Flexible Electrically Tunable Infrared Absorbing Metadevice and Its Preparation Method

Abstract

The present invention discloses a flexible electrically tunable infrared absorption metamaterial device, which includes a flexible support layer, a reflective layer, a phase change material layer, and a metamaterial structure layer arranged in sequence from bottom to top; wherein, the support layer is a flexible mica sheet with a thickness of 5-100 μm; the reflective layer is a metal nano-film with a thickness of 60-1000 nm; the phase change material layer is a phase change material film with dynamically variable optical properties, with a thickness of 50-500 nm; the metamaterial structure layer is an ultra-thin metal nano-disk array with a thickness of 10-100 nm. The ultra-thin metal nano-disk array is composed of sub-wavelength metal nano-disks and can excite surface plasmon resonance in the mid-infrared band. Further, the present invention also provides a preparation method for such a device. The optical response of the flexible electrically tunable infrared absorption metamaterial device disclosed by the present invention can be dynamically regulated by the change of an externally applied current and has a large adjustment range for the mid-infrared light absorption rate.

Description

Technical Field

[0001] The present invention belongs to the fields of dynamic optical metamaterial devices and flexible optical devices, and particularly relates to a flexible electro-controlled infrared absorption metamaterial device based on electro-controlled flexible phase change materials. Background Art

[0002] Phase change materials (such as vanadium dioxide materials, germanium antimony tellurium alloy materials) provide important implementation solutions for the design of dynamic tunable optical metamaterial devices. Based on the significant changes in their optical properties during the phase change process, the optical response of the metamaterial device can be dynamically changed under the action of external excitation. However, the use of phase change materials often requires a relatively high annealing temperature. For example, the reamorphization process of germanium antimony tellurium alloy materials (such as Ge2Sb2Te5, Ge3Sb2Te6, etc.) requires a temperature exceeding 800K, and the preparation of vanadium dioxide (VO2) materials usually requires high-temperature annealing treatment of samples at a temperature exceeding 723K. Due to the requirement of high-temperature stability, the above-mentioned optical phase change materials can usually only be designed on inorganic rigid materials such as glass wafers, silicon wafers, quartz wafers or sapphire wafers, which significantly limits the application of phase change materials in flexible optical metamaterial devices.

[0003] In the past two decades, flexible optical metamaterial devices have developed rapidly. Based on the deformable properties (such as bendability, stretchability, twistability, compressibility, etc.) of flexible substrates under mechanical forces, some flexible optoelectronic detectors, flexible biosensors, and wearable optical devices with excellent performance have been designed and realized. These devices are usually designed on some flexible organic materials, such as polydimethylsiloxane (PDMS), polystyrene (PS), polyimide (PI), polyethylene terephthalate (PET), polyethylene oxide (PEG) or polycarbonate (PC), etc. However, these flexible organic materials do not have thermal stability; they can only maintain stable physical and chemical properties at temperatures below 500K. When the device temperature is too high, these materials will undergo thermal cracking or melting, and cannot maintain stable material properties; this is in contradiction with the use temperature of the phase change materials described above.

[0004] At present, although there are some special methods (such as inkjet printing method or buffer layer method, etc.) that can realize the preparation of phase change material thin films on the above-mentioned flexible organic materials, the phase change material thin films prepared by these methods are often loose and porous, and it is impossible to further design sub-wavelength micro-nano structures above them. Therefore, they cannot be applied to realize dynamically tunable flexible optical metadevices. Therefore, there are still certain difficulties in how to apply metastructures to the flexible phase change material system to realize dynamically tunable flexible optical metadevices. In fact, there is no design scheme for applying metastructures to flexible phase change materials to realize dynamically tunable flexible optical metadevices reported in the literature so far. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a flexible electrically tunable infrared absorption metadevice realized by applying a metastructure to an electrically tunable flexible phase change material, so as to realize a large-range adjustment of the mid-infrared light absorption rate by applying an external current.

