Method of reducing the switching field of a ferroelectric material
By setting electrodes on both sides of the ferroelectric material to form a capacitor, and connecting it in series with a dielectric capacitor to form a ferroelectric-dielectric system, the problem of excessive flipping electric field in traditional ferroelectric materials is solved, and the flipping electric field is effectively reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI
- Filing Date
- 2025-01-06
- Publication Date
- 2026-07-07
AI Technical Summary
Traditional ferroelectric materials have excessively large switching electric fields, resulting in high power consumption and serious durability problems, which are difficult to effectively reduce with existing technologies.
Top and bottom electrodes are placed on opposite sides of the ferroelectric material to form a ferroelectric capacitor, which is then connected in series with a dielectric capacitor to form a ferroelectric-dielectric system, thereby suppressing ferroelectricity and reducing the flipping electric field.
It achieves a significant reduction in the flipping electric field, and is simple in principle, non-destructive, and has a large controllable range, making it suitable for different ferroelectric materials.
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Figure CN122349313A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ferroelectric materials and semiconductor devices, and in particular to a method for reducing the reversal electric field of ferroelectric materials. Background Technology
[0002] Ferroelectric materials are a class of materials exhibiting spontaneous polarization, and their polarization state can be controlled by an applied electric field. The hysteresis loop is one of the key characteristics of ferroelectric materials, encompassing several important parameters, including saturation polarization, remanent polarization, and reversal electric field strength. The reversal electric field strength (coercive field) is the applied electric field when the polarization is zero. Ferroelectric materials possess excellent piezoelectric, thermoelectric, dielectric, and nonlinear optical properties, leading to their widespread application in piezoelectric sensors, electrothermal cooling, non-volatile memories, and photodetectors.
[0003] The polarization state of ferroelectric materials reverses when the applied electric field is greater than the reversal electric field, including lead zirconate titanate (Pb(Zr)). x Ti 1-x Traditional ferroelectric materials, including barium titanate (BaTiO3), polyvinylidene fluoride (PVDF), and novel hafnium dioxide (HfO2)-based ferroelectric materials, generally suffer from excessively large switching electric fields. This not only hinders power consumption reduction but also leads to extremely challenging durability issues due to the accompanying high leakage conductivity.
[0004] The reversal electric field of ferroelectric materials is constrained by many factors. For ferroelectric thin films, the clamping effect of a rigid substrate due to electromechanical coupling significantly increases the reversal electric field. In recent years, the continuous development and maturation of flexible functional oxide thin film fabrication technology has brought hope for completely solving the substrate clamping effect. For example, compared to samples on rigid substrates, the reversal electric field of self-supported bismuth ferrite (BiFeO3) thin films obtained based on epitaxial lift-off processes is significantly reduced. However, removing the substrate clamping effect only makes the reversal electric field approach the intrinsic reversal electric field of the bulk material; it cannot reduce the reversal electric field indefinitely. If the intrinsic reversal electric field of the ferroelectric material itself is too large, the technical approach of flexible ferroelectric thin films is clearly ineffective. Besides the substrate clamping effect, the reversal electric field of ferroelectric thin films is also significantly affected by the film crystal orientation, twin domain density, doping, and stoichiometry. Targeted and effective attempts have been made to address these factors. For example, artificially introducing defects inside the film and at the film-substrate interface to reduce the activation energy of reverse domain nucleation and modulate the ferroelectric polarization reversal behavior can reduce the reversal electric field of BaTiO3 thin films. Despite significant progress in related research, these methods are often inefficient and expensive. Summary of the Invention
[0005] (a) Technical problems to be solved
[0006] To address the problem of excessively large reversal electric fields in existing ferroelectric materials, embodiments of the present invention provide a method for reducing the reversal electric field of ferroelectric materials. This method utilizes a ferroelectric material connected in series with a dielectric to reduce the reversal electric field of ferroelectric materials, breaking away from the limitations of traditional solutions. It features simple principle, non-destructive operation, low implementation difficulty, and large controllability.
