A vacuum evaporation coating method, evaporation source material and preparation method thereof

Abstract

The present invention provides a vacuum evaporation coating method, an evaporation source material, and a preparation method thereof. The preparation method comprises the following steps: mixing Ta2O5 coarse powder, a first doping source powder containing a first doping element, and a second doping source powder containing a second doping element to obtain a mixed powder; granulating the mixed powder to obtain particle cores; spraying Ta2O5 fine powder with a particle size of 0.1μm-0.5μm on the surface of the particle cores to coat the surface of the particle cores to form core-shell structured particles; and sintering the core-shell structured particles at a multi-stage temperature increase to form a single metastable phase evaporation source material, wherein the evaporation source material has no second phase precipitated Ta2O5. 5‑x Materials, where 0<x<0.2, Ta2O 5‑x The oxygen vacancy concentration in the core region of the material is higher than that in the outer shell region. The solution of the present invention improves the optical performance of the evaporation source while suppressing the splashing phenomenon and improving the surface smoothness of the film.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum evaporation coating materials, and in particular to a vacuum evaporation coating method, an evaporation source material and a preparation method thereof. Background Art

[0002] The rapid development of optical communications, laser processing, and precision optics has placed higher demands on the performance of optical thin films. This is especially true for applications such as filters, reflectors, and spectrometers, which require films with higher refractive index, lower surface roughness, and superior optical stability. Ta2O5 thin films, due to their high refractive index, excellent optical transparency, and chemical stability, have become a key material in the preparation of high-end optical thin films.

[0003] Currently, Ta2O5 thin films are primarily produced using physical vapor deposition methods such as electron beam evaporation. However, existing Ta2O5 evaporation source materials still present numerous challenges in practical applications. For example, during electron beam heating, adsorbed gases and structural defects within the material are released, leading to severe degassing. This often causes the pre-melting process to take longer than four hours, severely impacting production efficiency. Furthermore, bubbles easily form on the material surface during the pre-melting and evaporation stages, inducing spattering. Spattering particles deposit on the film surface, reducing the film's surface finish and increasing its defect density, impacting the performance stability and yield of the final optical device. Summary of the Invention

[0004] In order to solve the above problems, according to a first aspect of the present invention, a method for preparing an evaporation source material for vacuum evaporation coating is provided, comprising the following steps:

[0005] Ta2O5 coarse powder with a particle size of 1 μm-5 μm, a first doping source powder containing a first doping element, and a second doping source powder containing a second doping element are mixed to obtain a mixed powder, wherein the total atomic doping amount of the first doping element and the second doping element is 0.1 at%-1 at%;

[0006] Granulating the mixed powder to obtain particle cores with a particle size of 0.8 mm to 1.2 mm, and then spraying Ta2O5 fine powder with a particle size of 0.1 μm to 0.5 μm on the surface of the particle cores to coat the surface of the particle cores to form core-shell structure particles with a particle size of 2.5 mm to 3.5 mm;

[0007] At an oxygen partial pressure of 10 -5 atm-10 -4 Atm low oxygen partial pressure atmosphere, the core-shell structure particles are subjected to multi-stage temperature rising sintering to form a single metastable phase evaporation source material, the grain size of the evaporation source material is 20nm-50nm and there is no second phase precipitation of Ta2O 5-xMaterials, wherein 0<x<0.2, the Ta2O 5-x The oxygen vacancy concentration in the core region of the material is higher than that in the outer shell region.

[0008] According to a second aspect of the present invention, a vacuum evaporation coating method is provided, comprising the following steps:

[0009] The evaporation source material prepared according to the above preparation method was loaded into the evaporation crucible, and the evaporation chamber was evacuated to 1×10 -4 Pa-5×10 -4 Pa;

[0010] Heating the temperature to 1750°C-1850°C at a heating rate of 1°C / min-6°C / min and keeping the temperature for 1h-2h to pre-melt the evaporation source material;

[0011] The evaporation deposition rate is controlled to be 0.5nm / s-1.5nm / s, and the evaporated particles are deposited on the surface of the substrate at a temperature of 80℃-150℃. Evaporation is stopped after the preset film thickness is reached.

[0012] According to the solution of the embodiment of the present invention, the preparation method of the evaporation source material realizes the improvement from micro-defect control to the overall performance of the evaporation source material through multi-link collaborative design. First, by mixing Ta2O5 coarse powder, the first doping source powder and the second doping source powder, and controlling the total atomic doping amount of the first doping element and the second doping element in the range of 0.1at%-1at%, while effectively controlling the defect type and concentration, it avoids problems such as phase separation, second phase precipitation or increased optical absorption caused by excessive doping. The introduction of the two doping elements induces lattice distortion on the one hand, and indirectly affects the generation and distribution of oxygen vacancies by adjusting the binding energy of oxygen atoms on the other hand, laying the foundation for subsequent defect engineering control. Subsequently, the above-mentioned mixed powder is granulated to obtain a particle core with a particle size of 0.8mm-1.2mm, and Ta2O5 fine powder is sprayed on the surface of the particle core to form core-shell structure particles with a particle size of 2.5mm-3.5mm. The core-shell structure design naturally induces the formation of a radial defect density gradient during the sintering process, achieving the structural characteristics of high oxygen vacancy concentration in the core and low oxygen vacancy concentration in the shell, effectively alleviating the accumulation of thermal stress and improving the stability of the evaporation process. During the sintering process, a low oxygen partial pressure atmosphere is used, combined with a multi-stage heating program, to accurately induce the generation of oxygen vacancies in the Ta2O5 lattice, forming a Ta2O with a stoichiometric ratio close to the ideal state. 5-xphase (0<x<0.2). The low oxygen partial pressure environment avoids structural damage caused by excessive oxygen vacancies, while ensuring that the material maintains a single metastable phase, inhibiting the precipitation of secondary phases such as metallic tantalum or low-valent tantalum oxide, and improving the compositional uniformity and optical stability of the evaporation source material. The staged heating strategy further controls the grain growth process, stabilizing the final grain size at 20nm-50nm, effectively improving the material's density and uniformity, reducing gas escape channels during evaporation, and suppressing splashing and particle shedding.

[0013] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic flow chart showing a method for preparing an evaporation source material for vacuum evaporation coating according to one embodiment of the present invention is shown;

[0015] Figure 2 Shown Figure 1 Schematic flow chart of the method for preparing core-shell structure particles in step S200;

[0016] Figure 3 Shown Figure 1 Schematic flow chart of the method for preparing the evaporation source material in step S300;

[0017] Figure 4 A schematic flow chart of a vacuum evaporation coating method according to an embodiment of the present invention is shown;

[0018] Figure 5 shows a scanning transmission electron microscope-electron energy loss spectrum of an evaporation source material obtained by the method for preparing an evaporation source material for vacuum evaporation coating according to Example 1 of the present invention;

[0019] Figure 6 It shows an X-ray photoelectron spectrum of an evaporation source material obtained according to a method for preparing an evaporation source material for vacuum evaporation coating according to Example 1 of the present invention;

[0020] Figure 7 The figure shows an X-ray diffraction spectrum of an evaporation source material obtained according to a method for preparing an evaporation source material for vacuum evaporation coating according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0022] In embodiments of the present invention, the evaporation source material is used in high-end optical applications such as filters, reflectors, and spectrometers. These optical devices place extremely high performance requirements on the evaporation source material, typically including high refractive index, low absorption coefficient, high optical uniformity, low scattering loss, and excellent environmental stability.

