A heterojunction CeO2 / ZnO resistive switching corrosion-resistant thin film and its preparation method

Abstract

This invention discloses a heterojunction CeO2 / ZnO resistive switching film and its preparation method. Using cerium nitrate nonahydrate, zinc nitrate hexahydrate, and hexamethylenetetramine as raw materials, a heterojunction CeO2 / ZnO resistive switching film with micrometer-level thickness, good corrosion resistance, and adjustable resistivity is prepared by constant current electrodeposition combined with a hydrothermal method. This invention improves the corrosion resistance of the substrate by utilizing the electronic barrier at the heterojunction interface in the heterojunction CeO2 / ZnO resistive switching film to hinder the diffusion of corrosive ions to the substrate, and by utilizing the oxygen-binding capacity of oxygen vacancies in the film to prevent oxygen diffusion to the substrate. Furthermore, the oxygen vacancy concentration in the film can be controlled by applying voltage to facilitate film recycling.

Description

Technical Field

[0001] This invention relates to a method for preparing a resistive switching corrosion-resistant protective film, specifically a CeO2 / ZnO heterojunction film containing oxygen vacancy defects, which can achieve cyclic changes in film resistance by applying a voltage. Background Technology

[0002] Steel components or equipment used or operating in natural environments (atmosphere, seawater, soil, etc.) and various electrolyte solutions are prone to corrosion due to the electrochemical corrosion of the environmental media. Essentially, the reaction in a corrosion galvanic cell is mainly the anodic dissolution of iron (Fe → Fe2+). 2+ +2e - Depolarization with oxygen: O2 + 2H2O + 4e - →4OH - Or hydrogen depolarization 2H + +2e - →H2 process, which results in the formation of a large number of corrosion products on the steel surface, leading to a decline in steel performance and significant material loss. The rust layer on the steel surface consists of a loose and porous outer rust layer and a relatively dense inner rust layer, including iron oxides, hydroxyl oxides, and green rust compounds such as FeO, α-Fe2O3, Fe(OH)2, Fe(OH)3, α-FeOOH, β-FeOOH, γ-FeOOH, and δ-FeOOH. A rust layer on the steel surface, if it has high density, can produce a good corrosion resistance to the substrate (Yamashita M, Shimizu T, Konishi H, et al. Structure and protective performance of atmospheric corrosion product of Fe-Cr alloy film analyzed by Mossbauerspectroscopy and with synchrotron radiation X-rays[J]. Corrosion Science, 2003, 45(2):381-394). However, the formation of a dense rust layer takes a long time. For example, weathering steel requires more than 3 years of stabilization time in an atmospheric environment. Carbon steel, as well as steel with high SO2 content and high Cl content, requires a much longer time to form a dense rust layer. -Weathering steel exposed to high humidity and prolonged immersion environments is unlikely to form a protective rust layer (Shi Zhenjia, Wang Lei, Chen Nan, et al. Research status of rust layer and its stabilization treatment on weathering steel surface [J]. Corrosion Science and Protection Technology, 2015, 40(11): 1195-1199). Therefore, preparing corrosion-resistant coatings on steel materials is one of the most widely used corrosion protection methods. With the rapid development of industry, higher requirements have been placed on the performance of corrosion-resistant coatings, and developing better corrosion-resistant coatings is also one of the research hotspots.

[0003] Corrosion-resistant coating protection involves creating an artificial barrier on the surface of steel materials to separate the steel surface from the environment, blocking direct contact between the steel materials and corrosive media, thereby reducing the corrosion rate of the materials and improving the corrosion resistance of the steel materials. Resistive switching film is a material that can achieve reversible switching between a high-resistivity state and a low-resistivity state under the action of an external electric field. When the resistive switching film works in air at different temperatures, oxygen ions in the environment will be adsorbed on the surface of the film and recombine with oxygen vacancies in the film. Thus, the high-resistivity state resistance of the resistive switching film increases with the increase of oxygen content in the air and ambient temperature; while the resistance of the low-resistivity state remains basically unchanged, thus giving it the effect of environmental shielding and reinforcement (Wang YL, Jiang ZH, Liu XR, et al. Influence of treating frequency on microstructure and properties of Al2O3 coating on 304 stainless steel by cathodic plasma electrolytic deposition[J]. Applied Surface Science, 2009, 255(21): 8836-8840). The resistive switching property originates from the large number of oxygen vacancies within the material. These oxygen vacancies drift under the influence of an electric field, forming conductive filaments that cause the material to transition to a low-resistivity state. Conversely, the breakage of these conductive filaments causes the material to return to a high-resistivity state, thus achieving a reversible transition between high and low resistance states. Materials with resistive switching properties discovered so far mainly include sulfides, organic thin films, and metal oxides.

