Chemical vapor deposition preparation method for realizing natural bending VO2 nanowire with controllable curvature radius

Abstract

The invention belongs to the technical field of a VO2 low-dimensional structure growth process, and particularly relates to a chemical vapor deposition preparation method for realizing a natural bending VO2 nanowire with a controllable curvature radius. According to the method, a chemical vapor deposition system formed by a sliding rail type tube furnace is selected, a Si / SiO2 substrate is selected as a substrate, V2O5 powder is taken as a precursor, and controllable preparation of the bent VO2 nanowires with different curvature radiuses is successfully realized by comprehensively regulating and controlling growth parameters of chemical vapor deposition (CVD); the bottleneck that only conventional linear VO2 nanowires can be prepared through an existing chemical vapor deposition method is broken through. The bent VO2 nanowires with different curvature radiuses, which are prepared by the method disclosed by the invention, are relatively high in quality, good in crystallinity and uniformity, excellent in MIT characteristic and special in mechanical property. The method has the advantages of simplicity in operation, high repeatability, no toxic waste gas emission and the like, and is beneficial to large-scale popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of VO2 low-dimensional structure growth processes, and particularly relates to a chemical vapor deposition preparation method for realizing naturally curved VO2 nanowires with a controllable radius of curvature. Background Art

[0002] Vanadium dioxide (VO2) is a functional material with excellent metal-insulator phase transition characteristics (MIT). VO2 has the excellent characteristic that its phase transition temperature is close to room temperature. Within a certain temperature range, VO2 can achieve the mutual transformation between the low-temperature insulating phase and the high-temperature metallic phase. During the transformation process, the crystal lattice structure of VO2 undergoes the mutual transformation between the monoclinic structure (insulating phase) and the rutile structure (metallic phase), and significant changes in optical, electrical, and magnetic properties will occur during this process, among which the resistance change amplitude can reach 3 to 5 orders of magnitude. Due to the excellent MIT characteristics of VO2, it has important application potential in the fields of intelligent materials, flexible electronic devices, sensors, and optical regulation. For example, in intelligent windows, VO2 can automatically adjust the transmitted heat according to the change of the external temperature; in the optoelectronic field, the MIT characteristics of VO2 can be used to develop new optical switch devices; in the sensor field, VO2 is widely used in sensor development because of its sensitive response to external stimuli such as temperature, pressure, and electric field. In short, VO2 shows great application potential in multiple fields by virtue of its unique MIT characteristics. With the progress of nanoscience and technology and materials science, the performance of VO2 can be improved by further regulating its nanostructure through optimizing the growth method, opening up broad prospects for its application in future intelligent materials and devices.

[0003] In recent years, VO2 nanowires have attracted extensive attention due to their high specific surface area, good single-crystal structure, excellent mechanical properties, and electron transport characteristics. Compared with VO2 thin films and bulk materials, VO2 nanowires have higher surface energy and more surface active sites, thus having better optoelectronic properties and stronger thermal and electrical responses. Compared with traditional straight VO2 nanowires, bent VO2 nanowires have richer mechanical properties and MIT characteristics, etc. Secondly, bent VO2 nanowires not only exhibit unique morphological characteristics but also possess the ability to regulate local stress and mechanical properties, which provides new possibilities for the mechanical-electrical coupling effect in flexible devices. However, the current research on the formation mechanism of the bent morphology of VO2 nanowires and the regulation methods is still insufficient. Especially, there is still a lack of systematic theoretical and technical guidance on how to control their bending degree under different preparation conditions. At the same time, the current technical means have limited control accuracy for this bent morphology and are difficult to meet the requirements of flexible electronic devices for high-performance and highly controllable materials. Therefore, it is of great significance to develop a preparation method that can precisely regulate the morphology of bent VO2 nanowires. This method not only helps to reveal the formation mechanism of the bent morphology of nanowires but also is expected to provide new materials and design ideas for fields such as flexible electronics, strain sensors, and optical regulation. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the present invention proposes a chemical vapor deposition preparation method for realizing naturally bent VO2 nanowires with a controllable radius of curvature. This method can achieve the controllable growth of bent VO2 nanowires with different radii of curvature by comprehensively controlling the quenching temperature and holding time. Moreover, the naturally bent VO2 nanowires prepared by this method have excellent MIT characteristics and special mechanical properties.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of the present invention provides a chemical vapor deposition preparation method for realizing naturally bent VO2 nanowires with a controllable radius of curvature. This method includes the following steps:

[0007] S1. Select a CVD system with a rail-type tube furnace as the main body, use a Si / SiO2 substrate, and use V2O5 powder as the precursor. Place the precursor and the substrate on the left and right sides of the central heat source of the CVD tube furnace at a distance of 2 - 4 cm, and make the distance between the precursor and the substrate 4 - 8 cm;

[0008] S2. Raise the temperature in the tube furnace to the target temperature of 800 - 900 °C at a heating rate of 7 - 15 °C / min and hold for 2 - 5 h. Set the deposition pressure to 2000 - 2500 Pa during the heating process, and adjust the pressure to 750 - 810 Pa during the holding process;

[0009] S3. After the heat preservation is completed, quickly move the heating center of the rail-type tube furnace away from the vanadium source and the substrate, so that the substrate with grown VO2 is quickly cooled to room temperature to achieve quenching; or, after the heat preservation is completed, first reduce the temperature inside the tube to 500-700 °C, and then quickly move the heating center of the rail-type tube furnace away from the vanadium source and the substrate, so that the substrate with grown VO2 is quickly cooled to room temperature to achieve quenching; finally, complete the growth of the naturally bent VO2 nanowires.

[0010] The present invention realizes the preparation of naturally bent VO2 nanowires by comprehensively regulating conditions such as gas flow rate, the distance between the precursor and the substrate, nucleation-growth temperature, deposition pressure and time, quenching temperature and time, etc. Different from the preparation method of the straight VO2 nanowires grown normally, in the present invention, during the heating process, the deposition pressure is maintained at 2000 Pa - 2500 Pa to effectively increase the concentration of V2O5 vapor in the tube, thereby increasing the number of nucleation sites at the substrate and providing sufficient initial vanadium source for subsequent growth; during the heat preservation process, the deposition pressure inside the tube is reduced to 750 - 810 Pa to effectively inhibit the lateral epitaxial growth of VO2 nanowires, thereby promoting the one-dimensional growth of VO2 nanowires and forming a nanowire structure with a high aspect ratio. At the same time, due to the large difference in the preparation conditions in the two growth stages, the growth orientations of VO2 nanowires in the two processes are different, thus forming a sandwich-like core-shell structure, making the lattice orientations of the central layer and the two sides different, and the central layer and the shell layers on both sides thus have different thermal expansion coefficients. Therefore, due to the thermal expansion difference between the inside and outside caused by the temperature change during the cooling process, the nanowires are promoted to bend. In addition, by controlling the cooling time, the nanowires are bent with different curvature radii, and combined with the quenching process, the temperature of the nanowires drops rapidly, so that the curvature of the nanowires changes differently, and finally the purpose of controlling the size of the curvature radius of the nanowires is achieved.

[0011] Preferably, the distance between the precursor and the substrate is 5 - 7 cm.

[0012] Preferably, the purity of the V2O5 powder ≥ 99.6%.

[0013] Preferably, in S3, after the heat preservation is completed, the temperature inside the tube is reduced to 500 - 700 °C at a rate of 8 - 12 °C / min.

[0014] Preferably, during quenching, the deposition pressure inside the tube is still maintained at 750 - 810 Pa.

[0015] Preferably, the deposition gas in the CVD tube furnace is nitrogen or nitrogen, and the gas flow rate during the growth process ≤ 85 sccm.

[0016] Preferably, before adjusting the air pressure in the CVD tube furnace, the inside of the CVD tube furnace is first evacuated to a vacuum state, and then the furnace pipeline is cleaned with deposition gas for 3 - 5 minutes.

[0017] Preferably, the Si / SiO2 substrate is successively cleaned with acetone, ethanol, and water before use.

[0018] Preferably, the mass of V2O5 grown by the CVD tube furnace at one time is ≤ 450 mg.