[0023] Based on the above application background, those skilled in the art generally believe that the evaporation source material should have high purity and low defect characteristics. Specifically, high-purity Ta2O5 materials are widely used because defects are recognized as the main deterioration factor of optical properties. Under high vacuum and high temperature evaporation conditions, defects may cause the thermal stability of the material to decrease, promote further oxidation or decomposition, and then cause fluctuations in the composition of evaporated particles, affecting the stability of the evaporation rate, and accompanied by gas release or splashing. In order to ensure that the evaporation source material has a single and stable evaporation temperature, as well as smooth and controllable evaporation behavior, the field generally tends to use high-density, high-purity Ta2O5 bulk materials as evaporation source materials.

[0024] However, even if high-purity Ta2O5 material is used, the material is prone to oxygen deficiency under high-temperature vacuum evaporation conditions, which leads to deviations in the stoichiometric ratio of the material and a decrease in the melting point, which in turn causes decomposition, degassing, and splashing, significantly affecting the surface finish and film stability of the film. In order to improve the quality of the film, studies have introduced oxygen ion beam assisted deposition technology, which increases the oxygen content in the film by increasing the oxygen flux density during the deposition process, thereby improving the density and insulation properties. Although this method has improved the microstructure and electrical properties of the film to a certain extent, it has limitations. For example, this method relies on oxygen ion assisted deposition equipment, which increases the complexity of the process and production costs, and is only modified during the film deposition stage. It fails to optimize the evaporation source material from the source and cannot fundamentally solve the problems of oxygen desorption, decomposition, and splashing during the evaporation process.

[0025] In this context, the inventors of this application conducted in-depth research. In view of the problems of complex process and limited effect of high-density, high-purity Ta2O5 bulk materials and the subsequent introduction of oxygen ion beam assisted technology in the thin film deposition stage, the inventors further explored the improvement of evaporation performance by introducing a dual-phase structure into the evaporation source material itself. Specifically, the inventors tried to use a process of granulating and sintering a mixed powder of Ta2O5 and metal Ta, hoping to form a phase containing Ta2O5 and Ta2O5. 5-xPhase (0.1<x<1.5) dual-phase structure materials are used to improve the thermal stability of the material and inhibit oxygen desorption, decomposition and splashing during high-temperature evaporation. However, experimental results show that although the dual-phase structure delays the oxygen desorption process to a certain extent and effectively suppresses the splashing phenomenon in the early stage of evaporation, the surface smoothness of the film is improved. However, as the evaporation time increases, the metal Ta is prone to charge accumulation in a high-temperature vacuum environment, resulting in an imbalance in the local thermal field distribution, which in turn triggers the formation of splash points. In addition, the dual-phase interface, as a potential thermally unstable area, is prone to aggravate local stress concentration, resulting in fluctuations in the composition of the evaporated particles and a gradual decrease in the smoothness of the film layer. Therefore, the dual-phase structure has failed to effectively guarantee the long-term stability of the evaporation process and the quality of the film, and there are still obvious shortcomings.

[0026] Based on the summary of previous research experience, the inventors broke through the traditional technical bias of "eliminating defects" and proposed to construct a single metastable phase Ta2O with defects and stable structure by precisely controlling the defect type and defect concentration. 5-x Materials can improve the thermal stability and evaporation uniformity of evaporation source materials from the source, effectively suppress splashing, significantly improve the smoothness and film quality of the film, while maintaining or even synergistically enhancing the optical properties. Figure 1 FIG1 shows a schematic flow chart of a method for preparing an evaporation source material for vacuum evaporation coating according to an embodiment of the present invention. Figure 1 As shown, the preparation method comprises:

[0027] Step S100: mixing Ta2O5 coarse powder with a particle size of 1 μm-5 μm, a first doping source powder containing a first doping element, and a second doping source powder containing a second doping element to obtain a mixed powder, wherein the total atomic doping amount of the first doping element and the second doping element is 0.1 at%-1 at%;

[0028] Step S200, granulating the mixed powder to obtain particle cores with a particle size of 0.8 mm to 1.2 mm, and then spraying Ta2O5 fine powder with a particle size of 0.1 μm to 0.5 μm on the surface of the particle cores to coat the surface of the particle cores to form core-shell structure particles with a particle size of 2.5 mm to 3.5 mm;

[0029] Step S300, when the oxygen partial pressure is 10 -5 atm-10 -4 Atm low oxygen partial pressure atmosphere, the core-shell structure particles were sintered in multiple stages to form a single metastable phase evaporation source material with a grain size of 20nm-50nm and no second phase precipitation of Ta2O 5-x Materials, where 0<x<0.2, Ta2O 5-x The oxygen vacancy concentration in the core region of the material is higher than that in the outer shell region.

[0030] According to the solution of the embodiment of the present invention, the preparation method of the evaporation source material realizes the improvement from micro-defect control to the overall performance of the evaporation source material through multi-link collaborative design. First, by mixing Ta2O5 coarse powder, the first doping source powder and the second doping source powder, and controlling the total atomic doping amount of the first doping element and the second doping element in the range of 0.1at%-1at%, while effectively controlling the defect type and concentration, it avoids problems such as phase separation, second phase precipitation or increased optical absorption caused by excessive doping. The introduction of the two doping elements induces lattice distortion on the one hand, and indirectly affects the generation and distribution of oxygen vacancies by adjusting the binding energy of oxygen atoms on the other hand, laying the foundation for subsequent defect engineering control. Subsequently, the above-mentioned mixed powder is granulated to obtain a particle core with a particle size of 0.8mm-1.2mm, and Ta2O5 fine powder is sprayed on the surface of the particle core to form core-shell structure particles with a particle size of 2.5mm-3.5mm. The core-shell structure design naturally induces the formation of a radial defect density gradient during the sintering process, achieving the structural characteristics of high oxygen vacancy concentration in the core and low oxygen vacancy concentration in the shell, effectively alleviating the accumulation of thermal stress and improving the stability of the evaporation process. During the sintering process, a low oxygen partial pressure atmosphere is used, combined with a multi-stage heating program, to accurately induce the generation of oxygen vacancies in the Ta2O5 lattice, forming a Ta2O with a stoichiometric ratio close to the ideal state. 5-x phase (0<x<0.2). The low oxygen partial pressure environment avoids structural damage caused by excessive oxygen vacancies, while ensuring that the material maintains a single metastable phase, inhibiting the precipitation of secondary phases such as metallic tantalum or low-valent tantalum oxide, and improving the compositional uniformity and optical stability of the evaporation source material. The staged heating strategy further controls the grain growth process, stabilizing the final grain size at 20nm-50nm, effectively improving the material's density and uniformity, reducing gas escape channels during evaporation, and suppressing splashing and particle shedding.