[0004] Zinc oxide (ZnO) is a direct bandgap N-type semiconductor with a narrow bandgap (3.37 eV), high electron binding energy (60 meV), and a large number of vacancy-type defects. These properties make ZnO widely used in photocatalysis, solar cells, gas sensors, and photodiodes. Research shows that because vacancy-type defects (mainly oxygen vacancies) in zinc oxide are generated, drifted, or disappear with voltage changes, its resistance changes with voltage. Therefore, it is a good resistive switching thin film material. Cerium oxide (CeO2) is a narrow bandgap N-type semiconductor. Rare earth elements have abundant electronic structures; their unique 4f electron layer structure, abundant electron energy, and strong spin-orbit coupling determine the unique optical, electrical, and magnetic properties of rare earth elements and their compounds. Furthermore, CeO2... 3+ With Ce 4+ The reversible valence state changes of cerium make it easy for oxygen vacancies to form and dissipate, and cerium ions and oxygen vacancies have strong conductivity, making CeO2 a highly valuable resistive switching material. In recent years, oxide heterojunctions have been extensively studied. For example, some literature investigated the effect of the oxide-oxide interface on oxygen ion migration during resistive switching in ZnO / ZrO2 oxide heterojunctions. In the heterojunction, completely different resistive switching behaviors exist under voltages of different polarities, demonstrating that the change in the interface barrier height between oxides determines the oxygen ion migration process, leading to resistive switching behavior directly dependent on voltage polarity. By controlling the cutoff voltage of the process, the interfacial resistive switching behavior of oxide heterojunctions can be used as a controllable and stable multi-state memory device (Xu Zedong, Yu Lina, Xu Xiaoguang, Miao Jun, Jiang Yong, Effect of oxide / oxide interface on polarity dependent resistive switching behavior in ZnO / ZrO2 heterostructures, Applied Physics Letters, 2014, 104, 192903). Compared with single-layer thin films, oxide heterojunctions exhibit superior characteristics such as high stability and high cycle life as memory cells in resistive switching memory. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a heterojunction CeO2 / ZnO resistive switching corrosion-resistant thin film and its preparation method. The heterojunction CeO2 / ZnO resistive switching thin film utilizes the electronic potential barrier at the heterojunction interface to hinder the diffusion of corrosive ions to the substrate, and employs the oxygen-binding capacity of oxygen vacancies in the film to further impede oxygen diffusion to the substrate, thereby improving the corrosion resistance of the film substrate. Furthermore, the oxygen vacancy concentration in the film can be controlled by applying a voltage to facilitate film recycling. The technical objective of this invention is achieved through the following technical solution.

[0006] A heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film and its preparation method are carried out according to the following steps:

[0007] Step 1: A three-electrode system is used, with the substrate material as the working electrode, to perform constant current electrodeposition to obtain a CeO2 thin film on the substrate material. The current density during constant current electrodeposition is -1 mA / cm². 2 ~-3mA / cm 2 The deposition time is 15-120 min; during constant current electrodeposition, the electrolyte is a cerium nitrate aqueous solution with a concentration of 0.02-0.2 mol / L.

[0008] In step 1, the substrate material is pretreated as follows: the substrate is sanded with 600, 1200, 1500 and 2000 grit sandpaper in sequence until the surface is smooth. After sanding, the substrate is cleaned with deionized water, ultrasonicated in anhydrous ethanol for 5-30 minutes, and then dried for later use.

[0009] In step 1, in the three-electrode system, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum sheet electrode with an area of ​​1 cm². 2 Platinum sheet electrodes.

[0010] In step 1, during constant current electrodeposition, the current density is -1 mA / cm². 2 ~-2mA / cm 2 The deposition temperature is room temperature (20-25 degrees Celsius) and the deposition time is 20-60 minutes.

[0011] In step 1, the electrolyte is an aqueous solution of cerium nitrate with a concentration of 0.1-0.2 mol / L.

