Two-dimensional non-layered metal oxide film growth method based on electrochemical driving passivation liquid metal printing and application of two-dimensional non-layered metal oxide film growth method

Abstract

The invention discloses a two-dimensional non-layered metal oxide film growth method based on electrochemical driving passivation liquid metal printing and application of the two-dimensional non-layered metal oxide film growth method. High-purity metal is placed on a high-purity metal bearing substrate Al foil, heating is conducted, and after the high-purity metal is melted and oxidized, oxide containing impurities on the surface is removed; the method comprises the following steps of: exposing fresh liquid-state high-purity metal, lightly touching the surface of the liquid-state high-purity metal by using a transfer substrate to paste a metal oxide film, and removing the liquid-state high-purity metal on the surface of the substrate to obtain an ultrathin (the thickness is less than 2nm) large-area two-dimensional non-layered metal oxide film. The method can also be used for image recognition. The switching ratio of the memristor provided by the invention is gt; 104, the retention time gt is determined; 104 s, the anti-fatigue characteristic gt; after 104 cycles, the recognition precision of the neuromorphic encrypted image is 98.6%, and a foundation is laid for a new-generation neuromorphic computing chip.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional non-layered materials and electronic devices, and particularly relates to a method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing and its application. Background Technology

[0002] Two-dimensional (2D) metal oxides have broad application prospects in electronics, optoelectronics, energy storage and conversion, thanks to their wide bandgap, high dielectric constant, excellent mechanical flexibility, and memristor properties. Among them, two-dimensional non-layered metal oxide thin films (NMOs) are an important subclass, overcoming the structural limitations of traditional three-dimensional metal oxides and exhibiting unique electronic structures, surface activities, and optical properties. The surface of 2D NMOs contains numerous unsaturated dangling bonds, endowing the materials with abundant active sites. This characteristic enables the materials to exhibit extremely high activity in adsorption and catalytic reactions, significantly improving their performance in catalysis and sensing applications. However, the high reactivity of these dangling bonds often leads to undesirable chemical reactions or structural rearrangements during material thinning, thereby impairing the material's stability and performance. This presents a key challenge for achieving further thickness reduction.

[0003] Against this backdrop, researchers have explored various synthetic methods to prepare two-dimensional NMOs. However, operational challenges arising from the complexity of existing methods such as chemical vapor deposition (CVD) persist during development. Building upon this, a liquid metal printing (LMP) process was established. Liquid metals possess atomically flat surfaces, making them an ideal natural platform for synthesizing two-dimensional materials. Their atomically flat surfaces and ultra-high surface mobility facilitate the synthesis of ultrathin, uniform oxide layers. However, most LMP methods to date require the synthesis of metal oxides in a glove box under controlled oxygen conditions (10–100 ppm), resulting in stringent operating conditions.

[0004] Therefore, providing a simple and environmentally compatible method for synthesizing NMOs that can prepare large-area, ultrathin two-dimensional NMOs and effectively improve their performance in fields such as electronic devices is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing and its applications. The method of this invention possesses high controllability and repeatability, providing an efficient technical means for the preparation of large-area, ultrathin two-dimensional non-layered metal oxide thin film materials, and solving the technical challenge of thinning non-layered metal oxide thin films. The method of this invention offers precise control and is suitable for preparing large-area, ultrathin two-dimensional non-layered metal oxide thin film materials.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivation liquid metal printing, comprising the following steps: placing high-purity metal on a high-purity metal substrate, heating it until the high-purity metal melts and oxidizes, removing oxides containing impurities from the surface to expose fresh liquid high-purity metal, lightly touching the surface of the liquid high-purity metal with a transfer substrate to adhere the metal oxide thin film, removing the liquid high-purity metal from the surface of the transfer substrate to obtain a two-dimensional non-layered metal oxide thin film;

[0008] The high-purity metal substrate is an Al foil.

[0009] When the high-purity metal substrate is an active Al foil, liquid Bi comes into contact with the Al foil. The electrode potential of Al is significantly lower than that of Bi, causing Al to spontaneously act as the anode and preferentially undergo oxidation. At this point, Bi is located in the cathode region, forming electrochemical coupling and driving the reaction pathway. The electrochemical passivation effect shifts the rate-determining step of the oxidation reaction to the anodic dissolution process of Al. This mechanism effectively increases the overpotential of the Bi oxidation reaction, thereby reducing the oxidation rate of liquid Bi and enabling the production of ultrathin (thickness less than 2 nm), large-area two-dimensional non-layered metal oxide films.

[0010] Furthermore, the high-purity metal is selected from Bi, Zn, or In, and the purity of each metal is not less than 99.99%.

[0011] Furthermore, the heating temperature is not lower than the melting point of the high-purity metal.

[0012] Furthermore, when the high-purity metal is Bi, the heating temperature is 300-350℃; when the high-purity metal is Zn, the heating temperature is 400-450℃; and when the high-purity metal is In, the heating temperature is 200-250℃.

[0013] Furthermore, the high-purity metal substrate was polished before use to remove the aluminum oxide from its surface.

[0014] Furthermore, before use, the transfer substrate includes a pretreatment step: the transfer substrate is sequentially subjected to ultrasonic cleaning with ultrapure water, acetone, isopropanol and ethanol, dried with nitrogen, and treated with oxygen plasma.

[0015] Furthermore, the oxidation time is 1-30 seconds.

[0016] Furthermore, the transfer substrate is a SiO2 / Si substrate.

[0017] The present invention also provides a two-dimensional non-layered metal oxide thin film prepared according to the above method.

[0018] The present invention also provides an application of the above-mentioned two-dimensional non-layered metal oxide thin film in the fabrication of memristors.

[0019] The present invention also provides a memristor, which is prepared from the above-mentioned two-dimensional non-layered metal oxide thin film.

[0020] The memristor of this invention can be used for encryption of numbers and images, and also for image recognition.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] (1) The present invention adopts an electrochemical driven passivation strategy, which can significantly reduce the thickness of two-dimensional non-layered metal oxide films and successfully achieve the controllable preparation of centimeter-level two-dimensional non-layered metal oxide films with a thickness of less than 2 nm, which significantly improves the uniformity and size controllability of ultrathin oxide films.

[0023] (2) This invention adopts a dual coupling mechanism of electrochemical interface modulation and substrate engineering printing, driven by electrochemical passivation, which improves the oxidation barrier of two-dimensional non-layered metal oxides and reduces their thickness, providing a new paradigm for the preparation of high-quality, ultrathin two-dimensional non-layered materials.

[0024] (3) The liquid metal printing method provided by the present invention is simple to operate, completes oxide transfer under natural environmental conditions, requires only a conventional heating stage, and does not require vacuum or protective atmosphere, and can achieve the growth of ultrathin non-layered metal oxide films on a large area substrate (1 cm × 1 cm);

[0025] (4) The present invention has high process compatibility and can effectively overcome the technical bottleneck of two-dimensionalization of non-layered materials;

[0026] (5) The on / off ratio of the memristor prepared in this invention is >10. 4 Retention time > 10 4 s, fatigue resistance >10 4 In the second cycle, the accuracy of neuromorphic encrypted image recognition reached 98.6%, laying the foundation for the next generation of neuromorphic computing chips. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1A schematic diagram of the two-dimensional non-layered metal oxide thin film growth method based on electrochemically driven passivated liquid metal printing provided by the present invention.

[0029] Figure 2 A schematic diagram of the atomic structure of the α-Bi₂O₃ thin film prepared in Example 1 (a), a large-scale (centimeter-scale) physical image of the α-Bi₂O₃ thin film on the SiO₂ / Si substrate (b), an optical microscope image of the large-area α-Bi₂O₃ thin film on the SiO₂ / Si substrate (c), an atomic force microscope microscopic image of the α-Bi₂O₃ thin film (d) and statistical distribution results of the thickness of the α-Bi₂O₃ thin film (e), an X-ray diffraction pattern of the α-Bi₂O₃ thin film (f), and X-ray photoelectron spectroscopy fitting results of the α-Bi₂O₃ thin film at the Bi 4f nuclear level (g) and the O 1s nuclear level (h).

[0030] Figure 3 In the image, a is a high-angle annular dark-field scanning transmission electron microscope image of the α-Bi2O3 thin film prepared in Example 1, b is the fast Fourier transform mode corresponding to the image shown in a, c is an enlarged view of a and the atomic structure model with axial projection

[001] , d is the intensity line contour extracted from the rectangular area marked by the white dot dashed line in c, eg is the high-angle annular dark-field image of the α-Bi2O3 thin film and its corresponding energy dispersive X-ray energy spectrum mapping image of Bi and O elements, and h is a high-resolution transmission electron microscope image of the α-Bi2O3 thin film.

[0031] Figure 4 The diagram shows a conventional metal oxidation process in Comparative Example 1 (a) and an electrochemical passivation mechanism of α-Bi2O3 grown on Al foil in Example 1 (b).

[0032] Figure 5 The color changes of liquid Bi prepared in Examples 1 and Comparative Examples 1-3 on glass substrate (ae), SiO2 / Si substrate (fj), Au foil (ko), and Al foil (pt) as oxidation time increased (1s, 5s, 10s, 15s, 20s);

[0033] Figure 6 The color changes of the α-Bi2O3 films prepared in Example 1 and Comparative Examples 1-2 on the glass substrate (ae), Au foil (fj), and Al foil (ko) as oxidation time increased (1s, 5s, 10s, 20s, 30s);

[0034] Figure 7 The contact angle of liquid Bi on the glass substrate (ad) and aluminum foil (eh) in Example 1 changes over time, corresponding to 0h, 1h, 2h and 3h respectively;

[0035] Figure 8 The images show: (a) a large-scale (centimeter-scale) physical image of In2O3 prepared in Example 2 on a SiO2 / Si substrate; (b) X-ray photoelectron spectroscopy fitting results of the In2O3 thin film at the In 3d nuclear level (b) and the O 1s nuclear level (c); (d) an optical microscope image of a large area of ​​In2O3 on a SiO2 / Si substrate; (e) an atomic force microscope image of In2O3; (f) a high-resolution transmission electron microscope image of In2O3; and (g) a selected area electron diffraction pattern.

[0036] Figure 9 The images show: (a) a large-scale (centimeter-scale) physical image of ZnO prepared in Example 3 on a SiO2 / Si substrate; (b) X-ray photoelectron spectroscopy fitting results of the ZnO thin film at the Zn 2p nuclear level (b) and O 1s nuclear level (c); (d) an optical microscope image of large-area ZnO on a SiO2 / Si substrate; (e) an atomic force microscope image of ZnO; (f) a high-resolution transmission electron microscope image of ZnO; and (g) a selected area electron diffraction pattern.

[0037] Figure 10 A schematic diagram of the Ag / α-Bi₂O₃ / Si memristor structure prepared in Example 1 (a), semi-logarithmic IV characteristic curve (b), duration of high resistance state (HRS) and low resistance state (LRS) (c), response time of input and output voltages (d), and 10 4 The next complete switching cycle (e) and 10 4 In the next scan cycle, HRS and LRS (top) and I LRS / I HRS (Below) fatigue resistance (f), where the dashed lines in f represent 10 4 Average I within each scan cycle LRS I HRS (Above) and I LRS / I HRS The value of (below);

[0038] Figure 11 The process of encrypting and decrypting digital strings using the Ag / α-Bi2O3 / Si memristor prepared in Example 1 is illustrated in (a), the process of encrypting and decrypting images is illustrated in (b), a schematic diagram of a two-layer fully connected neural network is illustrated in (c), and the image recognition accuracy is illustrated in (d). Detailed Implementation

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0041] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0042] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0043] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0044] An embodiment of the present invention provides a method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivation liquid metal printing, comprising the following steps: placing high-purity metal on a high-purity metal substrate; placing the high-purity metal substrate on which the high-purity metal is placed on a heating stage for heating; heating until the high-purity metal melts; removing the upper oxide film with a glass slide to expose a clean liquid high-purity metal surface for subsequent oxidation to generate a fresh metal oxide film; lightly touching the liquid high-purity metal surface with a transfer substrate to adhere the metal oxide film; and removing the liquid high-purity metal from the transfer substrate surface with a cotton swab dipped in alcohol to obtain an ultrathin (thickness less than 2 nm), large-area two-dimensional non-layered metal oxide thin film, which is a centimeter-scale two-dimensional non-layered metal oxide thin film with a thickness of less than 2 nm;

[0045] The high-purity metal substrate is an Al foil.

[0046] This invention uses high-purity metal as raw material and modulates the surface passivation treatment of the Al foil supporting the high-purity metal substrate through electrochemical interface modulation. Combined with substrate-engineered liquid metal printing technology, a centimeter-scale two-dimensional non-layered metal oxide film with a thickness of less than 2 nm is grown under natural environmental conditions. This invention, through an electrochemical interface modulation strategy, precisely maintains the surface potential of the high-purity metal below the corrosion potential, ensuring that the Gibbs free energy change ΔG = nFE > 0, eliminating the thermodynamic driving force of spontaneous oxidation, and effectively suppressing the spontaneous thickening phenomenon of oxides on the surface of the liquid high-purity metal. This invention selects Al foil as the substrate supporting the high-purity metal and optimizes the substrate interface energy. Its high surface energy characteristics promote the uniform spreading of the liquid high-purity metal, achieving complete wetting.

[0047] In a preferred embodiment of the present invention, the Al foil has a size of 6 cm × 6 cm, and the mass of high-purity metal placed on the Al foil of this size is 4-6 g.

[0048] In a preferred embodiment of the present invention, the high-purity metal is selected from Bi, Zn or In, and the purity of each metal is not less than 99.99%.

[0049] In a preferred embodiment of the present invention, the heating temperature is not lower than the melting point of the high-purity metal.

[0050] In a preferred embodiment of the present invention, when the high-purity metal is Bi, the heating temperature is 300-350°C; when the high-purity metal is Zn, the heating temperature is 400-450°C; and when the high-purity metal is In, the heating temperature is 200-250°C.

[0051] In a preferred embodiment of the present invention, the high-purity metal (Bi, Zn, or In) is in solid form. For example, the high-purity metal used is Bi granules, Zn granules, or In granules.

[0052] In a preferred embodiment of the present invention, the average thickness of the obtained two-dimensional non-layered metal oxide ZnO film is 1.7 nm, the average thickness of the obtained two-dimensional non-layered metal oxide Bi2O3 film is 1.3 nm (the thinnest thickness of the Bi2O3 film can reach 0.8 nm), and the average thickness of the obtained two-dimensional non-layered metal oxide In2O3 film is 1.5 nm, and the maximum lateral dimension of all films is 1 cm.

[0053] In a preferred embodiment of the present invention, the high-purity metal substrate is polished before use to remove the aluminum oxide on its surface.

[0054] In a preferred embodiment of the present invention, the transfer substrate is further subjected to a pretreatment step before use: the transfer substrate is sequentially subjected to ultrasonic cleaning with ultrapure water, acetone, isopropanol and ethanol, with an ultrasonic power of 40W, each ultrasonic cleaning lasting 10 minutes, then dried with nitrogen, and then subjected to oxygen plasma treatment.

[0055] In a preferred embodiment of the present invention, the oxidation time is 1-30 seconds.

[0056] In a preferred embodiment of the present invention, the transfer substrate is a SiO2 / Si substrate, which is cut from Si / SiO2 at the wafer-level.

[0057] For example, the SiO2 / Si substrate can be prepared by cutting the wafer-level Si / SiO2 into 2 cm × 2 cm pieces.

[0058] Embodiments of the present invention also provide a two-dimensional non-layered metal oxide thin film prepared according to the above method.

[0059] Embodiments of the present invention also provide an application of the above-described two-dimensional non-layered metal oxide thin film in the fabrication of memristors.

[0060] An embodiment of the present invention also provides a memristor, which is prepared from the above-described two-dimensional non-layered metal oxide thin film.

[0061] The memristor provided by this invention can be used for digital and image encryption, and also for image recognition. The memristor provided by this invention has an on / off ratio >10. 4 Retention time > 10 4 s, fatigue resistance >10 4 In the second iteration, the accuracy of neuromorphic encrypted image recognition was 98.6%.

[0062] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0063] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0064] It should be noted that all aspects not described in detail in this invention are conventional operating methods in the field and are not the focus of this invention. For example, the specific methods for depositing Au on a glass slide by vapor deposition are all completed using conventional methods.

[0065] The technical solution of the present invention will be further illustrated by the following embodiments.

[0066] Example 1

[0067] A method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivation liquid metal printing, comprising the following steps:

[0068] S1. The wafer-level SiO2 / Si substrates are cut into 1 cm × 1 cm independent substrates. The resulting SiO2 / Si substrates are then subjected to ultrasonic cleaning sequentially with ultrapure water, acetone, isopropanol, and ethanol. Each ultrasonic cleaning is performed at a power of 40 W for 10 minutes. Finally, the substrates are dried with a nitrogen gun for later use. After cleaning, the SiO2 / Si substrates are treated with O plasma (oxygen plasma) at a power of 50 W for 5 minutes before use. The 1 cm × 1 cm SiO2 / Si substrates obtained from this treatment are used as transfer substrates.

[0069] S2. Polish the Al foil in advance to remove the surface aluminum oxide, and cut it into 6 cm × 6 cm. Use the Al foil with a size of 6 cm × 6 cm obtained by the above treatment as a carrier for the high-purity metal substrate.

[0070] S3. Using 99.99% pure Bi particles as the high-purity metal, with a Bi particle amount of 4g, electrochemically driven passivation liquid metal printing was performed. The specific process was as follows: the high-purity metal Bi particles were placed on an Al foil, and the Al foil with Bi particles was placed on a heating stage. The heating stage was heated to 350℃ to melt the solid Bi particles. Then, the oxide containing impurities on the surface was removed with a glass slide to expose fresh liquid Bi. At this time, due to the large interfacial energy of the Al foil, the liquid Bi was wetted on it (contact angle <90°). After waiting for oxidation (oxidation time is 1-30s), the oxide film was pasted onto the SiO2 / Si substrate pretreated in step S1. Since the interaction force between the oxide film and the liquid metal is less than that between the oxide film and the SiO2 / Si substrate, it is easy to transfer it. Subsequently, the residual liquid metal impurities on the surface were removed with a cotton swab soaked in alcohol, and finally a large-area, ultra-thin metal oxide film was obtained, denoted as α-Bi2O3 film.

[0071] Figure 1 A schematic diagram of the two-dimensional non-layered metal oxide thin film growth method based on electrochemically driven passivated liquid metal printing provided by the present invention.

[0072] Figure 2 Image a shows that α-Bi₂O₃ in the thin film of Example 1 has a monoclinic P₂¹ / c crystal structure, which was then analyzed using large-area physical imaging and optical microscopy. Figure 2 Figures b and c) confirm that it is a centimeter-scale thin film that can be grown in a controlled manner. Figure 2 As shown in Figure d, the α-Bi₂O₃ thin film prepared in this invention exhibits precise thickness control (0.8 nm). Furthermore, statistical AFM data comparisons were performed on the synthesized samples. Figure 2The α-Bi₂O₃ film exhibits sub-nanometer thickness uniformity (1.3 nm ± 0.4 nm). X-ray diffraction patterns of the α-Bi₂O₃ film show that this is attributed to the (111) and (120) crystal planes. Figure 2 The 4f core energy level spectrum of Bi4f is consistent with that of the monoclinic P21 / c space group (PDF number 41-1449). The spectrum shows a characteristic double peak at 158.6 eV (4f...). 7 / 2 ) and 163.9 eV (4f 5 / 2 ), corresponding to Bi in α-Bi2O3 3+ The ion's spin orbital splits to 5.3 eV. The characteristic peak at 157 eV (corresponding to elemental bismuth) was not detected, further confirming the efficiency of the oxidation process and the absence of metallic bismuth residue. Figure 2 (g). Deconvolution analysis of the O 1s XPS spectrum revealed two distinct peaks: 530.8 eV corresponding to Bi-O-Bi bonding, and 532.3 eV corresponding to the SiO2 substrate peak. Figure 2 (h), which proves that the synthesized α-Bi2O3 film has excellent composition and phase purity.

[0073] Figure 3 Image a is a high-angle annular dark-field scanning transmission electron microscope image of the α-Bi₂O₃ thin film prepared in Example 1; image b is the fast Fourier transform mode corresponding to the image shown in image a; image c is an enlarged view of image a and the atomic structure model with

[001] axial projection; image d is the intensity line profile extracted from the rectangular area marked by the white dotted line in image c; image eg is the high-angle annular dark-field image of the α-Bi₂O₃ thin film and its corresponding energy dispersive X-ray spectral mapping image of Bi and O elements; image h is a high-resolution transmission electron microscope image of the α-Bi₂O₃ thin film. Figure 3 As can be seen from image a, a highly ordered atomic structure is observed along the

[001] band axis. Notably, the entire image exhibits a uniform and defect-free morphology, with no bismuth vacancies, indicating that the prepared α-Bi2O3 film possesses excellent crystal quality. The measured lattice spacings are 0.54 nm and 0.40 nm, corresponding to the (100) and (020) planes of α-Bi2O3, respectively. Figure 3 Figure b shows the relevant Fast Fourier Transform (FFT) analysis, which provides further insights into the crystal structure of α-Bi₂O₃. Furthermore, Figure 3 The magnified HAADF-STEM image in the middle c shows a clear atomic arrangement, which is in high agreement with the structural model observed in the

[001] direction. Figure 3 The intensity line profile extracted from the white dashed rectangle in the middle (c) Figure 3(d) clearly shows the intensity at each Bi atom pillar, demonstrating the high quality and excellent uniformity of the synthesized α-Bi₂O₃. Furthermore, elemental mapping based on energy dispersive spectroscopy (EDS) shows that bismuth and oxygen are uniformly distributed in the film. Figure 3 The successful synthesis and compositional uniformity of α-Bi₂O₃ were confirmed by the analysis of high-resolution transmission electron microscopy (HRTEM) images. The lattice spacing was measured to be 0.22 nm. Figure 3 (h), and ( The surfaces are very well matched, exhibiting a consistent in-plane lattice orientation, indicating that the thin film synthesized by the electrochemically driven passivation liquid metal printing strategy of this invention has high crystallinity.

[0074] Comparative Example 1

[0075] Same as Example 1, except that the substrate supporting the high-purity metal is a 7.5 cm × 2.5 cm glass sheet.

[0076] Comparative Example 2

[0077] Same as Example 1, except that the substrate carrying the high-purity metal is a 7.5 cm × 2.5 cm Au foil; wherein the preparation method of the 7.5 cm × 2.5 cm Au foil is as follows: Au with a thickness of 60 nm is deposited on a 7.5 cm × 2.5 cm glass plate by vapor deposition to obtain an Au foil with a size of 7.5 cm × 2.5 cm.

[0078] Comparative Example 3

[0079] Same as Example 1, except that the substrate supporting the high-purity metal is a 2 cm × 2 cm SiO2 / Si.

[0080] The preparation method and pretreatment of the 2 cm × 2 cm SiO2 / Si in this comparative example are as follows: The wafer-level SiO2 / Si is cut into independent substrates of 2 cm × 2 cm size. The obtained SiO2 / Si substrates are ultrasonically cleaned sequentially with ultrapure water, acetone, isopropanol and ethanol. The ultrasonic power is 40W and the ultrasonication time is 10 min each time. Finally, they are dried with a nitrogen gun and set aside for later use.

[0081] Figure 4Figure b shows that when the high-purity metal substrate is an active metal Al foil, liquid Bi comes into contact with the Al foil. The electrode potential of Al is significantly lower than that of Bi, causing Al to spontaneously act as the anode and preferentially undergo oxidation. At this time, Bi is located in the cathode region, forming electrochemical coupling and driving the reaction pathway. The electrochemical passivation effect shifts the rate-determining step of the oxidation reaction to the anodic dissolution process of Al. This mechanism effectively increases the overpotential of the Bi oxidation reaction, thereby reducing the oxidation rate of liquid Bi. This phenomenon does not occur in traditional liquid metal oxidation processes (i.e., when the high-purity metal substrate is a glass plate or an inert metal). Figure 4 (a)

[0082] Figure 5 The color changes of liquid Bi prepared for Examples 1 and Comparative Examples 1-3 on glass substrates (ae), SiO2 / Si substrates (fj), Au foil (ko), and Al foil (pt) were observed. It was noted that the oxidation rate of liquid Bi significantly increased with increasing oxidation time (1s, 5s, 10s, 15s, 20s) on these substrates with lower metallic reactivity than Bi. This acceleration was observed in the distinct differences in the color changes on the surface of liquid Bi; the deeper the color change, the thicker the oxide layer. Compared to metallic Bi, this oxide layer exhibited unique optical properties, including plasmonic behavior or interference effects caused by its thickness. As the oxidation process progressed, the thickness of the oxide layer gradually increased, thereby altering the optical interference and surface plasmonic resonance mechanisms, leading to changes in the optical appearance.

[0083] Figure 6 The optical microscope images of the α-Bi₂O₃ films prepared in Examples 1 and Comparative Examples 1-2 on glass substrates (ae), Au foils (fj), and Al foils (ko) show color changes. It can be seen that with increasing oxidation time (1s, 5s, 10s, 20s, 30s), the thickness of the α-Bi₂O₃ films prepared on the glass substrate and Au foil changes significantly, and the color gradually deepens, while the uniformity decreases. However, the thickness of the α-Bi₂O₃ film prepared on the Al foil does not change significantly with increasing oxidation time, and the film continuity remains good.

[0084] Figure 7The figures show the changes in the contact angle of liquid Bi on a glass substrate (ad) and an Al foil (eh) over time in Example 1, corresponding to 0h, 1h, 2h, and 3h, respectively. It can be seen that on the Al foil, due to the relatively high surface energy of the Al foil among active metals, the contact angle is low (θ = 13.8°), which is beneficial for forming a uniform and large-area film. The decrease in contact angle over time is attributed to the increased surface energy gradient caused by the penetration of bismuth atoms into the aluminum foil. In contrast, on the glass substrate, the contact angle remains high and stable (θ > 90°), reflecting the lack of electronic interaction between the non-metallic surface and the liquid metal, resulting in a non-wetting state.

[0085] Example 2

[0086] The difference from Example 1 is that in step S3, the high-purity metal is replaced with an equal mass of In particles (purity of 99.99%), that is, the amount of In particles used is 4g; the heating table temperature is 250℃, and the oxidation time is 10s.