[0006] The specific technical solutions of the present invention include:

[0007] Solution 1: A flexible electrically tunable infrared absorption metadevice, comprising a flexible support layer, a reflective layer, a phase change material layer, and a metasructure layer arranged in sequence from bottom to top; the support layer is a flexible mica sheet with a thickness of 5-100 μm; the reflective layer is a metal nano-film with a thickness of 60-1000 nm; the phase change material layer is a phase change material thin film with dynamically variable optical properties, with a thickness of 50-500 nm; the metasructure layer is an ultra-thin metal nano-disk array with a thickness of 10-100 nm, and the ultra-thin metal nano-disk array is composed of sub-wavelength metal nano-disks, which can excite surface plasmon resonance in the mid-infrared band. This flexible electrically tunable infrared absorption metadevice can be connected to an external circuit through electrodes.

[0008] As a preferred solution, the flexible mica sheet is an artificial synthetic fluorophlogopite sheet prepared by mechanical exfoliation.

[0009] As a preferred solution, the reflective layer can be a metal nano-film with high reflectivity such as gold nano-film, silver nano-film, aluminum nano-film, etc.

[0010] As a preferred solution, the phase change material layer can be a phase change material such as vanadium dioxide (VO2), germanium antimony tellurium alloy, etc.

[0011] As a preferred solution, the metal nano-disks can be prepared on the phase change material layer by techniques such as electron beam lithography, ultraviolet lithography, etc.

[0012] As a preferred embodiment, the diameter of the metal nanodisc is 200 - 600 nm, and the thickness is 10 - 100 nm.

[0013] As a preferred embodiment, the metal nanodisc arrays are arranged in a two-dimensional simple square lattice, and the arrangement period is 300 - 1000 nm.

[0014] As a preferred embodiment, the material of the metal nanodisc can be selected from metal materials such as gold, silver, aluminum, and magnesium that can excite surface plasmon resonance. More preferably, the material of the metal nanodisc is gold.

[0015] Embodiment 2: A method, characterized in that it is used to prepare the flexible electro-optically tunable infrared absorption metamaterial device described in any one of Embodiment 1 and its preferred embodiments, and mainly includes the following steps:

[0016] Provide a flexible mica sheet;

[0017] Prepare a reflective layer on the flexible mica sheet;

[0018] Prepare a phase change material layer on the gold nanomembrane;

[0019] Fabricate an ultrathin metal nanodisc array on the phase change material layer by electron beam lithography and ultraviolet lithography processes to form a metamaterial structure layer.

[0020] As a preferred embodiment, the flexible mica sheet is prepared by mechanical exfoliation; the reflective layer is obtained by depositing a metal nanomaterial film on the flexible mica sheet by magnetron sputtering technology; the phase change material layer is obtained by growing a phase change material film on the gold nanomembrane by high-temperature annealing oxidation method.

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

[0022] (1) The present invention innovatively combines the metamaterial structure with the flexible phase change material to realize a flexible electro-optically tunable infrared absorption metamaterial device based on the flexible phase change material; compared with the flexible phase change material film, the introduction of the metamaterial structure can excite surface plasmon resonance in the mid-infrared band, thereby significantly improving the ability of the flexible device to dynamically regulate the optical response.

[0023] (2) Compared with the flexible phase change material film, after innovatively introducing the plasmonic metamaterial structure on the flexible phase change material, through reasonable parameter design of each structural layer, the optical functions of the device can be greatly enriched; for example, the dynamic electro-optically tunable optical response performance of the flexible device can still be maintained stable when the device is in a bent state.

[0024] (3) The flexible electro-controlled infrared absorption metadevice proposed by the present invention can achieve a dynamic change in the optical absorption rate between 20% and 90% at the resonance wavelength position within the working band, with a large dynamic adjustment range.

[0025] (4) The flexible electro-controlled infrared absorption metadevice provided by the present invention operates in the mid-infrared atmospheric transparent window band (wavelength range of 3 - 5 μm), and has good application prospects. Description of the Drawings

[0026] Figure 1 In the figures: (a) is a schematic structural diagram of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention in a bent state; (b) is an optical photograph of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention in a bent state (the scale in the figure represents 10 mm); (c) is an optical micrograph near the metamaterial structure region of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention (the scale in the figure represents 50 μm); (d) is a scanning electron micrograph of the metamaterial structure region of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention (the scale in the figure represents 1 μm).

