Preparation method of cerium-doped hafnium oxide-based ferroelectric film and ferroelectric film
By using deionized water instead of part of the organic solution in the preparation of hafnium oxide-based ferroelectric films, the cerium ions are reduced by using the crystal nucleus and the pyrolysis process generated by the hydrolysis reaction, the problems of high cost and insufficient stability in the prior art are solved, and performance improvement and environmental protection effects are achieved.
Patent Information
- Application Number
- CN202510524563.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-29
AI Technical Summary
In the prior art, the sol-gel method is expensive to prepare hafnium oxide-based ferroelectric films and the ferroelectric phase is not stable enough, making it difficult to meet the needs of green development and performance improvement.
Deionized water is used to replace part of the organic solution, and the product generated by the hydrolysis reaction is used as the crystal nucleus. Combined with the drying and pyrolysis process, some cerium ions are reduced to trivalent, increase oxygen vacancy, promote the formation of the ferroelectric phase, and reduce costs.
The performance improvement of ferroelectric films has been achieved, the preparation cost is reduced, environmental pollution is reduced, and the ferroelectric performance and the hydrophilicity of the film are enhanced.
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Figure CN120383476A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field of ferroelectric thin film preparation, and particularly relates to a preparation method of cerium-doped hafnium oxide-based ferroelectric thin film and a ferroelectric thin film. Background Art
[0002] As a new type of non-volatile memory, hafnium oxide-based ferroelectric memory is expected to break through the development bottleneck of traditional storage structures with its characteristics such as high-speed read and write, low power consumption, high retention, and radiation resistance, thus further promoting the development of storage technology. Hafnium oxide-based ferroelectric thin film with a stable ferroelectric phase and a certain polarization value is the key for ferroelectric memory to exhibit storage performance. At present, for hafnium oxide-based ferroelectric thin film, it is an urgent need for practical application to stabilize its ferroelectric properties and reduce raw material costs. At the same time, reducing environmental pollution is a necessary measure to implement the national concept of promoting green development. The organic combination of the two has promoted the research work of synergistic action with new strategies on the basis of using traditional thin film preparation methods. The macroscopic ferroelectric properties of hafnium oxide-based ferroelectric thin film are mainly determined by the precursor. Studying the preparation of the precursor provides a theoretical basis and guidance for stabilizing the performance of ferroelectric thin film in devices.
[0003] Currently, in the preparation of hafnium oxide-based ferroelectric thin film by sol-gel method as in Patent CN 111029244 A, a fully organic solution configuration (acetic acid and acetylacetone) is generally adopted; hafnium acetylacetonate is used as the hafnium source, which is expensive. At the same time, due to technical limitations of the sol-gel method, the orthorhombic ferroelectric phase of the prepared ferroelectric thin film is not stable enough. Summary of the Invention
[0004] One aspect of this application provides a preparation method of cerium-doped hafnium oxide-based ferroelectric thin film, including:
[0005] S1. Mix deionized water and hafnium chloride to obtain a hafnium chloride solution. The reaction between the deionized water and the hafnium chloride can refine the grains of the formed ferroelectric thin film;
[0006] S2. Mix cerium nitrate hexahydrate and ethylene glycol methyl ether to obtain a cerium nitrate solution;
[0007] S3. Mix the hafnium chloride solution and the cerium nitrate solution to obtain a precursor solution;
[0008] S4. Coat the precursor solution on a substrate, and perform drying, pyrolysis, and annealing treatments to obtain a cerium-doped hafnium oxide-based ferroelectric thin film; among them, the drying and pyrolysis processes can convert some tetravalent cerium ions in the precursor solution into trivalent cerium ions.
[0009] Furthermore, the volume ratio of the deionized water to the precursor solution is 20%-40%, and the molar concentration of the precursor solution is 0.1-0.2 mol / L.
[0010] Furthermore, the molar concentration of the precursor solution is 0.1 mol / L.
[0011] Furthermore, the volume ratio of the deionized water to the precursor solution is 40%.
[0012] Furthermore, hafnium chloride accounts for 85% of the molar concentration of the precursor solution; cerium nitrate accounts for 15% of the molar concentration of the precursor solution.