[0087] Figure 8 The images show: (a) a large-area (centimeter-scale) physical image of the In2O3 thin film prepared in Example 2 on a SiO2 / Si substrate; (b) X-ray photoelectron spectroscopy fitting results of the In2O3 thin film at the In 3d nuclear level (b) and the O 1s nuclear level (c); (d) an optical microscope image of the large-area In2O3 on the SiO2 / Si substrate; (e) an atomic force microscope image of In2O3; (f) a high-resolution transmission electron microscope image of In2O3; and (g) a selected area electron diffraction pattern. The large-area physical image and optical microscope image of the In2O3 thin film on the SiO2 / Si substrate confirm that it is a controllably grown centimeter-scale thin film. Figure 8 (a and d). In the In 3d core level spectrum, the X-ray photoelectron spectrum was resolved to 3d... 5 / 2 (444.7 eV) and 3d 3 / 2 (452.2 eV) spin-orbit bimodal ( Figure 8 (b). High-resolution O 1s spectrum ( Figure 8 (c) further reveals lattice oxygen (531.0 eV) and Si-O signal (532.5 eV) in the In-O bond, the latter likely originating from the interface with the SiO2 substrate. Figure 8 (d) indicates that the synthesized In2O3 film has high purity. Figure 8 As shown in Figure e, the In2O3 thin film prepared by this invention has precise thickness control (1.5 nm). Figure 8 The study revealed the highly ordered atomic structure of In₂O₃. Figure 8 The value of g indicates that In2O3 has a single crystal structure within the field of view, which fully demonstrates that the synthesized In2O3 has excellent crystal quality.

[0088] Example 3

[0089] The difference from Example 1 is that in step S3, the high-purity metal is replaced with an equal mass of Zn particles (purity of 99.99%), that is, the amount of Zn particles used is 4g; the heating table temperature is 420℃ and the oxidation time is 10s.

[0090] Figure 9 The images show: (a) a large-area (centimeter-scale) physical image of ZnO prepared in Example 3 on a SiO2 / Si substrate; (b) X-ray photoelectron spectroscopy fitting results of the ZnO thin film at the Zn 2p nuclear level (b) and O 1s nuclear level (c); (d) optical microscope image of the large-area ZnO on the SiO2 / Si substrate; (e) atomic force microscope image of ZnO; (f) high-resolution transmission electron microscope image of ZnO; and (g) selected area electron diffraction pattern. The large-area physical image and optical microscope image of ZnO on the SiO2 / Si substrate confirm the controllable growth of centimeter-scale thin films. Figure 9 (a and d). In high-resolution Zn 2p energy spectrum ( Figure 9 In (b), the peak values ​​at 1044.8 eV and 1021.9 eV are related to Zn 2p 1 / 2 and Zn 2p 3 / 2 The spin-orbit coupling doublets are well-consistent, which is characteristic of the oxidized Zn state. High-resolution O 1s spectrum ( Figure 9 (c) further reveals the lattice oxygen (531.0 eV) and Si-O signal (532.2 eV) in the Zn-O bond, the latter possibly originating from the interface with the SiO2 substrate. Figure 9 (d) indicates that the ZnO thin film synthesized in this invention has high purity. Figure 9 As shown in Figure e, the ZnO thin film prepared by this invention has precise thickness control (1.7 nm). Figure 9 The study revealed the highly ordered atomic structure of ZnO. Figure 9 The value of g indicates that the material has a polycrystalline structure within the field of view, which fully demonstrates that the ZnO synthesized in this invention has excellent crystal quality.

[0091] Application Example 1

[0092] The α-Bi₂O₃ thin film prepared in Example 1 was used to fabricate a memristor. The thickness of the α-Bi₂O₃ thin film was 1.3 nm. The specific preparation process was as follows: the wafer-level Si was cut into independent substrates of 1 cm × 1 cm. The obtained Si substrates were ultrasonically cleaned sequentially with ultrapure water, acetone, isopropanol and ethanol. The ultrasonic power was 40 W for 10 min each time. Finally, the substrates were dried with a nitrogen gun for later use. Ag with a thickness of 25 nm was thermally vapor-deposited using a mask, with Ag as the top electrode and the Si substrate as the bottom electrode, to obtain the Ag / α-Bi₂O₃ / Si memristor.

[0093] Electrical tests were performed on the above Ag / α-Bi2O3 / Si memristor using a probe station. The results are shown in [Figure number missing]. Figure 10 and Figure 11 . Figure 10 The diagram shows the structure of an Ag / α-Bi2O3 / Si memristor (a), its semi-logarithmic IV characteristic curve (b), the duration of the high resistance state (HRS) and low resistance state (LRS) (c), and the response time of the input and output voltages (d). 4 The next complete switching cycle (e) and 10 4 In the next scan cycle, HRS and LRS (top) and I LRS / I HRS (Below) Fatigue resistance, the dashed lines represent 10 4 Average I within each scan cycle LRS I HRS (Above) and I LRS / I HRS The value (f) of (below). From Figure 10 It can be seen that the Ag / α-Bi2O3 / Si memristor exhibits typical bipolar resistive switching behavior, which is verified by the semi-logarithmic IV characteristic curve. Figure 10 (b) A transition from the high resistance state (HRS) to the low resistance state (LRS) was observed at 2 V, confirming the completion of the setup process. Conversely, the reset process peaked at -2.6 V, where the abrupt change from LRS to HRS occurred, indicating filament breakage. To minimize Joule heating, the threshold current (Icc) for LRS operation was maintained at 1 × 10⁻⁶. -3 A. Retention characteristics were evaluated at a 1 V read voltage. The device was at 10... 4 It displays 1.5×10 within s. 4 The on / off current ratio is high, and the current drift is extremely small, indicating excellent stability in both resistive states. Figure 10 c). The switching speed of Ag / α-Bi2O3 / Si memristors is less than 3 ms ( Figure 10 (d). The device has been subjected to 10 hours of curing at room temperature. 4It still exhibits excellent cycle durability after the second voltage scan, and the state retention time exceeds 3 × 10⁻⁶. 3 Second( Figure 10 in ef).

[0094] Figure 11 The encryption and decryption processes of digital strings (a), images (b), a schematic diagram of a two-layer fully connected neural network (c), and the image recognition accuracy (d) are simulated using Ag / α-Bi2O3 / Si memristors. The α-Bi2O3-based memristor exhibits excellent digital RS characteristics, enabling reversible conversion from HRS to LRS under an electric field. This invention designs an encryption matrix system based on a memristor full adder. This system, when expanded to an m × n array, first achieves complete encryption / decryption of the digital string (1895). Figure 11 (a). When dealing with complex data structures, the system further demonstrates full functionality for binarizing 1024×1024 grayscale school badge images, with all decrypted outputs maintaining visual consistency with the original input. Figure 11 (b) A two-layer fully connected neural network was used for quantitative evaluation of the feature preservation of the encryption system. This network was trained on a decrypted, modified version of the National Institute of Standards and Technology (MNIST) handwritten digit dataset, achieving a recognition accuracy of 98.6% using the decrypted data. Figure 11 medium cd).

[0095] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing, characterized in that, Includes the following steps: High-purity metal is placed on a substrate supporting high-purity metal and heated until it melts and oxidizes. The oxide containing impurities on the surface is removed, exposing fresh liquid high-purity metal. A transfer substrate is used to lightly touch the surface of the liquid high-purity metal to adhere a metal oxide film. The liquid high-purity metal on the surface of the transfer substrate is then removed to obtain a two-dimensional non-layered metal oxide film. The high-purity metal substrate is an Al foil.

2. The method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing according to claim 1, characterized in that, The high-purity metal is selected from Bi, Zn or In, and the purity of each metal is not less than 99.99%.

3. The method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing according to claim 1, characterized in that, The heating temperature shall not be lower than the melting point of the high-purity metal.

4. The method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing according to claim 2, characterized in that, When the high-purity metal is Bi, the heating temperature is 300-350℃; And / or, when the high-purity metal is Zn, the heating temperature is 400-450℃; And / or, when the high-purity metal is In, the heating temperature is 200-250°C.

5. The method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing according to claim 1, characterized in that, Before using the high-purity metal substrate, a polishing step is also included.

6. The method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing according to claim 1, characterized in that, Before use, the transfer substrate also includes a pretreatment step: the transfer substrate is ultrasonically cleaned sequentially with ultrapure water, acetone, isopropanol and ethanol, dried with nitrogen, and then treated with oxygen plasma.

7. The method for growing two-dimensional non-layered metal oxide thin films based on electrochemically driven passivated liquid metal printing according to claim 1, characterized in that, The oxidation time is 1-30 seconds.

8. A two-dimensional non-layered metal oxide thin film, prepared by the preparation method according to any one of claims 1-7.

9. The application of a two-dimensional non-layered metal oxide thin film as described in claim 8 in the fabrication of memristors.

10. A memristor, characterized in that, It is prepared from the two-dimensional non-layered metal oxide thin film as described in claim 8.

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