[0012] Step 2: Coat the substrate material obtained in Step 1 with ZnO seed solution, and fire it in an air atmosphere at a temperature of 400-500℃ for 30-60 minutes. After cooling to room temperature (20-25℃) in the furnace, a ZnO seed layer is obtained. In the ZnO seed solution, the solvent is ethanol, and the solutes are zinc acetate and ethanolamine. The concentration of zinc acetate is 0.3-0.8 mol / L, and the concentration of ethanolamine is 0.3-0.8 mol / L.

[0013] In step 2, the ZnO seed solution is coated onto the substrate material using a static spin coating method at a speed of 1500-3000 r / min for 10-30 s. After spin coating, the solution is dried. The spin coating process is repeated 2-8 times.

[0014] In step 2, the ZnO seed solution is prepared with ethanol as the solvent and zinc acetate and ethanolamine as the solutes. The concentration of zinc acetate is 0.5-0.8 mol / L and the concentration of ethanolamine is 0.3-0.5 mol / L.

[0015] In step 2, the firing temperature is 450-500℃ and the firing time is 40-60 minutes.

[0016] Step 3: The substrate material obtained in Step 2 is placed in a hydrothermal solution for a hydrothermal reaction. The hydrothermal reaction temperature is 60-90℃, and the reaction time is 3-8 hours. In the hydrothermal solution, the solvent is water, and the solutes are zinc nitrate and hexamethylenetetramine. The concentrations of zinc nitrate and hexamethylenetetramine are 0.01-0.025 mol / L and 0.01-0.025 mol / L, respectively.

[0017] In step 3, the substrate material obtained in step 2 is placed at a 45° angle in a hydrothermal solution to carry out a hydrothermal reaction.

[0018] In step 3, after the hydrothermal reaction, the sample is cooled to room temperature (20-25 degrees Celsius) in the furnace. The sample is then taken out, rinsed with deionized water and anhydrous ethanol, and dried to obtain a heterojunction CeO2 / ZnO resistive switching film.

[0019] In step 3, the hydrothermal reaction temperature is 80-90℃ and the hydrothermal reaction time is 3-5h.

[0020] In step 3, in the hydrothermal solution, the solvent is water, and the solutes are zinc nitrate and hexamethylenetetramine, with the concentrations of zinc nitrate and hexamethylenetetramine being 0.02-0.025 mol / L and 0.02-0.025 mol / L respectively.

[0021] Step 4: Place the heterojunction CeO2 / ZnO resistive switching film prepared in step 3 in an inert gas atmosphere for annealing. Start from room temperature (20-25 degrees Celsius) and increase the temperature at a rate of 1-5 degrees Celsius / min to the annealing temperature (300-450 degrees Celsius). Anneal for 0.5-1.5 hours. After annealing, cool the film in the furnace to room temperature (20-25 degrees Celsius) and then remove it.

[0022] In step 4, the inert gas protective atmosphere is nitrogen, helium, or argon.

[0023] In step 4, a tube furnace is selected for annealing.

[0024] In step 4, the annealing temperature is 300-400℃ and the annealing time is 1-1.5h.

[0025] This invention utilizes cerium nitrate, zinc nitrate, and hexamethylenetetramine as raw materials to prepare a heterojunction CeO2 / ZnO resistive switching film with micron-level thickness, excellent corrosion resistance, and adjustable resistivity via electrodeposition combined with a hydrothermal method. This invention employs a combination of electrodeposition and hydrothermal methods to prepare a heterojunction CeO2 / ZnO resistive switching film, thereby reducing the corrosion rate of the steel substrate and extending the service life of the resistive switching film by utilizing its resistive switching properties. The method of this invention allows for direct in-situ growth of the film on the substrate material, achieving protection of the substrate material and preventing corrosion damage. The heterojunction CeO2 / ZnO resistive switching film prepared by this invention not only possesses excellent corrosion resistance but also allows for the control of oxygen vacancy concentration and polarization resistance by applying voltage, facilitating the recycling of the film.

