High-reflection tunable optical thin film based on selenium-based phase change material

Abstract

The invention belongs to the field of optical thin films, and particularly relates to a high-reflection tunable optical thin film based on a selenium-based phase change material. The high-reflection tunable optical thin film provided by the invention comprises the following structures which are sequentially stacked from bottom to top: (TD) sTs + 1PTs + 2, T represents a transparent conductive layer, D represents a dielectric layer, and P represents a selenium-based phase change material layer; s represents the number of repeated stacking cycles, and s is a positive integer. According to the optical thin film, the thickness parameter of each layer in the optical thin film and the phase change state of the selenium-based phase change material layer are cooperatively regulated and controlled, so that a color developing device with color selective reflection and spectrum dynamic adjustable characteristics is successfully constructed, and dynamic spectrum regulation and control can be realized in a visible light wave band range; the device has the advantages of high reflectivity, high switching speed, non-volatile state, low power consumption, good device circulation stability and the like.

Description

Technical Field

[0001] The present application belongs to the field of optical films, and more specifically, relates to a high-reflection tunable optical film based on selenium-based phase change materials. Background Art

[0002] Compared with spectral dynamic control technologies such as mechanical deformation and electrochemical reaction, spectral dynamic control based on phase change materials has the advantages of fast response, non-volatility, low power consumption, and flexibility, and shows great application prospects in low-power display terminals, intelligent interactive interfaces, optical information processing and other fields.

[0003] However, there are still two major problems that need to be solved in the spectral dynamic modulation technology based on phase change materials: first, optical devices based on multi-element phase change materials are prone to composition segregation during the material phase change process, resulting in poor device cyclic stability; second, existing optical devices have low device reflectivity due to the large absorption loss of phase change materials in the visible light band.

[0004] Therefore, it is necessary to develop a tunable optical film with high reflectivity for visible light waves and excellent device cyclic stability. Summary of the Invention

[0005] In response to the defects of the existing technology, the purpose of this application is to provide a highly reflective tunable optical film based on selenium-based phase change materials, aiming to solve the problems of existing optical films prepared based on sulfur-based phase change materials, such as large absorption loss in the visible light band, low reflection efficiency of visible light waves, and poor device reliability.

[0006] To achieve the above objectives, in a first aspect, the present application provides a highly reflective tunable optical film based on a selenium-based phase change material, the film comprising a structure stacked sequentially from bottom to top: (TD) s T s+1 PT s+2 , where T represents the transparent conductive layer, D represents the dielectric layer, and P represents the selenium-based phase change material layer; s represents the number of repeated stacking cycles, and s is a positive integer.

[0007] Preferably, in the aforementioned optical film, the bottommost transparent conductive layer and the topmost transparent conductive layer can function as bottom and top electrodes. Applying an electric pulse to the optical film generates Joule heating, thereby heating the selenium-based phase-change material layer and causing it to undergo a phase transition. Furthermore, the topmost transparent conductive layer can also serve as an anti-oxidation layer, preventing the selenium-based phase-change material layer from oxidizing upon contact with air, which could affect the performance of the optical film. This layer also acts as an anti-reflection film, transmitting non-target wavelengths of reflected light to improve the color purity of the target reflected light.

[0008] Preferably, the material of the above-mentioned transparent conductive layer is indium tin oxide and / or aluminum-doped zinc oxide.

[0009] Preferably, the material of the above-mentioned dielectric layer is one or more of silicon dioxide, magnesium fluoride, and aluminum oxide.

[0010] Preferably, the material of the above-mentioned selenium-based phase change material layer is elemental selenium.

[0011] Preferably, the number s of the above-mentioned repeated stacking cycles is 1 to 3.

[0012] Preferably, the number s of the above-mentioned repeated stacking cycles is 2.

[0013] Further preferably, the above-mentioned optical thin film includes a structure stacked in sequence from bottom to top: T1D1T2D2T3PT4; where T1 is the first transparent conductive layer, D1 is the first dielectric layer, T2 is the second transparent conductive layer, D2 is the second dielectric layer, T3 is the third transparent conductive layer, P is the selenium-based phase change material layer, and T4 is the fourth transparent conductive layer.

