silver niobate film. Further observation using piezoelectric microscopy (PFM) reveals that the self-supporting single-crystal AgNbO3 film exhibits good polarization, displaying double hysteresis loops and low residual polarization. Its nanoribbons can withstand cyclic bending and possess good shape recovery. Attached Figure Description
[0017] Figure 1 This is a comparison of XRD test results of the self-supporting silver niobate film before and after transfer in Example 2 of the present invention; Figure 2 Phase and amplitude diagrams of PFM characterization of the self-supporting silver niobate thin film prepared in this invention; Figure 3 This is a PE test diagram from an embodiment of the present invention; Figure 4 This is an IV test diagram from an embodiment of the present invention. Detailed Implementation
[0018] The endpoints and any values of the ranges disclosed in this invention are not limited to the precise range thresholds, and these range thresholds should be understood to include values close to these range thresholds. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.
[0019] The following describes in detail, with reference to the accompanying drawings, a method for preparing a flexible self-supporting silver niobate thin film according to an embodiment of this specification.
[0020] Example 1 The specific steps for preparing a silver niobate thin film based on a strontium aluminate sacrificial layer are as follows: The silver niobate thin film based on a strontium aluminate sacrificial layer provided by this invention has the following structure from bottom to top: substrate, sacrificial layer, and functional layer. The substrate is a strontium titanate (SrTiO3, abbreviated as STO) substrate; the sacrificial layer material is strontium aluminate (Sr3Al2O6, abbreviated as SAO); and the functional layer material is silver niobate (AgNbO3, abbreviated as ANO).
[0021] The thickness of the SAO sacrificial layer is approximately 40 nm, the sputtering time is 10 min, and the deposition time is 10 min. The thickness of the ANO functional layer is 250 nm.
[0022] Example 2 A method for preparing a flexible self-supporting silver niobate thin film, the specific implementation steps of which are as follows: The method for preparing a self-supporting silver niobate thin film based on a strontium aluminate sacrificial layer provided by the present invention includes the following steps: (1) First, place the STO substrate in an acetone solution and ultrasonically clean it for 10 minutes to remove the stains on its surface. Then, place it in an alcohol solution and ultrasonically clean it for 10 minutes. After taking it out, blow it dry with high-purity nitrogen gas for later use.
[0023] (2) Use silver paste to attach the STO substrate to the heater tray.
[0024] (3) Place the heater tray with the STO substrate attached into the vacuum chamber of the pulsed laser deposition system. After closing the chamber's sealing door, turn on the mechanical pump, then slowly open the bypass valve. Once the pressure inside the chamber drops below 5 Pa, close the bypass valve. Turn on the molecular pump start switch, then slowly open the fore-stage valve and the gate valve until the pressure is pumped down to 2 × 10⁻⁶ Pa. -4Pa. Initiate heating, adjust the gate valve to a slightly open position, and inject oxygen at a flow rate of 50 sccm into the chamber. Adjust the gate valve to stabilize the pressure within the chamber at 5 Pa. Wait for the temperature to reach 750℃ in preparation for sputtering. To remove contaminants from the target surface, perform a 10-minute pre-sputtering before the formal deposition of the strontium aluminate film. Then, perform the formal sputtering of the strontium aluminate film for 10 minutes, followed by deposition for 10 minutes, forming a strontium aluminate sacrificial layer on the strontium titanate substrate. Next, adjust the temperature to 550℃ and the pressure to 7.6 Pa, and begin depositing the silver niobate film. Sputter for 60 minutes and then deposit for 10 minutes, forming a silver niobate functional layer on the strontium aluminate sacrificial layer. Afterward, close the gate valve and the molecular pump. Once the rotation speed drops to 0, close the forestage valve and the mechanical pump, and fill the chamber with nitrogen gas, forming an STO / SAO / ANO thin film structure on the substrate.