[0026] (1) Good corrosion resistance: The prepared CeO2 / ZnO resistive switching film (including 304 stainless steel substrate) was sealed with epoxy resin, leaving only the side with the CeO2 / ZnO film exposed, and the four sides were sealed, leaving 1 cm exposed in the center of the film side. 2 The area; and the area after sealing is 1 cm². 2 Untreated 304 stainless steel (i.e., the substrate material), CeO2 film (using 304 stainless steel as the substrate material, CeO2 film obtained using the method in step 1 of this invention), and ZnO film (using 304 stainless steel as the substrate material, without electrodeposition of cerium dioxide film, ZnO film obtained using steps 2-4 of this invention) were used as control samples. Using a calomel electrode and a platinum sheet as the reference and counter electrodes, the electrochemical impedance spectroscopy and polarization curves of the resistive switching film samples in 3.5 wt% NaCl aqueous solution were measured using an Autolab302 electrochemical workstation. Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, where Figure 2 for Figure 1 The enlarged view in the lower left corner shows that the prepared CeO2 / ZnO resistive switching film has a large impedance arc radius. Calculations show that the CeO2 / ZnO film achieves a protection efficiency of 99.23% for the steel substrate. Compared to the 304 stainless steel substrate and the control sample, the corrosion potential of the CeO2 / ZnO resistive switching film shifts significantly positively, and the corrosion current density decreases by two orders of magnitude. This indicates that the CeO2 / ZnO resistive switching film provides excellent protection for 304 stainless steel operating in a chloride ion environment.

[0027] (2) Excellent resistive switching performance: The CeO2 / ZnO resistive switching film was sealed, and a calomel electrode and a platinum sheet were used as the reference and counter electrodes, respectively. The electrochemical impedance spectroscopy of the resistive switching sample after cyclic pressurization in 3.5% NaCl solution was measured using an Autolab 302 electrochemical workstation. Figure 5 and Figure 6 As shown, where Figure 6 for Figure 5 A magnified view of the lower left corner, with each cycle ranging from 0.5 to 12 hours. From Figure 5 and 6 It can be seen that the impedance arc radius of the resistive switching film decreases after cyclic pressurization, that is, the resistance value decreases; however, as the immersion time increases, the impedance arc radius gradually increases, that is, the resistance value increases. This means that the prepared CeO2 / ZnO resistive switching film can achieve autonomous control of the film polarization resistance through cyclic pressurization, which is beneficial for the recycling of the resistive switching film.

[0028] (3) The CeO2 / ZnO resistive switching film of the present invention was tested, as shown in the attached figure. Figure 7 As shown in Figure 9, the CeO2 / ZnO resistive switching film of the present invention forms a structure of cerium dioxide film and zinc oxide film on the substrate material SS304, with uniform element distribution; it exhibits obvious XRD characteristic peaks of cerium dioxide and zinc oxide, as well as characteristic peaks of austenite and ferrite of the substrate material SS304. Attached Figure Description

[0029] Figure 1 The Nyquist plots (1) show CeO2, ZnO, and CeO2 / ZnO films in a 3.5 wt% NaCl aqueous solution.

[0030] Figure 2 The Nyquist plots (2) show CeO2, ZnO, and CeO2 / ZnO films in a 3.5 wt% NaCl aqueous solution.

[0031] Figure 3 This is a Bode plot of CeO2, ZnO, and CeO2 / ZnO films in a 3.5 wt% NaCl aqueous solution.

[0032] Figure 4 This is a polarization curve of CeO2, ZnO, and CeO2 / ZnO thin films in a 3.5 wt% NaCl aqueous solution.

[0033] Figure 5 The electrochemical impedance spectroscopy (EIS) of the CeO2 / ZnO resistive switching film of the present invention under cyclic pressure conditions in a 3.5 wt% NaCl aqueous solution is shown in Figure 1.

[0034] Figure 6The electrochemical impedance spectroscopy (EIS) of the CeO2 / ZnO resistive switching film of the present invention under cyclic pressure conditions in a 3.5 wt% NaCl aqueous solution is shown in Figure 2.

[0035] Figure 7 This is a cross-sectional SEM image of the CeO2 / ZnO heterojunction resistive switching thin film of the present invention.

[0036] Figure 8 This is a microstructure and elemental distribution diagram of the CeO2 / ZnO heterojunction resistive switching film of the present invention.

[0037] Figure 9 This is the XRD pattern of the CeO2 / ZnO heterojunction resistive switching film of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to these specific examples.

[0039] Example 1

[0040] (1) Substrate treatment: Use 600, 1200, 1500 and 2000 grit sandpaper to grind the 304 stainless steel substrate until the surface is smooth. After grinding, clean the substrate with deionized water, sonicate it in anhydrous ethanol for 5 minutes, and blow it dry for later use.

