A method for remote molten salt-assisted preparation of ZrO2 thin films, and ZrO2 thin films, MIM flexible capacitors and their preparation methods.

Abstract

The application belongs to the field of nanometer materials, and provides a method for preparing a ZrO2 film by remote molten salt assistance, the ZrO2 film, a MIM flexible capacitor and a preparation method thereof. Zirconium carbide is used as a zirconium source, remote binary alkali metal halide gas phase molecules are used to assist the volatilization, and a trace amount of oxygen released by an environment or a substrate is used to assist the growth of the zirconia film. The prepared film is continuous and dense, has uniform thickness and smooth surface, and the preparation method is simple and easy to operate. The zirconia film has high dielectric constant and is a good dielectric layer material. A MIM (flexible metal-semiconductor-metal) capacitor is constructed based on the zirconia film. In a 300-time high-strength bending state, the capacitor still has stable capacitance performance.

Description

Technical Field

[0001] This invention belongs to the field of new materials and relates to a method for remote molten salt-assisted preparation of two-dimensional ZrO2 thin films, a MIM flexible capacitor and its preparation method. Background Technology

[0002] In recent years, with the rapid development of the electronics and information industry, there are increasingly stringent requirements for the integration, miniaturization, and dedimensionality of microelectronic chips. Achieving the integration and compatibility of micro / nano devices with silicon-based circuits is a major challenge that needs to be overcome quickly. However, due to the physical limitations of traditional silicon-based semiconductor materials at extreme scales, their device performance is unlikely to maintain its advantages in the post-Moore's Law era, and the performance of silicon-based semiconductors is difficult to sustain. With the increasing attention given to two-dimensional materials such as graphene and transition metal oxides, their unique electronic structure and excellent physicochemical properties, such as large electron band gaps and high mobility, can play a crucial role in highly integrated circuits. Therefore, two-dimensional materials have gradually become one of the hot research areas. Two-dimensional materials, short for two-dimensional atomic crystal materials, refer to materials with a thickness reaching the nanometer scale (0.1-100 nm), where charge carriers can only move in a two-dimensional plane, thus exhibiting many unique properties.

[0003] The microelectronics industry's continuous development relies on faster and higher-density integrated circuits, which are made up of millions of metal-oxide-semiconductor (MOS) field-effect transistors. Complementary metal-oxide-semiconductor (CMOS) has driven the development of computers for decades; however, silicon-based CMOS has now reached the scale limits of Moore's Law. The gate leakage current generated by the direct tunneling of electrons through ultrathin silicon dioxide (SiO2) has become extremely large, making it unsuitable for miniaturized MOS devices. Further improvements in transistor performance require breakthroughs in materials technology. Finding a replacement for SiO2 as the gate dielectric material for standard MOS technology is a challenging task, necessitating the use of materials with high dielectric constants (high κ). Two-dimensional nano-oxide materials are a new class of materials with rich band structures, simple crystal structures, strong field-effect controllability, and ultra-flat surfaces. Among them, two-dimensional nano-zirconia thin films (ZrO2) can theoretically fill the inherent defects of SiO2.

[0004] Meanwhile, ZrO2 thin films, as Group IVB metal oxide thin films, possess many excellent properties not found in other group metal oxides. For example, they exhibit very low absorption efficiency for photons in the 300nm-1000nm wavelength range, excellent thermal stability, high mechanical stability, and a high damage threshold. Due to these superior optical properties unmatched by other thin films, ZrO2 thin films are widely used in various optical thin films. ZrO2 materials are used as optical thin films in optical components such as filters, beam splitters, antireflective coatings, and anti-reflective coatings, especially in optical devices requiring a high optical damage threshold. Its high dielectric constant, large electron bandgap, high density, high hardness, strong wear resistance, high fracture toughness, low thermal conductivity, and extreme chemical inertness make it an excellent high-temperature resistant material and ceramic insulating material. Its good biocompatibility, aesthetics, and high hardness also make it an excellent material in clinical dentistry. Currently, it is widely used in mechanical, electronic, biological, chemical, aerospace, and optical fields.