[0031] In step S100, the selected Ta2O5 coarse powder with a particle size of 1 μm-5 μm can be directly obtained through commercial channels, and its particle size is defined as the median particle size (D 50 ) is in the range of 1μm-5μm. The coarse powder material is 99.99% high-purity Ta2O5, which meets the purity requirements of high-end optical evaporation source materials. It is well known in the art that powder particle size is closely related to sintering behavior. Specifically, the smaller the particle size, the larger the specific surface area of ​​the powder, the higher the activity, and the stronger the sintering driving force, which can easily lead to over-sintering and abnormal grain growth. The larger the particle size, the more difficult it is to sinter densify, and it is easy to leave pores inside the material, forming a loose structure, and easily causing splashing and decomposition during the evaporation process. Therefore, D 50Ta2O5 coarse powder with a particle size of 1μm-5μm achieves a balance between particle size and surface area, balancing sintering density and grain size uniformity. This helps to subsequently form a dense, fine-grained sintered body, improving the overall structural stability of the evaporation source material. More importantly, coarse powder with a particle size within this range has a long oxygen diffusion path and slow diffusion rate during sintering, making it easier to generate oxygen vacancy defects in a low oxygen partial pressure environment, leading to a higher oxygen vacancy concentration in the core region. In the subsequent step S200, Ta2O5 fine powder with a particle size of 0.1μm-0.5μm is used to coat the core particles. This fine powder has high activity and fast oxygen diffusion, resulting in a low defect concentration in the shell region after sintering. By rationally matching the particle sizes of the coarse and fine powders, an initial core-shell activity difference is established, naturally inducing the formation of a stable oxygen vacancy gradient structure during the sintering process, namely, high defects in the core and low defects in the shell. This effectively improves the thermal stability and evaporation uniformity of the evaporation source material, suppresses spatter, and improves the optical quality of the subsequently deposited film.

[0032] In some embodiments, the first doping source powder contains a cation with a valence of +5 in the oxide and an ionic radius similar to that of Ta. 5+ The first doping source powder may be, for example, niobium pentoxide (Nb2O5), vanadium pentoxide (V2O5), tungsten pentoxide (W2O5), or antimony pentoxide (Sb2O5). In some embodiments, the second doping source powder may be a powder containing a metal element with a +4 valence in the oxide and an ionic radius similar to Ta. 5+ Oxide doping source powder of a metal element close to the first doping source powder. The second doping source powder can be, for example, zirconium oxide (ZrO2), titanium oxide (TiO2) or hafnium oxide (HfO2) powder. The total atomic doping amount of the first doping element and the second doping element is 0.1at%-1at%, for example, it can be 0.1at%, 0.3at%, 0.5at%, 0.8at% or 1at%. The total atomic doping amount refers to the percentage of the total number of atoms of the doping metal element (excluding oxygen) to the total number of atoms of the material. In some preferred embodiments, the atomic doping amount of the first doping element is 0.05at%-0.6at%, and the atomic doping amount of the second doping element is 0.05at%-0.4at%.

[0033] In the embodiment of the present invention, a first doping element and a second doping element are used and the total doping amount is controlled within the range of 0.1at%-1at% to form a synergistic control mechanism. 5+ Similar charge number and ionic radius can enter the Ta2O5 lattice without obvious damage, maintaining the integrity of the crystal structure and high optical transparency, while at the same time, by fine-tuning the lattice stress, suppressing excessive oxygen deficiency and stabilizing the high defect density metastable phase. 5+, introducing a slight charge imbalance in the lattice, promoting the formation of controlled oxygen vacancies, further regulating the concentration and distribution of oxygen vacancies, and improving the defect uniformity and evaporation stability within the material. Through the synergistic effect of dual doping, bidirectional regulation of oxygen vacancy generation energy and defect formation behavior is achieved, effectively avoiding the problems of defect loss or lattice destruction caused by single doping. In addition, the total amount of doping is controlled at an extremely low level, which not only ensures the stability and integrity of the lattice structure, but also avoids problems such as increased impurity absorption, decreased transmittance, and reduced laser damage threshold caused by excessive doping.

[0034] Figure 2 Shown Figure 1 FIG. 1 is a schematic flow chart of a method for preparing core-shell structure particles in step S200. Figure 2 As shown, the method for preparing the core-shell structure particles in step S200 includes:

[0035] Step S210, pre-treating the mixed powder;

[0036] Step S220, using a high-speed rotary granulator, with the assistance of oil-free compressed air, to granulate the mixed powder;

[0037] Step S230, drying and screening the particle cores;

[0038] Step S240, using a powder spraying device to evenly spray Ta2O5 fine powder with a particle size of 0.1 μm-0.5 μm on the surface of the particle core in a high-speed rotating granulator;

[0039] Step S250, drying the particles obtained in step S240 under hot air at 60°C-80°C;

[0040] In step S260 , the particles obtained in step S250 are sieved to obtain core-shell structure particles with a particle size of 2.5 mm to 3.5 mm.

[0041] In step S210, a small amount of dispersant such as polyvinyl alcohol may be added to the mixed powder during pretreatment to improve powder dispersibility and granule formability. The mixed powder is then dried appropriately to remove surface adsorbed moisture and prevent agglomeration during granulation.

[0042] In step S220, the high-speed rotating granulator can be, for example, a fluidized bed granulator, a spray granulator or a pan granulator. During the granulation process, the droplet size, spray rate and drying temperature are controlled to make the particle size D 50 The particle size is concentrated in the range of 0.8mm-1.2mm. In this step, a small amount of deionized water or low-concentration PVA solution can be sprayed as a nucleating liquid to promote the aggregation and nucleation of powder particles.

[0043] In step S230, the particle cores are dried to remove surface moisture and prevent abnormal particle size growth during subsequent coating. After drying, particles with excessively large or small particle sizes can be screened to ensure uniform particle size.

[0044] In step S240, the Ta2O5 fine powder can be pre-ultrasonic dispersed to prevent agglomeration. To enhance the coating effect, a small amount of deionized water or an alcohol solution can be simultaneously sprayed through atomization to form a uniform bonding layer between the Ta2O5 fine powder and the core particle surface, preventing the Ta2O5 fine powder from falling off and increasing the coating density. By adjusting the spraying amount and coating time, the core-shell coating layer thickness is adjusted to maintain a stable overall particle size within the range of 2.5 mm to 3.5 mm.

[0045] In step S250, the hot air temperature of 60°C-80°C can accelerate the volatilization of water, avoid cracking or local sintering of the particles caused by high temperature, and prevent size changes. Therefore, the overall particle size of the particles after drying is basically the same as the particle size produced in step S240.

[0046] In step S260, the purpose of screening is to remove particles with excessive particle size, ensure uniform particle size distribution, and avoid problems such as uneven particle size and large density differences in the subsequent sintering process.