[0041] (2) CeO2 thin film electrodeposition: A three-electrode system was used, with the reference electrode (RE) being a saturated calomel electrode and the counter electrode (CE) being a 1 cm² electrode. 2 The platinum sheet electrode, the working electrode (WE) is the 304 stainless steel sample treated in step (1), the electrolyte is an aqueous solution of cerium nitrate nonahydrate with a concentration of 0.15 mol / L, and the deposition current density is -2.5 mA / cm². 2 The deposition temperature was room temperature (20-25 degrees Celsius) and the deposition time was 90 minutes.

[0042] (3) ZnO seed layer: Prepare an ethanol solution containing 0.6 mol / L zinc acetate dihydrate and 0.6 mol / L ethanolamine. Apply the solution to the sample with CeO2 film by static spin coating at 2000 r / min for 20 s. After spin coating, blow dry. Repeat the spin coating process 4 times. Then, fire the sample at 450℃ for 60 min. After cooling to room temperature in the furnace, take it out to obtain the ZnO seed layer.

[0043] (4) CeO2 / ZnO resistive switching film: The sample with the ZnO seed layer was placed at a 45° angle in an aqueous solution containing 0.015 mol / L zinc nitrate (hexahydrate) and 0.015 mol / L hexamethylenetetramine. The hydrothermal reaction temperature was 65℃ and the hydrothermal reaction time was 7h. After the reaction, the sample was cooled to room temperature in the furnace. The sample was taken out, rinsed with deionized water and anhydrous ethanol, and then dried to obtain CeO2 / ZnO resistive switching film.

[0044] (5) Post-treatment: Place the sample in a boat and put it in a tube furnace. First, purge the air in the device with nitrogen, then evacuate the vacuum. Repeat this process 3 times. Finally, purge with nitrogen and seal the furnace. The heating rate is 2℃ / min, the annealing temperature is 350℃, and the annealing time is 1h. After annealing, the sample is cooled to room temperature in the furnace and then removed.

[0045] Example 2

[0046] (1) Substrate treatment: Use 600, 1200, 1500 and 2000 grit sandpaper to grind the 304 stainless steel substrate until the surface is smooth. After cleaning the ground substrate with deionized water, sonicate it in anhydrous ethanol for 15 minutes, and then blow it dry for later use.

[0047] (2) CeO2 thin film electrodeposition: A three-electrode system was used, with the reference electrode (RE) being a saturated calomel electrode and the counter electrode (CE) being a 1 cm² electrode. 2 The platinum sheet electrode, the working electrode (WE) is the 304 stainless steel sample treated in step (1), the electrolyte is a 0.1 mol / L aqueous solution of cerium nitrate nonahydrate, and the deposition current density is -2 mA / cm². 2 The deposition temperature was room temperature (20-25 degrees Celsius) and the deposition time was 15 minutes.

[0048] (3) ZnO seed layer: Prepare an ethanol solution containing 0.4 mol / L zinc acetate dihydrate and 0.4 mol / L ethanolamine. Apply the solution to the sample with CeO2 film by static spin coating at 3000 r / min for 30 s. After spin coating, blow dry. Repeat the spin coating process 6 times. Then, fire the sample at 450℃ for 60 min. After slowly cooling to room temperature, remove the sample to obtain the ZnO seed layer.

[0049] (4) CeO2 / ZnO resistive switching film: The sample with the ZnO seed layer was placed at a 45° angle in an aqueous solution containing 0.025 mol / L zinc nitrate hexahydrate and 0.025 mol / L hexamethylenetetramine. The hydrothermal reaction temperature was 70°C and the hydrothermal reaction time was 6 h. After the reaction, the sample was cooled to room temperature in the furnace. The sample was then taken out, rinsed with deionized water and anhydrous ethanol, and dried to obtain CeO2 / ZnO resistive switching film.

[0050] (5) Post-treatment: Place the sample in a boat and put it in a tube furnace. First, purge the air in the device with nitrogen, then evacuate the furnace. Repeat this process 3 times. Finally, purge with nitrogen and seal the furnace. The heating rate is 3℃ / min, the annealing temperature is 400℃, and the annealing time is 1h. After annealing, the sample is cooled to room temperature in the furnace and then removed.

[0051] Example 3

[0052] (1) Substrate treatment: Use 600, 1200, 1500 and 2000 grit sandpaper to grind the 304 stainless steel substrate until the surface is smooth. After grinding, clean the substrate with deionized water, sonicate it in anhydrous ethanol for 5 minutes, and blow it dry for later use.

