An electrically visible-infrared response metasurface film and a preparation method thereof

Abstract

The application is based on electrochromic material technology, and particularly relates to an electrochromic visible-infrared response super surface film and a preparation method thereof. The preparation method comprises the following steps: step-by-step magnetron sputtering, depositing a conductive layer, tantalum pentoxide and tungsten oxide film on a substrate in sequence to form a device bottom electrode, a dielectric layer and an electrochromic layer; based on a mask, the film is subjected to a gluing-photolithography process, the electrochromic layer is etched by an argon ion beam to realize super surface pattern preparation; and the film is subjected to an annealing process in an air atmosphere to crystallize the tungsten oxide layer. The application has good visible-infrared compatible response performance, and simultaneously realizes visible color change and high variable emissivity in an infrared wave band (2.5-15 mu m).

Description

Technical Field

[0001] This invention belongs to the field of electrochromic materials technology, specifically relating to an electrochromic visible-infrared responsive metasurface thin film and its preparation method. Background Technology

[0002] Electrochromism refers to the phenomenon where, under the influence of an applied alternating electric field, the optical properties of a material, such as absorptivity, transmittance, or reflectivity, undergo stable and reversible changes due to the insertion and extraction of ions and electrons within the material. This manifests as a stable and reversible change in the material's color or transparency. Traditional electrochromic designs have focused on applications in the ultraviolet-visible-near-infrared (NIR) region, such as smart windows, automotive rearview mirrors, and optical displays. However, with the increasing demand for intelligent control of the infrared light band in recent years, electrochromic materials with infrared emissivity control capabilities, such as tungsten oxide, have begun to be widely studied.

[0003] Based on theoretical foundations such as surface plasmon resonance, impedance matching, and near-field enhancement effects, high absorption of the target incident spectrum can be achieved by designing metastructures of the absorption structure, such as circuit-simulated absorbers, metal nanoparticle surfaces, and metal-dielectric-metal sandwich structures, thus overcoming the intrinsic wavelength absorption limitations of materials. Currently, there are few micro / nanostructure designs for tungsten oxide electrochromic thin films, and most only consider the benefits of large specific surface area, short ion diffusion distance leading to fast response speed and high coloring efficiency, without investigating the application of micro / nanostructures in the infrared electrochromic response of tungsten oxide. Therefore, improving the infrared electrochromic performance of tungsten oxide through metasurface design and preparing electrochromic thin films with high infrared emissivity is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of existing technologies. This invention provides an electro-induced visible-infrared responsive metasurface thin film and its preparation method. By introducing a dielectric layer and designing a tungsten oxide metasurface structure, the emissivity of the thin film in the high infrared emissivity response state is further improved, thereby exhibiting good visible-infrared compatible response performance. This invention has good visible-infrared compatible response performance and simultaneously achieves high emissivity variation in both the visible color-changing and infrared bands (2.5–15 μm).

[0005] The objective of this invention can be achieved through the following methods:

[0006] In a first aspect, the present invention provides a method for preparing an electro-induced visible-infrared responsive metasurface thin film, comprising the following steps:

[0007] S1. Stepwise magnetron sputtering is used to deposit a conductive layer, a tantalum pentoxide layer, and a tungsten oxide thin film sequentially on a non-conductive material substrate to form the bottom electrode, dielectric layer, and electrochromic layer of the device.

[0008] Alternatively, stepwise magnetron sputtering can be used to deposit a tantalum pentoxide layer and a tungsten oxide thin film sequentially on a conductive material substrate to form a dielectric layer and an electrochromic layer.

[0009] S2. The electrochromic layer is photolithographically and developed using a photoresist coating-photolithography process; then the electrochromic layer is etched to remove the photoresist and form a metasurface pattern.

[0010] S3. Anneal the electrochromic layer to crystallize it, thus obtaining an electrochromic visible-infrared responsive metasurface film.

[0011] As one embodiment of the present invention, in step S1, the non-conductive material substrate includes at least one of silicon wafer, BaF2, SiO2, and ITO glass.

[0012] As one embodiment of the present invention, in step S1, the conductive material substrate includes at least one of silver sheet, copper sheet, iron sheet, tin sheet, and aluminum sheet.

[0013] As one embodiment of the present invention, in step S1, the material of the conductive layer is the same as the material of the conductive material substrate, that is, the material of the conductive layer includes at least one of silver sheet, copper sheet, iron sheet, tin sheet and aluminum sheet.

[0014] In one embodiment of the present invention, in step S1, the loading power of the magnetron sputtering is 100-300W.

[0015] In one embodiment of the present invention, in step S1, the magnetron sputtering deposition of the conductive layer is carried out in an argon atmosphere with an argon gas flow rate of 40-70 sccm; the magnetron sputtering deposition of the tantalum pentoxide layer and the tungsten oxide film are carried out in an argon and oxygen atmosphere with an argon and oxygen gas flow rate ratio of 30-60 sccm: 3-4 sccm.

[0016] In step S1 of this invention, the working gas pressure in the magnetron sputtering deposition of tungsten oxide thin film is 4.5-6 mTorr.

[0017] In one embodiment of the present invention, in step S1, the purity of the conductive layer, tantalum pentoxide, and tungsten oxide target used in magnetron sputtering is greater than 99.99%.

[0018] In one embodiment of the present invention, in step S1, the thickness of the conductive layer is 50 nm to 220 nm, the thickness of the tantalum pentoxide layer is 100 nm to 350 nm, and the thickness of the tungsten oxide film is 82 nm to 320 nm. In this invention, increasing the thickness of the tantalum pentoxide layer can improve the emissivity, but an excessively thick tantalum pentoxide layer will reduce the efficiency of the electrochromic reaction and increase the preparation time, making it unsuitable for large-scale production. The emissivity value increases as the thickness of the tungsten oxide layer decreases, but a thinner tungsten oxide layer leads to increased transmittance, resulting in low visible color-changing capability. Therefore, the thicknesses of the conductive layer, tantalum pentoxide layer, and tungsten oxide film in this invention are designed to meet the requirements of impedance matching and surface plasmon resonance excitation, thereby achieving perfect absorption in the target wavelength band.

[0019] In this invention, the bottom electrode, dielectric layer, and electrochromic layer of the device correspond to the conductive layer, tantalum pentoxide layer, and tungsten oxide thin film, respectively.

[0020] As one embodiment of the present invention, in step S2, the method of photoresist coating-photolithography includes: spin-coating photoresist on a tungsten oxide thin film, baking and curing it, then performing mask ultraviolet exposure to transfer the mask pattern onto the photoresist and completing the development.

[0021] Furthermore, the photoresist includes at least one of the positive photoresist AZ5214, S1800, BCI-3511, and AZ50XT. Among them, AZ5214E ​​is a positive / negative reversible photoresist.

[0022] Furthermore, the curing temperature is 95-110℃; the UV exposure time of the mask is 13-15s.

[0023] In one embodiment of the present invention, in step S2, argon ion beam is used for etching, and the etching thickness is the same as the thickness of the electrochromic layer.

[0024] In this invention, the metasurface pattern is prepared by photolithography and development using a mask with a front photolithographic mask pattern; wherein the front photolithographic mask pattern is a periodically arranged regular polygonal pattern.

[0025] As one embodiment of the present invention, in step S2, the metasurface pattern is the same front-side photolithographic mask pattern as the mask.

[0026] In one embodiment of the present invention, in step S3, the annealing process is carried out in an air atmosphere at a temperature of 450-550°C for 2-3.5 hours. In this invention, the annealing process is performed in a muffle furnace.

[0027] Secondly, the present invention also provides an electro-visible-infrared responsive metasurface thin film obtained by the preparation method described above, the thin film comprising a substrate, a conductive layer, a dielectric layer and an electrochromic layer; or, the thin film comprising a substrate, a dielectric layer and an electrochromic layer.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Based on the infrared electrochromic characteristics and refractive index and extinction coefficient variation characteristics of tungsten oxide electrochromic material, this invention designs and optimizes the stacking of tungsten oxide layer-dielectric material layer-metal reflective layer with different thickness combinations according to the principle of circuit simulation absorber and surface plasmon resonance, so as to achieve high infrared absorption effect brought about by impedance matching and surface plasmon resonance excitation under the high emission state of tungsten oxide, and obtain higher overall emissivity performance.

[0030] 2. This invention is based on the principle of surface plasmon resonance and near-field enhancement effect of metamaterial absorbers, and designs metamaterials with regular polygonal periodic units. Due to the propagating plasmon resonance effect of the patterned tungsten oxide array, high absorption is achieved in the infrared band with matched structural parameters, which enhances the interaction between the tungsten oxide electrochromic layer and mid-infrared light in the high-emission state, and further improves the variable emissivity of tungsten oxide in the mid-infrared band.

[0031] 3. The tungsten oxide layer of the present invention serves as an electrochromic layer, placed on the surface of the electrochromic material to meet the requirements of the plasmon resonance effect and achieve absorption changes in the target wavelength band; the tantalum pentoxide layer serves as a dielectric layer, which can effectively achieve the surface plasmon resonance effect with the tungsten oxide layer and the metal layer, and synergistically improve the variable emissivity.

[0032] 4. Compared with traditional electrochromic devices, this invention realizes an electrochromic film with good visible-infrared compatible response performance, which is of great significance to the development of infrared electrochromic films. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0034] Figure 1 This is a sample image of the electro-visible-infrared responsive metasurface thin film in Example 1;

[0035] Figure 2 The X-ray diffraction pattern of the electro-visible-infrared responsive metasurface thin film in Example 1;

[0036] Figure 3 This is a schematic diagram of the structure of the photomask pattern used in Example 1;

[0037] Figure 4 The image shows the emissivity curves of the electro-visible-infrared responsive metasurface film in Example 1 in the faded and colored states within the range of 2.5–15 μm.

[0038] Figure 5 The image shows the emissivity curves of the electro-visible-infrared responsive metasurface film in Comparative Example 1 in the bleached and colored states within the range of 2.5–15 μm. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0040] Example 1

[0041] (1) Using a single-sided polished silicon wafer (crystal orientation 100) as a substrate, aluminum, tantalum pentoxide and tungsten oxide thin films were deposited sequentially by magnetron sputtering. The aluminum, tantalum pentoxide and tungsten oxide targets used for sputtering were all 99.99% pure and 76.2 mm in diameter.

[0042] (2) A 100W DC power supply was applied to the aluminum target, and argon gas was introduced into the sputtering chamber at a flow rate of 60 sccm. A 200nm thick aluminum film was sputtered on the substrate. An RF power supply was used to complete the sputtering of the tantalum pentoxide layer and the tungsten oxide layer on top of the aluminum film. The loading power of the tantalum pentoxide target was 300W, the sputtering atmosphere was argon and oxygen at a flow rate of 30 sccm:3 sccm, and the thickness of the tantalum pentoxide layer was 200nm. The loading power of the tungsten oxide target was 150W, the flow rate was 60 sccm:4 sccm, the working pressure was 5mTorr, and the thickness of the tungsten oxide layer was controlled at 300nm. The sputtering preparation was completed.

[0043] (3) A positive photoresist AZ5214 was spin-coated onto the sputtered film, baked and cured at 100°C, and then subjected to UV exposure for approximately 15 seconds to transfer the mask pattern onto the photoresist. After development, the tungsten oxide layer was etched using an argon ion beam to a thickness of 300 nm. The photoresist was removed, and a front-side photomask pattern identical to the mask was obtained on the tungsten oxide film.

[0044] (4) The film was placed in a muffle furnace and held at 550°C for 3 hours. After completion, the electro-visible-infrared responsive metasurface film was obtained. Sample images are shown below. Figure 1 As shown.

[0045] In this embodiment, the XRD pattern of the thin film is as follows: Figure 2 As shown, the spectrum exhibits sharp peaks with a characteristic peak of maximum intensity at approximately 25°, indicating that the annealed tungsten oxide possesses high crystallinity. The photolithographic mask used in this embodiment has a square structure pattern, with the green shaded area representing the mask pattern. Specific graphic parameters are as follows: Figure 3 As shown.

[0046] The electrochemical performance of this electroluminescent visible-infrared responsive metasurface film was tested using a Wuhan KOST CS310 electrochemical analyzer. 0.1 M PC-LiClO4 was used as the electrolyte, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. Chronoamperometry (CA) was performed on the electroluminescent visible-infrared responsive metasurface film. A voltage ranging from -2 V to +2.5 V was applied and held for 90 s. Analysis showed that the coloring and fading response times of the film were 20.0 s and 10.2 s, respectively, indicating that the electroluminescent visible-infrared responsive metasurface film possesses a high electrochemical reaction rate.

[0047] The infrared emissivity of the electro-visible-infrared responsive metasurface thin film in this embodiment was measured in the wavelength range of 2.5–15 μm. The spectrum of the thin film in the 2.5–15 μm range is shown below. Figure 4 As shown in the figure. Analysis of the infrared spectra indicates that its emissivity in the infrared band of 2.5–15 μm can reach 51.3%.

[0048] Example 2

[0049] ITO conductive glass with a thickness of 1 mm or less and an area of ​​less than 4 inches was selected as the substrate material. The same process parameters as in Example 1 were used to complete the sputtering of tantalum pentoxide and tungsten oxide thin films, metasurface pattern preparation, and thin film annealing. The electro-induced visible-infrared responsive metasurface thin film obtained in this example, due to the use of ITO conductive glass transparent in the visible spectrum, not only possesses the same mid-infrared emissivity capability as in Example 1, but also achieves good transmittance modulation performance in the visible band.

[0050] Comparative Example 1

[0051] The preparation method of this comparative electro-induced visible-infrared responsive metasurface thin film includes the following steps:

[0052] (1) Using a single-sided polished silicon wafer (crystal orientation 100) as a substrate, aluminum, tantalum pentoxide and tungsten oxide thin films were deposited sequentially by magnetron sputtering. The aluminum, tantalum pentoxide and tungsten oxide targets used for sputtering were all 99.99% pure and 76.2 mm in diameter.

[0053] (2) A 100W DC power supply was applied to the aluminum target, and argon gas was introduced into the sputtering chamber at a flow rate of 60 sccm to sputter a 200 nm thick aluminum film onto the substrate. Positive photoresist AZ5214 was spin-coated onto the sputtered aluminum film, baked and cured at 100°C, and then subjected to UV exposure for approximately 15 seconds to transfer the mask pattern onto the photoresist. After development, the aluminum film was etched using an argon ion beam to a thickness of 200 nm. The photoresist was removed, revealing a front-side photomask pattern identical to the original mask on the aluminum film.

[0054] (3) The sputtering of the tantalum pentoxide layer and the tungsten oxide layer on the aluminum film was completed by using an RF power supply. The loading power of the tantalum pentoxide target was 300W, the sputtering atmosphere was argon and oxygen with a flow rate of 30sccm:3sccm, and the thickness of the tantalum pentoxide layer was 200nm. The loading power of the tungsten oxide target was 150W, the flow rate was 60sccm:4sccm, the working pressure was 5mTorr, and the thickness of the tungsten oxide layer was controlled at 300nm. The sputtering preparation was completed.

[0055] (4) The film is placed in a muffle furnace and kept at 550°C for 3 hours. After completion, the electro-visible-infrared responsive metasurface film is obtained.

[0056] The infrared emissivity of the electrochromic thin film obtained in this comparative example was measured in the wavelength range of 2.5–15 μm. The spectrum of the thin film in the 2.5–15 μm range is shown below. Figure 5 As shown in the figure. Analysis of the infrared spectra indicates that its emissivity in the infrared band between 2.5 and 15 μm can reach 38.17%.

[0057] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing an electro-visible-infrared responsive metasurface thin film, characterized in that, The preparation method includes the following steps: S1. Stepwise magnetron sputtering is used to deposit a conductive layer, a tantalum pentoxide layer, and a tungsten oxide thin film sequentially on a non-conductive material substrate to form the bottom electrode, dielectric layer, and electrochromic layer of the device. Alternatively, stepwise magnetron sputtering can be used to deposit a tantalum pentoxide layer and a tungsten oxide thin film sequentially on a conductive material substrate to form a dielectric layer and an electrochromic layer. S2. The electrochromic layer is photolithographically and developed using a photoresist coating-photolithography process; then the electrochromic layer is etched to remove the photoresist and form a metasurface pattern. The photoresist coating-photolithography process includes: spin-coating photoresist onto a tungsten oxide film, curing it, performing mask ultraviolet exposure, transferring the mask pattern onto the photoresist, and completing the development process; The metasurface pattern is a periodically arranged regular polygonal pattern; S3. Anneal the electrochromic layer to crystallize it, thus obtaining an electrochromic visible-infrared responsive metasurface film.

2. The preparation method according to claim 1, characterized in that, In step S1, the non-conductive material substrate includes at least one of silicon wafer, BaF2, SiO2, and ITO glass.

3. The preparation method according to claim 1, characterized in that, In step S1, the conductive material substrate includes at least one of silver sheet, copper sheet, iron sheet, tin sheet, and aluminum sheet.

4. The preparation method according to claim 1, characterized in that, In step S1, the thickness of the conductive layer is 50 nm to 220 nm, the thickness of the tantalum pentoxide layer is 100 nm to 350 nm, and the thickness of the tungsten oxide film is 82 nm to 320 nm.

5. The preparation method according to claim 1, characterized in that, The curing temperature is 95-110℃; the UV exposure time of the mask is 13-15s.

6. The preparation method according to claim 1, characterized in that, In step S2, etching is performed using an argon ion beam, and the etching thickness is the same as the electrochromic layer thickness.

7. The preparation method according to claim 1, characterized in that, In step S3, the annealing process is carried out in an air atmosphere at a temperature of 450-550°C for 2-3.5 hours.

8. An electro-visible-infrared responsive metasurface thin film obtained by the preparation method according to any one of claims 1 to 7.

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