[0007] (II) Technical Solution
[0008] To address the aforementioned technical problems, embodiments of the present invention propose a method for reducing the reversal electric field of ferroelectric materials.
[0009] According to a first aspect of the present invention, a method for reducing the reversal electric field of a ferroelectric material is provided, comprising: a method for reducing the reversal electric field of a ferroelectric material, characterized in that the method comprises: setting a top electrode and a bottom electrode on opposite sides of the ferroelectric material to form a ferroelectric capacitor; connecting the ferroelectric capacitor and a dielectric capacitor in series to form a ferroelectric-dielectric system to suppress the ferroelectricity of the ferroelectric material and reduce the reversal electric field of the ferroelectric material.
[0010] In some exemplary embodiments, the degree of reduction in the reversing electric field of the ferroelectric material is related to the capacitance value of the dielectric capacitance.
[0011] In some exemplary embodiments, the larger the capacitance value of the dielectric capacitor, the closer the physical behavior of the ferroelectric-dielectric system under an electric field is to that of a ferroelectric; and the smaller the capacitance value of the dielectric capacitor, the closer the physical behavior of the ferroelectric-dielectric system under an electric field is to that of a dielectric.
[0012] In some exemplary embodiments, the material of the top electrode includes one of a metal, a conductive oxide, or a conductive nitride; and the material of the bottom electrode includes one of a metal, a conductive oxide, or a conductive nitride.
[0013] In some exemplary embodiments, the fabrication method of the top electrode includes one of electron beam evaporation, pulsed laser deposition, or magnetron sputtering; and the fabrication method of the bottom electrode includes one of electron beam evaporation, pulsed laser deposition, or magnetron sputtering.
[0014] In some exemplary embodiments, the ferroelectric material includes one of inorganic ferroelectric thin films, organic ferroelectric thin films, inorganic ferroelectric materials, or organic ferroelectric materials.
[0015] In some exemplary embodiments, the preparation method of ferroelectric materials includes one of the following: sol-gel method, metal-organic chemical vapor deposition, pulsed laser deposition, or solid-state crystal growth method.
[0016] In some exemplary embodiments, the dielectric capacitor includes one of an electrolytic capacitor, a ceramic capacitor, or a monolithic capacitor.
[0017] In some exemplary embodiments, the same dielectric capacitor reduces the reversing electric field to different degrees for different ferroelectric materials.
[0018] (III) Beneficial Effects
[0019] As can be seen from the above technical solutions, the method, apparatus, equipment, and medium for reducing the reversal electric field of ferroelectric materials provided by the embodiments of the present invention have at least the following beneficial effects:
[0020] (1) The method of reducing the reversal electric field of ferroelectric materials by connecting ferroelectric materials in series with dielectrics breaks away from the limitations of traditional schemes and has the characteristics of simple principle, non-destructive, easy implementation and large control range. Attached Figure Description
[0021] The above-described features, other objects, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:
[0022] Figure 1 The schematic diagram illustrates a process flow of a method for reducing the reversal electric field of a ferroelectric material according to an embodiment of the present invention;
[0023] Figure 2 The illustration shows Pb(Zr) according to an embodiment of the present invention. 0.2 Ti 0.8 )Schematic diagram of the O3 film capacitor-ceramic capacitor system;
[0024] Figure 3 The diagram illustrates the PV curve of a Pb(Zr0.2Ti0.8)O3 thin-film capacitor-ceramic capacitor system under an applied voltage according to an embodiment of the present invention.
[0025] Figure 4 A schematic diagram of the structure of a BaTiO3 thin-film capacitor-ceramic capacitor system according to an embodiment of the present invention is shown; and
[0026] Figure 5 The diagram illustrates the PV curve of a BaTiO3 thin-film capacitor-ceramic capacitor system under an applied voltage according to an embodiment of the present invention. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0028] Figure 1 The illustration shows a schematic flowchart of a method for reducing the reversing electric field of a ferroelectric material according to an embodiment of the present invention.
