Vanadium dioxide microstructure pattern and laser direct writing preparation method

Abstract

The application discloses a vanadium dioxide microstructure pattern and a laser direct writing preparation method. Firstly, amorphous vanadium dioxide film is prepared on a substrate by reaction magnetron sputtering using a pure V target; then the amorphous vanadium dioxide film is fixed on a laser processing platform; high-temperature effect generated by laser irradiation of the surface of the object is used to perform direct writing annealing on the amorphous vanadium dioxide film; the area subjected to laser direct writing is converted from amorphous vanadium dioxide structure into a vanadium dioxide microstructure pattern with phase transition characteristics; and the shape of the vanadium dioxide microstructure pattern can be directly regulated by a displacement device of the laser processing platform. The direct writing method is simple and efficient, the substrate temperature is low during sputtering, the working pressure and the oxygen-argon ratio span during sputtering are large, and the process is simple and easy to repeat. Laser direct writing annealing can directly write and prepare a vanadium dioxide microstructure pattern with a line width less than 8 microns; the pattern structure can be arbitrarily matched and changed by adjusting the displacement platform; and the preparation process is simple and has low equipment dependence.

Description

Technical Field

[0001] This invention relates to the field of vanadium dioxide microstructure pattern processing and preparation, specifically to a vanadium dioxide microstructure pattern and a laser direct writing preparation method. Background Technology

[0002] In recent years, due to the exacerbated greenhouse effect caused by increased carbon emissions, governments worldwide have proposed plans to reduce carbon emissions and achieve "carbon neutrality." A 2019 report by the International Energy Agency indicated that building-related carbon emissions account for 30% of global carbon emissions, with heating and cooling accounting for over 45% of building-related carbon emissions. Reducing building heating and cooling energy consumption and improving energy efficiency within buildings can effectively reduce carbon emissions. According to the second law of thermodynamics, objects are constantly exchanging heat with their surroundings through conduction, convection, and radiation. The temperature changes of most objects on Earth are closely related to solar radiation. Similarly, the rational use of radiative heat exchange can also regulate building temperature. Radiative cooling materials, which lower the surface temperature of objects by radiating energy into space, are a promising building thermal management material.

[0003] Traditional radiative cooling materials cannot change their emissivity with temperature variations, limiting their use to regions with high average annual temperatures. In high-latitude regions with lower average annual temperatures, these materials can actually increase building heating energy consumption. Given my country's vast latitudinal span and significant north-south climate differences, developing emissivity-tunable radiative cooling materials is more in line with my country's national conditions. Vanadium dioxide (VO2) is well-known for its reversible phase transition from monoclinic to rutile phase. This phase transition can be driven by heat, light, electricity, and stress, and is accompanied by abrupt changes in the material's photoelectric properties before and after the transition. It has enormous application potential in fields such as thermochromic smart windows, threshold switches, and tunable metamaterials. VO2-based tunable radiative cooling devices can improve energy utilization efficiency and reduce energy consumption and related carbon emissions.

[0004] Emissivity-tunable radiative cooling devices based on the phase transition characteristics of VO2 rely on the research foundation of metasurface structures. Metasurface arrays composed of periodically arranged subwavelength unit structures can modulate the electromagnetic properties of the entire metasurface structure by changing its unit structure, thereby modulating the amplitude, phase, and polarization of characteristic electromagnetic waves. By changing parameters such as the shape and size of the vanadium dioxide metasurface structure units, a selective response to 8-14 μm infrared radiation can be achieved, with the absorption coefficient in the corresponding band modulated by the vanadium dioxide phase transition. At low temperatures, the absorption coefficient is low, reducing external radiation energy; at high temperatures, the absorption coefficient is high, enhancing external radiation, thus achieving adjustment of infrared emissivity. However, existing hard mask technology cannot directly fabricate subwavelength metasurface unit structures on thin films, requiring additional photolithography processes. The more complex processes increase fabrication costs, hindering large-scale application in construction.