[0005] ZrO2 is a typical high-κ material that can form three different crystal structures at different temperatures: monoclinic phase (m-ZrO2), cubic phase (c-ZrO2), and tetragonal phase (t-ZrO2). While some progress has been made in preparing ZrO2 thin films using the sol-gel method, the resulting zirconia films exhibit poor density and are produced from expensive raw materials with complex preparation processes. Furthermore, due to the high melting point and difficulty in volatilizing the ZrO2 precursor, current microelectronic processes often employ atomic layer deposition (ALD) using low-melting-point organic sources, resulting in nanoscale grains. The key to solving this problem is to invent a simple method that can produce dense zirconia thin films and improve film quality. Summary of the Invention

[0006] The problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art, and to provide a method for remote molten salt-assisted preparation of two-dimensional ZrO2 thin films, a two-dimensional ZrO2 thin film, and a flexible capacitor device based on two-dimensional ZrO2 thin films.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for remote molten salt-assisted preparation of two-dimensional ZrO2 thin films, comprising the following steps:

[0008] Step 1: Place the quartz tube horizontally, place the zirconium source in the central constant temperature zone of the quartz tube, and place the halide flux in the upstream low temperature zone of the quartz tube.

[0009] Step 2: Place the substrate above the zirconium source and set the vertical distance between the substrate and the zirconium source to 3-5 mm;

[0010] Step 3: Inert gas with a first flow rate of Q1 is introduced into the quartz tube for a duration of t1;

[0011] Step 4: Heat the quartz tube while introducing a second inert gas with a flow rate of Q2 as a carrier gas. Heat the quartz tube until the central constant temperature zone reaches temperature T1 and the upstream low temperature zone reaches temperature T2, and then keep it at that temperature for a time of t2.

[0012] Step 5: After the heat preservation time t2, stop heating the quartz tube and turn off the inert gas flow of the second flow rate Q2. Allow the quartz tube to cool naturally to room temperature, and a continuous and dense two-dimensional ZrO2 film can be obtained on the substrate.

[0013] In some of these implementations, Q1 = 220-260 sccm, t1 = 1-5 min;

[0014] In some of these embodiments, Q2 = 15-25 sccm, T1 = 950-1000℃, T2 = 850-900℃, and t2 = 20-30 min;

[0015] In some embodiments, the upstream low-temperature zone of the quartz tube is located 7-9 cm from the center of the quartz tube;

[0016] In some embodiments, the halide flux is a binary alkali metal halide;

[0017] In some embodiments, the zirconium source is zirconium carbide micron-sized particles;

[0018] In some embodiments, the substrate is any one of a fluorine-phlogopite substrate, a sapphire substrate, a molybdenum substrate, a tungsten substrate, or a stainless steel substrate.

[0019] In some embodiments, the halide flux is a mixture of sodium chloride powder and potassium chloride powder, wherein the mass ratio of sodium chloride powder to potassium chloride powder is 1:1.

[0020] In some embodiments, placing the zirconium source in the central isothermal zone of the quartz tube and placing the halide flux in the upstream low-temperature zone of the quartz tube specifically involves:

[0021] The zirconium source is placed in a quartz boat, and the quartz boat containing the zirconium source is placed in the central constant temperature zone of the quartz tube.

[0022] The halide flux is placed in a quartz boat, and the quartz boat containing the zirconium source is placed in the upstream low-temperature zone of the quartz tube.

[0023] The process involves using two quartz boats to hold the zirconium source and flux, respectively. The zirconium source is placed in the isothermal zone at the center of the quartz tube, while the substrate is placed in the same quartz boat, directly above the zirconium source at a vertical distance of 3-5 mm. The flux is placed in the low-temperature zone upstream of the quartz tube. Using chemical vapor deposition (CVD), by adjusting the isothermal temperature T1 at the center of the quartz tube, controlling the amounts of zirconium source and flux, and regulating the carrier gas flow rate Q2, a dense and uniform ZrO2 film is ultimately grown on the substrate.

[0024] In the above reaction, the zirconium source and flux sublimate upon reaching a certain temperature during heating. Sodium chloride and potassium chloride vapors are transported to the center of the quartz tube via a small gas flow (Q2) to assist in the sublimation of high-melting-point zirconium carbide. During the high-temperature stage, the quartz tube and quartz boat release trace amounts of oxygen, and the carrier gas (99.9% pure Ar) carries a small amount of oxygen. The sublimated zirconium carbide comes into contact with the trace oxygen in the atmosphere, and the two react chemically to produce ZrO2 and carbon monoxide products. Simultaneously, sodium chloride and potassium chloride etch the substrate surface, creating defects and increasing surface dangling bonds, significantly enhancing its surface chemical activity and adsorption properties. Therefore, ZrO2 can more easily nucleate and grow on the substrate, while carbon monoxide gas flows into the tail gas collection device with the argon gas.

[0025] Because the Gibbs free energy of zirconium carbide is greater than that of zirconium oxide, the reaction of zirconium carbide with oxygen at high temperatures to form ZrO2 lowers the Gibbs free energy of the system. This causes the reaction to spontaneously proceed in the direction of ZrO2 formation, making it easier to form the ZrO2 product. The substrate and the grown material are connected by van der Waals forces. The material undergoes van der Waals epitaxial growth on the substrate plane. After growing to a certain size, the materials are brought into contact and spliced ​​together to ultimately form a continuous film.

[0026] During the growth process described above, the amount of flux must be strictly controlled. Because zirconium carbide has an extremely high melting point (~3540℃) and is not easily volatilized, a flux is needed to assist in its sublimation. Preferably, sodium chloride and potassium chloride are used as fluxes, and the mass ratio of the zirconium source to the halide flux is 10:3-6:5. If too much flux is used, excessive impurities will be generated on the substrate and material, affecting the material's growth; if too little flux is used, the auxiliary effect will be insufficient, resulting in inadequate precursor sublimation supply and preventing the acquisition of a continuous thin film.

[0027] In the above growth process, the size of the precursor is particularly important. To prepare continuous ZrO2 thin films, the specific surface area of ​​the precursor needs to be strictly controlled. In some embodiments, the mass ratio of the zirconium source to the halide flux is 10:3-6:5, and the particle size of the zirconium source bulk needs to be controlled within 2-5 μm. The zirconium source bulk should not be too small. If the zirconium source bulk is small, the specific surface area of ​​the same mass of zirconium source increases, the precursor supply rate is too fast, and the number of nucleation sites on the substrate increases, which is not conducive to crystal growth and easily leads to grain agglomeration, making it difficult to form large-area thin films. If the zirconium source bulk is large, the specific surface area of ​​the same mass of zirconium source is too small, the precursor supply rate is too slow, which is not conducive to crystal growth and makes it difficult to form large-area thin films.

[0028] In the above growth process, the carrier gas flow rate is particularly important. To grow a continuous film, the carrier gas flow rate needs to be strictly controlled. The carrier gas flow rate used in this invention is controlled at Q2 = 15-25 sccm. The carrier gas flow rate should not be too small; if it is too small, it will not achieve effective transport, resulting in a small amount of flux vapor delivered to the zirconium source, failing to achieve the desired fluxing effect. Conversely, the carrier gas flow rate should not be too large; if it is too large, the transported flux vapor will quickly bypass the zirconium source, preventing it from fully contacting the zirconium source and failing to achieve the desired fluxing effect, thus preventing the formation of a zirconium oxide film.

[0029] During the aforementioned growth process, the flux holding temperature must be strictly controlled. Preferably, the distance between the flux holding temperature and the isothermal center is 7-9 cm, with a temperature range of T2 = 850-900℃. If the flux holding temperature is too high, it will easily sublimate and be transported out of the reaction zone by the carrier gas, failing to achieve the desired fluxing effect. If the flux holding temperature is too low, it cannot sublimate, and the carrier gas cannot transport it to the isothermal zone to contact the zirconium source, also failing to achieve the desired fluxing effect.

