Anti-oxidation metal film structure and preparation method thereof

Abstract

The invention relates to the technical field of electrochromism, and discloses an anti-oxidation metal film structure and a preparation method thereof. The first transparent conductive oxide layer is positioned on the glass substrate; the metal functional layer is positioned on the first transparent conductive oxide layer; and the second transparent conductive oxide layer is positioned on the metal functional layer. According to the invention, a sandwich structure is provided, and the metal functional layer is completely coated by the two compact transparent conductive oxide layers, so that direct contact between air (oxygen and water vapor) and metal is physically isolated, and the problem that active metal prepared by vacuum magnetron sputtering is easy to oxidize and corrode is solved; the metal film covered with the transparent conductive oxide layer is subjected to heat treatment at the temperature of 300-400 DEG C, and the outer oxide is subjected to structural recombination and densification in the air atmosphere, so that a protective layer with excellent barrier property is formed.

Description

Technical Field

[0001] This invention belongs to the field of electrochromic technology, specifically relating to an anti-oxidation metal thin film structure and its preparation method. Background Technology

[0002] Transparent conductive films are key functional layers in modern optoelectronic devices, widely used in touchscreens, solar cells, electrochromic devices (such as smart windows and auto-dimming rearview mirrors for automobiles), and various display devices. To achieve both high transmittance and low resistance, thin films of metals such as silver and aluminum, or their alloys, are often introduced between transparent conductive oxide layers as highly conductive functional layers. However, these metals (especially reactive metals) are chemically active, and even when prepared using processes such as vacuum magnetron sputtering, their surfaces will gradually oxidize and corrode when exposed to an atmosphere containing oxygen and water vapor for extended periods. Oxidation of the metal layer leads to a significant decrease in its conductivity and reflectivity, thus affecting the optoelectronic performance and long-term reliability of the entire device; in severe cases, it can cause film adhesion failure and peeling, ultimately resulting in complete loss of device function.

[0003] Therefore, how to simultaneously solve the problems of poor environmental stability (easy oxidation) and weak adhesion to the substrate without sacrificing the excellent optoelectronic properties of the metal thin film has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide an anti-oxidation metal thin film structure and its preparation method to solve the performance degradation problem of the core functional layer in existing EC lenses under harsh conditions such as long-term humid heat and high ultraviolet radiation, caused by the instability of the material's own oxidation state or slow oxidation at the interface. This invention aims to improve the environmental stability and reliability of the device under long-term use while maintaining excellent electrochromic performance.

[0005] Based on the above concept, the technical solution adopted by this invention is as follows: According to a first aspect of the present invention, an anti-oxidation metal thin film structure is provided, comprising: Glass substrate; A first transparent conductive oxide layer located on the glass substrate; A metal functional layer located on the first transparent conductive oxide layer; And a second transparent conductive oxide layer located on the metal functional layer.

[0006] In some embodiments, the first transparent conductive oxide layer and the second transparent conductive oxide layer are highly dense thin films formed after heat treatment.

[0007] Optionally, the materials of the first transparent conductive oxide layer and the second transparent conductive oxide layer are any one of indium tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, and fluorine-doped tin oxide.

[0008] Optionally, the material of the metal functional layer is any one of silver, aluminum, or a silver-aluminum alloy.

[0009] In some embodiments, the thickness of the metal functional layer is 10-200 nm.

[0010] In some embodiments, the thickness of both the first transparent conductive oxide layer and the second transparent conductive oxide layer is 20-100 nm. According to a second aspect of the present invention, a method for preparing the metal thin film structure described in any one of the above claims is provided, comprising the following steps: S1. Provide glass substrate; S2. Deposit a first transparent conductive oxide layer on the glass substrate; S3. Deposit a metal functional layer on the first transparent conductive oxide layer; S4. Deposit a second transparent conductive oxide layer on the metal functional layer; S5. Perform heat treatment to densify the first transparent conductive oxide layer and the second transparent conductive oxide layer.

[0011] In some embodiments, the heat treatment in step S5 is performed in an atmospheric environment, with a heat treatment temperature of 300~400°C and a heat treatment time of 60~100 minutes. According to a third aspect of the present invention, an application of a metal thin film structure is provided, which is applied to an anti-oxidation electrochromic device.