[0053] (2) CeO2 thin film electrodeposition: A three-electrode system was used, with the reference electrode (RE) being a saturated calomel electrode and the counter electrode (CE) being a 1 cm² electrode. 2 The platinum sheet electrode was used, with the working electrode (WE) made of 304 stainless steel. The electrolyte was a 0.05 mol / L solution of cerium nitrate nonahydrate, and the deposition current density was -2 mA / cm². 2 The deposition temperature was room temperature, and the deposition time was 15 minutes.

[0054] (3) ZnO seed layer: Prepare an ethanol solution containing 0.75 mol / L zinc acetate dihydrate and 0.75 mol / L ethanolamine. Apply the solution to the sample with CeO2 film by static spin coating at 3000 r / min for 30 s. After spin coating, blow dry. Repeat the spin coating process 6 times. Then, calcine the sample at 500℃ for 60 min. After slowly cooling to room temperature, remove the sample to obtain the ZnO seed layer.

[0055] (4) CeO2 / ZnO resistive switching film: The sample with the ZnO seed layer was placed at a 45° angle in an aqueous solution containing 0.025 mol / L zinc nitrate hexahydrate and 0.015 mol / L hexamethylenetetramine. The hydrothermal reaction temperature was 90℃ and the hydrothermal reaction time was 6h. After the reaction, the sample was cooled to room temperature in the furnace. The sample was then taken out, rinsed with deionized water and anhydrous ethanol, and dried to obtain CeO2 / ZnO resistive switching film.

[0056] (5) Post-treatment: Place the sample in a boat and put it in a tube furnace. First, purge the air in the device with nitrogen, then evacuate the vacuum, repeating twice. Finally, purge with nitrogen and seal. The heating rate is 2℃ / min, the annealing temperature is 300℃, and the annealing time is 0.5h. After annealing, cool the sample to room temperature in the furnace and then remove it.

[0057] Example 4

[0058] (1) Substrate treatment: Use 600, 1200, 1500 and 2000 grit sandpaper to grind the 304 stainless steel substrate until the surface is smooth. After grinding, clean the substrate with deionized water, sonicate it in anhydrous ethanol for 5 minutes, and blow it dry for later use.

[0059] (2) CeO2 thin film electrodeposition: A three-electrode system was used, with the reference electrode (RE) being a saturated calomel electrode and the counter electrode (CE) being a 1 cm² electrode. 2 The platinum sheet electrode was used, with the working electrode (WE) made of 304 stainless steel. The electrolyte was a 0.15 mol / L solution of cerium nitrate nonahydrate, and the deposition current density was -1 mA / cm². 2 The deposition temperature was room temperature, and the deposition time was 30 minutes.

[0060] (3) ZnO seed layer: Prepare an ethanol solution containing 0.5 mol / L zinc acetate dihydrate and 0.5 mol / L ethanolamine. Apply the solution to the sample with CeO2 film by static spin coating at 3000 r / min for 30 s. After spin coating, blow dry. Repeat the spin coating process 5 times. Then, fire the sample at 500℃ for 30 min. After slowly cooling to room temperature, take it out to obtain the ZnO seed layer.

[0061] (4) CeO2 / ZnO resistive switching film: The sample with the ZnO seed layer was placed at a 45° angle in an aqueous solution containing 0.02 mol / L zinc nitrate hexahydrate and 0.02 mol / L hexamethylenetetramine. The hydrothermal reaction temperature was 70°C and the hydrothermal reaction time was 4 h. After the reaction, the sample was cooled to room temperature in the furnace. The sample was then taken out, rinsed with deionized water and anhydrous ethanol, and dried to obtain CeO2 / ZnO resistive switching film.

[0062] (5) Post-treatment: Place the sample in a boat and put it in a tube furnace. First, purge the air in the device with nitrogen, then evacuate the furnace. Repeat this process 3 times. Finally, purge with nitrogen and seal the furnace. The heating rate is 4℃ / min, the annealing temperature is 450℃, and the annealing time is 0.5h. After annealing, the sample is cooled to room temperature in the furnace and then removed.

[0063] Example 5

[0064] (1. Substrate treatment: Use 600, 1200, 1500 and 2000 grit sandpaper to grind the 304 stainless steel substrate until the surface is smooth. After grinding, clean the substrate with deionized water, sonicate it in anhydrous ethanol for 15 minutes, and blow it dry for later use.

