Composite modified material for lithium niobate wafer

Abstract

The invention discloses a composite modified material for a lithium niobate wafer, and relates to the technical field of nano materials. The material is composed of an anti-corrosion passivation matrix and a function enhancement component, wherein the anti-corrosion matrix adopts a silicon nitride / SiO2 multi-layer composite layer, atomic layer deposition titanium dioxide and magnetron sputtering aluminum oxide to form cascade protection; the functional layer comprises lead sulfide nanoparticles and nano silicon dioxide, and is directionally modified by a silane coupling agent and a perfluoropolyether surfactant. During preparation, PbS nano-particles are synthesized by combining a PECVD-ALD-magnetron sputtering stepped deposition process (200-150 DEG C) with a solvothermal method, and finally, the PbS nano-particles are formed through spin coating-annealing (300-400 DEG C). The optical loss of the material under the wavelength of 1550 nm is smaller than 0.2 dB / cm, the acid and alkali corrosion resistance is larger than 240 h, the lead dissolution rate is smaller than 0.1 ppm, the interface state density is reduced by 2 orders of magnitude, the contradiction between lithium niobate wafer surface degradation, photoelectric property degradation and lead-containing material environment risk is solved, and the material is suitable for 5G optical waveguide and quantum integrated device packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and particularly to a composite modification material for lithium niobate wafers. Background Art

[0002] As a ferroelectric material, lithium niobate wafers have a high Curie temperature (about 1210 °C), a wide transparent window (0.35 - 5.5 μm), and excellent electro-optic coefficients (r 33 ≈30.8 pm / V), making it an ideal substrate for optical waveguides, modulators, frequency converters, and surface acoustic wave filters. In the fields of 5G communication, quantum optics, and integrated photonics, the demand for thin film and high performance of lithium niobate wafers is particularly urgent. However, the surface of lithium niobate wafers is prone to degradation in high temperature, high temperature, or chemical corrosion environments, resulting in the decline of device performance. For example, in a humid or acidic environment, lithium ions may dissolve out or the crystal structure may be damaged on the surface of lithium niobate, thereby reducing the device life and reliability. In addition, the interface defects and surface roughness of lithium niobate wafers have a significant impact on their optoelectronic properties. In optical waveguide applications, surface scattering and interface absorption will lead to an increase in optical loss; in surface acoustic wave devices, surface defects may cause acoustic wave propagation loss and reduce the filter efficiency. Therefore, developing a surface modification material that can simultaneously provide corrosion protection, passivate interface defects, and enhance functionality has become the key to solving the above problems.

[0003] To address the surface problems of lithium niobate wafers, researchers have developed various modification techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), and wet chemical coatings. These techniques aim to improve the wafer performance by depositing protective or functional layers. Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD)PVD (such as magnetron sputtering) and CVD (such as plasma-enhanced chemical vapor deposition, PECVD) are commonly used to deposit oxide (such as SiO2, Al2O3) or nitride (such as Si3N4) thin films on the surface of lithium niobate. These thin films can provide certain corrosion resistance protection and mechanical stability. For example, the SiO2 layer, due to its high chemical stability and low refractive index, is commonly used as the cladding material for optical waveguides; the Si3N4 layer, due to its high hardness and corrosion resistance, is used to enhance surface durability. However, it is difficult for a single-material thin film to simultaneously meet the multiple requirements of corrosion resistance, interface passivation, and function enhancement. In addition, PVD and CVD processes have limitations in high-precision thickness control and uniformity. Especially in complex multi-layer structures, interface stress may cause film cracking or peeling. Atomic Layer Deposition (ALD)ALD has shown excellent performance in the surface modification of lithium niobate due to its atomic-level precision and excellent film uniformity. ALD can deposit ultra-thin passivation layers (such as Al2O3, TiO2), effectively reducing interface defects and improving chemical stability. For example, Al2O3 thin films (with a thickness of 5-10 nm) have been proven to significantly reduce charge trapping and chemical reactivity on the surface of lithium niobate. However, the ALD process is costly and has a slow deposition rate, which limits its application in large-scale production. In addition, a single ALD thin film is difficult to provide complex functionality, such as optoelectronic enhancement or infrared absorption. Wet Chemical Coatings and Nanoparticle CompositesWet chemical methods (such as sol-gel method, spin coating, or dip coating) are commonly used to introduce organic-inorganic composite coatings or nanoparticle layers on the surface of lithium niobate. These coatings can achieve specific properties by adding functional nanoparticles (such as metal oxides, sulfides). For example, lead sulfide (PbS) nanoparticles, due to their narrow bandgap (about 0.41 eV) and excellent infrared absorption characteristics, are used in photodetectors and photocatalytic devices. However, the adhesion and long-term stability of wet chemical coatings are poor, and the dispersion and particle size control of nanoparticles have a significant impact on performance. In addition, the environmental safety issues of lead-containing materials also need special attention.