[0012] The beneficial effects of this invention are as follows: 1. This invention provides a "sandwich" sandwich structure, in which the metal functional layer is completely covered by two dense transparent conductive oxide layers, which physically isolates the direct contact between air (oxygen, water vapor) and the metal, thus solving the problem of easy oxidation and corrosion of active metals prepared by vacuum magnetron sputtering.

[0013] 2. In this invention, a metal thin film covered with a transparent conductive oxide layer is heat-treated at a temperature of 300-400℃. The outer oxide layer undergoes structural reorganization and densification in the air atmosphere, forming a protective layer with excellent barrier properties. Attached Figure Description

[0014] Figure 1 This is a flowchart of the preparation process of the anti-oxidation metal thin film of the present invention; Figure 2 This is a structural diagram of the present invention. Detailed Implementation

[0015] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0016] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, the technical or scientific terms used in this application should be understood in their ordinary sense by one of ordinary skill in the art to which this invention pertains. The words “a” or “one” and similar terms used in this application specification and claims do not indicate a limitation of quantity, but rather indicate the presence of at least one. “A plurality” means two or more. The words “comprising” or “including” and similar terms mean that the element or object preceding “comprising” or “including” covers the element or object listed following “comprising” or “including” and its equivalents, and does not exclude other elements or objects. The words “connected” or “linked” and similar terms are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect. The words “above” and / or “below” and similar terms are for ease of description only and are not limited to a location or spatial orientation. The singular forms “a,” “the,” and “the” used in this application specification and appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0017] Oxidative corrosion, which occurs when metals come into contact with air, is a significant manifestation of performance degradation caused by chemical reactions with the environmental medium. Taking iron as an example, in humid air, it primarily undergoes electrochemical corrosion: iron atoms lose electrons to become ferrous ions, oxygen gains electrons and reacts with water to form hydroxide ions, which combine to form ferrous hydroxide. This intermediate product is further oxidized to ferric hydroxide, and ultimately transforms into loose rust. Silver, in a sulfur-containing atmosphere, readily reacts with hydrogen sulfide to form silver sulfide, causing its surface to gradually darken and affecting its optical and electrical properties.

[0018] Based on the aforementioned commonalities, in practical applications such as electrochromic car mirrors (whose structure often includes upper and lower lens assemblies), the lower lens assembly often uses a high-reflectivity metal alloy as the functional layer. If this alloy film is directly exposed to the atmospheric environment, it will continuously undergo chemical and electrochemical reactions with oxygen, water vapor, and other elements in the environment, leading to film corrosion, interface deterioration, and ultimately film peeling or failure. Once the reflective function deteriorates or is lost, it will directly cause the entire device's color-changing performance and optical signal to fail normally, seriously affecting the product's reliability and lifespan.

[0019] The technical concept of this invention includes: First, there is a technical problem that existing functional thin films of active metals such as silver and aluminum, prepared by processes such as vacuum magnetron sputtering, will still react with oxygen and water vapor on their surface when exposed to the atmosphere for a long time, leading to oxidation and corrosion. This, in turn, causes a decrease in the conductivity of the thin film, a decrease in reflectivity, and a deterioration in the interface adhesion, ultimately affecting the reliability and service life of the device.

[0020] Secondly, this invention designs a sandwich structure of "transparent conductive oxide / metal / transparent conductive oxide" and, in conjunction with a specific atmospheric heat treatment process, densifies the upper and lower transparent conductive oxide layers at high temperatures, thereby forming a complete, stable, and highly dense oxide protective barrier on the surface of the metal functional layer. This solution fundamentally blocks direct contact between the metal layer and the environment without affecting its original high conductivity and high reflectivity photoelectric properties, significantly improving the film's oxidation resistance and long-term environmental stability.

[0021] Therefore, in order to simultaneously achieve excellent optoelectronic performance and long-term reliable protection of metal thin films, this invention adopts a solution that combines structural design and process innovation. By constructing a dense oxide encapsulation layer on the surface of the metal layer, a balance is achieved between efficient oxidation prevention, strong adhesion, and high performance maintenance.