[0014] Preferably, the thicknesses of the above-mentioned first transparent conductive layer, the second transparent conductive layer, and the third transparent conductive layer are each independently 30 nm to 70 nm.

[0015] Preferably, the thickness of the above-mentioned fourth transparent conductive layer is 60 nm to 150 nm.

[0016] Preferably, the thickness of the above-mentioned dielectric layer is 40 nm to 100 nm.

[0017] Preferably, the thickness of the above-mentioned selenium-based phase change material layer is 40 nm to 70 nm.

[0018] Preferably, the above-mentioned high-reflection tunable optical thin film is applied to a light response sensor, a temperature sensor, and a color display based on its high-reflection characteristics.

[0019] Generally speaking, compared with the prior art, the above technical solutions conceived by this application mainly have the following technical advantages: (1) The high-reflection tunable optical thin film based on selenium-based phase change material provided by this application has a refractive index difference among the transparent conductive layer, the dielectric layer, and the selenium-based phase change material layer, and their mutual overlap forms a dielectric mirror, which can make light of a specific wavelength undergo constructive interference, thereby enhancing the intensity of the reflected light and achieving efficient reflection of light of a specific wavelength. In addition, by applying means such as electrical excitation or laser excitation, the phase state transition of the selenium-based phase change material layer is regulated to achieve dynamic regulation of the reflection spectrum of the optical thin film in the visible light band.

[0020] (2) This application utilizes the cooperative regulation mechanism between the thickness parameters of each layer in the optical thin film and the phase change state of the selenium-based phase change material layer to construct a color display device with both color-selective reflection and spectral dynamic tunability. Among them, by adjusting the thicknesses of the transparent conductive layer, the dielectric layer, and the selenium-based phase change material layer, selective and efficient reflection of the three primary colors of red, green, and blue can be achieved.

[0021] (3) Compared with the existing optical thin films based on chalcogenide phase change materials, the optical thin film provided in this application uses elemental selenium as the functional material for light field regulation, effectively solving the problems of large optical losses in the visible light band of the optical thin film based on chalcogenide phase change materials and compositional segregation during the phase transition process of the phase change material. It has excellent material stability and regulation consistency, and the device stability of the optical thin film is good.

[0022] (4) Compared with spectral dynamic regulation technologies such as mechanical deformation and electrochemical reactions, the optical thin film provided in this application has the advantages of fast response, non-volatility, low power consumption, and flexibility. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of the high-reflection tunable optical thin film based on selenium-based phase change material provided in this application; Figure 2 is a schematic structural diagram of the high-reflection tunable optical thin film based on selenium-based phase change material provided in the embodiment of this application; Figure 3 is the reflection spectrum of the optical thin film provided in Embodiment 1 of this application; Figure 4 is the chromaticity diagram of the optical thin film provided in Embodiment 1 of this application; Figure 5 is the reflection spectrum of the optical thin film provided in Embodiment 2 of this application; Figure 6 is the chromaticity diagram of the optical thin film provided in Embodiment 2 of this application; Figure 7 is the reflection spectrum of the optical thin film provided in Embodiment 3 of this application; Figure 8 is the chromaticity diagram of the optical thin film provided in Embodiment 3 of this application. Detailed Embodiments

[0024] In order to make the objectives, technical solutions, and advantages of this application clearer, the following further elaborates on this application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0025] In the description of the present application, it should be understood that the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In this text, the symbol " / " indicates that the associated objects are in an "or" relationship. For example, A / B means A or B.

[0026] In the specification and claims of the present application, the terms "first", "second", "third", "fourth", etc. are used to distinguish different objects, rather than to describe the specific order of the objects, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0027] In the description of the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly speaking, using words such as "exemplary" or "for example" aims to present relevant concepts in a specific manner.

[0028] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality of" refers to two or more.