[0019] The second aspect of the present invention provides natural bent VO2 nanowires prepared by the preparation method described in the first aspect.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The present invention discloses a chemical vapor deposition preparation method for realizing natural bent VO2 nanowires with controllable radius of curvature. A chemical vapor deposition system composed of a slide rail type tube furnace is selected, an Si / SiO2 substrate is selected as the substrate, and V2O5 powder is used as the precursor. The precursor and the substrate are respectively placed at 2 - 4 cm on the left and right sides of the central heat source of the CVD tube furnace, so that the distance between the precursor and the substrate is 4 - 8 cm; then the temperature in the tube furnace is raised to the target temperature of 800 - 900 °C at a heating rate of 7 - 15 °C / min and kept warm for 2 - 5 h. During the process of slowly raising the temperature to the nucleation growth temperature, the deposition air pressure is set to 2000 - 2500 Pa; during the subsequent heat preservation nucleation growth process, the air pressure in the tube is adjusted to 750 - 810 Pa and maintained until the growth ends. After the heat preservation ends, the tube furnace is quickly moved away from the vanadium source and the substrate, so that the substrate with grown VO2 is quickly cooled to room temperature to achieve quenching, and finally the growth of natural bent VO2 nanowires is completed. By comprehensively regulating conditions such as gas flow rate, the distance between the precursor and the substrate, the air pressure change during the deposition process, deposition time, quenching temperature, and heat preservation time, the present invention successfully realizes the controllable preparation of bent VO2 nanowires with different radii of curvature, breaking through the bottleneck that the existing chemical vapor deposition method can only prepare conventional straight VO2 nanowires; and the bent VO2 nanowires prepared by this method have high quality, good crystallinity and uniformity, and excellent MIT characteristics and special mechanical properties. In addition, the present invention has the advantages of simple process operation, easy parameter control, high repeatability, and no toxic and harmful waste gas emissions, which is conducive to large-scale popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Natural growth bent VO2 nanowires with different radii of curvature (a - f correspond to Examples 1 - 6 respectively);

[0023] Figure 2Raman spectra of VO2 nanowires with different radii of curvature (a-c correspond to Example 1, Example 3, and Example 4 respectively);

[0024] Figure 3 High-resolution transmission electron microscopy image of the bent VO2 nanowires prepared in Example 1;

[0025] Figure 4 Quantitative nano-mechanical properties of the bent VO2 nanowires (a-b correspond to Example 1 and Example 4 respectively);

[0026] Figure 5 Electrical properties of the bent VO2 nanowires (a-b correspond to Example 1 and Example 4 respectively). Detailed implementation manners

[0027] The following further describes the detailed implementation manners of the present invention. It should be noted here that the description of these implementation manners is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the following various implementation manners of the present invention can be combined with each other as long as they do not conflict with each other.

[0028] The experimental methods in the following examples are all conventional methods unless otherwise specified, and the test materials used in the following examples are all available through conventional commercial channels unless otherwise specified.

[0029] Example 1:

[0030] This example provides a chemical vapor deposition preparation method for realizing naturally bent VO2 nanowires with a controllable radius of curvature. A chemical vapor deposition system with a rail-type tube furnace as the main body (Anhui Beike Equipment Technology Co., Ltd., model BTF-1200C-Φ25, hereinafter referred to as CVD tube furnace) is used for the preparation of materials. The specific operation process includes the following steps:

[0031] (1) Substrate selection: Use a Si / SiO2 substrate;

[0032] (2) Substrate cleaning: First, put the substrate into acetone and ultrasonically clean it for 5 minutes to remove surface impurities; then put the substrate into absolute ethanol and ultrasonically clean it for 5 minutes to remove the acetone on the surface; then put the substrate into pure water and ultrasonically clean it for 5 minutes to remove the absolute ethanol on the surface; finally, blow dry the surface of the substrate with dry nitrogen for standby;

[0033] (3) Preparation of the precursor: Select 450 mg of V2O5 powder with a purity of 99.6% as the precursor;

[0034] (4) Preparation before deposition: High-purity nitrogen with a purity of 99.999% is selected as the deposition gas. The prepared substrate and V2O5 powder are respectively placed in a tube furnace. The precursor and the substrate are located 2 cm and 3 cm on the left and right sides of the central heat source of the CVD tube furnace respectively (the distance between the precursor and the substrate is 5 cm). After placing the substrate and V2O5 powder, first use a vacuum pump to pump the air pressure in the tube to vacuum, and then purge the tube with high-purity nitrogen with a flow rate of 300 sccm for 5 minutes. After the cleaning is completed, set the flow rate of high-purity nitrogen to 85 sccm, introduce gas into the tube and adjust the angle valve between the vacuum pump and the tube furnace to keep the air pressure in the tube furnace at 2000 Pa;

[0035] (5) Deposition: Heat the CVD tube furnace to 800 °C at a heating rate of 10 °C / min, and then keep it at 800 °C for 3 hours. During the deposition growth, when the temperature does not reach 800 °C, keep the air pressure in the tube at 2000 Pa; after reaching 800 °C, reduce the deposition pressure to 770 Pa and continue to keep it for 3 hours. After the heat preservation is completed, cool down at a rate of 10 °C / min. When the temperature in the tube drops to 500 °C, quickly move the heating center of the sliding rail type tube furnace away from the vanadium source and the substrate, so that the substrate with grown VO2 is rapidly cooled to room temperature to achieve quenching. During this period, continue to keep the deposition pressure in the tube at 770 Pa. Thus, natural bent VO2 as shown in Figure 1 a is obtained. The curvature radius of the bent VO2 nanowires prepared under this condition is about 18 μm. Its Raman spectrum is as shown in Figure 2 which shows its typical M-phase structure inside; the high-resolution transmission electron microscopy image is as shown in Figure 3 which further shows the lattice structure of its typical M-phase; the quantitative nano-mechanical properties are as shown in Figure 4 a. Its modulus shows a "sandwich" structure with small values in the two side regions and large values in the middle region; the electrical properties are as shown in Figure 5 a. At the beginning (i.e., 40 °C), the current order of magnitude of the VO2 nanowires with a curvature radius of 18 μm is about 10-9 A. When the temperature reaches 126 °C, its conductivity changes significantly by about 4 orders of magnitude.

[0036] Example 2:

[0037] This example provides a chemical vapor deposition preparation method for realizing natural bent VO2 nanowires with a controllable curvature radius. A chemical vapor deposition system with a sliding rail type tube furnace as the main body is selected for material preparation. The specific operation process includes the following steps:

[0038] (1) Substrate selection, substrate cleaning, precursor preparation and preparation before deposition are the same as in Example 1;

[0039] (2) Deposition: Heat the CVD tube furnace to 800 °C at a heating rate of 10 °C / min, and then hold it at 800 °C for 3 h. During the deposition growth, when the temperature has not reached 800 °C, keep the pressure inside the tube at 2000 Pa; after reaching 800 °C, reduce the deposition pressure to 770 Pa and continue to hold for 3 h. After the holding is completed, cool down at a rate of 10 °C / min. When the temperature inside the tube drops to 600 °C, quickly move the heating center of the slide rail type tube furnace away from the vanadium source and the substrate, so that the substrate with VO2 grown on it is rapidly cooled to room temperature to achieve quenching. During this period, the deposition pressure inside the tube is still kept at 770 Pa. Thus, natural bent VO2 as shown in Figure 1 Figure b is obtained. The radius of curvature of the bent VO2 nanowires prepared under this condition is about 30 μm.

[0040] Example 3:

[0041] This example provides a chemical vapor deposition preparation method for realizing natural bent VO2 nanowires with a controllable radius of curvature. A chemical vapor deposition system with a slide rail type tube furnace as the main body is selected for the preparation of materials. The specific operation process includes the following steps:

[0042] (1) The substrate selection, substrate cleaning, precursor preparation, and pre-deposition preparation are the same as those in Example 1;

[0043] (2) Deposition: Heat the CVD tube furnace to 800 °C at a heating rate of 10 °C / min, and then hold it at 800 °C for 3 h. During the deposition growth, when the temperature has not reached 800 °C, keep the pressure inside the tube at 2000 Pa; after reaching 800 °C, reduce the deposition pressure to 770 Pa and continue to hold for 3 h. After the holding is completed, cool down at a rate of 10 °C / min. When the temperature inside the tube drops to 700 °C, quickly move the heating center of the slide rail type tube furnace away from the vanadium source and the substrate, so that the substrate with VO2 grown on it is rapidly cooled to room temperature to achieve quenching. During this period, the deposition pressure inside the tube is still kept at 770 Pa. Thus, natural bent VO2 as shown in Figure 1 Figure c is obtained. The radius of curvature of the bent VO2 nanowires prepared under this condition is about 126 μm. Its Raman spectrum is as shown in Figure 2 Figure b, showing its typical M-phase structure inside.