[0022] This application provides an anti-oxidation metal thin film structure, comprising: Glass substrate; A first transparent conductive oxide layer located on the glass substrate; A metal functional layer located on the first transparent conductive oxide layer; And a second transparent conductive oxide layer located on the metal functional layer.

[0023] This application also provides a method for preparing the above-described metal thin film structure, comprising the following steps: S1. Provide glass substrate; S2. Deposit a first transparent conductive oxide layer on the glass substrate; S3. Deposit a metal functional layer on the first transparent conductive oxide layer; S4. Deposit a second transparent conductive oxide layer on the metal functional layer; S5. Perform heat treatment to densify the first transparent conductive oxide layer and the second transparent conductive oxide layer.

[0024] This invention provides a "sandwich" structure that completely encapsulates the metal functional layer with two dense transparent conductive oxide layers, physically isolating the direct contact between air (oxygen, water vapor) and the metal, thus solving the problem of easy oxidation and corrosion of active metals prepared by vacuum magnetron sputtering. The metal film covered with the transparent conductive oxide layer is heat-treated at a temperature of 300-400℃, and the outer oxide layer undergoes structural reorganization and densification in the air atmosphere, forming a protective layer with excellent barrier properties.

[0025] The metal thin film structure described in this application includes a glass substrate; a first transparent conductive oxide layer on the glass substrate; a metal functional layer on the first transparent conductive oxide layer; and a second transparent conductive oxide layer on the metal functional layer. It is mainly used in optoelectronic devices with stringent requirements for long-term environmental stability and photoelectric performance, such as... Figure 2 As shown.

[0026] In this embodiment, an anti-oxidation metal thin film structure is provided. This structure includes a glass substrate, a first transparent conductive oxide layer, a metal functional layer, and a second transparent conductive oxide layer. The glass substrate provided in step S1 is preferably a soda-lime silicate glass, borosilicate glass, or quartz glass with high surface flatness, and its thickness is typically between 0.5 mm and 3 mm, specifically selected according to the mechanical strength and optical requirements of the final device. Before use, the glass substrate must undergo a rigorous pretreatment process including alkaline solution cleaning, acidic solution neutralization, deionized water rinsing, and high-purity nitrogen drying to ensure that its surface cleanliness and chemical activity meet the requirements for high-quality thin film deposition.

[0027] In this embodiment, the first transparent conductive oxide layer is located on the glass substrate. In step S2, this layer is formed by physical vapor deposition, preferably magnetron sputtering. The main functions of the first transparent conductive oxide layer are: firstly, as a stable interface layer bonded to the glass substrate, its material properties effectively alleviate the internal stress caused by the mismatch in thermal expansion coefficients between the glass and the subsequent metal functional layers; secondly, as a bottom electrode, providing a lateral conductive path for the entire thin film structure; and thirdly, as a substrate for the subsequent deposition of metal functional layers, its surface morphology and chemical state directly affect the nucleation, growth mode, and adhesion of the metal functional layers. The material of the first transparent conductive oxide layer is selected from any one of indium tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, or fluorine-doped tin oxide. Taking the most commonly used indium tin oxide as an example, its thickness is controlled between 20 nanometers and 100 nanometers, preferably 50 nanometers. Within this thickness range, the layer can maintain a transmittance higher than 85% in the visible light band while maintaining its sheet resistance at a low level of 10 to 50 ohms, thereby achieving a good balance between optical transmission and electrical conduction. During the deposition process, by precisely controlling the oxygen partial pressure, sputtering power, and substrate temperature in the sputtering atmosphere, thin films with specific crystal orientation, low defect density, and smooth surfaces can be obtained.