[0005] This invention starts from the interconversion mechanism of different VO2 crystal phases during annealing and introduces a laser direct writing technique for preparing VO2 microstructure patterns. This technique enables the direct writing of VO2 metasurface structures on the surface of amorphous vanadium oxide thin films, providing technical support for the preparation of radiative cooling devices with tunable emissivity based on the phase transition characteristics of VO2. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing vanadium dioxide microstructure patterns by laser direct writing. The vanadium dioxide microstructure pattern direct writing technology of the present invention has low equipment dependence, simple operation, fewer process steps, and short product cycle.

[0007] The technical solution adopted in this invention is as follows:

[0008] A laser direct writing method for preparing vanadium dioxide microstructure patterns includes the following steps:

[0009] (1.1) An amorphous vanadium oxide thin film is deposited on the substrate in advance by reactive magnetron sputtering;

[0010] (1.2) The prepared amorphous vanadium oxide thin film is transferred to a laser processing platform, and then the laser is used to perform direct writing processing on the surface of the amorphous vanadium oxide thin film. Due to the photothermal effect, the area irradiated by the laser direct writing generates a high temperature environment of more than 400°C locally, completing the annealing process. The final product is a vanadium dioxide microstructure pattern.

[0011] As a preferred embodiment, the substrate is selected from glass substrate, quartz substrate, sapphire substrate, or silicon substrate.

[0012] As a preferred method, in step (1.1), a metal V target with a purity of 99.99% is used as the sputtering source, and an amorphous vanadium oxide thin film is deposited in the substrate temperature range of 20-200℃ using reactive magnetron sputtering. The atomic percentage of V in the vanadium oxide thin film is 30%-70%, and the remainder is oxygen.

[0013] As a preferred embodiment, in step (1.2), the laser has a power greater than 100mW and a spot area less than 50μm. 2 The light spot energy density is greater than 2mW / μm 2 A continuous laser with an output laser wavelength of less than 2μm.

[0014] As a preferred embodiment, the laser processing platform is equipped with a microscopic imaging system and a displacement platform. The microscopic imaging system enables real-time 1000x magnified monitoring of the processing area, and the displacement platform is used for continuous movement at a speed greater than 1μm / s.

[0015] As a preferred embodiment, the laser processing platform fills the laser processing area with a gas, which is selected from air, pure nitrogen, and argon.

[0016] As a preferred embodiment, step (1.1) specifically includes the following steps: ① placing the substrate in a 3.0×10 -2 Pa-1.0×10 -3 In a vacuum environment of Pa;

[0017] ② Under a pure Ar working gas pressure of 5Pa-20Pa, a pure V metal target is pre-sputtered for 10-20 minutes with a sputtering current of 0.3A to remove the surface oxide layer;

[0018] ③ Next, using an atmosphere with an oxygen / argon flow ratio of 1:20-1:90 and a working gas pressure of 0.8Pa-3.0Pa, an amorphous vanadium oxide thin film is deposited on the substrate described in step ①. During sputtering, the substrate temperature is 20℃-200℃, the deposition thickness is 200-400nm, and the vanadium / oxygen atom ratio in the amorphous vanadium oxide thin film is 1:0.5-1:2.3.

[0019] As a preferred method, the prepared amorphous vanadium oxide thin film is transferred to a laser processing platform, the laser power and spot area are set, the amorphous vanadium oxide is directly irradiated with the laser in a predetermined atmosphere, and the annealed vanadium dioxide microstructure pattern is processed using a displacement platform.

[0020] The present invention also provides a vanadium dioxide microstructure pattern, which is prepared by any of the above methods, and the pattern linewidth is less than 8 μm.

[0021] The present invention has the following beneficial effects:

[0022] 1. Amorphous vanadium oxide thin films are prepared by reactive magnetron sputtering. The substrate temperature is low during sputtering, and the working gas pressure and oxygen-argon ratio can vary widely. The process is simple and easy to repeat.

[0023] 2. The annealing atmosphere required for the laser direct writing annealing preparation of vanadium dioxide microstructures in this invention is simple, and the annealing process can be carried out in air without the need for additional vacuum equipment.

[0024] 3. Existing methods for preparing vanadium dioxide microstructure patterns include photolithography and hard mask methods. Both methods require pre-designed mask structures, and one mask can only correspond to one pattern structure. Furthermore, photolithography involves numerous process steps and high preparation costs. Hard mask methods cannot stably prepare microstructures with linewidths below 50 μm. This invention allows for direct writing to prepare vanadium dioxide microstructure patterns with linewidths less than 8 μm. By adjusting the displacement platform, the pattern structure can be arbitrarily combined and varied. The preparation process is simple and has low equipment dependence. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall process for preparing vanadium dioxide microstructure patterns according to the present invention.

[0026] Figure 2 Raman comparison images of the laser-annealed region, the surrounding unannealed amorphous vanadium oxide region, and the monoclinic vanadium dioxide thin film.

[0027] Figure 3 This is a magnified microscope image of the laser-written vanadium dioxide microstructure pattern of the present invention.

[0028] Figure 4 This is an infrared comparison image of the laser-written vanadium dioxide microstructure pattern of the present invention under high temperature and low temperature conditions. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0030] Example 1:

[0031] This embodiment provides a laser direct writing method for preparing vanadium dioxide microstructure patterns, including the following steps:

[0032] (1.1) Prepare a vanadium target with a purity of 99.99% and a quartz substrate. Use the vanadium target as the sputtering source. Dry the cleaned quartz substrate with nitrogen and place it in the substrate holder. After closing the sputtering cavity, evacuate the sputtering cavity to a vacuum of 3.0 × 10⁻⁶. -2At 20 Pa, the argon valve was opened, and the vacuum level of the sputtering chamber was adjusted to 20 Pa. The substrate rotation power supply was turned on. After the atmosphere in the sputtering chamber stabilized, the vanadium target was pre-sputtered at room temperature for 10 minutes at a sputtering current of 0.3 A under a pure Ar working pressure of 20 Pa to remove the surface oxide layer. Then, an atmosphere with an oxygen / argon flow ratio of 1:90 was used to maintain a working pressure of 3.0 Pa in the sputtering chamber. An amorphous vanadium oxide film with a thickness of 400 nm was deposited on the quartz substrate at 20 °C. The vanadium / oxygen atom ratio in the amorphous vanadium oxide film was 1:0.5. After sputtering, the target was allowed to cool naturally for 10 minutes. After the sputtering cathode cooled, the pre-deposited amorphous vanadium oxide film was removed.

[0033] (1.2) The pre-deposited amorphous vanadium oxide thin film is transferred to a laser processing platform equipped with a microscopic imaging system and a displacement platform. The microscopic imaging system provides real-time 1000x magnification monitoring of the processing area, and the displacement platform is used for continuous movement at a speed greater than 1 μm / s. The laser power is adjusted to 100mW, and the spot area is 40 μm. 2 The energy density of the light spot is approximately 2.5 mW / μm. 2 The output laser wavelength is less than 2μm. The laser processing platform's built-in microscopic imaging system is used to locate the laser-directed area. The amorphous vanadium oxide surface is heated and annealed by direct laser illumination, creating a high-temperature environment exceeding 400℃ locally. Using the laser processing platform's displacement platform's preset program, the laser illumination time is set to 5 seconds. A 10×10 circular array of vanadium dioxide (7μm in diameter) is annealed on the amorphous vanadium oxide surface. The entire laser annealing process is carried out at room temperature in air, ultimately yielding a vanadium dioxide microstructure pattern with a linewidth less than 7μm.