[0044] Example 4:

[0045] This example provides a chemical vapor deposition preparation method for realizing natural bent VO2 nanowires with a controllable radius of curvature. A chemical vapor deposition system with a slide rail type tube furnace as the main body is selected for the preparation of materials. The specific operation process includes the following steps:

[0046] (1) The substrate selection, substrate cleaning, precursor preparation, and pre-deposition preparation are the same as those in Example 1;

[0047] (2) Deposition: Heat the CVD tube furnace to 800 °C at a heating rate of 10 °C / min, and then keep it at 800 °C for 3 h. During the deposition growth, when the temperature has not reached 800 °C, keep the gas pressure inside the tube at 2000 Pa; after reaching 800 °C, reduce the deposition gas pressure to 770 Pa and continue to keep it for 3 h. After the heat preservation is completed, quickly move the heating center of the slide rail type tube furnace away from the vanadium source and the substrate, so that the substrate with grown VO2 is rapidly cooled to room temperature to achieve quenching. During this period, the deposition gas pressure inside the tube is still kept at 770 Pa. Thus, natural bent VO2 as shown in Figure 1 d is obtained. The VO2 nanowires prepared under this condition are almost all straight lines. Its Raman spectrum is as shown in Figure 2 c, showing its typical M-phase structure inside; the quantitative nano-mechanical properties are as shown in Figure 4 b. Its modulus shows a "sandwich" structure with small values in the two side regions and a large value in the middle region; the electrical properties are as shown in Figure 5 b. When the curvature of the VO2 nanowire increases to ∞, the phase transition temperatures during the heating and cooling processes are 164 °C and 138 °C respectively, which are higher than the phase transition temperature with a curvature of 18 μm. Obviously, the phase transition temperature (including the heating and cooling processes) and the width of the temperature hysteresis window increase with the increase of the curvature radius. The natural bent VO2 nanowires have more excellent MIT characteristics.

[0048] Example 5:

[0049] This example provides a chemical vapor deposition preparation method for realizing natural bent VO2 nanowires with a controllable curvature radius. A chemical vapor deposition system with a slide rail type tube furnace as the main body is selected for the preparation of materials. The specific operation process includes the following steps:

[0050] (1) The substrate selection, substrate cleaning, precursor preparation and pre-deposition preparation are the same as those in Example 1;

[0051] (2) Deposition: Heat the CVD tube furnace to 800 °C at a heating rate of 10 °C / min, and then keep it at 800 °C for 2 h 30 min. During the deposition growth, when the temperature has not reached 800 °C, keep the gas pressure inside the tube at 2000 Pa. After reaching 800 °C, reduce the deposition gas pressure to 770 Pa and continue to keep it for 2 h 30 min. After the heat preservation is completed, quickly move the heating center of the slide rail type tube furnace away from the vanadium source and the substrate, so that the substrate with grown VO2 is rapidly cooled to room temperature to achieve quenching. During this period, the deposition gas pressure inside the tube is still kept at 770 Pa. Thus, natural bent VO2 as shown in Figure 1 e is obtained. The curvature radius of the bent VO2 nanowires prepared under this condition is about 90 μm.

[0052] Example 6:

[0053] This embodiment provides a chemical vapor deposition preparation method for realizing a natural-bent VO2 nanowire with a controllable radius of curvature. A chemical vapor deposition system with a rail-type tube furnace as the main body is selected for material preparation. The specific operation process includes the following steps:

[0054] (1) Substrate selection, substrate cleaning, precursor preparation, and pre-deposition preparation are the same as in Embodiment 1;

[0055] (2) Deposition: Heat the CVD tube furnace to 800 °C at a heating rate of 10 °C / min, and then keep it at 800 °C for 2 h. During the deposition growth period, when the temperature has not reached 800 °C, keep the pressure inside the tube at 2000 Pa; after reaching 800 °C, reduce the deposition pressure to 770 Pa and continue to keep it for 2 h. After the heat preservation ends, quickly move the heating center of the rail-type tube furnace away from the vanadium source and the substrate, so that the substrate with grown VO2 is rapidly cooled to room temperature to achieve quenching. During this period, the deposition pressure inside the tube is still kept at 770 Pa. Thus, natural-bent VO2 as shown in Figure 1 f is obtained. The radius of curvature of the bent VO2 nanowire prepared under this condition is greater than 115 μm.