[0013] Furthermore, the coating process includes: spin-coating the precursor solution on the substrate at a segmented rotation speed to obtain a uniform wet film; wherein, the first-stage spin-coating rotation speed is 500 rmp, the time is 10 s, the second-stage spin-coating rotation speed is 5000 rmp, and the time is 30 s;
[0014] The drying temperature is 180 °C and the time is 180 s; the pyrolysis temperature is 350 °C and the time is 180 s;
[0015] Furthermore, after repeating the spin-coating, drying, and pyrolysis steps several times, annealing crystallization is performed, including:
[0016] The first annealing, the temperature is 400 °C, and the time is 300 s;
[0017] The second annealing, the temperature is 800 °C, and the time is 350 s.
[0018] On the other hand, the present application proposes a ferroelectric thin film, which is made by the preparation method of the cerium-doped hafnium oxide-based ferroelectric thin film in any of the above technical solutions. The chemical formula of the ferroelectric thin film is CeO 2-x :HfO2.
[0019] Furthermore, the doping concentration of cerium is 15% of the molar amount of hafnium oxide.
[0020] Furthermore, the remanent polarization value (2Pr) of the ferroelectric thin film ≥ 32 μC / cm 2 .
[0021] The above technical solutions of the present invention have at least the following beneficial technical effects:
[0022] The present application optimizes the precursor solution of the hafnium oxide-based ferroelectric thin film by changing the substances contained in the existing precursor: using deionized water as the solution of hafnium chloride, and the product generated by the hydrolysis reaction of hafnium chloride and deionized water serves as a heterogeneous core during crystallization, which can refine the crystal grains; during the drying and pyrolysis processes, deionized water causes a reduction reaction of cerium oxide, Ce 3+The increase in the content makes the oxygen vacancies increase by an appropriate amount. In the ferroelectric thin film, the appropriate oxygen vacancies reduce the formation barrier of the ferroelectric phase, promote the formation of the ferroelectric phase, and thus improve the ferroelectric properties. Moreover, the presence of deionized water in the precursor enhances the hydrophilicity of the ferroelectric thin film. In addition, replacing a part of the organic solution in the prior art with deionized water reduces the cost and pollution. Description of the Drawings
[0023] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0024] Figure 1 It is a flowchart of a method for preparing a cerium-doped hafnium oxide-based ferroelectric thin film provided by an embodiment of the present application;
[0025] Figure 2 It is a ferroelectric performance PE diagram of a cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1.
[0026] Figure 3 It is a saturation polarization diagram of cerium-doped hafnium oxide-based ferroelectric thin films with the volume of deionized water being 0%, 20%, and 40% of the precursor solution in the present application.
[0027] Figure 4 It is the grain size range of a cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1.
[0028] Figure 5 It is the grain size range of a cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 20% of the precursor solution in Example 2.
[0029] Figure 6 It is the grain size range of a cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 0% of the precursor solution in Example 3.
[0030] Figure 7 It is an XPS elemental analysis diagram of a cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1.
[0031] Figure 8 It is an XPS elemental analysis diagram of a cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 0% of the precursor solution in Example 3.
[0032] Figure 9It is the O1s elemental analysis diagram of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1.
[0033] Figure 10 It is the O1s elemental analysis diagram of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 0% of the precursor solution in Example 3.
[0034] Figure 11 It is the XRD peak separation ratio diagram of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1.
[0035] Figure 12 It is the XRD peak separation ratio diagram of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 0% of the precursor solution in Example 3. Detailed implementation manners
[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will elaborate on each embodiment of the present application with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in each embodiment of the present application, many technical details are provided to help readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented. The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation manners of the present application. The embodiments can be combined with each other and cross-referenced on the premise of not conflicting with each other.
[0037] Currently, in the prior art, the sol-gel method uses a fully organic solution to prepare the precursor; the organic solution and hafnium source are expensive, and due to technical limitations, the orthorhombic ferroelectric phase of the prepared ferroelectric thin film is not stable enough.