[0030] In some embodiments, by adjusting the above-mentioned process parameters, a polycrystalline dense two-dimensional ZrO2 film composed of a large number of rectangular ZrO2 nanoparticles can be prepared on the substrate, and the thickness of the two-dimensional ZrO2 film is 200-500 nm.

[0031] A second aspect of the present invention provides a two-dimensional ZrO2 thin film, which is prepared by the aforementioned method.

[0032] The ZrO2 thin film prepared by this invention is a non-layered material with a monoclinic crystal structure and the chemical formula m-ZrO2.

[0033] A third aspect of this invention provides a method for fabricating a MIM-type flexible capacitor, the method comprising the following steps:

[0034] Step 1: Using the aforementioned method for preparing two-dimensional ZrO2 thin films, a two-dimensional ZrO2 thin film is prepared on a molybdenum substrate with a thickness of 20 μm.

[0035] Step 2: Deposit a metal electrode on the side of the two-dimensional ZrO2 thin film away from the molybdenum substrate to obtain the MIM-type flexible capacitor.

[0036] In some embodiments, the deposition of the metal electrode in step two specifically involves: firstly depositing a Cr layer with a thickness of 8-15 nm on the side of the two-dimensional ZrO2 thin film away from the molybdenum substrate as a metal contact layer, and then depositing an Au layer with a thickness of 50-70 nm on the metal contact layer as an electrode.

[0037] A fourth aspect of the present invention provides a MIM-type flexible capacitor, which is prepared by the aforementioned method. Attached Figure Description

[0038] Figure 1 This is a diagram of the experimental setup used to grow two-dimensional ZrO2 thin films according to the present invention;

[0039] Figure 2 This is a crystal structure diagram of the ZrO2 prepared in this invention;

[0040] Figure 3 This is an optical microscope image of the ZrO2 thin film prepared in Example 1;

[0041] Figure 4 This is an optical microscope image of the ZrO2 thin film prepared in Example 1;

[0042] Figure 5 The Raman spectrum of the ZrO2 thin film prepared in Example 1;

[0043] Figure 6 This is an optical microscope image of the ZrO2 thin film prepared in Example 2;

[0044] Figure 7 This is an optical microscope image of the ZrO2 thin film prepared in Example 3;

[0045] Figure 8 An optical microscope image of the ZrO2 thin film prepared in Comparative Example 1;

[0046] Figure 9 An optical microscope image of the ZrO2 thin film prepared in Comparative Example 2;

[0047] Figure 10 An optical microscope image of the ZrO2 thin film prepared in Comparative Example 3;

[0048] Figure 11 An optical microscope image of the ZrO2 thin film prepared in Comparative Example 4;

[0049] Figure 12 An optical microscope image of the ZrO2 thin film prepared on the sapphire substrate in Example 4;

[0050] Figure 13 An optical microscope image of the ZrO2 thin film prepared on the molybdenum substrate in Example 4;

[0051] Figure 14 SEM image of the ZrO2 thin film prepared on the tungsten substrate in Example 4;

[0052] Figure 15 SEM image of the ZrO2 thin film prepared on the stainless steel substrate in Example 4;

[0053] Figure 16 Optical microscope image of the ZrO2 thin film prepared in Comparative Example 5;

[0054] Figure 17 The capacitance-frequency characteristic curve of Embodiment 1 of the flexible capacitor device;

[0055] Figure 18 The current density voltage characteristic curve of Example 1 of the flexible capacitor device;

[0056] Figure 19 The graph shows the capacitance-frequency characteristic curve of the flexible capacitor device in Example 1 after multiple bending. Detailed Implementation

[0057] To better understand this invention, the following will provide a detailed and systematic description of the invention in conjunction with accompanying drawings and exemplary cases, but the content of this invention is not limited to the following content.

[0058] A method for remote molten salt-assisted preparation of two-dimensional ZrO2 thin films

[0059] Example 1

[0060] Weigh 50 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 980 °C at a rate of 25 °C / min. When the fluxes sodium chloride and potassium chloride are placed 7-8 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 30 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. The optical microscope image is shown below. Figure 3 As shown in Figure 4, the ZrO2 film is uniform and continuous with high quality. The mica part is modified by sodium chloride and potassium chloride, and the grown ZrO2 film has a regular hexagonal shape. Figure 5 The Raman spectrum of the thin film prepared in this embodiment is shown at 179, 192, 222, 310, 335, 347, and 382 cm⁻¹. -1 The characteristic peaks shown indicate that the material is a monoclinic ZrO2 phase.