[0056] It can be seen from Embodiments 1-3 that by utilizing the significant temperature difference between the deposition process and the quenching stage, the thermal expansion coefficients of the center and the side edges of the VO2 nanowire are different. Further, by utilizing the non-uniform thermal expansion during the quenching process, the VO2 nanowire can be promoted to bend, thereby preparing a bent VO2 nanowire. At the same time, the degree of difference in thermal expansion can be regulated by controlling the quenching temperature and quenching time, etc., and further, the regulation of the radius of curvature of the bent VO2 nanowire can be realized. It can be seen from Embodiment 4 and Embodiments 5 and 6 that the heat preservation stage is a key stage for lattice growth and stacking. Appropriately shortening the heat preservation time can lead to insufficiently dense lattice arrangement and stacking, and defects such as dislocations and slips appear, making it more likely to deform under the influence of quenching, and thus a bent VO2 nanowire is prepared.

[0057] In summary, the present invention has successfully realized the controllable preparation of bent VO2 nanowires with different radii of curvature by comprehensively regulating the growth parameters of chemical vapor deposition (CVD) (such as quenching temperature and the duration of the heat preservation process, etc.). The bent VO2 nanowires with different radii of curvature prepared by the method of the present invention have high quality, good crystallinity and uniformity, excellent MIT characteristics and special mechanical properties. Moreover, the present invention has the advantages of simple operation, high repeatability, and no toxic waste gas emissions, which is conducive to large-scale popularization and application.

[0058] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

Claims

1. A chemical vapor deposition preparation method for realizing a naturally curved VO2 nanowire with a controllable radius of curvature, characterized in that It includes the following steps: S1. Select a CVD system with a slide rail type tube furnace as the main body, use a Si / SiO2 substrate, and use V2O5 powder as the precursor. Place the precursor and the substrate on the left and right sides of the central heat source of the CVD tube furnace at a distance of 2 - 4 cm, and make the distance between the precursor and the substrate 4 - 8 cm; S2. Increase the temperature in the tube furnace to the target temperature of 800 - 900 °C at a heating rate of 7 - 15 °C / min and keep it for 2 - 5 h. Set the deposition pressure to 2000 - 2500 Pa during the heating process, and adjust the pressure to 750 - 810 Pa during the heat preservation process; S3. After the heat preservation is completed, quickly move the heating center of the slide rail type tube furnace away from the vanadium source and the substrate, so that the substrate with VO2 grown on it is quickly cooled to room temperature to achieve quenching; or, after the heat preservation is completed, first lower the temperature in the tube to 500 - 700 °C, and then quickly move the heating center of the slide rail type tube furnace away from the vanadium source and the substrate, so that the substrate with VO2 grown on it is quickly cooled to room temperature to achieve quenching; finally, complete the growth of the naturally bent VO2 nanowires.

2. The chemical vapor deposition preparation method of a natural-bending VO2 nanowire with controllable radius of curvature according to claim 1, characterized in that, The distance between the precursor and the substrate is 5 - 7 cm.

3. The chemical vapor deposition preparation method of a natural bent VO2 nanowire with controllable radius of curvature according to claim 1, characterized in that, The purity of the V2O5 powder ≥ 99.6%.

4. A chemical vapor deposition preparation method for realizing a natural bent VO2 nanowire with a controllable radius of curvature according to claim 1, characterized in that, In S3, after the heat preservation is completed, lower the temperature in the tube to 500 - 700 °C at a rate of 8 - 12 °C / min.

5. The chemical vapor deposition preparation method of a natural-curved VO2 nanowire with controllable radius of curvature according to claim 1, characterized in that, During quenching, the deposition pressure in the tube is still kept at 750 - 810 Pa.

6. The chemical vapor deposition preparation method of a natural bent VO2 nanowire with a controllable radius of curvature according to claim 1, characterized in that, The deposition gas in the CVD tube furnace is nitrogen or nitrogen, and the gas flow rate during the growth process ≤ 85 sccm.

7. A chemical vapor deposition preparation method for realizing a natural curved VO2 nanowire with a controllable radius of curvature according to claim 1, characterized in that, Before adjusting the pressure in the CVD tube furnace, first evacuate the CVD tube furnace to a vacuum state, and then clean the furnace pipeline with the deposition gas for 3 - 5 min.

8. The chemical vapor deposition preparation method of a natural bent VO2 nanowire with a controllable radius of curvature according to claim 1, characterized in that, The Si / SiO2 substrate is sequentially cleaned with acetone, ethanol and water before use.

9. The chemical vapor deposition preparation method of a natural bent VO2 nanowire with controllable radius of curvature according to claim 1, characterized in that, The mass of V2O5 grown by the CVD tube furnace each time is 450 mg.

10. The naturally bent VO2 nanowires prepared by the preparation method described in any one of claims 1 - 9.

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