[0027] Reference numerals in the drawings: ① - flexible substrate layer, ② - reflective layer, ③ - phase change material layer, ④ - metamaterial structure layer.

[0028] Figure 2 In the figures: (a) is the measurement result of the absorption spectrum of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention in a flat state varying with the applied current in the 2.85 - 4.85 μm band, and the current value increases from 270 to 300 mA; (b) is the measurement result of the reflection spectrum of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention in a flat state varying with the applied current in the 2.85 - 4.85 μm band, and the current value increases from 270 to 300 mA; (c) is the variation of the absorption rate and reflection rate of the flexible electro-controlled infrared absorption metadevice in a flat state with the applied current when the incident light wavelength is 3.48 μm; (d) is the measurement result of the absorption spectrum of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention in a bent state varying with the applied current in the 2.85 - 4.85 μm band, and the current value increases from 270 to 300 mA; (e) is the measurement result of the reflection spectrum of the flexible electro-controlled infrared absorption metadevice provided by the embodiment of the present invention in a bent state varying with the applied current in the 2.85 - 4.85 μm band, and the current value increases from 270 to 300 mA; (f) is the variation of the absorption rate and reflection rate of the flexible electro-controlled infrared absorption metadevice in a bent state with the applied current when the incident light wavelength is 3.48 μm.

[0029] Figure 3Chinese: (a) shows the variation of the absorption rate at the resonance wavelength position of the flexible electro-regulated infrared absorption metadevice provided by the embodiment of the present invention in the flat state and several bending states with the curvature radius in the range of 23 - 10 mm. The applied currents are 0 mA (solid line) and 300 mA (dashed line) respectively; (b) shows the experimental results of the relative absorption rate variation of the flexible electro-regulated infrared absorption metadevice provided by the embodiment of the present invention in the flat state and several bending states with the curvature radius in the range of 23 - 10 mm. Specific Embodiment

[0030] Next, we will further elaborate on the present invention in combination with specific embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific design schemes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0031] Embodiment 1:

[0032] As Figure 1 (a) shows, Embodiment 1 discloses a flexible electro-regulated infrared absorption metadevice designed and prepared based on the above electro-regulated flexible phase change material system. Its optical response can be dynamically regulated by the change of the applied current, mainly including a flexible support layer ①, a reflection layer ②, a phase change material layer ③, and a metastructure layer ④ arranged in sequence from bottom to top.

[0033] The flexible support layer ① is a flexible mica sheet prepared by the mechanical exfoliation method. The material of the mica sheet is an artificially synthesized fluorophlogopite sheet, and its thickness distribution is about 10 - 20 μm.

[0034] The reflection layer ② is a gold nanometer thin film deposited on the flexible mica sheet by magnetron sputtering technology, and its thickness distribution is about 90 - 110 nm; this gold nanometer thin film is flat and dense, and has good broadband high reflectivity properties in the mid-infrared band.

[0035] The phase change material layer ③ is a vanadium dioxide material grown on the gold nanometer thin film by high-temperature annealing oxidation method, and its thickness distribution is about 90 - 110 nm; this vanadium dioxide thin film is flat and dense, and the optical properties of the material in the mid-infrared band can change significantly during its phase change process.

[0036] The metastructure layer ④ is an array of metal nanodisks, and its material is gold; the diameter of the metal nanodisks is about 420 - 430 nm, and the thickness distribution is about 15 - 25 nm; the metal nanodisks are arranged in a two-dimensional simple square lattice, and its period is about 680 - 720 nm.

[0037] Figure 1(b) shows the sample optical photograph of the flexible electrically tunable infrared absorption metadevice provided in Embodiment 1 of the present invention in the bent state, demonstrating that the optical metadevice designed and fabricated based on the electrically tunable flexible phase change material system also has good mechanical bendability.