[0028] In this embodiment, the metal functional layer is located on top of the first transparent conductive oxide layer. In step S3, the metal functional layer is deposited. This layer is the core functional unit of the thin film structure, primarily responsible for high electrical conductivity and high optical reflectivity. The material of the metal functional layer is selected from silver, aluminum, copper, and their alloys. When silver is chosen, its highest bulk conductivity among all metals and extremely high reflectivity in the visible and infrared bands are utilized. When aluminum is chosen, its excellent ultraviolet to infrared reflectivity and lower cost are utilized. When copper is chosen, its high conductivity (second only to silver) and cost advantage are utilized. The thickness of the metal functional layer is 10 nanometers to 200 nanometers. If the thickness is less than 10 nanometers, the metal thin film may be difficult to form a continuous and dense layer, exhibiting island-like growth, resulting in extremely high resistance and unstable optical performance. If the thickness exceeds 200 nanometers, although the improvement in conductivity and reflectivity is limited, it will unnecessarily increase material costs and deposition time, and may affect the mechanical stability of the overall structure due to increased internal stress. Preferably, the silver layer has a thickness of 20-50 nanometers, the aluminum layer has a thickness of 80-150 nanometers, and the copper layer has a thickness of 30-70 nanometers. The metal layer is deposited by magnetron sputtering in an inert atmosphere (such as argon). Key process parameters include low sputtering power (to control grain size and surface roughness) and a suitable substrate temperature (typically between room temperature and 150°C) to promote the formation of a dense, smooth metal film with an excellent crystal structure.

[0029] In this embodiment, the second transparent conductive oxide layer is located above the metal functional layer. In step S4, the second transparent conductive oxide layer is deposited. This layer is essentially the same as the first transparent conductive oxide layer in terms of material selection, thickness range, and deposition process. Its core function is to form a complete encapsulation system together with the first transparent conductive oxide layer, completely encapsulating the metal functional layer. This "sandwich" structure physically constructs the first barrier against direct attack from corrosive environmental media (such as oxygen, water vapor, sulfides, etc.) on the metal functional layer. The deposited transparent conductive oxide film is usually amorphous or microcrystalline, and microscopic defects may exist within the film, such as grain boundaries, pores, pinholes, and oxygen vacancies caused by deviations in stoichiometry. These defects can become rapid channels for the penetration and diffusion of corrosive environmental media, leading to slow degradation of the internal metal functional layer over long-term effects. Furthermore, the layers are mainly bonded by physical adsorption and van der Waals forces, resulting in relatively weak interfacial bonding strength, which poses a risk of delamination under thermal or mechanical stress.

[0030] In this embodiment, the method for preparing the metal thin film structure includes a heat treatment step. Step S4 involves heat treating the metal thin film structure to densify the first and second transparent conductive oxide layers. Specifically, a substrate with a complete multilayer film deposited is placed in an atmospheric environment (i.e., air) and heat-treated at a temperature range of 300°C to 400°C for 60 to 100 minutes. The heat treatment provides sufficient diffusion kinetic energy to the atoms or ions in the transparent conductive oxide film. For amorphous films, this process induces a transformation to a crystalline state; for microcrystalline films, it promotes grain growth and recrystallization. This process effectively reduces the number of grain boundaries within the film, narrows the grain boundary width, and promotes the overall relaxation of the film structure to a more stable state, thereby significantly reducing the porosity of the film and increasing its bulk density. During the heat treatment, limited atomic interdiffusion occurs at the interface between the transparent conductive oxide layer and the metal functional layer. This interdiffusion phenomenon forms a compositionally gradual transition layer in the interface region, rather than a sharp physical interface. This transition layer can effectively alleviate the thermal mismatch stress caused by the difference in thermal expansion coefficients of the two materials, and transform the interlayer bonding from mainly relying on weak physical adsorption to partially transforming it into stronger chemical bonding or diffusion bonding, thereby significantly improving interlayer adhesion and overall mechanical integrity.

[0031] The structural design of the glass substrate, first transparent conductive oxide layer, metal functional layer, and second transparent conductive oxide layer provided in this embodiment, through a densification process in an atmospheric environment, produces a metal thin film structure that combines excellent initial photoelectric properties (high conductivity, high transmittance / high reflectance) with outstanding long-term environmental stability. This structure, by forming a dense oxide encapsulation shell, solves the technical challenges of easy oxidation of reactive metals (such as aluminum and copper) and the potential sulfidation or corrosion of noble metals (such as silver) in specific environments, while simultaneously enhancing the overall mechanical reliability and service life of the thin film. The thin film structure described in this invention can be widely applied in electrochromic devices requiring high reliability (such as automotive auto-dimming rearview mirrors and smart windows), high-performance transparent electrodes, low-emissivity coated glass, and other precision optical components.