[0029] The design idea of the reflection tunable optical thin film provided in the present application is based on a Bragg reflector, which is a multilayer film structure formed by alternately stacking high-refractive-index and low-refractive-index dielectric materials. The optical thickness of each thin film is a quarter of the central wavelength. Its principle is to utilize the interference effect of light at the interfaces of multiple dielectrics to achieve high reflectivity within a specific wavelength range. In order to improve the color purity of the reflected light, the thicknesses of the respective dielectric layers are selectively adjusted, and a dielectric material is covered on the top layer of the reflector as an antireflection film to transmit non-target wavelength reflected light.

[0030] The present application provides a high-reflection tunable optical thin film based on a selenium-based phase change material, as Figure 1 shown, the thin film includes a structure stacked in sequence from bottom to top: (TD) s T s+1 PT s+2 , where T represents a transparent conductive layer, D represents a dielectric layer, and P represents a selenium-based phase change material layer; s represents the number of repeated stacking cycles, and s is a positive integer. Among them, (TD) is a periodic unit of the Bragg reflector, composed of a pair of high-refractive-index film layers and low-refractive-index film layers.

[0031] In some embodiments, the number of repeated stacking cycles s is 1 to 3. When the number of repeated stacking cycles s is 2 to 3, (TD) sThe s layers of transparent conductive layer T are made of the same material or at least two layers of the same material or completely different materials, (TD) s The s dielectric layers D in the embodiment are made of exactly the same material or at least two layers of the same material or completely different materials.

[0032] In a preferred embodiment, the number of repeated stacking periods s is 2. Based on this, the highly reflective tunable optical film based on selenium-based phase change material provided by the present application is as follows: Figure 2 As shown, it includes a structure stacked in sequence from bottom to top: T1D1T2D2T3PT4; wherein T1 is the first transparent conductive layer, D1 is the first dielectric layer, T2 is the second transparent conductive layer, D2 is the second dielectric layer, T3 is the third transparent conductive layer, P is a selenium-based phase change material layer, and T4 is the fourth transparent conductive layer.

[0033] In the optical film provided in the present application, there is a refractive index difference between the transparent conductive layer, the dielectric layer and the selenium-based phase change material layer, which overlap with each other to form a dielectric reflector, which can cause constructive interference of light of a specific wavelength, thereby enhancing the intensity of the reflected light and achieving efficient reflection of light of a specific wavelength.

[0034] In some embodiments, the thicknesses of the transparent conductive layer, dielectric layer, and selenium-based phase-change material layer are determined based on the materials used for each layer, their refractive index, and the target wavelength of reflected light. By adjusting the thickness of each thin film layer, the present application can adjust the device's reflection color within the visible light range. As the thickness of each thin film layer increases, the reflection peak shifts toward longer wavelengths.

[0035] In some embodiments, the transparent conductive layer is made of indium tin oxide (ITO) and / or aluminum-doped zinc oxide. The bottommost transparent conductive layer and the topmost transparent conductive layer can serve as bottom and top electrodes. Applying an electric pulse to the optical film generates Joule heating, thereby heating the selenium-based phase-change material layer and causing it to undergo a phase transition. Furthermore, the topmost transparent conductive layer can serve as an anti-oxidation layer, preventing the selenium-based phase-change material layer from oxidizing upon contact with air, which could affect the performance of the optical film. It also acts as an anti-reflection film, transmitting non-target wavelengths of reflected light to improve the color purity of the target reflected light. The thicknesses of the first, second, and third transparent conductive layers are each independently between 30 nm and 70 nm; the thickness of the fourth transparent conductive layer is between 60 nm and 150 nm. Excessively thin or thick fourth transparent conductive layers can result in reduced reflectivity or the formation of double peaks, affecting the intensity and color purity of the reflected light.

[0036] In some embodiments, the material of the above-mentioned dielectric layer is one of silicon dioxide (SiO2), magnesium fluoride (MgF2), and aluminum oxide (Al2O3). Its refractive index is lower than that of the material of the above-mentioned transparent conductive layer, and it can be used as the low-refractive-index film layer of the dielectric mirror. The material of the above-mentioned transparent conductive layer is used as the high-refractive-index film layer of the dielectric mirror. In some embodiments, the thicknesses of the above-mentioned first dielectric layer and the above-mentioned second dielectric layer are each independently 40 nm to 100 nm.

[0037] In some embodiments, the above-mentioned selenium-based phase change material layer uses elemental selenium as the functional material for optical field dynamic regulation. This material exists in a crystalline state and an amorphous state. By electrical pulse excitation or laser pulse excitation, the phase state of this material can be controlled to switch, thereby regulating its refractive index and extinction coefficient, and realizing spectral dynamic regulation in the visible light band. Specifically, when the selenium-based phase change material layer is in an amorphous state, the optical thin film reflects incident light in a specific wavelength range and has good wavelength selectivity; when the selenium-based phase change material layer is controlled to change from an amorphous state to a crystalline state, its refractive index decreases, resulting in the breaking of the constructive interference condition formed in the amorphous state, and the peak position of the reflected light spectrum moves towards the short-wave direction.

[0038] Compared with the optical thin film based on chalcogenide phase change materials, the optical thin film based on selenium-based phase change materials provided in this application has lower optical loss in the visible light band, a lower phase change temperature threshold, and no component segregation phenomenon during the phase state transition of the selenium-based phase change material layer. It has excellent material stability and regulation consistency, and the optical thin film has good cycle stability and high reliability. In some embodiments, the thickness of the above-mentioned selenium-based phase change material layer is 40 nm to 70 nm.

[0039] It can be understood that this application does not limit the technology for preparing the above-mentioned optical thin film, and it can be any one of deposition and coating. Among them, the deposition technology includes physical vapor deposition and chemical vapor deposition. For example, but not limited to, layer-by-layer deposition on the substrate by radio frequency magnetron sputtering or thermal evaporation. In some embodiments, magnetron sputtering is performed under a protective atmosphere. The above-mentioned protective atmosphere includes but is not limited to argon, helium, neon, krypton, etc.

[0040] In some embodiments, before layer-by-layer coating on the substrate, the substrate is also pre-treated. Among them, the above-mentioned pre-treatment includes but is not limited to ultrasonic cleaning. For example, the substrate is ultrasonically cleaned with acetone, alcohol, and deionized water in sequence, and after cleaning, it is blown clean with nitrogen to obtain a pre-treated substrate.

[0041] In some embodiments, the material of the above-mentioned substrate can be but is not limited to silicon dioxide.

[0042] In summary, the highly reflective tunable optical thin film based on selenium-based phase change material provided by this application utilizes the collaborative control mechanism of the thickness parameters of each layer and the phase change state of the selenium-based phase change material layer to construct a color display device with both color-selective reflection and spectral dynamic tunability. It realizes dynamic spectral regulation in the visible light band range, has the advantages of high reflectivity, fast switching speed, non-volatile state, low power consumption, and good device cycle stability, effectively solving the problems of large optical loss of existing optical thin films in the visible light band and high nucleation randomness and easy occurrence of composition segregation during the phase transition process of phase change materials. The highly reflective tunable optical thin film provided by this application has broad application prospects in the fields of low-power display terminals, intelligent interaction interfaces, optical information processing, etc.

[0043] On the other hand, this application also provides the application of the above-mentioned highly reflective tunable optical thin film in optical response sensors, temperature sensors, and color displays.

[0044] It should be understood that materials with the same or similar types, models, qualities, properties, or functions as the reagents and instruments used in the following embodiments can be used to implement this application. The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0045] The following are examples: Example 1 This example provides a highly reflective tunable optical thin film based on selenium-based phase change material. Its structural schematic diagram is as Figure 2 shown. A first transparent conductive layer T1, a first dielectric layer D1, a second transparent conductive layer T2, a second dielectric layer D2, a third transparent conductive layer T3, a selenium-based phase change material P, and a fourth transparent conductive layer T4 are sequentially arranged from bottom to top on a transparent substrate. Among them, the transparent substrate uses silicon dioxide (SiO2), the first / second / third / fourth transparent conductive layers use indium tin oxide (ITO), the first / second dielectric layers use silicon dioxide (SiO2), and the selenium-based phase change material layer uses elemental selenium (Se). The thicknesses of the first / second / third transparent conductive layers are all 45 nm, the thickness of the fourth transparent conductive layer is 80 nm, the thicknesses of the first / second dielectric layers are all 65 nm, and the thickness of the selenium-based phase change material layer is 45 nm.

[0046] By applying an electrical pulse or a laser pulse, the selenium-based phase change material layer in the highly reflective tunable optical thin film is changed from the amorphous state to the crystalline state. The reflection spectrum of the highly reflective tunable optical thin film provided by this example is calculated using Essential Macleod simulation software (as Figure 3 shown, where a and c respectively represent the amorphous state and the crystalline state of the selenium-based phase change material layer). The chromaticity diagram is obtained through reflection spectrum processing ( Figure 4, using the CIE1931 standard colorimetric system). After calculation, when the selenium-based phase change material layer is in the amorphous state, the high-reflectivity band of the device corresponds to the blue light band, the peak reflectivity is higher than 50%, and it appears blue on the chromaticity diagram; when the selenium-based phase change material layer is in the crystalline state, the high-reflectivity band of the device moves to the short wave, the peak position moves about 40 nm, the peak reflectivity is higher than 70%, and it appears purple on the chromaticity diagram. That is, the high-reflectivity tunable optical thin film based on the selenium-based phase change material provided in this embodiment can switch between selectively reflecting blue and purple.

[0047] Example 2 This embodiment provides a high-reflectivity tunable optical thin film based on a selenium-based phase change material, and its structural schematic diagram is as Figure 2 shown. A first transparent conductive layer T1, a first dielectric layer D1, a second transparent conductive layer T2, a second dielectric layer D2, a third transparent conductive layer T3, a selenium-based phase change material P, and a fourth transparent conductive layer T4 are sequentially arranged from bottom to top on a transparent substrate. Among them, the transparent substrate uses silicon dioxide (SiO2), the first / second / third / fourth transparent conductive layers use indium tin oxide (ITO), the first / second dielectric layers use silicon dioxide (SiO2), and the selenium-based phase change material layer uses elemental selenium (Se). The thicknesses of the first / second / third transparent conductive layers are all 55 nm, the thickness of the fourth transparent conductive layer is 100 nm, the thicknesses of the first / second dielectric layers are all 75 nm, and the thickness of the selenium-based phase change material layer is 50 nm.

[0048] By applying an electrical pulse or a laser pulse, the selenium-based phase change material layer in the high-reflectivity tunable optical thin film is changed from the amorphous state to the crystalline state. The reflection spectrum of the high-reflectivity tunable optical thin film provided in this embodiment is calculated using Essential Macleod simulation software (as Figure 5 shown, where a and c respectively represent the amorphous state and the crystalline state of the selenium-based phase change material layer), and a chromaticity diagram is obtained through reflection spectrum processing ( Figure 6 ). After calculation, when the selenium-based phase change material layer is in the amorphous state, the high-reflectivity band of the device corresponds to the green light band, the peak reflectivity is higher than 50%, and it appears green on the chromaticity diagram; when the selenium-based phase change material layer is in the crystalline state, the high-reflectivity band of the device moves to the short wave, the peak position moves about 50 nm, the peak reflectivity is higher than 70%, and it appears blue on the chromaticity diagram. That is, the high-reflectivity tunable optical thin film based on the selenium-based phase change material provided in this embodiment can switch between selectively reflecting green and blue.