[0004] Although the above technologies have made certain progress in the modification of lithium niobate wafers, there are still the following deficiencies: Limitations of single materials Single-material thin films (such as SiO2, Al2O3) are difficult to simultaneously meet the multiple requirements of corrosion resistance, passivation effect, and function enhancement. For example, although the SiO2 layer can provide corrosion protection, its improvement of optoelectronic properties is limited; PbS nanoparticles can enhance infrared absorption, but their chemical stability is poor. Interface problems of multi-layer structures Although multi-layer composite thin films (such as Si3N4 / SiO2) can improve performance, the difference in thermal expansion coefficients and interface stress between different materials may lead to film cracking or peeling. In addition, traditional deposition technologies pose challenges in the thickness control and uniformity of multi-layer structures. Process complexity and cost Existing modification technologies (such as ALD, PECVD) usually require high-temperature or vacuum environments, with complex processes and high energy consumption, which is not conducive to large-scale production. Although wet chemical methods have lower costs, the coating uniformity and long-term stability are insufficient. Lack of functionality Current modified materials mainly focus on protection functions and less attention is paid to the enhancement of optoelectronic properties. For example, in photonic integrated circuits or infrared detectors, lithium niobate wafers need to have both excellent optical response and surface stability, while the existing material systems are difficult to meet this requirement. Environmental and safety issues Although lead-containing nanoparticles (such as PbS) have excellent optoelectronic properties, their potential toxicity and environmental risks limit the scope of application. In addition, some organic solvents and precursors (such as trimethylaluminum) may generate hazardous wastes during the preparation process.

[0005] In recent years, the development of nanomaterial technology has provided new opportunities for the modification of lithium niobate wafers. For example, the strategy of combining multi-layer composite thin films with nanoparticles has been proven to significantly improve material performance; the combination of advanced deposition technologies (such as ALD, PECVD) and wet chemical methods can achieve a balance between high precision and low cost. In addition, the controllable synthesis technology of functional nanoparticles (such as sulfides, oxides) provides the possibility for optimizing optoelectronic properties. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to propose a composite modified material for lithium niobate wafers to overcome the defects in the prior art such as the difficulty in coordinating corrosion resistance and functionality, the decline of optoelectronic properties caused by interface defects, poor process compatibility of multi-layer structures, and insufficient controllability of environmental risks of lead-containing materials, and to achieve the technical effects of high corrosion resistance-passivation-function enhancement integration, low-temperature and efficient preparation process, stable dispersion of nanoparticles, and environmentally friendly treatment.

[0007] The technical solution adopted is as follows: a composite modification material for lithium niobate wafers. By weight, the corrosion-resistant passivation matrix material: a silicon nitride / SiO2 multi-layer composite layer of 50-70 parts, with a single-layer thickness of 50-100 nm; an atomic layer deposition passivation film of 20-30 parts, with a thickness ≤ 80 nm; an alumina layer, with a thickness ≤ 10 nm; the functional enhancement material: lead sulfide nanoparticles of 5-15 parts, with a particle size of 5-10 nm; the auxiliary component: 2-5 parts of silane coupling agent, 3-8 parts of nano-silica, and 0.5-1.5 parts of perfluoropolyether surfactant.

[0008] Preferably, the parameters of the nano-silica are as follows: the particle size is 20-50 nm, and the specific surface area ≥ 200 m 2 / g.