[0047] In step S200, the mixed powder is first prepared into a particle core with a particle size of 0.8mm-1.2mm through a granulation process, providing a basic guarantee for the structural stability and particle morphology uniformity of the subsequent material. The moderate core particle size effectively balances the initial surface area and particle activity, avoiding agglomeration and sintering abnormalities caused by excessively fine powder, and ensuring that the particles have good densification ability and dimensional stability during the subsequent sintering process. At the same time, the core particle size provides a reasonable surface area carrier for subsequent shell coating, which is conducive to uniformly coating Ta2O5 fine powder and forming an ideal core-shell interface structure. Secondly, by uniformly coating Ta2O5 fine powder on the surface of the particle core, a core-shell structure is gradually constructed. This core-shell design introduces a defect density gradient in the radial direction, that is, the core region has a higher defect density, while the shell region maintains a lower defect density, laying the foundation for subsequent defect regulation and improved evaporation stability. This structure can induce the formation of a gradient in the distribution of oxygen vacancies during the sintering process. In addition, the overall particle size is stable within the range of 2.5mm-3.5mm. This particle size range takes into account the filling density and pre-melting efficiency of the evaporation source material in the electron beam evaporation coating equipment, which can not only ensure the uniformity and density of the evaporation source filling, but also help to improve the rate stability of the evaporation process and the film formation quality.

[0048] Figure 3 Shown Figure 1 FIG. 1 is a schematic flow chart of the method for preparing the evaporation source material in step S300. Figure 3 As shown, the method for preparing the evaporation source material in step S300 includes:

[0049] Step S310, when the oxygen partial pressure is 10 -5 atm-10 -4 atm low oxygen partial pressure atmosphere, raising the temperature to a first preset temperature at a first heating rate, and maintaining the temperature for a first preset time;

[0050] Step S320, raising the temperature to a second preset temperature at a second heating rate and keeping the temperature for a second preset time;

[0051] Step S330, raising the temperature to a third preset temperature at a third heating rate and keeping the temperature for a third preset time, wherein the second preset temperature is greater than the first preset temperature and less than the third preset temperature;

[0052] In step S340 , the evaporation source material is formed by cooling the evaporation source material to room temperature at a preset cooling rate.

[0053] In step S310, the first heating rate is 2°C / min-5°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min or 5°C / min, or any other value between 2°C / min and 5°C / min. The first preset temperature is 400°C-600°C, for example, it can be 400°C, 500°C or 600°C, or any other value between 400°C and 600°C. The first preset time is 0.5h-1h, for example, it can be 0.5h, 0.8h or 1h, or any other value between 0.5h and 1h. The first heating rate is set to 2°C / min-5°C / min, and the heating rate is controlled to be low, which is conducive to uniform temperature distribution inside the system and avoids rapid heating resulting in excessive temperature difference between the interior and surface of the particles, thereby generating thermal stress or microcracks. The first preset temperature is set between 400°C and 600°C. This temperature range promotes the removal of adsorbed gases, moisture, and some surface hydroxyl groups in the precursor, reducing the risk of gas release during subsequent high-temperature sintering while providing a clean and stable surface environment for subsequent defect generation. The first preset time is set to 0.5-1 hour, providing sufficient time for initial degassing and composition homogenization, thereby avoiding localized sintering unevenness or particle breakage caused by residual gases during the subsequent high-temperature stage.

[0054] In step S320, the second heating rate is 8°C / min-12°C / min, for example, it can be 8°C / min, 9°C / min, 10°C / min or 12°C / min, or any other value between 8°C / min and 12°C / min. The second preset temperature is 1000°C-1300°C, for example, it can be 1000°C, 1100°C, 1200°C or 1300°C, or any other value between 1000°C and 1300°C. The second preset time is 1h-2h, for example, it can be 1h, 1.5h or 2h, or any other value between 1h and 2h. The second heating rate is set to 8°C / min-12°C / min. The faster heating rate helps to quickly cross the sensitive area of ​​initial grain growth, reduce abnormal grain growth, and promote the uniform formation of fine grains. The second preset temperature is controlled at 1000℃-1300℃. This temperature range is an important stage for the densification and sintering of Ta2O5 materials. It is also a sensitive temperature range for the generation of oxygen vacancies. Within this temperature range, the oxygen diffusion activity is enhanced, the material loses oxygen locally and in a controlled manner, and the metastable Ta2O is promoted. 5-x The second preset time is 1h-2h, which ensures sufficient heat treatment time to complete the initial sintering densification and the uniform introduction of oxygen vacancy defects, while avoiding abnormal grain growth caused by excessive heat preservation.

[0055] In step S330, the third heating rate is 2°C / min-5°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min or 5°C / min, or any other value between 2°C / min and 5°C / min. The third preset temperature is 1400°C-1800°C, for example, it can be 1400°C, 1500°C, 1600°C or 1800°C, or any other value between 1400°C and 1800°C. The third preset time is 2h-4h, for example, it can be 2h, 3h or 4h, or any other value between 2h and 4h. The third heating rate returns to 2°C / min-5°C / min, and a lower heating rate is used to enter the high temperature stage, which helps the system to slowly release internal stress and avoid crystal structure destruction or uneven densification due to temperature mutation. The third preset temperature is set to 1400℃-1800℃, which is close to the high temperature stability zone of Ta2O5, and can further promote the densification of material grains and stabilize the metastable Ta2O 5-x (0<x<0.2) structure, while high temperature induces further accumulation of oxygen vacancies in the inner core region, forming a clear defect gradient distribution with high inner and low outer regions. The third preset time is 2h-4h. The longer high temperature holding time helps complete crystal growth and stress release, forming a uniform and fine grain size (20nm-50nm), and further stabilizes the oxygen vacancy concentration, preventing defect agglomeration or migration from causing local phase separation.

[0056] In this step S340, the preset cooling rate is 2°C / min-5°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min or 5°C / min, or any other value between 2°C / min and 5°C / min. The preset cooling rate is set to 2°C / min-5°C / min. Slower cooling helps to further release the residual thermal stress accumulated during the high-temperature sintering process, and prevents the material from causing thermal cracks or microstructural stress concentration problems due to rapid cooling. The low-speed cooling process is also conducive to stabilizing the oxygen vacancies and lattice distortion formed during the sintering process, avoiding excessive repair of oxygen vacancies during the cooling process, thereby maintaining the preset oxygen vacancy concentration and defect gradient structure, and ensuring that the material has good long-term evaporation stability and long-term film uniformity.