[0038] To solve the above problems, an embodiment of the present application provides a method for preparing a cerium-doped hafnium oxide-based ferroelectric thin film, specifically including:
[0039] S1. Weigh hafnium chloride and add it to deionized water, stir until it is fully dissolved to obtain a hafnium chloride solution; hafnium chloride is hydrolyzed to form tiny particles, which serve as the nucleation substrate during crystallization, promoting nucleation. The reaction between deionized water and hafnium chloride can refine the grains of the formed ferroelectric thin film.
[0040] S2. Weigh cerium nitrate hexahydrate (Ce(NO3)3·6H2O), mix it with ethylene glycol methyl ether, and stir until it is fully dissolved to obtain a cerium nitrate solution. Among them, there is no sequential order between the preparation of the hafnium chloride solution in step S1 and the preparation of the cerium nitrate solution in step S2.
[0041] S3. Mix the hafnium chloride solution and the cerium nitrate solution, and stir until completely dissolved to obtain a precursor solution;
[0042] S4. Coat the precursor solution on a substrate, and perform treatments such as drying, pyrolysis, and annealing to obtain a cerium-doped hafnium oxide-based ferroelectric thin film. Among them, during the drying and pyrolysis processes, some tetravalent cerium ions in the precursor solution can be transformed into trivalent cerium ions. The substrate can be heavily doped P-type silicon. Cerium nitrate is decomposed into cerium ions and nitrate ions in ethylene glycol monomethyl ether. During the drying and pyrolysis processes, the cerium ions react with the water molecules in the solution.
[0043] In this application, the precursor solution of the hafnium oxide-based ferroelectric thin film is optimized by changing the substances contained in the precursor in the prior art: using deionized water as the solution of hafnium chloride, and the product generated by the hydrolysis reaction between hafnium chloride and deionized water serves as a heterogeneous core during crystallization, which can refine the grain size; during the drying and pyrolysis processes (mainly pyrolysis), cerium nitrate pyrolyzes to form cerium oxide, and deionized water reacts with cerium oxide in a reduction reaction, and part of Ce 4+ is transformed into Ce 3+ , and the content of Ce 3+ increases, so that an appropriate amount of oxygen vacancies is introduced. Through the characteristic of oxygen vacancies stabilizing the orthorhombic phase, the ferroelectricity is enhanced; in the ferroelectric thin film, appropriate oxygen vacancies reduce the formation barrier of the ferroelectric phase, promoting the formation of the orthorhombic ferroelectric phase, thereby improving the ferroelectric performance; moreover, the presence of deionized water in the precursor enhances the hydrophilicity of the ferroelectric thin film, and replacing part of the organic solution (replacing acetic acid) in the prior art with deionized water reduces environmental pollution; replacing hafnium acetylacetonate in the prior art with hafnium chloride reduces the cost by nearly 20 times.
[0044] In an embodiment of this application, the volume ratio of deionized water to the precursor solution is 20%-40%; the molar concentration of the precursor solution is 0.1-0.2 mol / L. Preferably, the volume ratio of deionized water to the precursor solution is 40%. The molar concentration of the precursor solution is 0.1 mol / L.
[0045] Preferably, hafnium chloride accounts for 85% of the molar concentration of the precursor solution; cerium nitrate accounts for 15% of the molar concentration of the precursor solution.
[0046] In an embodiment of this application, during the preparation of the hafnium chloride solution, the mixture of hafnium chloride and deionized water is placed in a magnetic stirrer and stirred until completely dissolved;
[0047] Optionally, during the preparation of the cerium nitrate solution, the mixture of cerium nitrate hexahydrate and ethylene glycol monomethyl ether is placed in a magnetic stirrer and stirred until completely dissolved.
[0048] Optionally, during the preparation of the precursor solution, the mixture of hafnium chloride solution and cerium nitrate solution is placed in a magnetic stirrer and stirred until completely dissolved.
[0049] In one embodiment of the present application, the coating process includes:
[0050] The spin coater spins the precursor solution on the substrate at a segmented rotation speed to obtain a uniform wet film; specifically: the first-stage spin coating rotation speed is 500 rmp, the time is 10 s, the second-stage spin coating rotation speed is 5000 rmp, and the time is 30 s.
[0051] After forming a wet film on the substrate, it is dried on a hot plate or in an oven. The drying temperature is 180 °C and the time is 180 s.