[0065] (2) CeO2 thin film electrodeposition: A three-electrode system was used, with the reference electrode (RE) being a saturated calomel electrode and the counter electrode (CE) being a 1 cm² electrode. 2The platinum sheet electrode was used, with the working electrode (WE) made of 304 stainless steel. The electrolyte was a 0.15 mol / L solution of cerium nitrate nonahydrate, and the deposition current density was -2.3 mA / cm². 2 The deposition temperature was room temperature, and the deposition time was 60 minutes.

[0066] (3) ZnO seed layer: Prepare an ethanol solution containing 0.35 mol / L zinc acetate dihydrate and 0.35 mol / L ethanolamine. Apply the solution to the sample with CeO2 film by static spin coating at 3000 r / min for 15 s. After spin coating, blow dry. Repeat the spin coating process 6 times. Then, fire the sample at 400℃ for 40 min. After slowly cooling to room temperature, remove the sample to obtain the ZnO seed layer.

[0067] (4) CeO2 / ZnO resistive switching film: The sample with the ZnO seed layer was placed at a 45° angle in an aqueous solution containing 0.02 mol / L zinc nitrate hexahydrate and 0.01 mol / L hexamethylenetetramine. The hydrothermal reaction temperature was 80°C and the hydrothermal reaction time was 5 h. After the reaction, the sample was cooled to room temperature in the furnace. The sample was then taken out, rinsed with deionized water and anhydrous ethanol, and dried to obtain CeO2 / ZnO resistive switching film.

[0068] (5) Post-treatment: Place the sample in a boat and put it in a tube furnace. First, purge the air in the device with nitrogen, then evacuate the furnace. Repeat this process 4 times. Finally, purge with nitrogen and seal the furnace. The heating rate is 5℃ / min, the annealing temperature is 350℃, and the annealing time is 0.5h. After annealing, the sample is cooled to room temperature in the furnace and then removed.

[0069] Adjusting the process parameters according to the present invention can achieve the preparation of heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin films, which, after testing, exhibit performance essentially consistent with that of the present invention. The present invention has been described above as exemplary. It should be noted that any simple modifications, alterations, or other equivalent substitutions that can be made by those skilled in the art without creative effort, without departing from the core of the present invention, fall within the protection scope of the present invention.

Claims

1. A heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film, characterized in that, Follow these steps: Step 1: A three-electrode system is used, with the substrate material as the working electrode, to perform constant current electrodeposition to obtain a CeO2 thin film on the substrate material. The current density during constant current electrodeposition is -1 mA / cm². 2 ~-3mA / cm 2 The deposition time is 15-120 min; when performing constant current electrodeposition, the electrolyte is an aqueous solution of cerium nitrate with a concentration of 0.02-0.2 mol / L. Step 2: Coat the substrate material obtained in Step 1 with ZnO seed solution, and fire it in an air atmosphere at a temperature of 400-500℃ for 30-60 minutes. After cooling to room temperature (20-25℃) in the furnace, a ZnO seed layer is obtained. In the ZnO seed solution, the solvent is ethanol, and the solutes are zinc acetate and ethanolamine. The concentration of zinc acetate is 0.3-0.8 mol / L, and the concentration of ethanolamine is 0.3-0.8 mol / L. Step 3: The substrate material obtained in Step 2 is placed in a hydrothermal solution for hydrothermal reaction. The hydrothermal reaction temperature is 60-90℃, and the hydrothermal reaction time is 3-8h. In the hydrothermal solution, the solvent is water, and the solutes are zinc nitrate and hexamethylenetetramine. The concentration of zinc nitrate is 0.01-0.025mol / L, and the concentration of hexamethylenetetramine is 0.01-0.025mol / L. Step 4: Place the heterojunction CeO2 / ZnO resistive switching film prepared in step 3 in an inert gas atmosphere for annealing. Start from room temperature (20-25 degrees Celsius) and increase the temperature at a rate of 1-5 degrees Celsius / min to the annealing temperature (300-450 degrees Celsius). Anneal for 0.5-1.5 hours. After annealing, cool the film in the furnace to room temperature (20-25 degrees Celsius) and then remove it.

2. The heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 1, characterized in that, In step 1, in the three-electrode system, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum sheet electrode; during constant current electrodeposition, the current density is -1 mA / cm². 2 ~-2mA / cm 2 The deposition temperature was room temperature (20-25 degrees Celsius), the deposition time was 20-60 minutes, and the electrolyte was a cerium nitrate aqueous solution with a concentration of 0.1-0.2 mol / L.