[0057] The grain size of the evaporation source material that can be finally formed is controlled within the range of 20nm-50nm, which increases the number of grains and makes their distribution uniform, and significantly increases the total area of ​​the grain boundaries. This helps to evenly release the driving force during the sintering process, promotes close packing of particles, significantly reduces residual porosity, improves the density of the material, and forms a continuous, dense and complete microstructure, avoiding structural fragility caused by defects such as holes and microcracks. In contrast, coarse-grained materials are prone to loose accumulation and unsintered holes, which become the main channels for gas escape during high-temperature evaporation. The close arrangement of small grains can effectively reduce the number and size of internal holes. The fine and uniform grain boundary structure can inhibit the formation of microcracks and weak connection areas near the coarse grain boundaries. At the same time, the fine grain boundary network effectively hinders gas diffusion, extends the diffusion path, and inhibits gas aggregation and escape. Through this microstructural optimization, the internal gas diffusion of the material is significantly hindered, effectively suppressing the degassing and splashing phenomena during the evaporation process, and can improve the thermal stability and film quality of the evaporation source material. Ta2O 5-x The material has no second phase precipitation, and the material maintains a single metastable phase structure, avoiding the problem of unstable evaporation behavior caused by the presence of second phases such as low-valent tantalum oxide or metallic tantalum inside the material. The presence of the second phase usually leads to uneven local chemical composition and physical properties. During high-temperature vacuum evaporation, there are differences in the gas escape rate, evaporation melting point and thermal stability between different phases, which can easily form local gas enrichment, expansion or voids on the evaporation surface, inducing uneven melting of the evaporation surface, and ultimately leading to adverse phenomena such as splashing and bursting. Spattering not only seriously affects the surface finish of the film, but may also cause the formation of microparticle inclusions inside the film, reducing the optical uniformity and light transmittance of the film, and even reducing the laser damage threshold. In contrast, the single metastable phase of Ta2O in the embodiment of the present application 5-x The material has uniform crystal phase, consistent melting point distribution, coordinated thermal expansion behavior, and uniform material escape during evaporation, effectively avoiding local overheating and bubble aggregation, and significantly reducing the probability of splashing.

[0058] It should be explained that, in the embodiments of the present application, "metastable phase" refers to a material crystal phase whose energy state is higher than the global thermodynamically stable state, but has long-term thermodynamic stability under operating conditions such as room temperature and normal pressure or vacuum. This phase will not spontaneously transform into a thermodynamically stable phase when external disturbances such as heating or external force are insufficient to overcome its energy barrier, and it has a certain metastable stability. Specifically, the metastable phase uses the Ta2O5 crystal structure as a skeleton, introduces controlled density of oxygen vacancies, dislocations and other point defects into the lattice, and regulates the local energy state of the lattice through defect engineering. Under the preparation and application conditions of the embodiments of the present invention, the metastable phase material can maintain the stability of the phase composition and microstructure under high temperature vacuum conditions, and avoid decomposition or transformation to a low oxidation state phase.

[0059] The present invention prepares a single metastable phase Ta2O 5-x The process of evaporating source materials requires comprehensive coordination of multiple technical links, including doping control, core-shell particle design, and sintering processes, and each parameter must be precisely matched to achieve the ideal microstructure and macroscopic performance. Due to the complex nonlinear coupling relationship between various process variables, even a slight change in any single parameter can disrupt the overall synergistic effect, resulting in uneven material structure or performance degradation. Due to the extremely narrow overall process window, it is impossible to achieve the target performance by simply adjusting a single variable. Precise process control and parameter matching must be maintained throughout the entire process.

[0060] In some embodiments, the method for preparing the evaporation source material for vacuum evaporation coating further includes the following steps: subjecting the evaporation source material to oxygen plasma treatment to form a passivation layer on the surface of the evaporation source material having an oxygen vacancy concentration lower than that in the outer shell area, and the thickness of the passivation layer is 2nm-10nm. In this step, the atmosphere during the oxygen plasma treatment is high-purity oxygen with a purity ≥99.999%, the plasma excitation mode is radio frequency plasma or microwave plasma, and the working pressure is 0.1Pa-1Pa. The temperature of the plasma treatment is room temperature or heated to below 100°C, and the treatment time is 1min-10min, preferably 3min-5min. The thickness of the passivation layer can be, for example, 2nm, 3nm, 5nm, 8nm or 10nm, or any other value between 2nm and 10nm.

[0061] By subjecting the evaporation source material to oxygen plasma treatment, a large number of highly reactive particles, including high-energy oxygen atoms, oxygen ions, and free radicals, are generated. These particles react with oxygen vacancies on the material's surface, effectively filling surface defects. Simultaneously, low-energy ion bombardment promotes surface atomic rearrangement, improving surface density and uniformity. Due to the limited depth of plasma action, a passivation layer with higher oxygen content and lower defect density forms only on the surface of the material. This passivation layer, together with the inner high-defect density regions, creates a radial defect gradient structure, further enhancing surface stability. Forming a passivation layer with a thickness of 2nm-10nm on the evaporation source material effectively reduces surface activity, inhibiting oxygen escape and surface decomposition reactions during high-temperature evaporation, and significantly improving the thermal stability of the evaporation source. The passivation layer alleviates localized thermal stress concentration, reduces spattering, ensures the continuity and stability of the evaporation process, prevents rapid initial evaporation and localized collapse, and extends the service life of the evaporation source. The precisely controlled thickness of the passivation layer ensures surface protection while maintaining the consistency of the evaporated components and chemical composition, thus avoiding adverse effects on the film's optical properties.

[0062] In some embodiments, during the oxygen plasma treatment of the evaporation source material, a gas containing a doping element is introduced simultaneously to form a passivation layer containing the doping element, and the doping element is selected from nitrogen, silicon or boron. The atomic concentration of the doping element in the passivation layer containing the doping element is 0.2at%-0.8at%, for example, it can be 0.2at%, 0.3at%, 0.6at% or 0.8at%, or it can be any other value between 0.2at%-0.8at%. Compared with the aforementioned passivation layer preparation process without doping elements, in addition to maintaining the same process parameters such as plasma power, processing pressure and substrate temperature, this embodiment appropriately extends the oxygen plasma treatment time, and the treatment time is 5min-30min, for example, it can be 5min, 10min, 15min, 20min, 25min or 30min, or it can be any specific value within the range of 5min-30min.

[0063] The introduction of doping elements can effectively regulate the surface electronic structure, further reducing oxygen vacancy concentrations and enhancing surface density and thermal stability. Nitrogen, silicon, or boron atoms form a stabilizing network on the surface, improving the passivation layer's resistance to high-temperature evaporation environments and reducing surface decomposition and spattering under high-temperature conditions. Doping the passivation layer also optimizes the uniformity of particle release during evaporation, improving film thickness uniformity and optical smoothness during film formation, reducing the absorption coefficient, and increasing the laser damage threshold and transmittance after film formation, further enhancing the service stability and optical properties of the evaporation source material.

[0064] In another embodiment, the method for preparing an evaporation source material for vacuum evaporation coating further includes the following step: annealing the evaporation source material having a passivation layer formed on its surface at 300°C-500°C for a time of 0.5h-1.5h. In this step, the annealing temperature may be, for example, 300°C, 400°C, or 500°C, or any other value between 300°C and 500°C. The annealing time may be, for example, 0.5h, 1h, or 1.5h, or any other value between 0.5h and 1.5h.