[0038] Figure 1 (c) shows the optical micrograph of the flexible electrically tunable infrared absorption metadevice provided in Embodiment 1 of the present invention near the metamaterial structure region: The square region in the middle of the photograph is the gold nanodisk array, and its side length is about 200 μm.

[0039] Figure 1 (d) shows the scanning electron micrograph of the metamaterial structure region of the flexible electrically tunable infrared absorption metadevice provided in Embodiment 1 of the present invention; it can be seen that the structural parameters of the gold nanodisks are consistent, the thickness is uniform, and there are no obvious defects.

[0040] Figure 2 shows the measurement results of the absorption spectrum and reflection spectrum of the flexible electrically tunable infrared absorption metadevice provided in Embodiment 1 of the present invention under different applied current inputs. Figure 2 (a) and Figure 2 (b) respectively show the measurement results of the absorption spectrum and reflection spectrum of the flexible electrically tunable infrared absorption metadevice provided in the embodiment of the present invention in the flat state in the wavelength range of 2.85 - 4.85 μm varying with the applied current, and the current value increases from 270 to 300 mA. When the current value continuously increases, both the absorption spectrum and reflection spectrum of the device change significantly; and this change has a maximum value at a wavelength of 3.48 μm. Figure 2 (c) shows the variation of the absorption rate and reflection rate of the flexible electrically tunable infrared absorption metadevice in the flat state with the applied current when the incident light wavelength is 3.48 μm. It can be seen that when the applied current value varies between 270 - 300 mA, the absorption rate of the device at a wavelength of 3.48 μm can achieve a dynamic change between 20% and 90%.

[0041] Meanwhile, the flexible electrically tunable infrared absorption metadevice provided in Embodiment 1 of the present invention can still maintain good performance of dynamically changing the electrically tunable infrared absorption spectrum in the bent state. Figure 2 (d) and Figure 2 (e) respectively show the measurement results of the absorption spectrum and reflection spectrum of the flexible electrically tunable infrared absorption metadevice provided in the embodiment of the present invention in the bent state in the wavelength range of 2.85 - 4.85 μm varying with the applied current, and the current value increases from 270 to 300 mA. Compared with Figure 2 (a) and Figure 2 (b), the device still maintains good ability to regulate the absorption spectrum and reflection spectrum of the device through an external current when in the bent state. Figure 2(f) Also shows the changes in the absorption rate and reflectance of the flexible electro-controlled infrared absorption metamaterial device in the bent state with the applied current when the incident light wavelength is 3.48 μm. At this time, the absorption rate of the device at a wavelength of 3.48 μm can still dynamically change between 20% and 90%.

[0042] The experimental results of Example 1 illustrate that the flexible electro-controlled infrared absorption metamaterial device given by the present invention, which is achieved by applying a metamaterial structure to an electro-controlled flexible phase change material, has the function of electro-controlling the change of infrared absorption spectrum in the mid-infrared band; at the same time, the device has good mechanical bendability and can maintain the same electro-control performance as in the flat state when in the bent state; in addition, the device can achieve a dynamic change in the mid-infrared absorption rate between 20% and 90% (wavelength is 3.48 μm), with a large dynamic adjustment range.

[0043] Example 2:

[0044] In this example, flexible electro-controlled infrared absorption metamaterial devices in the flat state and six different bent states are given, and their radius of curvature are infinity (flat state), 23 mm, 18 mm, 15 mm, 13 mm, 11 mm, and 10 mm respectively; other structures and parameters are the same as those in Example 1.

[0045] Based on the results of Example 1, which have illustrated that the flexible electro-controlled infrared absorption metamaterial device of the present invention has the function of electro-controlling the change of infrared absorption spectrum in the mid-infrared band, this example proves that the flexible electro-controlled infrared absorption metamaterial device can maintain stable electro-controlled absorption rate change performance in the bent state with a radius of curvature greater than or equal to 11 mm. Figure 3 (a) Plots the curve of the absorption rate of the metamaterial device changing with the radius of curvature at the resonance wavelength. It can be seen that when the applied current value is 0 mA, at the resonance wavelength, the absorption rate of the sample remains at about 90% (solid line) during the process of the metamaterial device being bent from the flat state to a radius of curvature of 11 mm. And when the applied current value is 300 mA, the curve of the absorption rate of the metamaterial device changing with the radius of curvature at the resonance wavelength is also given in Figure 3 (a) (dashed line). It can be seen that when the radius of curvature of the flexible electro-controlled infrared absorption metamaterial device gradually decreases, the absorption rate of the metamaterial device only increases very slightly. To further prove that the flexible electro-controlled infrared absorption metamaterial device in the present invention has stable electro-controlled absorption rate change performance, we plot the curve of the relative absorption rate change of the device at the resonance wavelength changing with its radius of curvature, as shown in Figure 3 (b). It can be seen that during the process of the metamaterial device being bent from the flat state to a radius of curvature of 11 mm, the relative absorption rate change of the device remains near 86%.

[0046] The experimental results of Example 2 show that by applying the metasurface structure to the electrically tunable flexible phase change material, the flexible electrically tunable infrared absorption metadevice provided by the present invention can maintain the stability of the electrically tunable performance during the process of bending from the self-flattened state to a curvature radius of 11 mm.

[0047] In summary, the present invention discloses a flexible electrically tunable infrared absorption metadevice realized by applying a metasurface structure to an electrically tunable flexible phase change material. The present invention can be widely used in the fields of flexible sensor devices, dynamic invisibility cloaks, and electrically tunable wearable devices.

[0048] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flexible electrically tunable infrared absorption metadevice, characterized in that, It includes a flexible support layer, a reflective layer, a phase change material layer, and a metasurface layer arranged in sequence from bottom to top; the flexible support layer is a flexible mica sheet with a thickness of 5 - 100 μm; the reflective layer is a metal nano-film with a thickness of 60 - 1000 nm; the phase change material layer is a phase change material film with dynamically variable optical properties and a thickness of 50 - 500 nm; the metasurface layer is an ultrathin metal nano-disk array with a thickness of 10 - 100 nm, and the ultrathin metal nano-disk array is composed of sub-wavelength metal nano-disks, which can excite surface plasmon resonance in the mid-infrared band; The diameter of the metal nano-disk is 200 - 600 nm; The metal nano-disks are arranged in a two-dimensional square lattice with a lattice period of 300 - 1000 nm.

2. The flexible electrically tunable infrared absorption metadevice according to claim 1, wherein The flexible mica sheet is an artificially synthesized fluorophlogopite sheet prepared by the mechanical exfoliation method.

3. The flexible electrically tunable infrared absorption metadevice according to claim 1, wherein The reflective layer is any one of a gold nano-film, a silver nano-film, and an aluminum nano-film.

4. The flexible electrically tunable infrared absorption metadevice according to claim 1, wherein The phase change material layer is a vanadium dioxide or germanium antimony telluride alloy material film.

5. The flexible electrically tunable infrared absorption metadevice according to claim 1, wherein The material of the metal nano-disk is any one of gold, silver, aluminum, and magnesium.

6. The flexible electrically tunable infrared absorption metadevice according to claim 5, characterized in that, The material of the metal nano-disk is gold.

7. A method for preparing the flexible electrically tunable infrared absorption metadevice according to any one of claims 1 to 6, characterized in that, It includes the following steps: Provide a flexible mica sheet; Prepare a reflective layer on the flexible mica sheet; Prepare a phase change material layer on the metal nano-film; Prepare an ultrathin metal nano-disk array on the phase change material layer by electron beam lithography or ultraviolet lithography to form a metasurface layer.

8. The method according to claim 7, wherein, The flexible mica sheet is prepared by the mechanical exfoliation method; The reflective layer is obtained by depositing a metal nano-material film on the flexible mica sheet through magnetron sputtering technology; The phase change material layer is obtained by growing a phase change material film on the metal nano-film through high-temperature annealing oxidation method.

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