[0009] Preferably, the silane coupling agent is 3-methacryloxypropyltrimethoxysilane, aminopropyltriethoxysilane, vinyltrimethoxysilane or octyltriethoxysilane; the perfluoropolyether surfactant is perfluoropolyether carboxylic acid, perfluoropolyether alcohol or perfluoropolyether acyl fluoride.

[0010] Preferably, the preparation method is as follows: Using plasma enhanced chemical vapor deposition technology, silicon nitride and SiO2 layers are alternately deposited on the surface of a clean lithium niobate wafer; then, an atomic layer deposition technology is used to deposit a titanium dioxide passivation film; an aluminum oxide layer is deposited on the surface of the passivation film by magnetron sputtering; then, lead sulfide nanoparticles are synthesized by a solvothermal method. The lead sulfide nanoparticles are dispersed in an ethanol solution 5-10 times its weight, and a silane coupling agent and a perfluoropolyether surfactant are added. Nano-silica is uniformly coated on the surface of the aluminum oxide layer by spin coating or dip coating and then dried. Finally, an annealing treatment is carried out at a temperature of 300-400 °C for 30-60 min and cooled to room temperature in an inert gas atmosphere. Preferably, the parameters for the alternate deposition are as follows: temperature 200-300 °C, the gas source is SiH4, and the radio frequency power is 100-200 W. Preferably, when depositing the titanium dioxide passivation film, the precursor is trimethylaluminum and the deposition temperature is 150-200 °C. Preferably, when magnetron sputtering to deposit the aluminum oxide layer, an Al target is used and the deposition temperature is 100-150 °C. Preferably, the method for synthesizing lead sulfide nanoparticles by a solvothermal method is as follows: Lead oxide and 1-octadecyl-3-methylimidazolium chloride are mixed at a mass ratio of 1:4, degassed at 110±2 °C for 2 h under argon protection to obtain a lead precursor solution; then, sulfur and N,N-dimethylformamide are dissolved at a weight ratio of 1:3 and ultrasonically treated at 80 °C for 30 min to obtain a sulfur precursor solution; when the lead precursor solution is heated to 150±5 °C, the sulfur precursor solution is injected at a rate of 2 mL / s, and the lead-sulfur molar ratio is controlled to be 1.05:1. The reaction is terminated by quenching with ice water. The crude product is centrifuged at 9000 rpm, and the final product is dispersed in chlorobenzene with a solid content controlled to be 10±0.5 mg / mL. Preferably, the drying temperature is 80-120 °C.

[0011] Silicon nitride (Si3N4), CAS No.: 12033-89-5. Silicon dioxide (SiO2), CAS No.: 7631-86-9. Titanium dioxide (TiO2), CAS No.: 13463-67-7. Aluminum oxide (Al2O3), CAS No.: 1344-28-1. Lead sulfide (PbS), CAS No.: 1314-87-0. 3-Methacryloxypropyltrimethoxysilane, CAS No.: 2530-85-0. Aminopropyltriethoxysilane, CAS No.: 919-30-2. Vinyltrimethoxysilane, CAS No.: 2768-02-7. Octyltriethoxysilane, CAS No.: 2943-75-1. Nano-silicon dioxide (SiO2), CAS No.: 7631-86-9. Sulfur (S), CAS No.: 7704-34-9. N, N-Dimethylformamide (DMF), CAS No.: 68-12-2. Ethanol, CAS No.: 64-17-5. Chlorobenzene, CAS No.: 108-90-7. Trimethylaluminum, CAS No.: 75-24-1. Silane (SiH4), CAS No.: 7803-62-5. Perfluoropolyether carboxylic acid, CAS No.: 51798-33-5. Perfluoropolyether alcohol, CAS No.: 90317-77-4. Perfluoropolyether acyl fluoride, CAS No.: 65208-35-7. Lead oxide (PbO), CAS No.: 1317-36-8. The CAS No. of 1-octadecyl-3-methylimidazolium chloride is 171058-19-8.

[0012] Thin film deposition equipment: Plasma Enhanced Chemical Vapor Deposition (PECVD), equipment model: Oxford Instruments PlasmaPro System 100, function: alternately deposit silicon nitride (Si3N4) and SiO2 multi-layer composite layers. Atomic Layer Deposition (ALD), equipment model: Beneq TFS500, function: deposit titanium dioxide (TiO2) passivation film. