A horizontal two-terminal memristor based on beta-teo2 nanosheet and a preparation method thereof

Abstract

The application belongs to the technical field of semiconductor memory devices, and discloses a horizontal two-terminal memristor based on beta-TeO2 nanosheet and a preparation method thereof.The memristor comprises a substrate, a beta-TeO2 nanosheet functional layer and a pair of metal electrodes; the beta-TeO2 nanosheet functional layer is arranged on the surface of the substrate; the pair of metal electrodes are arranged on the beta-TeO2 nanosheet functional layer at intervals and serve as a first electrode and a second electrode; the first electrode, the beta-TeO2 nanosheet functional layer and the second electrode jointly form a horizontal two-terminal memristor structure; and the beta-TeO2 nanosheet functional layer is used for oxygen vacancy migration and aggregation under the action of an applied electric field, so as to realize reversible switching between a high-resistance state and a low-resistance state.The two-dimensional nanosheet horizontal two-terminal memristor device has the advantages of simple structure, no need for electroforming, low operating voltage, high on-off ratio, good durability and excellent high-temperature retention performance, and can be used for neuromorphic computing devices.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductor memory devices, and more specifically, relates to a horizontally two-terminal memristor based on β-TeO2 nanosheets and its preparation method. Background Technology

[0002] Memristors typically rely on the migration of functional layer ions under the influence of an applied electric field to achieve reversible switching between high-resistivity and low-resistivity states. Due to their advantages such as simple structure, fast operation speed, low power consumption, and ease of integration, memristors are considered one of the important devices for non-volatile storage and neuromorphic computing in the post-Moore's Law era.

[0003] Existing memristor devices still suffer from problems such as high electroforming voltage, strong randomness of conductive channels, and insufficient device consistency, which affect their application in high-density storage and neuromorphic computing. Summary of the Invention

[0004] To address the above-mentioned deficiencies or improvement needs of existing technologies, this invention provides a horizontally-terminal memristor based on β-TeO2 nanosheets and its fabrication method, which solves the problems of high electroformation voltage, strong randomness of conductive channels, and insufficient device consistency in existing memristor devices. By using β-TeO2 nanosheets as the resistive switching functional layer and constructing a horizontally-terminal structure, the resistive switching characteristics of low voltage, high on / off ratio and no need for electroformation are achieved.

[0005] To achieve the above objectives, according to one aspect of the present invention, a horizontally two-ended memristor based on β-TeO2 nanosheets is provided, comprising a substrate, a β-TeO2 nanosheet functional layer, and a pair of metal electrodes; the β-TeO2 nanosheet functional layer is disposed on the surface of the substrate; the pair of metal electrodes are spaced apart on the β-TeO2 nanosheet functional layer and serve as a first electrode and a second electrode; the first electrode, the β-TeO2 nanosheet functional layer, and the second electrode together form a horizontally two-ended memristor structure; the β-TeO2 nanosheet functional layer is used to induce oxygen vacancy migration and accumulation under an applied electric field to achieve reversible switching between a high-resistivity state and a low-resistivity state.

[0006] The horizontally-ended memristor based on β-TeO2 nanosheets provided by the present invention has a SiO2 / Si substrate, comprising a Si layer and a SiO2 layer stacked together, wherein the β-TeO2 nanosheet functional layer is disposed on the surface of the SiO2 layer.

[0007] According to the horizontally bisected memristor based on β-TeO2 nanosheets provided by the present invention, both of the pair of metal electrodes are Au electrodes, and the Au electrodes together with the β-TeO2 nanosheet functional layer form an Au / β-TeO2 / Au horizontally bisected structure.

[0008] According to the horizontally-ended memristor based on β-TeO2 nanosheets provided by the present invention, the thickness of the β-TeO2 nanosheet functional layer is 1.5-7.5 nm; the spacing between the first electrode and the second electrode is 0.2-5 μm.

[0009] According to another aspect of the present invention, a method for fabricating a horizontally-terminal memristor based on β-TeO2 nanosheets as described in any of the preceding claims is provided, comprising: Provide substrate; β-TeO2 nanosheets are prepared and then fabricated on the surface of the substrate to form a β-TeO2 nanosheet functional layer. A pair of spaced metal electrodes are prepared, such that the pair of metal electrodes and the β-TeO2 nanosheet functional layer together form a horizontally bisected memristor structure.

[0010] According to the preparation method provided by the present invention, after forming the β-TeO2 nanosheet functional layer, the method further includes: drying the substrate and the β-TeO2 nanosheet functional layer to improve the adhesion stability between the β-TeO2 nanosheets and the substrate.

[0011] According to the preparation method provided by the present invention, β-TeO2 nanosheets are prepared by alloy surface oxidation; β-TeO2 nanosheets are deposited on the substrate surface by roller coating; the pair of metal electrodes are prepared by electron beam lithography and metal evaporation.

[0012] According to the preparation method provided by the present invention, the preparation of β-TeO2 nanosheets by alloy surface oxidation specifically includes: A tellurium selenide eutectic alloy consisting of 5% Te and 95% Se by mass was placed in an oxygen-containing atmosphere, and the oxidation temperature was controlled at 270-300 °C. β-TeO2 nanosheets were formed by utilizing the self-limiting oxidation reaction on the alloy surface.

[0013] According to the preparation method provided by the present invention, the oxygen-containing atmosphere is air, or a mixture of oxygen and an inert gas. When it is a mixture of oxygen and an inert gas, the volume fraction of oxygen is 20-35%.

[0014] The preparation method provided by the present invention further includes: In the process of preparing β-TeO2 nanosheets, the stoichiometry and oxygen vacancy concentration of β-TeO2 nanosheets were adjusted by changing the oxygen-containing atmosphere and / or oxidation time. When β-TeO2 nanosheets are deposited on the substrate surface using a roll coating process, the effective thickness of the β-TeO2 nanosheet functional layer is adjusted by changing the number of roll transfers.

[0015] In summary, compared with the prior art, the horizontally-terminal memristor based on β-TeO2 nanosheets and its preparation method provided by the present invention are superior: 1. Using β-TeO2 nanosheets as the resistive switching functional layer, its wide bandgap, high intrinsic resistance and oxygen vacancy migration characteristics are utilized to achieve reversible switching between high-resistivity and low-resistivity states under the action of an external electric field. At the same time, it is beneficial to reduce the device off-state current and stably switch the resistive state, thereby reducing the randomness of the conduction channel and improving the device consistency. The horizontal two-end structure results in a simple device structure and controllable electrode spacing, facilitating the observation and control of the resistive switching channel formation process within the β-TeO2 nanosheets. The resulting horizontal two-end structure memristor exhibits resistive switching characteristics without electroforming treatment, which helps to reduce the operating voltage and minimize initial device damage. 2. It is proposed that β-TeO2 nanosheets can be prepared by low-temperature surface oxidation, which has a low process temperature and good compatibility with semiconductor back-end processes; the β-TeO2 nanosheet functional layer can be prepared by rolling deposition on the substrate, which is a simple process and the thickness of the functional layer can be controlled by the number of rolling transfers, so that the device performance can be flexibly adjusted according to actual needs, improving flexibility and applicability. 3. It is proposed that the oxygen vacancy characteristics of β-TeO2 can be utilized to regulate the oxygen vacancy concentration in the nanosheets during the preparation of β-TeO2 nanosheets by controlling the oxygen atmosphere and oxidation time. This is beneficial to improving the flexibility and applicability of the prepared devices, and also to improving the stability and consistency of the devices by regulating the preparation of devices with stable resistive switching behavior. 4. The device of the present invention has the characteristics of high switching ratio, good durability and excellent retention performance, and can be used in the fields of high-performance memristors, non-volatile memory and neuromorphic computing devices. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the Au / β-TeO2 / Au horizontal memristor provided in an embodiment of the present invention.

[0017] Figure 2 This is the current-voltage characteristic curve of the Au / β-TeO2 / Au horizontal memristor in Embodiment 1 of the present invention under voltage scanning conditions.

[0018] Figure 3 This is a morphology image of the β-TeO2 nanosheets prepared in Example 1 of this invention under an optical microscope.

[0019] Figure 4 This is the Raman spectrum of the β-TeO2 nanosheets prepared in Example 1 of this invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Please see Figure 1 This embodiment provides a horizontally two-terminal memristor based on β-TeO2 nanosheets. The memristor includes a substrate, a β-TeO2 nanosheet functional layer, and a pair of metal electrodes. The β-TeO2 nanosheet functional layer is disposed on the surface of the substrate. The pair of metal electrodes are spaced apart on the β-TeO2 nanosheet functional layer and serve as the first electrode and the second electrode. The first electrode, the β-TeO2 nanosheet functional layer, and the second electrode together form a horizontally two-terminal memristor structure. The β-TeO2 nanosheet functional layer is used to induce oxygen vacancy migration and accumulation under an applied electric field to achieve reversible switching between a high-resistivity state and a low-resistivity state.

[0022] In this embodiment, a β-TeO2 nanosheet functional layer is selected as the sole resistive switching functional layer. β-TeO2 has a wide direct bandgap of approximately 3.7 eV and a high intrinsic resistance, which is beneficial for reducing off-state leakage current. Intrinsic defects such as oxygen vacancies in its lattice can migrate and modulate local conductive states under the action of an applied electric field. Thus, under the action of an applied electric field, reversible switching between high-resistivity and low-resistivity states can be achieved through the migration, aggregation, and recovery of oxygen vacancies. Furthermore, the memristor exhibits resistive switching characteristics without electroforming treatment, enabling reversible switching between high-resistivity and low-resistivity states under the action of an applied scanning voltage.

[0023] In some embodiments, the substrate is a SiO2 / Si substrate, comprising a Si layer and a SiO2 layer stacked together, and the β-TeO2 nanosheet functional layer is disposed on the surface of the SiO2 layer.

[0024] In some embodiments, both metal electrodes are Au electrodes, and the Au electrodes and the β-TeO2 nanosheet functional layer together form an Au / β-TeO2 / Au horizontal end structure. A spacer region is present between the pair of metal electrodes, and the β-TeO2 nanosheet functional layer is at least partially located within the spacer region to serve as a resistive switching channel connecting the first and second electrodes.

[0025] In some embodiments, the thickness of the β-TeO2 nanosheet functional layer is 1.5-7.5 nm; the spacing between the first electrode and the second electrode is 0.2-5 μm.

[0026] Furthermore, this embodiment also provides a method for fabricating a horizontally-terminal memristor based on β-TeO2 nanosheets as described in any of the above claims, the method comprising: Provide substrate; β-TeO2 nanosheets are prepared and then fabricated on the surface of the substrate to form a β-TeO2 nanosheet functional layer. A pair of spaced metal electrodes are prepared, such that the pair of metal electrodes and the β-TeO2 nanosheet functional layer together form a horizontally bisected memristor structure.

[0027] In some embodiments, after forming the β-TeO2 nanosheet functional layer, the method further includes: drying the substrate and the β-TeO2 nanosheet functional layer to improve the adhesion stability between the β-TeO2 nanosheets and the substrate.

[0028] In some embodiments, β-TeO2 nanosheets are prepared by alloy surface oxidation; β-TeO2 nanosheets are deposited on the substrate surface by a roller coating process; the pair of metal electrodes are prepared by electron beam lithography and metal evaporation processes.

[0029] In some embodiments, β-TeO2 nanosheets can also be prepared by a low-temperature surface oxidation method using tellurium selenide eutectic alloys. The preparation of β-TeO2 nanosheets using the alloy surface oxidation method specifically includes: A tellurium selenide eutectic alloy consisting of 5% Te and 95% Se by mass was placed in an oxygen-containing atmosphere, and the oxidation temperature was controlled at 270-300 °C. β-TeO2 nanosheets were formed by utilizing the self-limiting oxidation reaction on the alloy surface.

[0030] In some embodiments, the oxygen-containing atmosphere is air, or a mixture of oxygen and an inert gas. When it is a mixture of oxygen and an inert gas, for example, an O2 / N2 or O2 / Ar mixture, the volume fraction of oxygen is 20-35%. When the oxygen-containing atmosphere is air, the volume fraction of oxygen is 20-22%, preferably 20.9%. Additionally, molten eutectic droplets are formed at 270-300 °C, and oxidation is allowed to occur for 3-5 minutes, preferably 3 minutes, before each droplet diameter is rolled.

[0031] In some embodiments, the preparation method further includes: In the process of preparing β-TeO2 nanosheets, the stoichiometry and oxygen vacancy concentration of β-TeO2 nanosheets were adjusted by changing the oxygen-containing atmosphere and / or oxidation time. When β-TeO2 nanosheets are deposited on the substrate surface using a roll coating process, the effective thickness of the β-TeO2 nanosheet functional layer is adjusted by changing the number of roll transfers, thereby controlling the operating voltage, on / off ratio, and multi-level resistive state window of the memristor. The total thickness is mainly adjusted by repeated roll transfer stacking.

[0032] Example 1 This embodiment provides a horizontally-terminal memristor based on β-TeO2 nanosheets, the structure of which is as follows: Figure 1 As shown, the memristor includes an insulating substrate, a β-TeO2 nanosheet functional layer disposed on the surface of the insulating substrate, and a pair of metal electrodes disposed on the β-TeO2 nanosheet functional layer. The β-TeO2 nanosheet functional layer is located between the first electrode and the second electrode, serving as a resistive switching channel. The first electrode, the β-TeO2 nanosheet functional layer, and the second electrode together form an Au / β-TeO2 / Au horizontally-terminated memristor structure.

[0033] In this embodiment, the insulating substrate is a SiO2 / Si substrate, and the metal electrode is an Au electrode. The fabrication method of the horizontally two-terminal memristor based on β-TeO2 nanosheets provided in this embodiment includes the following steps: Substrate preparation: A SiO2 / Si substrate is provided and cleaned to remove particles, organic contaminants, and moisture from the substrate surface. The cleaned substrate is then dried before use.

[0034] β-TeO2 nanosheet functional layer deposition: The prepared β-TeO2 nanosheets are deposited on the surface of a SiO2 / Si substrate using a roll coating process, so that the β-TeO2 nanosheets are laid flat on the substrate surface to form a β-TeO2 nanosheet functional layer. After deposition, the sample can be dried to improve the adhesion stability between the β-TeO2 nanosheets and the substrate.

[0035] A tellurium selenide eutectic alloy composed of 5% Te and 95% Se by mass was placed in an oxygen-containing atmosphere, and the oxidation temperature was controlled at 270-300℃ to form β-TeO2 nanosheets through a self-limiting oxidation reaction on the alloy surface. Subsequently, the β-TeO2 nanosheets were deposited on the SiO2 surface of a SiO2 / Si substrate using a rolling transfer process, allowing the nanosheets to spread out and form a β-TeO2 nanosheet functional layer. Increasing the number of rolling transfers improved the coverage continuity of the functional layer and adjusted its effective thickness. After deposition, the sample was dried to improve the adhesion stability between the β-TeO2 nanosheets and the substrate.

[0036] Electrode pattern fabrication: Electron beam photoresist was spin-coated onto the substrate surface with a deposited β-TeO2 nanosheet functional layer and pre-baked. Subsequently, an electron beam lithography process was used to define a pair of spaced-apart electrode patterns above the β-TeO2 nanosheet functional layer. The electrode patterns spanned across both ends of the β-TeO2 nanosheet functional layer, with the β-TeO2 nanosheet region between the two electrodes serving as a horizontal resistive switching channel.

[0037] Metal electrode deposition: After defining the electrode pattern, an Au metal layer is deposited using a metal evaporation process to form the first and second electrodes. After deposition, a stripping process is performed to remove the metal layer in the non-electrode regions, yielding a pair of spaced-apart Au electrodes. These Au electrodes, together with the β-TeO2 nanosheet functional layer, form a horizontally connected memristor of Au / β-TeO2 / Au.

[0038] Device Testing: The fabricated device is connected to a semiconductor parameter testing system. A scanning voltage is applied between the first and second electrodes to test the IV characteristics of the device. In this embodiment, the voltage scan range is -3 V to 3 V, and the test current is approximately distributed in the range of 10 V. -14 A to 10 -9 A. Test results show that the device exhibits repeatable nonlinear conductivity modulation behavior without separate electroforming treatment.

[0039] Results analysis: like Figure 1 As shown, the memristor fabricated in this embodiment adopts a horizontal two-end structure. The device, from bottom to top, includes a Si substrate, a SiO2 insulating layer, a β-TeO2 nanosheet functional layer, and two Au electrodes spaced apart on the β-TeO2 nanosheet functional layer. The two Au electrodes serve as the first electrode and the second electrode, respectively, and the β-TeO2 nanosheet region between them forms a resistive switching channel, thereby forming an Au / β-TeO2 / Au horizontal two-end memristor structure.

[0040] like Figure 2 As shown, the Au / β-TeO2 / Au horizontal-terminal memristor exhibits significant nonlinear electrical transport characteristics in the scanning voltage range of -3 V to 3 V, with current magnitudes spanning 10. -14 A to 10 -9 A, and exhibited a repeatable hysteresis response during multiple scans. These results demonstrate that the β-TeO2 nanosheet functional layer can achieve conductivity modulation under an applied electric field. Since the existing test plots do not separately indicate the high-resistivity and low-resistivity states at a fixed readout voltage, the on / off ratio, SET voltage, and RESET voltage should be further determined based on the original test data.

[0041] like Figure 3As shown, the β-TeO2 nanosheets exhibit a distinct sheet-like morphology under an optical microscope, with lateral dimensions reaching the micrometer level. This indicates that the β-TeO2 nanosheets can be stably distributed on the substrate surface and are suitable for subsequent electrode patterning and horizontal end device construction.

[0042] like Figure 4 As shown, the Raman spectrum of β-TeO2 nanosheets shows a region located at approximately 176 cm⁻¹. - ¹、201 cm - ¹ and 609cm - The characteristic peak at ¹ indicates that β-TeO2 nanosheets can be obtained by alloy surface oxidation, and verifies the phase structure characteristics of the functional layer material.

[0043] In this embodiment, the β-TeO2 nanosheets possess a wide bandgap and high intrinsic resistance, which is beneficial for suppressing off-state leakage current. Simultaneously, defects such as oxygen vacancies in the β-TeO2 nanosheets can migrate and locally aggregate under the influence of an applied electric field, participating in the formation and modulation of conductive channels, thereby enabling the device to exhibit resistive-state modulation behavior. Compared to traditional vertical structure memristors, this embodiment employs a horizontal two-end structure, where the electrode spacing can be controlled via photolithography, facilitating adjustment of the resistive switching channel length and reducing device fabrication difficulty while improving structural observability.

[0044] Example 2 The difference between this embodiment and Embodiment 1 lies in that, within the oxidation temperature range of 270-300 °C, the oxygen-containing atmosphere, oxidation time, or a combination of both are varied to adjust the stoichiometry and oxygen vacancy concentration of the β-TeO2 nanosheets; simultaneously, the effective thickness and coverage continuity of the functional layer are adjusted by changing the number of rolling transfers. When the oxygen vacancy concentration is low, the electric field required to form a low-resistance conductive path increases; when the oxygen vacancy concentration is too high, the off-state leakage current increases. By keeping the oxygen vacancy concentration within a range that allows for reversible migration under an applied electric field without permanent conduction, the resistive state window and conductivity modulation behavior of the device can be controlled.

[0045] This embodiment illustrates that the oxygen-containing atmosphere, oxidation temperature, and oxidation time are mainly used to control the oxidation degree and oxygen vacancy concentration of β-TeO2 nanosheets, while the number of rolling transfers is mainly used to control the effective thickness and coverage continuity of the functional layer. These parameters can be adjusted in conjunction with the electrode spacing to change the oxygen vacancy migration distance, local electric field strength, and resistive switching channel formation conditions. Optionally, during the rolling preparation of the β-TeO2 nanosheet functional layer, 1-5 rolling transfers can be performed to achieve a thickness of 1.5-7.5 nm for the β-TeO2 nanosheet functional layer; more preferably, 2-3 rolling transfers can be performed to achieve a thickness of 3.0-4.5 nm for the β-TeO2 nanosheet functional layer.

[0046] Example 3 The difference between this embodiment and Embodiment 1 is that the effective length of the resistive switching channel in the β-TeO2 nanosheet functional layer is changed by adjusting the spacing between the first and second electrodes. When the electrode spacing is smaller, the path required for oxygen vacancy migration is shortened, which helps to reduce the device turn-on voltage; when the electrode spacing is larger, the path for forming the resistive switching channel increases, which helps to expand the device structure design window.

[0047] This embodiment illustrates that the horizontal two-end structure allows for direct adjustment of the resistive switching channel length through electrode pattern design, thereby enabling control over the device's operating voltage, switching stability, and device consistency. Optionally, the electrode spacing is 0.2-5 μm, preferably 0.5-2 μm, and more preferably 1 μm. At 3 V, the preferred range corresponds to approximately 1.5 × 10⁻⁶. 6 -6×10 6 Average channel electric field V / m.

[0048] Based on the wide bandgap, high intrinsic resistance, and tunable oxygen vacancies of β-TeO2, Examples 2 and 3 propose methods for controlling oxygen vacancy concentration. They also propose methods for controlling the thickness of the functional layer and the spacing between the two electrodes. This is beneficial for achieving coordinated control of oxygen vacancy concentration, effective thickness of the functional layer, and channel length while maintaining a low off-state current, thereby improving flexibility and applicability, reducing randomness, and constructing stable β-TeO2 memristor devices.

[0049] In summary, this embodiment achieves reversible switching of resistive states without electro-induced formation by using β-TeO2 nanosheets as the sole resistive switching functional layer and constructing an Au / β-TeO2 / Au horizontal two-terminal structure. This device features a simple structure, controllable fabrication process, low operating voltage, and high on / off ratio, making it suitable for memristors and neuromorphic computing hardware.

[0050] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A horizontally-terminal memristor based on β-TeO2 nanosheets, characterized in that, The device includes a substrate, a β-TeO2 nanosheet functional layer, and a pair of metal electrodes. The β-TeO2 nanosheet functional layer is disposed on the surface of the substrate. The pair of metal electrodes are spaced apart on the β-TeO2 nanosheet functional layer and serve as a first electrode and a second electrode. The first electrode, the β-TeO2 nanosheet functional layer, and the second electrode together form a horizontally-terminated memristor structure. The β-TeO2 nanosheet functional layer is used to induce oxygen vacancy migration and accumulation under an applied electric field to achieve reversible switching between a high-resistivity state and a low-resistivity state.

2. The horizontally-ended memristor based on β-TeO2 nanosheets as described in claim 1, characterized in that, The substrate is a SiO2 / Si substrate, comprising a Si layer and a SiO2 layer stacked together, and the β-TeO2 nanosheet functional layer is disposed on the surface of the SiO2 layer.

3. The horizontally-ended memristor based on β-TeO2 nanosheets as described in claim 1, characterized in that, Both of the metal electrodes are Au electrodes, and the Au electrodes together with the β-TeO2 nanosheet functional layer form an Au / β-TeO2 / Au horizontal end structure.

4. The horizontally-terminal memristor based on β-TeO2 nanosheets as described in claim 1, characterized in that, The thickness of the β-TeO2 nanosheet functional layer is 1.5-7.5 nm; the spacing between the first electrode and the second electrode is 0.2-5 μm.

5. A method for fabricating a horizontally-terminal memristor based on β-TeO2 nanosheets as described in any one of claims 1-4, characterized in that, include: Provide substrate; β-TeO2 nanosheets are prepared and then fabricated on the surface of the substrate to form a β-TeO2 nanosheet functional layer. A pair of spaced metal electrodes are prepared, such that the pair of metal electrodes and the β-TeO2 nanosheet functional layer together form a horizontally bisected memristor structure.

6. The preparation method according to claim 5, characterized in that, After forming the β-TeO2 nanosheet functional layer, the process further includes drying the substrate and the β-TeO2 nanosheet functional layer to improve the adhesion stability between the β-TeO2 nanosheets and the substrate.

7. The preparation method according to claim 5, characterized in that, β-TeO2 nanosheets were prepared by alloy surface oxidation; β-TeO2 nanosheets were deposited on the substrate surface by roller coating; the pair of metal electrodes were prepared by electron beam lithography and metal evaporation.

8. The preparation method according to claim 7, characterized in that, The preparation of β-TeO2 nanosheets using the alloy surface oxidation method specifically includes: A tellurium selenide eutectic alloy consisting of 5% Te and 95% Se by mass was placed in an oxygen-containing atmosphere, and the oxidation temperature was controlled at 270-300 °C. β-TeO2 nanosheets were formed by utilizing the self-limiting oxidation reaction on the alloy surface.

9. The preparation method according to claim 8, characterized in that, The oxygen-containing atmosphere is air, or a mixture of oxygen and an inert gas. When it is a mixture of oxygen and an inert gas, the volume fraction of oxygen is 20-35%.

10. The preparation method according to claim 7, characterized in that, Also includes: In the process of preparing β-TeO2 nanosheets, the stoichiometry and oxygen vacancy concentration of β-TeO2 nanosheets were adjusted by changing the oxygen-containing atmosphere and / or oxidation time. When β-TeO2 nanosheets are deposited on the substrate surface using a roll coating process, the effective thickness of the β-TeO2 nanosheet functional layer is adjusted by changing the number of roll transfers.

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