[0061] Example 2

[0062] Similarly, T1 in Example 1 was adjusted to 950°C.

[0063] Weigh 50 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low-temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 950 °C at a rate of 25 °C / min. When the fluxes sodium chloride and potassium chloride are placed 5-7 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 30 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. The optical microscope image is shown below. Figure 6 As shown, the ZrO2 film is uniform and continuous, with good grain quality.

[0064] Example 3

[0065] Similarly, t2 in Example 1 was adjusted to 20 min.

[0066] Weigh 50 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 980 °C at a rate of 25 °C / min. When the fluxes sodium chloride and potassium chloride are placed 7-8 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 20 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. The optical microscope image is shown below. Figure 7 As shown, the ZrO2 film exhibits good crystallinity and high density.

[0067] Comparative Example 1

[0068] The difference compared to Example 1 is that the mass of sodium chloride and potassium chloride is different.

[0069] Weigh 50 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 3 mg of sodium chloride powder and 3 mg of potassium chloride powder as flux and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 980 °C at a rate of 25 °C / min. When the flux sodium chloride and potassium chloride are placed 7-8 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 30 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. Optical microscope images are shown below. Figure 8 As shown, it can be seen that due to the reduction in flux dosage, its effect on assisting zirconium carbide volatilization is reduced, resulting in only a few ZrO2 nanocrystals growing on the mica. There are certain gaps between the grains, and they fail to grow into a continuous film.

[0070] Comparative Example 2

[0071] The difference compared to Example 1 is the quality of zirconium carbide.

[0072] Weigh 10 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low-temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 980 °C at a rate of 25 °C / min. When the fluxes sodium chloride and potassium chloride are placed 7-8 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 30 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. Optical microscope images are shown below. Figure 9As shown, many nanoparticles and nanowires grew on the mica, but failed to form a film. Because the zirconium carbide source used in this embodiment was of insufficient mass and supply, the number of ZrO2 particles grown was too small to form a film.

[0073] Comparative Example 3

[0074] The difference compared to Example 1 is the growth temperature.

[0075] Weigh 50 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 900 °C at a rate of 25 °C / min. When the fluxes sodium chloride and potassium chloride are placed 2-3 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 30 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. Optical microscope images are shown below. Figure 10 As shown, dense ZrO2 particles grow on the mica. Since zirconium carbide and ZrO2 are high-melting-point materials (zirconia melting point 3540℃, ZrO2 melting point 2700℃), and the growth temperature in this embodiment is 900℃, it is insufficient to allow the ZrO2 nanoparticles to grow epitaxially in and out of the plane. Consequently, the ZrO2 nanoparticles on the mica are relatively small and fail to coalesce into a film.

[0076] Comparative Example 4

[0077] The difference compared to Example 1 is the carrier gas flow rate.

[0078] Weigh 50 mg of zirconium carbide particles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the zirconium carbide particles. Place this quartz boat in the constant temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases from the quartz tube. Then, set the program to heat the center of the quartz tube to T1 = 980 °C at a rate of 25 °C / min. When the fluxes sodium chloride and potassium chloride are placed 7-8 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C, hold for t2 = 30 min. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 10 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. Optical microscope images are shown below. Figure 11 As shown, many ZrO2 nanoparticles grow on the mica. The particles are small because argon gas is used as the transport gas to carry the sublimated sodium chloride and potassium chloride vapors to the zirconium source in the center of the quartz tube as a flux for zirconium carbide. However, the flow rate of the transport gas argon is small, which is insufficient to transport enough sodium chloride gas to the zirconium source, resulting in insufficient zirconium source supply. Therefore, planar epitaxial growth cannot be achieved, and the ZrO2 nanoparticles fail to form a film.