3. The heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 1, characterized in that, In step 2, the ZnO seed solution is prepared with ethanol as the solvent and zinc acetate and ethanolamine as the solutes. The concentration of zinc acetate is 0.5-0.8 mol / L and the concentration of ethanolamine is 0.3-0.5 mol / L. The firing temperature is 450-500℃ and the firing time is 40-60 min.

4. The heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 1, characterized in that, In step 3, the hydrothermal reaction temperature is 80-90℃ and the hydrothermal reaction time is 3-5h; in the hydrothermal solution, the solvent is water, and the solutes are zinc nitrate and hexamethylenetetramine, with the concentrations of zinc nitrate and hexamethylenetetramine being 0.02-0.025mol / L and 0.02-0.025mol / L respectively.

5. The heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 1, characterized in that, In step 4, the inert gas protective atmosphere is nitrogen, helium, or argon; the annealing temperature is 300-400℃, and the annealing time is 1-1.5h.

6. A method for preparing a heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film, characterized in that, Follow these steps: Step 1: A three-electrode system is used, with the substrate material as the working electrode, to perform constant current electrodeposition to obtain a CeO2 thin film on the substrate material. The current density during constant current electrodeposition is -1 mA / cm². 2 ~-3mA / cm 2 The deposition time is 15-120 min; when performing constant current electrodeposition, the electrolyte is an aqueous solution of cerium nitrate with a concentration of 0.02-0.2 mol / L. Step 2: Coat the substrate material obtained in Step 1 with ZnO seed solution, and fire it in an air atmosphere at a temperature of 400-500℃ for 30-60 minutes. After cooling to room temperature (20-25℃) in the furnace, a ZnO seed layer is obtained. In the ZnO seed solution, the solvent is ethanol, and the solutes are zinc acetate and ethanolamine. The concentration of zinc acetate is 0.3-0.8 mol / L, and the concentration of ethanolamine is 0.3-0.8 mol / L. Step 3: The substrate material obtained in Step 2 is placed in a hydrothermal solution for hydrothermal reaction. The hydrothermal reaction temperature is 60-90℃, and the hydrothermal reaction time is 3-8h. In the hydrothermal solution, the solvent is water, and the solutes are zinc nitrate and hexamethylenetetramine. The concentration of zinc nitrate is 0.01-0.025mol / L, and the concentration of hexamethylenetetramine is 0.01-0.025mol / L. Step 4: Place the heterojunction CeO2 / ZnO resistive switching film prepared in step 3 in an inert gas atmosphere for annealing. Start from room temperature (20-25 degrees Celsius) and increase the temperature at a rate of 1-5 degrees Celsius / min to the annealing temperature (300-450 degrees Celsius). Anneal for 0.5-1.5 hours. After annealing, cool the film in the furnace to room temperature (20-25 degrees Celsius) and then remove it.

7. The method for preparing a heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 6, characterized in that, In step 1, in the three-electrode system, the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum sheet electrode; during constant current electrodeposition, the current density is -1 mA / cm². 2 ~-2mA / cm 2 The deposition temperature was room temperature (20-25 degrees Celsius), the deposition time was 20-60 minutes, and the electrolyte was a cerium nitrate aqueous solution with a concentration of 0.1-0.2 mol / L.

8. The method for preparing a heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 6, characterized in that, In step 2, the ZnO seed solution is prepared with ethanol as the solvent and zinc acetate and ethanolamine as the solutes. The concentration of zinc acetate is 0.5-0.8 mol / L and the concentration of ethanolamine is 0.3-0.5 mol / L. The firing temperature is 450-500℃ and the firing time is 40-60 min.

9. The method for preparing a heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 6, characterized in that, In step 3, the hydrothermal reaction temperature is 80-90℃ and the hydrothermal reaction time is 3-5h; in the hydrothermal solution, the solvent is water, and the solutes are zinc nitrate and hexamethylenetetramine, with the concentrations of zinc nitrate and hexamethylenetetramine being 0.02-0.025mol / L and 0.02-0.025mol / L respectively.

10. The method for preparing a heterojunction CeO2 / ZnO resistive switching and corrosion-resistant thin film according to claim 6, characterized in that, In step 4, the inert gas protective atmosphere is nitrogen, helium, or argon; the annealing temperature is 300-400℃, and the annealing time is 1-1.5h.

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