[0029] Depend on Figure 1 It is understood that a method for reducing the reversal electric field of ferroelectric materials according to an embodiment of the present invention includes steps S110-S120.
[0030] In step S110, a top electrode and a bottom electrode are respectively provided on opposite sides of the ferroelectric material to form a ferroelectric capacitor.
[0031] In this embodiment of the invention, the selection of materials for the top and bottom electrodes is crucial. They not only need to possess good conductivity to ensure efficient charge transport, but also need to form good interfacial contact with the ferroelectric material to reduce interfacial resistance and charge trapping. The materials for the top and bottom electrodes include one of the following: metals (such as platinum, gold, titanium, etc.), conductive oxides (such as indium tin oxide, zinc oxide, etc.), or conductive nitrides (such as titanium nitride, aluminum nitride, etc.). The selection of these materials depends on their conductivity, stability, and compatibility with the ferroelectric material.
[0032] In this embodiment of the invention, the top electrode is prepared by one of electron beam evaporation, pulsed laser deposition (PLD), or magnetron sputtering; and the bottom electrode is prepared by one of electron beam evaporation, pulsed laser deposition, or magnetron sputtering. Electron beam evaporation can provide high-purity thin films, suitable for applications requiring high material purity; PLD can precisely control the composition and structure of the thin film, suitable for preparing complex multi-component thin films; magnetron sputtering is widely used in large-scale production due to its efficient and uniform deposition characteristics. The specific method chosen depends on factors such as the required film quality, thickness uniformity, and preparation cost.
[0033] In some exemplary embodiments, the ferroelectric material includes one of the following: inorganic ferroelectric thin films (such as lead zirconate titanate PZT, potassium sodium niobate KNN, etc.), organic ferroelectric thin films (such as polyvinylidene fluoride PVDF and its copolymers, etc.), inorganic ferroelectric materials (such as Roche salt, potassium sodium tartrate, etc.), or organic ferroelectric materials (such as certain liquid crystal materials). The selection of these materials depends on their polarization intensity, switching speed, stability, and the requirements of the application scenario.
[0034] In some exemplary embodiments, methods for preparing ferroelectric materials include sol-gel methods, metal-organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), and solid-state crystal growth methods. Sol-gel methods are suitable for preparing thin films with complex shapes and structures; MOCVD can provide thin films with high uniformity and good crystallinity; PLD is widely used in the preparation of ferroelectric thin films because it can precisely control the composition and structure of the film; and solid-state crystal growth methods are suitable for preparing large-size, high-quality ferroelectric crystals.
[0035] In step S120, the ferroelectric capacitor and the dielectric capacitor are connected in series to form a ferroelectric-dielectric system, so as to suppress the ferroelectricity of the ferroelectric material and reduce the flip electric field of the ferroelectric material.
[0036] In a ferroelectric-dielectric system, dielectric capacitors and ferroelectric capacitors are connected in series and share the applied electric field. Because the dielectric constant of the dielectric material is typically much higher than the relative dielectric constant of the ferroelectric material in its polarized state, the dielectric capacitor responds more rapidly to the electric field and bears a larger voltage drop. This results in a reduction in the electric field strength experienced by the ferroelectric capacitor, thereby reducing the switching electric field.
[0037] In this embodiment of the invention, the degree of reduction in the reversal electric field of the ferroelectric material is related to the capacitance value of the dielectric capacitor. The capacitance value of the dielectric capacitor has a significant impact on the physical behavior of the ferroelectric-dielectric system. When the capacitance value of the dielectric capacitor is large, the system as a whole tends to exhibit ferroelectric characteristics, that is, the polarization state is easily reversed. However, as the capacitance value of the dielectric capacitor decreases, the system gradually tends to behave like a dielectric, and the reversal of the polarization state becomes more difficult. This balance relationship provides the possibility for flexible control of the reversal electric field of the ferroelectric material.