[0079] Example 4

[0080] This invention enables the growth of continuous and dense zirconium oxide films not only on fluorophlogopite substrates but also on other substrates that do not react with zirconium carbide or ZrO2. This embodiment uses different substrates to grow ZrO2 films, employing the same method as in Example 1. The substrates used include sapphire, molybdenum, tungsten, and 304 stainless steel. Optical microscope images of the sapphire and molybdenum films after growth are shown below. Figure 12 , 13 As shown; SEM images of the tungsten sheet and 304 stainless steel sheet after growth are shown below. Figure 14 , 15 As shown, continuous, dense, and high-quality ZrO2 films can be grown on different substrates.

[0081] Comparative Example 5

[0082] Comparative Example 5 is given below to further demonstrate the feasibility of the invention. The difference between the comparative example and the embodiment lies in the zirconium source used. The embodiment uses zirconium carbide powder as the zirconium source, while the comparative example uses ZrO2 nanoparticles as the zirconium source.

[0083] Weigh 50 mg of ZrO2 nanoparticles and place them on a semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place a 10 × 10 mm fluorophlogopite substrate 2 mm directly above the ZrO2 nanoparticles. Place this quartz boat in the constant-temperature zone at the center of the quartz tube. Take 10 mg of sodium chloride powder and 10 mg of potassium chloride powder as fluxes and place them on another semi-circular quartz boat with an outer diameter of 20 × 20 mm. Place this quartz boat in the low-temperature zone upstream of the quartz tube. Before the programmed temperature rise, purge the quartz tube with argon gas at Q1 = 240 sccm for t1 = 3 min to remove impurity gases. Then, set the program to heat the center of the quartz tube to T1 = 980 °C at a rate of 25 °C / min, and hold for t2 = 30 min. At this point, the sodium chloride and potassium chloride fluxes are placed 7-8 cm upstream of the center of the quartz tube, at a temperature of T2 = 870-890 °C. During the temperature ramp-up, the argon flow rate was adjusted to Q2 = 20 sccm. After growth, the tube furnace was allowed to cool naturally to room temperature, then the gas flow was turned off and the sample was removed. Optical microscope images are shown below. Figure 16 As shown, the mica surface is completely blank, and no ZrO2 film has grown.

[0084] A flexible capacitor based on two-dimensional ZrO2 thin film

[0085] Device Example 1

[0086] A dense two-dimensional zirconium oxide film was deposited on a molybdenum sheet with dimensions of 1 cm in length and width and a thickness of 20 μm. A 10 nm thick chromium layer was used as a contact, and a 60 nm thick gold layer was used as a metal electrode. The electrode was a square with a width of 220 μm, thus constructing a micro / nano MIM-type flexible capacitor. The device was attached to a probe station, and the device was connected to an impedance analyzer and a semiconductor measurement instrument via probes.

[0087] The capacitance-frequency curve of the two-dimensional zirconia device was tested using an impedance analyzer, and the current-voltage characteristic curve was tested using a semiconductor measuring instrument.

[0088] The impedance analyzer is model E4980A, and its frequency testing range is 0-2MHz.

[0089] The semiconductor measuring instrument is model PDAFS-Pro, and its voltage testing range is -70V to 70V.

[0090] When using a non-bending MIM-type flexible capacitor, the capacitance-frequency characteristic curves of the device at voltages of 0.5V, 1V, 1.5V, and 2V were tested using a semiconductor tester. The results are as follows: Figure 17 As shown, the device exhibits high capacitance performance. In the frequency range of 0-800kHz, the capacitance increases with increasing voltage; in the frequency range of 800kHz-2MHz, the capacitance decreases with increasing voltage.

[0091] When the MIM-type flexible capacitor is not bent, the current density of the device is tested using a semiconductor tester. The results are as follows: Figure 18 As shown, the leakage current is very small; even at a voltage of 70V, the leakage current density is only 2×10⁻⁶. -4 A / cm -2 .

[0092] The MIM-type flexible capacitor was bent 300 and 600 times respectively, and then the capacitance-frequency characteristic curve of the device at a voltage of 1V was tested using a semiconductor tester. The results are as follows. Figure 19 As shown, after 300 high-intensity bends, the capacitance decreased by only 5%; after 600 high-intensity bends, the capacitance also decreased by only 7%, demonstrating the ultra-stable performance of the flexible capacitor.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above merely illustrate several implementation methods of the present invention to facilitate a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for remote molten salt-assisted preparation of two-dimensional ZrO2 thin films, characterized in that, Includes the following steps: Step 1: Place the quartz tube horizontally, place the zirconium source in the central constant temperature zone of the quartz tube, and place the halide flux in the upstream low temperature zone of the quartz tube. The mass ratio of the zirconium source to the halide flux is 10:3-6:

5. The zirconium source is zirconium carbide micron particles, and the halide flux is a mixture of sodium chloride powder and potassium chloride powder. The upstream low temperature zone of the quartz tube is set at a distance of 7-9 cm from the center of the quartz tube. Step 2: Place the substrate above the zirconium source and set the vertical distance between the substrate and the zirconium source to 3-5 mm. The substrate is any one of fluorine-phlogopite substrate, sapphire substrate, molybdenum sheet substrate, tungsten sheet substrate or stainless steel substrate. Step 3: Inert gas with a flow rate of Q1 is introduced into the quartz tube for a duration of t1, where Q1 = 220-260 sccm and t1 = 1-5 min; Step 4: Heat the quartz tube while simultaneously introducing an inert gas with a flow rate of Q2 as a carrier gas. Heat the quartz tube until the central constant temperature zone reaches temperature T1 and the upstream low temperature zone reaches temperature T2, then maintain the temperature for a duration of t2. Where Q2 = 15-25 sccm, T1 = 950-1000℃, T2 = 850-900℃, and t2 = 20-30 min. Step 5: After the heat preservation time t2, stop heating the quartz tube and turn off the inert gas flow of the second flow rate Q2. Allow the quartz tube to cool naturally to room temperature, and a continuous and dense two-dimensional ZrO2 film can be obtained on the substrate.

2. The method for preparing two-dimensional ZrO2 thin films according to claim 1, characterized in that, The mass ratio of sodium chloride powder to potassium chloride powder is 1:

1.

3. The method for preparing two-dimensional ZrO2 thin films according to claim 1, characterized in that, In step one, placing the zirconium source in the central isothermal zone of the quartz tube and placing the halide flux in the upstream low-temperature zone of the quartz tube specifically involves: The zirconium source is placed in a quartz boat, and the quartz boat containing the zirconium source is placed in the central constant temperature zone of the quartz tube. The halide flux is placed in a quartz boat, and the quartz boat containing the halide flux is placed in the upstream low-temperature zone of the quartz tube.

4. The method for preparing two-dimensional ZrO2 thin films according to any one of claims 1-3, characterized in that, A polycrystalline dense two-dimensional ZrO2 film composed of a large number of rectangular ZrO2 nanoparticles can be prepared on the substrate, and the thickness of the two-dimensional ZrO2 film is 200-500 nm.

5. A two-dimensional ZrO2 thin film, characterized in that, The two-dimensional ZrO2 thin film is prepared by the method described in any one of claims 1-4.

6. A method for fabricating a MIM-type flexible capacitor, characterized in that, The method includes the following steps: Step 1: Prepare a two-dimensional ZrO2 thin film on a molybdenum substrate with a thickness of 20 μm using the method described in any one of claims 1-4; Step 2: Deposit a metal electrode on the side of the two-dimensional ZrO2 thin film away from the molybdenum substrate to obtain the MIM-type flexible capacitor.

7. The method for preparing a MIM-type flexible capacitor according to claim 6, characterized in that, The specific steps for depositing the metal electrode in step two are as follows: First, a Cr layer with a thickness of 8-15 nm is deposited on the side of the two-dimensional ZrO2 thin film away from the molybdenum substrate as a metal contact layer, and then an Au layer with a thickness of 50-70 nm is deposited on the metal contact layer as an electrode.

8. A MIM-type flexible capacitor, characterized in that, The MIM-type flexible capacitor is prepared using the method described in claim 6 or 7.

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