[0052] Pyrolysis is carried out after drying. The main functions of drying and pyrolysis are to decompose organic substances, cerium nitrate and chlorides, and remove impurities such as water and Cl - 、NO3 - and avoid defects during the subsequent annealing process; the pyrolysis temperature is 350 °C and the time is 180 s. During the drying and pyrolysis process of the present application, since deionized water is used in the precursor solution, part of Ce 4+ can be transformed into Ce 3+ , and the pyrolyzed cerium nitrate and hafnium chloride form the primary structure of the pre-crystallization of the CeO 2-x :HfO2 ferroelectric thin film.
[0053] After repeating the steps of spin coating, drying and pyrolysis several times, under a nitrogen atmosphere, staged annealing is carried out to make it fully crystallized, including: primary annealing, the temperature is 400 °C and the time is 300 s; then, secondary annealing, the temperature is 800 °C and the time is 350 s.
[0054] The following specific examples are further descriptions of the present application. The examples given cannot list all the implementation manners of the present application, and only some of them are taken as examples for illustration. The specific examples are as follows:
[0055] Example 1
[0056] Prepare hafnium chloride solution: Weigh 0.13613 g of hafnium chloride, add it to 2 ml of deionized water, and stir with a magnetic stirrer until fully dissolved to obtain a clear hafnium chloride solution.
[0057] Prepare cerium nitrate solution: Weigh 0.03256 g of cerium nitrate hexahydrate, add it to 3 ml of ethylene glycol methyl ether, and stir until fully dissolved to obtain a clear cerium nitrate solution.
[0058] Preparation of precursor dissolution: Mix the obtained hafnium chloride solution and cerium nitrate solution, stir until fully dissolved, and filter after standing to obtain the precursor solution. Among them, the proportion of deionized water is about 40%, and the proportion of ethylene glycol methyl ether is about 60%.
[0059] Spin coating: Spin coat the precursor solution on the silicon substrate at a segmented rotation speed. Among them, the first-stage spin coating rotation speed is 500 rmp, and the time is 10 s. The second-stage spin coating rotation speed is 5000 rmp, and the time is 30 s.
[0060] Drying: Conduct drying on a hot plate or in an oven. The drying temperature is 180 °C, and the time is 180 s.
[0061] Pyrolysis: The pyrolysis temperature is 350 °C, and the time is 180 s.
[0062] After repeating the steps of spin coating, drying, and pyrolysis 6 times, under a nitrogen atmosphere, perform staged annealing: The first annealing, the temperature is 400 °C, and the time is 300 s; then, the second annealing, the temperature is 800 °C, and the time is 350 s.
[0063] Example 2
[0064] Preparation of hafnium chloride solution: Weigh 0.13613 g of hafnium chloride, add it to 1 ml of ethylene glycol methyl ether, and stir with a magnetic stirrer until fully dissolved to obtain a clear hafnium chloride solution.
[0065] Preparation of cerium nitrate solution: Weigh 0.03256 g of cerium nitrate hexahydrate, add it to 4 ml of ethylene glycol methyl ether, and stir until fully dissolved to obtain a clear cerium nitrate solution.
[0066] Preparation of precursor dissolution: Mix the obtained hafnium chloride solution and cerium nitrate solution, stir until fully dissolved, and filter after standing to obtain the precursor solution. Among them, the proportion of deionized water is about 20%, and the proportion of ethylene glycol methyl ether is about 80%.
[0067] The remaining steps and parameters are the same as those in Example 1.
[0068] Example 3
[0069] Preparation of cerium nitrate solution: Weigh 0.03256 g of cerium nitrate hexahydrate, add it to 5 ml of ethylene glycol methyl ether, and stir until fully dissolved.
[0070] Preparation of precursor dissolution: Weigh 0.13613 g of hafnium chloride, directly mix it with the cerium nitrate solution, stir until fully dissolved, and filter after standing to obtain the precursor solution (the solution is all organic solution, and the proportion of deionized water is 0%).
[0071] The remaining steps and parameters are the same as those in Example 1.
[0072] Experimental detection: The ferroelectric thin films obtained in the above Examples 1, 2, and 3 were respectively detected. The experimental process observations and detection results are as follows.
[0073] The addition amount of deionized water plays a decisive role in the reduction of cerium ions. Deionized water with a content of less than 20% has a small reduction effect on cerium ions. A deionized water content of more than 40% will make the viscosity of the precursor solution too low, which is not conducive to film formation. The ferroelectric thin film formed from the precursor with a 40% deionized water content has better performance, specifically as Figures 2 to 12 shown:
[0074] Figure 2 Figure 9 is the ferroelectric performance PE diagram of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1. Among them, the abscissa represents the electric field strength applied to the ferroelectric thin film, and the ordinate represents the polarization value of the ferroelectric thin film under this electric field strength. Figure 2 It shows that the preferred volume of deionized water is 40% of the precursor solution, and it has better ferroelectric performance compared to the ferroelectric thin films prepared with 20% and 0%.
[0075] Figure 3 The large figure is the saturation polarization diagram of the cerium-doped hafnium oxide-based ferroelectric thin films with the volume of deionized water being 0%, 20%, and 40% of the precursor solution in Examples 3, 2, and 1 respectively; Figure 3 The embedded small figure is twice the remanent polarization value. From the comparison of the large figures in Figure 3 and the embedded small figures in Figure 3 it can be intuitively seen that: when the volume of deionized water is 40% of the precursor solution, compared with the cerium-doped hafnium oxide-based ferroelectric thin films prepared with 20% and 0%, the ability to store charges and the limit ability of polarization are higher.
[0076] Figure 4 Figure 25 is the grain size range of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 40% of the precursor solution in Example 1. Figure 5 Figure 27 is the grain size range of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 20% of the precursor solution in Example 2. Figure 6 Figure 29 is the grain size range of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 0% of the precursor solution in Example 3. Figure 4 , Figure 5 and Figure 6 The abscissa in represents the grain size, and the ordinate represents the relative frequency of the occurrence of this grain size. From Figure 4 , Figure 5 and Figure 6The grain size range and occurrence frequency are compared, and it can be seen that when the volume of deionized water is 40% of the precursor solution, the grain size of the ferroelectric thin film of cerium-doped hafnium oxide prepared is smaller than that of the ferroelectric thin films prepared with 20% and 0%.
[0077] Figure 7 It is the XPS elemental analysis diagram of the ferroelectric thin film of cerium-doped hafnium oxide prepared with the volume of deionized water being 40% of the precursor solution in Example 1. Figure 8 It is the XPS elemental analysis diagram of the ferroelectric thin film of cerium-doped hafnium oxide prepared with the volume of deionized water being 0% of the precursor solution in Example 3. The abscissa represents the binding energy - used to calibrate the element, and the ordinate represents the valence state intensity of the corresponding element. The following reaction occurs in the ferroelectric thin film with added water: 2Ce 4+ (s) + H2O(g) ---> 2Ce 3+ (s) + H2(g) + O2(g), Figure 7 and 8 By comparing the XPS elemental analysis diagrams of the ferroelectric thin films, it can be seen that the addition of deionized water makes the peak proportion of Ce 3+ larger, that is, the content increases.
[0078] Figure 9 It is the O1s elemental analysis diagram of the ferroelectric thin film of cerium-doped hafnium oxide prepared with the volume of deionized water being 40% of the precursor solution in Example 1. Figure 10 It is the O1s elemental analysis diagram of the ferroelectric thin film of cerium-doped hafnium oxide prepared with the volume of deionized water being 0% of the precursor solution in Example 3. Figure 9 and Figure 10 The three peaks respectively correspond to O A : adsorbed oxygen, O V : oxygen vacancy, O L : lattice oxygen, which represent the relative proportions of different types of oxygen in a sample. By comparing the O Figure 9 and Figure 10 O V peaks of the ferroelectric thin films, it can be seen that when the volume of deionized water is 40% of the precursor solution, compared with the ferroelectric thin film of cerium-doped hafnium oxide prepared with 20%, the relative proportion intensity of O V (oxygen vacancy) is larger, that is, the oxygen vacancy increases.
[0079] Figure 11 It is the XRD peak proportion diagram of the ferroelectric thin film of cerium-doped hafnium oxide prepared with the volume of deionized water being 40% of the precursor solution in Example 1. Figure 12It is the XRD peak ratio diagram of the cerium-doped hafnium oxide-based ferroelectric thin film prepared with the volume of deionized water being 0% of the precursor solution in Example 3. The XRD peak ratio represents the relative ratio of the ferroelectric orthorhombic phase (o-phase) to the non-ferroelectric tetragonal phase (t-phase). Among them, the abscissa represents the diffraction angle, and the ordinate represents the relative intensity. Figure 11 and Figure 12 It can be seen from the comparison that when the volume of deionized water is 40% of the precursor solution, compared with the cerium-doped hafnium oxide-based ferroelectric thin film prepared with 0%, the o-phase accounts for a larger proportion.
[0080] On the other hand, the present application proposes a ferroelectric thin film made by the preparation method of the cerium-doped hafnium oxide-based ferroelectric thin film in any of the above technical solutions. The chemical formula of the ferroelectric thin film is CeO 2-x :HfO2. Therefore, this ferroelectric thin film has all the advantages and beneficial effects of the above preparation method.
[0081] Preferably, the doping concentration of cerium is 15% of the molar amount of hafnium oxide.
[0082] Preferably, the remanent polarization value (2Pr) of the ferroelectric thin film ≥ 32 μC / cm 2 .
[0083] In the description of the present invention, the descriptions of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.
[0084] It should be understood that the above specific embodiments of the present application are only used for exemplary illustration or explanation of the principle of the present application, and do not constitute a limitation to the present application. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all changes and modification examples falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.
Claims
1. A preparation method of a cerium-doped hafnium oxide-based ferroelectric thin film, characterized in that, Including: S1. Mix deionized water with hafnium chloride to obtain a hafnium chloride solution. The reaction between the deionized water and the hafnium chloride can refine the grains of the formed ferroelectric thin film. S2. Mix cerium nitrate hexahydrate with ethylene glycol monomethyl ether to obtain a cerium nitrate solution. S3. Mix the hafnium chloride solution with the cerium nitrate solution to obtain a precursor solution. S4. Coat the precursor solution on a substrate, and perform drying, pyrolysis, and annealing treatments to obtain a cerium-doped hafnium oxide-based ferroelectric thin film. Among them, the drying and pyrolysis processes can convert some tetravalent cerium ions in the precursor solution into trivalent cerium ions.
2. The preparation method according to claim 1, wherein The volume ratio of the deionized water to the precursor solution is 20%-40%, and the molar concentration of the precursor solution is 0.1-0.2 mol / L.
3. The preparation method according to claim 2, characterized in that, The molar concentration of the precursor solution is 0.1 mol / L.
4. The preparation method according to claim 2, characterized in that, The volume ratio of the deionized water to the precursor solution is 40%.
5. The preparation method according to claim 2, wherein The hafnium chloride accounts for 85% of the molar concentration of the precursor solution; the cerium nitrate accounts for 15% of the molar concentration of the precursor solution.
6. The preparation method according to claim 1, characterized in that, The coating process includes: spin-coating the precursor solution on the substrate at a segmented rotation speed to obtain a uniform wet film. Among them, the rotation speed for the first-stage spin-coating is 500 rmp, and the time is 10 s; the rotation speed for the second-stage spin-coating is 5000 rmp, and the time is 30 s. The drying temperature is 180 °C, and the time is 180 s; the pyrolysis temperature is 350 °C, and the time is 180 s.
7. According to the method described in claim 1, wherein After repeating the spin-coating, drying, and pyrolysis steps several times, annealing crystallization is performed, including: The first annealing, the temperature is 400 °C, and the time is 300 s; The second annealing, the temperature is 800 °C, and the time is 350 s.
8. A ferroelectric thin film, characterized in that, Prepared by the method for preparing a cerium-doped hafnium oxide-based ferroelectric thin film according to any one of claims 1-7, the chemical formula of the ferroelectric thin film being CeO 2-x :HfO2.
9. The ferroelectric thin film according to claim 8, wherein The doping concentration of cerium is 15% of the molar amount of hafnium oxide.
10. The ferroelectric thin film according to claim 9, characterized in that, The remanent polarization value (2Pr) of the ferroelectric thin film ≥ 32 μC / cm 2 .