[0038] In this embodiment of the invention, the same dielectric capacitor reduces the switching electric field of different ferroelectric materials to varying degrees. This is mainly due to the different polarization mechanisms, domain structures, and switching dynamics of different ferroelectric materials. Therefore, in practical applications, it is necessary to select appropriate dielectric capacitors and control strategies based on the type and characteristics of the ferroelectric material.
[0039] Dielectric capacitors can be one of the following: electrolytic capacitors, ceramic capacitors, or monolithic capacitors. Electrolytic capacitors have large capacitance values and high energy density, making them suitable for applications requiring high capacitance values. Ceramic capacitors are widely used in high-frequency circuits due to their small size, light weight, and good stability. Monolithic capacitors are used in precision electronic equipment due to their good temperature stability and high-frequency characteristics. The specific type of dielectric capacitor chosen depends on factors such as the required capacitance value, frequency response, stability, and cost.
[0040] Figure 2 The illustration shows Pb(Zr) according to an embodiment of the present invention.0.2 Ti 0.8 )Schematic diagram of the O3 film capacitor-ceramic capacitor system; Figure 3 The diagram illustrates the PV curve of a Pb(Zr0.2Ti0.8)O3 thin-film capacitor-ceramic capacitor system under an applied voltage according to an embodiment of the present invention.
[0041] like Figure 2 As shown, according to the embodiment of the present invention, Pb(Zr) 0.2 Ti 0.8 The structure of the O3 thin-film capacitor-ceramic capacitor system includes: Au top electrode, Pb(Zr) electrode, and ceramic capacitor. 0.2 Ti 0.8 The fabrication process includes: cleaning the Nb:SrTiO3 substrate as the bottom electrode using a standard cleaning process (RCA process); and depositing a 100 nm layer of Pb(ZrO3) thin film, Nb:SrTiO3 bottom electrode, and ceramic capacitor on the surface of the Nb:SrTiO3 bottom electrode using magnetron sputtering at a temperature of 720 °C and an argon-oxygen ratio of 4:1. 0.2 Ti 0.8 O3 thin films are used as ferroelectric materials; furthermore, Pb(Zr) thin films are produced by electron beam evaporation. 0.2 Ti 0.8 A 30 nm Au top electrode was deposited on the surface of the O3 thin film under conditions of 10 kW power and 23 °C; the above Pb(Zr) electrode was then deposited using wires. 0.2 Ti 0.8 O3 film capacitors were connected in series with ceramic capacitors of different capacitance values.
[0042] To verify the actual effect, Pb(Zr) was measured using an oscilloscope graphical method. 0.2 Ti 0.8 PV curves of the O3 film capacitor-ceramic capacitor system. During the test, a triangular wave voltage with a frequency of 1kHz and an amplitude of 5V was applied to the system.
[0043] like Figure 3 As shown, when Pb(Zr) 0.2 Ti 0.8 When an O3 capacitor is not connected in series with a dielectric capacitor, the voltage drop across its terminals is the external voltage. According to the obtained PV curve, the reversal electric field is 309 kV / cm. When a 47 nF dielectric capacitor is connected in series, the PV curve narrows, and the reversal electric field decreases to 235 kV / cm. When the series capacitor is further reduced to 35 nF, the reversal electric field further decreases to 214 kV / cm. When the series capacitor is 15 nF, the reversal electric field becomes 94 kV / cm, relative to the Pb(Zr) capacitor without a dielectric capacitor. 0.2 Ti 0.8For O3, the reversal electric field is significantly reduced.
[0044] Figure 4 The schematic diagram illustrates the structure of a BaTiO3 thin-film capacitor-ceramic capacitor system according to an embodiment of the present invention; Figure 5 The diagram illustrates the PV curve of a BaTiO3 thin-film capacitor-ceramic capacitor system under an applied voltage according to an embodiment of the present invention.