[0025] (4) To dissolve the sacrificial layer, we attached the surface of the ANO / SAO heterostructure to a 0.5 mm thick polydimethylsiloxane (PDMS) film. Then, we immersed the entire sample in deionized water at room temperature until the Sr3Al2O6 layer was completely dissolved, allowing the AgNbO3 film to separate from the substrate.
[0026] The flowchart of the sacrificial layer dissolution process in Example 2 is as follows: Figure 1 As shown.
[0027] The following performance tests were performed on the above embodiments: A method for preparing a flexible, self-supporting silver niobate thin film was transferred to a silicon dioxide substrate for characterization and performance testing. We immersed the sample prepared in Example 2 in deionized water at room temperature until the Sr3Al2O6 layer was completely dissolved, allowing the AgNbO3 film to separate from the substrate. To characterize the structure and function, the AgNbO3 film was transferred onto a silicon substrate. First, a PDMS / AgNbO3 stack was transferred onto the silicon substrate. The substrate was then heated to 80°C for 10 minutes to reduce the PDMS viscosity, allowing the AgNbO3 film to peel off from the PDMS, ensuring clean and firm adhesion between the AgNbO3 film and the silicon substrate.
[0028] 1. XRD tests were performed on the AgNbO3 thin film prepared in Example 2. XRD scans were performed on the STO / SAO / ANO structure and the transferred PDMS / ANO, with scanning angles of 20-50°. The results showed that the transferred silver niobate thin film also had good crystallinity.
[0029] 2. PFM testing was performed on the AgNbO3 thin film prepared in Example 2. A 2×2 micrometer range was selected for scanning the AgNbO3 thin film. Voltages of 0V, 4V, 6V, 4V, and 0V were applied sequentially, and the phase diagram and amplitude diagram were recorded respectively. By analyzing the phase diagram and amplitude diagram, the polarization behavior and ferroelectric / antiferroelectric properties of the thin film were determined.
[0030] The results are as follows Figure 2 As shown, the phase diagram and amplitude diagram of the test indicate that the AgNbO3 film has good polarization. The self-supporting film prepared by this invention still maintains good polarization performance after peeling and transfer, and is not significantly damaged by the sacrificial layer dissolution and transfer process.
[0031] 3. Hysteresis loop testing was performed on the AgNbO3 thin film prepared in Example 2. The self-supported silver niobate thin film was transferred to a substrate with electrodes (such as a silicon substrate) to construct a test capacitor structure. A ferroelectric testing instrument was connected, and a periodically varying electric field was applied. The polarization intensity of the thin film under different electric fields was recorded, and hysteresis loops were plotted. The presence of double hysteresis loop characteristics was determined based on the loop shape, and parameters such as residual polarization intensity were analyzed. The results are as follows: Figure 3 As shown, the film exhibits double hysteresis loops and low residual polarization, indicating that the film retains the intrinsic electrical properties of antiferroelectric materials, which is beneficial for applications such as low-loss energy storage.
[0032] 4. The AgNbO3 thin film prepared in Example 2 was subjected to an IV test with 80 consecutive scans. A self-supporting silver niobate film transferred onto a silicon substrate was connected to an IV testing system. The voltage scan range was set, and 80 consecutive current-voltage (IV) scans were performed. The current response for each scan was recorded, and the changes in the current curves during the 80 scans were observed. The electrical stability of the film was determined by the repeatability of the multiple scans; if the curves largely overlapped, it indicated that the film had good stability. The results are as follows: Figure 4 As shown, the transferred AgNbO3 film exhibits good electrical stability and is capable of long-term reliable operation.
[0033] In summary, flexible self-supporting silver niobate films were prepared using pulsed laser deposition combined with a water-soluble strontium aluminate sacrificial layer. The films prepared in the examples exhibited excellent polarization characteristics, antiferroelectric properties, and electrical stability. This preparation method achieves damage-free exfoliation of the silver niobate film, and the resulting self-supporting film maintains good structural integrity and functional properties, making it suitable for the development of flexible functional devices based on perovskite oxides.