[0034] Example 2:

[0035] This embodiment provides a laser direct writing method for preparing vanadium dioxide microstructure patterns, including the following steps:

[0036] (1.1) Prepare a pure vanadium target and a quartz substrate. Install the pure vanadium target as the sputtering source. Dry the cleaned glass substrate with nitrogen and place it in the substrate holder. After closing the sputtering cavity, evacuate the sputtering cavity to a vacuum level of 1.0 × 10⁻⁶. -3At 5 Pa, the argon valve was opened, and the vacuum level of the sputtering chamber was adjusted to 5 Pa. The substrate rotation power supply was turned on. After the atmosphere in the sputtering chamber stabilized, the vanadium target was pre-sputtered at room temperature for 20 minutes at a sputtering current of 0.3 A under a pure Ar working pressure of 5 Pa to remove the surface oxide layer. Then, an atmosphere with an oxygen / argon flow ratio of 1:20 was used to maintain a working pressure of 0.8 Pa in the sputtering chamber. An amorphous vanadium oxide film with a thickness of 200 nm was deposited on the glass substrate at 200 °C. The vanadium / oxygen atom ratio in the amorphous vanadium oxide film was 1:2.3. After sputtering, the target was allowed to cool naturally for 10 minutes. After the sputtering cathode cooled, the pre-deposited amorphous vanadium oxide film was removed.

[0037] (1.2) The pre-deposited amorphous vanadium oxide thin film is transferred to a laser processing platform equipped with a microscopic imaging system and a displacement platform. The microscopic imaging system provides real-time 1000x magnification monitoring of the processing area, and the displacement platform is used for continuous movement at a speed greater than 1 μm / s. The laser power is adjusted to 150 mW, and the spot area is 50 μm. 2 The energy density of the light spot is approximately 3 mW / μm. 2 The output laser wavelength is less than 1μm. The laser platform's built-in magnification imaging system is used to locate the laser direct-light area. The surface of amorphous vanadium oxide is heated and annealed by laser direct writing, generating a high-temperature environment of more than 400°C in a local area. The laser processing platform's displacement system is used to continuously move the amorphous vanadium oxide to adjust the direct writing path and control the pattern shape of the generated vanadium dioxide. The vanadium dioxide microstructure pattern is processed by direct writing on the surface of amorphous vanadium oxide after annealing. The entire laser annealing process is carried out at room temperature in an argon atmosphere.

[0038] Example 3:

[0039] This embodiment provides a laser direct writing method for preparing vanadium dioxide microstructure patterns, including the following steps:

[0040] (1.1) Prepare a pure vanadium target and a silicon substrate. Install the pure vanadium target as the sputtering source. Dry the cleaned silicon substrate with nitrogen and place it in the substrate holder. After closing the sputtering cavity, evacuate the sputtering cavity to a vacuum level of 5.0 × 10⁻⁶. -3 At 10 Pa, the argon valve was opened, and the vacuum level of the sputtering chamber was adjusted to 10 Pa. The substrate rotation power supply was turned on. After the atmosphere in the sputtering chamber stabilized, the vanadium target was pre-sputtered at room temperature for 15 minutes under a pure Ar working pressure of 10 Pa to remove the surface oxide layer. Then, an atmosphere with an oxygen / argon flow ratio of 1:70 was used to maintain a working pressure of 0.8 Pa in the sputtering chamber. An amorphous vanadium oxide film with a thickness of 300 nm was deposited on the silicon substrate at 100 °C. The vanadium / oxygen atom ratio in the amorphous vanadium oxide film was 1:2. After sputtering, the target was allowed to cool naturally for 10 minutes. After the sputtering cathode cooled, the pre-deposited amorphous vanadium oxide film was removed.

[0041] (1.2) The pre-deposited amorphous vanadium oxide thin film is transferred to a laser processing platform equipped with a microscopic imaging system and a displacement platform. The microscopic imaging system provides real-time 1000x magnification monitoring of the processing area, and the displacement platform is used for continuous movement at a speed greater than 1 μm / s. The laser power is adjusted to 100mW, and the spot area is 20 μm. 2 The energy density of the light spot is approximately 5 mW / μm. 2 The laser platform utilizes its built-in magnification imaging system to locate the laser-directed area. The amorphous vanadium oxide surface is heated and annealed by laser direct writing, creating a high-temperature environment exceeding 400°C in a localized area. The laser processing platform's displacement system continuously moves the amorphous vanadium oxide to adjust the direct writing path, controlling the pattern shape of the generated vanadium dioxide. The vanadium dioxide microstructure pattern is then processed by direct writing on the amorphous vanadium oxide surface. The entire laser annealing process is carried out at room temperature in a nitrogen atmosphere, with the nitrogen filling pressure at one standard atmosphere.

[0042] The above embodiments are further illustrations of the present invention, and not intended to limit the scope of the invention. Various modifications and changes can be made without departing from the full scope of the invention.

Claims

1. A method for laser direct writing to prepare vanadium dioxide microstructure patterns, characterized in that... Includes the following steps: (1.1) An amorphous vanadium oxide thin film is deposited on the substrate by reactive magnetron sputtering in advance; step (1.1) specifically includes the following steps: ① Place the substrate at 3.010 -2 Pa-1.010 -3 In a vacuum environment of Pa; ② Under a pure Ar working gas pressure of 5Pa-20Pa, a pure V metal target is pre-sputtered for 10-20 minutes with a sputtering current of 0.3A to remove the surface oxide layer; ③ Next, using an atmosphere with an oxygen / argon flow ratio of 1:20-1:90 and a working gas pressure of 0.8Pa-3.0Pa, an amorphous vanadium oxide thin film is deposited on the substrate described in step ①. The substrate temperature during sputtering is 20℃-200℃, the deposition thickness is 200-400nm, and the vanadium / oxygen atom ratio in the amorphous vanadium oxide thin film is 1:0.5-1:2.

3. (1.2) The prepared amorphous vanadium oxide thin film is transferred to a laser processing platform, and then direct writing processing is performed on the surface of the amorphous vanadium oxide thin film by a laser. Due to the photothermal effect, a high temperature environment of more than 400°C is generated locally in the area irradiated by the laser direct writing, completing the annealing process. The final product is a vanadium dioxide microstructure pattern. In step (1.2), the laser has a power greater than 100mW and a spot area of ​​less than 50μm. 2 The light spot energy density is greater than 2mW / μm 2 A continuous laser with an output laser wavelength of less than 2μm.

2. The laser direct writing method for preparing vanadium dioxide microstructure patterns according to claim 1, characterized in that: The substrate is selected from glass substrate, quartz substrate, sapphire substrate, or silicon substrate.

3. The laser direct writing method for preparing vanadium dioxide microstructure patterns according to claim 1, characterized in that: In step (1.1), a metallic V target with a purity of 99.99% is used as the sputtering source, and an amorphous vanadium oxide thin film is deposited in the substrate temperature range of 20-200℃ using reactive magnetron sputtering. The atomic percentage of V in the vanadium oxide thin film is 30%-70%, and the remainder is oxygen.

4. The laser direct writing method for preparing vanadium dioxide microstructure patterns according to claim 1, characterized in that: The laser processing platform is equipped with a microscopic imaging system and a displacement platform. The microscopic imaging system enables real-time 1000x magnification monitoring of the processing area, and the displacement platform is used for continuous movement at a speed greater than 1μm / s.

5. The laser direct writing method for preparing vanadium dioxide microstructure patterns according to claim 1, characterized in that: The laser processing platform fills the laser processing area with gas, which is selected from air, pure nitrogen, and argon.

6. The laser direct writing method for preparing vanadium dioxide microstructure patterns according to claim 1, characterized in that: The prepared amorphous vanadium oxide thin film was transferred to a laser processing platform. The laser power and spot area were set, and the amorphous vanadium oxide was directly irradiated with the laser in a predetermined atmosphere. The annealed vanadium dioxide microstructure pattern was then processed using a displacement platform.

7. A vanadium dioxide microstructure pattern, characterized in that... The pattern is prepared by the method described in any one of claims 1 to 6, and the line width is less than 8 μm.

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