[0049] Example 3 This embodiment provides a high-reflectivity tunable optical thin film based on a selenium-based phase change material, and its structural schematic diagram is as Figure 2As shown, a first transparent conductive layer T1, a first dielectric layer D1, a second transparent conductive layer T2, a second dielectric layer D2, a third transparent conductive layer T3, a selenium-based phase change material P, and a fourth transparent conductive layer T4 are sequentially arranged from bottom to top on a transparent substrate. Among them, the transparent substrate uses silicon dioxide (SiO2), the first / second / third / fourth transparent conductive layer uses indium tin oxide (ITO), the first / second dielectric layer uses silicon dioxide (SiO2), and the selenium-based phase change material layer uses elemental selenium (Se). The thicknesses of the first / second / third transparent conductive layers are all 65 nm, the thickness of the fourth transparent conductive layer is 130 nm, the thicknesses of the first / second dielectric layers are all 95 nm, and the thickness of the selenium-based phase change material layer is 60 nm.

[0050] By applying an electrical pulse or a laser pulse, the selenium-based phase change material layer in the high-reflection tunable optical thin film is changed from an amorphous state to a crystalline state, and the reflection spectrum of the high-reflection tunable optical thin film provided in this embodiment is calculated using Essential Macleod simulation software (as Figure 7 shown, where a and c respectively represent the amorphous state and the crystalline state of the selenium-based phase change material layer), and a chromaticity diagram is obtained through reflection spectrum processing ( Figure 8 ). Through calculation, when the selenium-based phase change material layer is in the amorphous state, the high-reflectivity band of the device corresponds to the red light band, the peak reflectivity is higher than 50%, and it appears red on the chromaticity diagram; when the selenium-based phase change material layer is in the crystalline state, the high-reflectivity band of the device moves to the short wave, the peak position moves about 60 nm, the peak reflectivity is higher than 65%, and it appears yellow on the chromaticity diagram, that is, the high-reflection tunable optical thin film based on the selenium-based phase change material provided in this embodiment can switch between selectively reflecting red and yellow.

[0051] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A highly reflective tunable optical thin film based on selenium-based phase change materials, characterized in that The thin film includes a structure stacked sequentially from bottom to top: (TD) s T s+1 PT s+2 , where T represents a transparent conductive layer, D represents a dielectric layer, P represents a selenium-based phase change material layer; s represents the number of repeated stacking cycles, and s is a positive integer.

2. The highly reflective tunable optical thin film according to claim 1, wherein The material of the transparent conductive layer is indium tin oxide and / or aluminum-doped zinc oxide.

3. The highly reflective tunable optical thin film according to claim 1, characterized in that, The material of the dielectric layer is one or more of silicon dioxide, magnesium fluoride, and aluminum oxide.

4. The highly reflective tunable optical thin film according to claim 1, wherein The material of the selenium-based phase change material layer is elemental selenium.

5. The highly reflective tunable optical thin film according to any one of claims 1 to 4, characterized in that, The number s of the repeated stacking periods is 1 to 3.

6. The highly reflective tunable optical thin film according to claim 5, wherein The number s of the repeated stacking periods is 2; The thin film includes a structure stacked in sequence from bottom to top: T1D1T2D2T3PT4; where T1 is the first transparent conductive layer, D1 is the first dielectric layer, T2 is the second transparent conductive layer, D2 is the second dielectric layer, T3 is the third transparent conductive layer, P is the selenium-based phase change material layer, and T4 is the fourth transparent conductive layer.

7. The highly reflective tunable optical thin film according to claim 6, wherein The thicknesses of the first transparent conductive layer, the second transparent conductive layer, and the third transparent conductive layer are each independently 30 nm to 70 nm; and / or, The thickness of the fourth transparent conductive layer is 60 nm to 150 nm.

8. The highly reflective tunable optical thin film according to claim 1 or 6, characterized in that The thickness of the dielectric layer is 40 nm to 100 nm.

9. The highly reflective tunable optical thin film according to claim 1 or 6, characterized in that, The thickness of the selenium-based phase change material layer is 40 nm to 70 nm.

10. The highly reflective tunable optical thin film according to any one of claims 1 to 9, characterized in that, Based on the application of the high reflection characteristic in a light response sensor, a temperature sensor, and a color display.

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