[0032] Based on the core concept proposed in this invention, those skilled in the art will understand that the protection scope of the "anti-oxidation metal thin film structure" is not limited to the specific materials, parameters, and process steps explicitly listed in the embodiments of the specification. As long as the core technical means of "completely encapsulating the metal functional layer through two layers of transparent conductive oxide and densifying the oxide layer to form a high-barrier encapsulation" is adopted to solve the environmental stability problem of the metal functional layer, then the technical solution falls within the protection scope of this invention.

[0033] Regardless of whether the specific material of the transparent conductive oxide layer is indium tin oxide, aluminum-doped zinc oxide, or other metal oxides that meet the requirements of transparency and conductivity, and regardless of whether its deposition method is magnetron sputtering, pulsed laser deposition, or other physical vapor deposition techniques, such as using different sputtering gas ratios or power densities, all of these constitute equivalent transformations or simple extensions of the transparent conductive oxide layer described in this invention. This design, by changing the specific material system or deposition parameters, further achieves the common functions of transparency, conductivity, and protective encapsulation, and should all be covered by the patent scope of this invention.

[0034] Regardless of whether the specific material of the metal functional layer is pure silver, pure aluminum, copper, or an alloy thereof in any proportion, and regardless of how its thickness is specifically selected within the 10-200 nanometer range defined in the claims, such as optimizing the thickness for different applications (high reflectivity or high conductivity), all these are considered conventional adjustments to the metal functional layer of this invention. This design, by adjusting the composition and thickness of the metal layer, further optimizes its optoelectronic properties to meet the needs of different scenarios, and should be covered by the patent scope of this invention.

[0035] Regardless of whether the densification heat treatment is carried out in an atmosphere, oxygen-enriched air, or an atmosphere with controlled oxygen partial pressure, and regardless of how the specific temperature-time parameter combination is adjusted within the range defined in the claims, such as matching the crystallization temperature for different transparent conductive oxide materials, all of these constitute conventional optimization of the heat treatment process parameters described in this invention. This design, by adjusting the heat treatment atmosphere and process window, further achieves a balance between optimal densification effect and production efficiency of the transparent conductive oxide layer, and should be covered by the patent scope of this invention.

[0036] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. The invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0037] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An anti-oxidation metal thin film structure, characterized in that, include: Glass substrate; A first transparent conductive oxide layer located on the glass substrate; A metal functional layer located on the first transparent conductive oxide layer; And a second transparent conductive oxide layer located on the metal functional layer.

2. The anti-oxidation metal thin film structure according to claim 1, characterized in that, The first transparent conductive oxide layer and the second transparent conductive oxide layer are high-density thin films formed after heat treatment.

3. The anti-oxidation metal thin film structure according to claim 1, characterized in that, The materials of the first transparent conductive oxide layer and the second transparent conductive oxide layer are any one of indium tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, and fluorine-doped tin oxide.

4. The anti-oxidation metal thin film structure according to claim 1, characterized in that, The material of the metal functional layer is any one of silver, aluminum, or a silver-aluminum alloy.

5. The anti-oxidation metal thin film structure according to claim 1, characterized in that, The thickness of the metal functional layer is 10-200 nm.

6. The anti-oxidation metal thin film structure according to claim 1, characterized in that, The thickness of both the first transparent conductive oxide layer and the second transparent conductive oxide layer is 20-100 nm.

7. A method for preparing a metal thin film structure as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Provide glass substrate; S2. Deposit a first transparent conductive oxide layer on the glass substrate; S3. Deposit a metal functional layer on the first transparent conductive oxide layer; S4. Deposit a second transparent conductive oxide layer on the metal functional layer; S5. Perform heat treatment to densify the first transparent conductive oxide layer and the second transparent conductive oxide layer.

8. The method for preparing a metal thin film structure according to claim 7, characterized in that, The heat treatment described in step S5 is carried out in an atmospheric environment, with a heat treatment temperature of 300~400℃ and a heat treatment time of 60~100 minutes.

9. The metal thin film structure prepared by the method according to any one of claims 7-8, characterized in that, It is used in electrochromic devices for oxidation prevention.

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