[0065] By annealing the evaporation source material with a passivation layer formed on the surface, the structure and function of the passivation layer can be further optimized. Appropriate heat treatment promotes surface atomic migration and rearrangement, repairs microscopic defects introduced by plasma treatment, improves surface density and uniformity, and reduces surface oxygen vacancy concentration. Through annealing densification treatment, the oxygen escape rate and decomposition risk of the surface layer during high-temperature evaporation can be effectively reduced, the thermal stability of the evaporation source material can be improved, and splashing and surface shedding can be suppressed. At the same time, annealing releases surface residual stress, reduces the probability of microcrack initiation, improves the mechanical stability of the evaporation process and the uniform release behavior of evaporated particles, and further improves the thickness uniformity and optical smoothness of the deposited film. Overall, this annealing process gives the evaporation source material excellent surface stability and film-forming properties without destroying the internal defect gradient structure and oxygen vacancy concentration control. The process is mild and has good compatibility, making it suitable for large-scale preparation and high-end optical applications. In addition, for the passivation layer containing doping elements such as nitrogen, silicon or boron, the annealing process helps to uniformly distribute and stably solidify the doping elements on the surface, inhibit element enrichment or segregation, and enhance the thermal and chemical stability of the passivation layer.

[0066] Figure 4 FIG1 shows a schematic flow chart of a vacuum evaporation coating method according to an embodiment of the present invention. Figure 4 As shown, the vacuum evaporation coating method includes:

[0067] Step S101: Load the evaporation source material prepared according to the above preparation method into the evaporation crucible, and evacuate the evaporation chamber to a vacuum of 1×10 -4 Pa-5×10 -4 Pa;

[0068] Step S102: heating the temperature to 1750°C-1850°C at a heating rate of 1°C / min-6°C / min and keeping the temperature for 1 hour-2 hours to pre-melt the evaporation source material;

[0069] Step S103 , controlling the evaporation deposition rate to be 0.5 nm / s-1.5 nm / s, depositing the evaporated particles on the surface of the substrate at a temperature of 80° C.-150° C., and stopping the evaporation after reaching a preset film thickness.

[0070] In step S101, the evaporation chamber can be evacuated to a vacuum of 1×10 -4 Pa, 2×10 -4 Pa, 3×10 -4 Pa or 5×10 -4 Pa, or 1×10 -4 Pa-5×10 -4 Any other value in Pa.

[0071] In step S102, the heating rate may be, for example, 1°C / min, 2°C / min, 4°C / min, or 6°C / min, or any other value between 1°C / min and 6°C / min. The heating temperature may be, for example, 1750°C, 1800°C, or 1850°C, or any other value between 1750°C and 1850°C. The holding time may be, for example, 1 hour, 1.5 hours, or 2 hours, or any other value between 1 hour and 2 hours.

[0072] In step S103, the evaporation deposition rate may be, for example, 0.5 nm / s, 15 nm / s, or 1.5 nm / s, or any other value between 0.5 nm / s and 1.5 nm / s. The temperature of the substrate surface may be, for example, 80° C., 100° C., 120° C., or 150° C., or any other value between 80° C. and 150° C.

[0073] The process parameter control in the embodiments of this application ensures that the evaporation source material has higher thermal stability and evaporation uniformity under high-temperature vacuum evaporation conditions, significantly reducing undesirable phenomena such as spattering and outgassing, and improving the density, smoothness, and optical properties of the deposited film. Compared with existing processes, this invention not only achieves breakthroughs in evaporation process stability, but also improves key performance indicators such as film thickness uniformity, refractive index consistency, low scattering loss, and high laser damage threshold.

[0074] The following specific examples and comparative examples are used to illustrate the criticality and importance of the process steps of this application.

[0075] Example 1:

[0076] A first embodiment of the present invention provides a method for preparing an evaporation source material for vacuum evaporation coating, comprising:

[0077] Step 1: Ta2O5 coarse powder, Nb2O5 powder and ZrO2 powder with a particle size of 2-3 μm are mixed to obtain a mixed powder, wherein the atomic doping amount of Nb is 0.3 at%, and the atomic doping amount of Zr is 0.2 at%.

[0078] Step 2: Dry the mixed powder at 80°C for 2 h to remove surface adsorbed moisture;

[0079] Step 3: Using a disc granulator, during the granulation process, under the condition of oil-free compressed air assistance, the spray droplet size of 0.1wt% polyvinyl alcohol aqueous solution was controlled to be about 80μm, the spray rate was 50mL / min, the disc inclination angle was set to 50°, the disc speed was set to 30rpm, and the drying temperature was controlled to 70℃. Through the above process conditions, the particle size D 50 Particle cores are distributed in the range of 0.8mm-1.2mm;

[0080] Step 4: Dry the granule cores and sieve them to remove particles that are too large or too small;

[0081] Step 5: using a powder spraying device in a disc granulator, Ta2O5 fine powder with a particle size of 0.3 μm-0.4 μm is evenly sprayed on the surface of the particle core at a rate of 2 g / min;

[0082] Step 6: Dry the particles obtained in step 5 under hot air at 60°C;

[0083] Step 7: Screening the particles obtained in step 6 to obtain core-shell structure particles with a particle size of 2.5 mm to 3 mm;

[0084] Step 8: When the oxygen partial pressure is 10 -4 Atm low oxygen partial pressure atmosphere, the temperature was raised to 500 ° C at 3 ° C / min and kept at this temperature for 0.5 h, wherein the low oxygen partial pressure atmosphere was achieved by doping high-purity argon (99.999%) with trace oxygen (1ppm-10ppm);

[0085] Step 9: Raise the temperature to 1100°C at a rate of 10°C / min and keep at this temperature for 1.5 hours;

[0086] Step 10: Raise the temperature to 1700°C at 4°C / min and keep at this temperature for 3 hours;

[0087] Step 11: Cooling to room temperature at 3° C. / min to form an evaporation source material.

[0088] Figure 5 The scanning transmission electron microscope-electron energy loss spectrum of the evaporation source material obtained by the preparation method of the evaporation source material for vacuum evaporation coating according to the first embodiment of the present invention is shown. Figure 5 Figure A in the middle shows a HAADF-STEM image of an evaporation source material for vacuum evaporation coating according to Example 1 of the present invention, in which the EELS scanning line position mark is shown. Figure 5 Figure B in the middle shows an EELS graph of the evaporation source material for vacuum evaporation coating according to Example 1 of the present invention, in which the O / Ta atomic ratio varies with radial distance. Figure 5Figure C in the middle shows the EELS element surface distribution diagram of the evaporation source material for vacuum evaporation coating according to the first embodiment of the present invention. Figure 6 Figure D in the middle shows the OK edge energy loss spectrum of the evaporation source material used for vacuum evaporation coating according to Example 1 of the present invention.

[0089] Depend on Figure 5 As shown in Figure A, there is a significant difference in brightness between the particle center and the particle edge, revealing a distinct core-shell structure. The curve in Figure B shows a distinct U-shaped trend, with the O / Ta ratio at the particle edge being approximately 2.35-2.40, while decreasing to approximately 2.00-2.05 at the particle center. This indicates a radial oxygen gradient, with oxygen-rich outer shells and higher oxygen vacancies in the inner core. This confirms that the oxygen vacancy concentration in the core of the evaporated source material is higher than that in the outer shell. In Figure C, the red region corresponds to high oxygen concentration, while the blue region corresponds to low oxygen concentration. The particle periphery exhibits a red-yellow hue, while the center is blue, further confirming the core-shell distribution of oxygen, with oxygen-rich outer shells and oxygen-deficient inner cores. The main peak in Figure D, at approximately 530 eV, is attributed to π-electron transitions on the OK edge, representing the normal coordination structure of oxygen and tantalum. The peak shows no significant shift or splitting, indicating that the oxygen vacancies are primarily distributed as point defects, without causing large-scale lattice structure transformations or the formation of heterogeneous phases, indicating that the evaporated source material is metastable.

[0090] Figure 6 The X-ray photoelectron spectrum of the evaporation source material obtained according to the method for preparing the evaporation source material for vacuum evaporation coating according to Example 1 of the present invention is shown. In order to ensure the reliability and accuracy of the oxygen vacancy signal measured by XPS, the sample was vacuum dried before the XPS measurement in this embodiment and the sample was dried under high vacuum (<10 -7 The test is completed under the conditions of 1000 Pa, which can significantly reduce the presence of surface adsorbents and reduce the interference signals of foreign hydroxyl groups and water molecules. The XPS detection depth is 5nm-10nm, which can effectively characterize the distribution of oxygen vacancies from the surface to the shallow layer of the material. Figure 6 As shown in the O1s high-resolution spectrum fitting process, the main peak was observed at about 530.0eV, corresponding to the coordinated oxygen signal of the Ta-O lattice bond, and the secondary peak appeared near 531.5eV, which can be attributed to the oxygen vacancy-related state caused by local oxygen deficiency in the crystal structure. After Gaussian-Lorentz mixed fitting analysis, the proportion of oxygen vacancy peak area to total peak area is about 3.5%, which is significantly lower than the typical level of >10% in common defect-enriched oxides, indicating that the material of this embodiment contains only trace oxygen vacancies. Figure 5 The trend of the O / Ta ratio determined by the electron energy loss spectrum further proves that the evaporation source material has a slight stoichiometric deviation as a whole, and the corresponding stoichiometric expression can basically be determined as Ta2O 5-x (0 <x<0.2)。

[0091] Figure 7 FIG1 shows an X-ray diffraction spectrum of an evaporation source material obtained according to a method for preparing an evaporation source material for vacuum evaporation coating according to an embodiment of the present invention. Figure 7 As shown, the XRD diffraction pattern shows multiple characteristic diffraction peaks, mainly located at 2θ=22.7°, 28.3°, 36.8°, 49.5° and 55.7°. These diffraction peaks match those of standard β-Ta2O5, and no diffraction peaks of metallic tantalum, low-valent tantalum oxide (such as TaO, Ta2O3) or other impurities are observed. Further comparison with the standard diffraction card shows that there is no characteristic peak of metallic tantalum Ta (110) near 38°, nor is there a characteristic peak of Ta2O3 near 34°, indicating that no low-valent tantalum oxide or metallic tantalum second phase precipitation is detected in the sample. In addition, although the peaks at 2θ=22.7°, 28.3°, 36.8°, 49.5° and 55.7° are clear, they all have a certain width and do not have very sharp peaks. The background noise is low, which is a typical nano-grain XRD pattern. According to conventional experience and the Scherrer formula, the grain size is estimated to be 20nm-50nm. This proves that the Ta2O 5-x (0<x<0.2) The grain size of the material is 20nm-50nm and there is no second phase precipitation.

[0092] Example 2:

[0093] A second embodiment of the present invention provides a method for preparing an evaporation source material for vacuum evaporation coating. This method differs from the first embodiment only in that, after step 11, this second embodiment further includes a 12th step: treating the evaporation source material with high-purity oxygen (≥99.999%) using an oxygen plasma to form a passivation layer on the surface of the evaporation source material having an oxygen vacancy concentration lower than that in the outer shell region. The passivation layer has a thickness of 4 nm. The RF power of the oxygen plasma treatment is 100 W, and the treatment time is 15 minutes.

[0094] Example 3:

[0095] Embodiment 3 of the present invention provides a method for preparing an evaporation source material for vacuum evaporation coating. The difference between this preparation method and embodiment 2 is that the high-purity oxygen in step 12 is replaced by nitrogen-containing oxygen, and the oxygen plasma treatment time is adjusted to 15 minutes.

[0096] Example 4:

[0097] Embodiment 3 of the present invention provides a method for preparing an evaporation source material for vacuum evaporation coating. The only difference between this preparation method and embodiment 3 is that, after step 12, the following step is also included: annealing the evaporation source material with a passivation layer formed on the surface at 500°C for 0.5h.

[0098] Comparative Example 1:

[0099] The only difference between Comparative Example 1 and Example 1 is that ZrO2 powder is not mixed in step 1.

[0100] Comparative Example 2:

[0101] The only difference between Comparative Example 1 and Example 1 is that step 3 is modified as follows: using a pan granulator, during the granulation process, with the assistance of oil-free compressed air, the spray droplet size of the 0.1 wt% polyvinyl alcohol aqueous solution is controlled to be approximately 20-30 μm, the spray rate is controlled to be 80-90 mL / min, the pan inclination angle is set to 35°, the pan speed is set to 65 rpm, and the drying temperature is controlled to be 50°C. Step 5 is removed, and step 7 is replaced by the following: the granules obtained in the previous step are sieved to obtain granules with a particle size of 2.5 mm to 3 mm.

[0102] Comparative Example 3:

[0103] The difference between the comparative example 3 and the embodiment 1 is that the steps 8 to 10 are replaced by: -4 Atm low oxygen partial pressure atmosphere, the temperature was raised to 1400 ° C at 8 ° C / min and kept at this temperature for 3 hours, wherein the low oxygen partial pressure atmosphere was achieved by doping trace oxygen (1ppm-10ppm) in high-purity argon (99.999%).

[0104] In order to verify the performance of the evaporation source material applied to vacuum evaporation coating, the evaporation source materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to vacuum evaporation coating according to the following steps:

[0105] The obtained evaporation source material was loaded into the evaporation crucible, and the evaporation chamber was evacuated to 3×10 -4 Pa;

[0106] The temperature was raised to 1800°C at a heating rate of 2°C / min to pre-melt the evaporation source material;

[0107] The evaporation deposition rate is controlled to be 1 nm / s, and the evaporated particles are deposited on the surface of the substrate at a temperature of 100°C. Evaporation is stopped after reaching a preset film thickness, which is 1.5 μm.

[0108] Table 1 below shows the performance characterization results of the evaporation source materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 after vacuum evaporation coating according to the above-described steps. The determination of spattering is based on real-time monitoring of the entire pre-melting process. The different pre-melting times in the Examples and Comparative Examples are determined based on the material pre-melting conditions.

[0109] The film density is obtained by deducing the film thickness and crystal control parameters.