[0045] like Figure 4 The structure of the BaTiO3 thin-film capacitor-ceramic capacitor system according to an embodiment of the present invention includes an Au top electrode, a BaTiO3 thin film, an Nb:SrTiO3 bottom electrode, and a ceramic capacitor. The fabrication method includes: cleaning the Nb:SrTiO3 substrate using an RCA process; depositing a 50 nm thick BaTiO3 thin film on the surface of the Nb:SrTiO3 bottom electrode using laser pulse deposition at a temperature of 700°C, a laser energy of 300 mJ, and an oxygen partial pressure of 200 mTorr; depositing a 30 nm thick Au top electrode on the surface of the BaTiO3 thin film using electron beam evaporation at a power of 10 kW and a temperature of 23°C; and connecting the BaTiO3 thin-film capacitor in series with ceramic capacitors of different capacitance values using wires.
[0046] The PV curve of the BaTiO3 film capacitor-ceramic capacitor system was measured using an oscilloscope graphical method. During the test, a triangular wave voltage with a frequency of 1 kHz and an amplitude of 5 V was applied to the system.
[0047] like Figure 5 As shown, when the BaTiO3 capacitor is not connected in series with a dielectric capacitor, the voltage drop across its terminals is the external voltage. According to the obtained PV curve, the magnitude of the switching electric field is 521 kV / cm. When the series capacitor is 100 nF, the PV curve narrows, and the magnitude of the switching electric field decreases to 396 kV / cm. When the series capacitor is further reduced to 68 nF, the magnitude of the switching electric field further decreases to 334 kV / cm. When the series capacitor is 35 nF, the switching electric field becomes 152 kV / cm, which is a significant reduction compared to BaTiO3 without a series dielectric capacitor.
[0048] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for reducing the reversal electric field of ferroelectric materials, characterized in that, The method includes: A top electrode and a bottom electrode are respectively disposed on opposite sides of the ferroelectric material to form a ferroelectric capacitor; and The ferroelectric capacitor and the dielectric capacitor are connected in series to form a ferroelectric-dielectric system, so as to suppress the ferroelectricity of the ferroelectric material and reduce the flipping electric field of the ferroelectric material.
2. The method according to claim 1, characterized in that, The degree to which the reversing electric field of the ferroelectric material decreases is related to the capacitance value of the dielectric capacitor.
3. The method according to claim 2, characterized in that, The larger the capacitance value of the dielectric capacitor, the closer the physical behavior of the ferroelectric-dielectric system under an electric field is to that of a ferroelectric material; and The smaller the capacitance value of the dielectric capacitor, the closer the physical behavior of the ferroelectric-dielectric system under an electric field is to that of a dielectric.
4. The method according to claim 1, characterized in that, The material of the top electrode includes one of a metal, a conductive oxide, or a conductive nitride; and The material of the bottom electrode includes one of metal, conductive oxide, or conductive nitride.
5. The method according to claim 1, characterized in that, The top electrode is prepared by one of electron beam evaporation, pulsed laser deposition, or magnetron sputtering.
6. The method according to claim 1, characterized in that, The method for fabricating the bottom electrode includes one of electron beam evaporation, pulsed laser deposition, or magnetron sputtering.
7. The method according to claim 1, characterized in that, The ferroelectric material includes one of inorganic ferroelectric thin films, organic ferroelectric thin films, inorganic ferroelectric materials, or organic ferroelectric materials.
8. The method according to claim 1, characterized in that, The preparation method of the ferroelectric material includes one of the following: sol-gel method, metal-organic chemical vapor deposition, pulsed laser deposition, or solid crystal growth method.
9. The method according to claim 1, characterized in that, The dielectric capacitor includes one of the following: electrolytic capacitor, ceramic capacitor, or monolithic capacitor.
10. The method according to claim 1, characterized in that, The same dielectric capacitor reduces the reversing electric field to different degrees for different ferroelectric materials.