[0034] In the description of this specification, the reference to terms such as "embodiment," "various embodiments," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or preparation example is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments. The above descriptions are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing a flexible self-supporting silver niobate thin film, characterized in that, Includes the following steps: S1: Pretreatment of the strontium titanate substrate; S2: Place the strontium titanate substrate into a vacuum chamber, evacuate, heat up, inject oxygen, pre-sputter with a strontium aluminate target for 10 min, then perform formal sputtering for 10 min, and deposit for 10 min to form a strontium aluminate sacrificial layer on the strontium titanate substrate. Then sputter with a silver niobate target for 60 min and deposit for 10 min to form a silver niobate functional layer on the strontium aluminate sacrificial layer. S3: Polydimethylsiloxane is attached to the surface of the silver niobate functional layer, and then the supporting layer is immersed in deionized water at ambient temperature. The strontium aluminate sacrificial layer is dissolved to obtain a self-supporting silver niobate film.
2. The method for preparing a flexible self-supporting silver niobate thin film according to claim 1, characterized in that, The pretreatment in step S1 involves first immersing the strontium titanate substrate in an acetone solution for ultrasonic cleaning for 10 minutes to remove surface contaminants, then immersing it in an alcohol solution for ultrasonic cleaning for 10 minutes, and finally drying it with high-purity nitrogen gas for later use.
3. The method for preparing a flexible self-supporting silver niobate thin film according to claim 1, characterized in that, After step S1, close the gate valve and the molecular pump. When the rotation speed drops to 0, close the fore-stage valve and the mechanical pump. Then, fill the chamber with nitrogen gas, forming a thin film structure of STO / SAO / ANO.
4. The method for preparing a flexible self-supporting silver niobate thin film according to claim 1, characterized in that, The specific operation of step S2 is as follows: S21: Place the strontium titanate substrate into the vacuum chamber, close the chamber's sealing door, turn on the mechanical pump, and then slowly open the bypass valve. Once the pressure inside the chamber drops below 5 Pa, close the bypass valve. S22: Turn on the molecular pump start switch, then slowly open the fore-stage valve and gate valve until the pressure reaches 2×10⁻⁶. -4 Pa; S23: Start heating, adjust the gate valve to the slightly open state, inject oxygen at a flow rate of 50 sccm into the chamber, and adjust the gate valve to stabilize the pressure in the chamber at 5 Pa. S24: Wait for the temperature to rise to 750℃ in preparation for sputtering. In order to remove contaminants on the target surface, a 10-minute pre-sputtering is performed before the formal deposition of the strontium aluminate film. The formal sputtering of the strontium aluminate film is performed for 10 minutes, followed by a 10-minute deposition to form a strontium aluminate sacrificial layer on the strontium titanate substrate. Then, the temperature is adjusted to 550℃ and the pressure is adjusted to 7.6 Pa to begin the deposition of the silver niobate film. The sputtering is performed for 60 minutes, followed by a 10-minute deposition to form a silver niobate functional layer on the strontium aluminate sacrificial layer.
5. The method for preparing a flexible self-supporting silver niobate thin film according to claim 1, characterized in that, Before step S3 and before peeling, we attach the surface of the ANO / SAO heterostructure to a 0.5 mm thick polydimethylsiloxane film. Then, we immerse the entire sample in deionized water at room temperature. This process continues until the Sr3Al2O6 layer is completely dissolved, allowing the AgNbO3 film to separate from the substrate.
6. The method for preparing a flexible self-supporting silver niobate thin film according to claim 1, characterized in that, In step S2, the thickness of the strontium aluminate sacrificial layer is about 40 nm, and the sputtering time is 10 min.
7. The method for preparing a flexible self-supporting silver niobate thin film according to claim 1, characterized in that, In step S3, the thickness of the silver niobate functional layer is 250 nm.