[0110] First, film thickness was measured using X-ray reflectivity (XRR). Combined with key crystal control parameters controlled during the process, a mapping relationship between film thickness and density was established using an existing deposition-structure database model. This allowed the density of the film to be inferred under the corresponding process conditions. This method was validated for this material system by comparing XRR with mass density for multiple batches of samples, with an error within ±0.05 g / cm³. The results are reported in g / cm³. Surface roughness (Ra) was measured using a non-contact AFM (ScanAsyst-Air probe) with a filter bandwidth of 0.1µm to 5µm and a scan rate of 1Hz over 5µm × 5µm and 1µm × 1µm areas, respectively. The arithmetic mean roughness (Ra) was calculated and averaged across ≥5 randomly selected fields. The refractive index at 550nm was measured using a visible-near-infrared variable-angle ellipsometer (VASE, 300-1000nm, incident angles of 65° / 70° / 75°) using the Cauchy + Tauc-Lorentz model to obtain n(λ). Ten random points on the film surface were tested and the average refractive index was calculated. The scattering loss was measured using an integrating sphere scattering measurement system (λ = 532nm, incident beam spot 2mm, f / 6.5 optical path) to determine the difference between total transmission and collimated transmission. This was converted to scattering loss in parts per million (ppm). The measurements were taken at five random points on the sample surface and averaged. The laser damage threshold (LIDT) was tested in accordance with ISO 21254-1:2011 (S-on-1) using an Nd:YAG laser with λ = 1064nm, τ = 10ns, 10Hz; a spot diameter of 0.25mm, and an energy step size of 0.5J / cm. 2 , the energy level was increased step by step at 15 independent locations, and the 0% damage probability threshold was recorded and averaged. The data in Table 1 is as follows:

[0111]

[0112] As shown in Table 1 above, the optical films obtained in Examples 1 to 4 exhibit significant performance advantages. The film prepared in Example 1 had a pre-melting treatment time of 1.5 hours and no obvious splashing phenomenon, and its film density reached 8.12 g / cm 3 , surface finish is 0.35nm, refractive index is 2.07, scattering loss is 80ppm, and laser damage threshold is 9.2J / cm2 . With the improvement of the process, the performance of the films of Examples 2 to 4 was further improved, the film density was increased to 8.19g / cm³, the surface smoothness was 0.28nm, the refractive index was 2.10, the scattering loss was reduced to 56ppm, and the laser damage threshold reached 9.8J / cm². This shows that the present invention effectively improves the performance of the evaporation source material by precisely controlling the defect type and concentration, constructing a core-shell structure, adopting multi-stage temperature rising sintering, forming a passivation layer and annealing processes, thereby improving the density, surface smoothness and optical uniformity of the film, reducing the scattering loss and increasing the laser damage threshold.

[0113] In comparison, the film performance of Comparative Examples 1 to 3 was significantly inferior. The pre-melting treatment in Comparative Example 1 lasted 3 hours and exhibited significant spattering. The film density was only 7.85 g / cm³, the surface finish was 0.55 nm, the refractive index was 2.00, the scattering loss was 1200 ppm, and the laser damage threshold was 7.0 J / cm². Comparative Examples 2 and 3 presented similar results, with longer pre-melting treatment times and significant spattering. All performance indicators were lower than those in the examples.

[0114] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an evaporation source material for vacuum evaporation coating, characterized in that: The steps include: A Ta2O5 coarse powder having a particle size of 1 μm to 5 μm, a first doping source powder containing a first doping element, and a second doping source powder containing a second doping element are mixed to obtain a mixed powder, wherein the total atomic doping amount of the first doping element and the second doping element is 0.1 at% to 1 at%. The first doping source powder is niobium pentoxide, vanadium pentoxide, tungsten pentoxide, or antimony pentoxide powder, and the second doping source powder is zirconium oxide, titanium oxide, or hafnium oxide powder; Granulating the mixed powder to obtain particle cores with a particle size of 0.8 mm to 1.2 mm, and then spraying Ta2O5 fine powder with a particle size of 0.1 μm to 0.5 μm on the surface of the particle cores to coat the surface of the particle cores to form core-shell structure particles with a particle size of 2.5 mm to 3.5 mm; At an oxygen partial pressure of 10 -5 atm-10 -4 Atm low oxygen partial pressure atmosphere, the core-shell structure particles are subjected to multi-stage temperature rising sintering to form a single metastable phase evaporation source material, wherein the evaporation source material has a grain size of 20nm-50nm and no second phase precipitation of Ta2O 5-x Materials, wherein 0<x<0.2, the Ta2O 5-x The oxygen vacancy concentration in the core region of the material is higher than that in the outer shell region; The oxygen partial pressure is 10 -5 atm-10 -4 Atm low oxygen partial pressure atmosphere, the core-shell structure particles are subjected to multi-stage temperature raising sintering to form a single metastable phase evaporation source material, comprising the following steps: At an oxygen partial pressure of 10 -5 atm-10 -4 atm low oxygen partial pressure atmosphere, raising the temperature to a first preset temperature at a first heating rate, and maintaining the temperature for a first preset time; Raising the temperature to a second preset temperature at a second heating rate and keeping the temperature for a second preset time; Raising the temperature to a third preset temperature at a third heating rate and maintaining the temperature for a third preset time, wherein the second preset temperature is greater than the first preset temperature and less than the third preset temperature; Cooling to room temperature at a preset cooling rate to form the evaporation source material; The first preset temperature is 400° C.-600° C., and the first preset time is 0.5 h-1 h; The second preset temperature is 1000° C.-1300° C., and the second preset time is 1 hour-2 hours; The third preset temperature is 1400° C.-1800° C., and the third preset time is 2 hours-4 hours; The first heating rate, the third heating rate and the preset cooling rate are all 2°C / min-5°C / min, and the second heating rate is 8°C / min-12°C / min.

2. The preparation method according to claim 1, characterized in that The following steps are also included: The evaporation source material is subjected to oxygen plasma treatment to form a passivation layer on the surface of the evaporation source material with an oxygen vacancy concentration lower than that of the shell region, and the thickness of the passivation layer is 2nm-10nm.

3. The preparation method according to claim 2, characterized in that During the oxygen plasma treatment of the evaporation source material, a gas containing a doping element is introduced simultaneously to form a passivation layer containing the doping element, wherein the doping element is selected from nitrogen, silicon or boron.

4. The preparation method according to claim 3, characterized in that The atomic concentration of the doping element in the passivation layer containing the doping element is 0.2 at % to 0.8 at %.

5. The preparation method according to claim 4, characterized in that The radio frequency power of the oxygen plasma treatment is 50 W-200 W, and the treatment time is 5 min-30 min.

6. The preparation method according to any one of claims 3 to 5, characterized in that The following steps are also included: The evaporation source material with a passivation layer formed on the surface is annealed at 300° C.-500° C. for 0.5 h-1.5 h.

7. A vacuum evaporation coating method, characterized in that: The steps include: The evaporation source material prepared by the preparation method according to any one of claims 1 to 6 was loaded into an evaporation crucible, and the evaporation chamber was evacuated to 1×10 -4 Pa-5×10 -4 Pa; Heating the temperature to 1750°C-1850°C at a heating rate of 1°C / min-6°C / min and keeping the temperature for 1h-2h to pre-melt the evaporation source material; The evaporation deposition rate is controlled to be 0.5nm / s-1.5nm / s, and the evaporated particles are deposited on the surface of the substrate at a temperature of 80℃-150℃. Evaporation is stopped after the preset film thickness is reached.

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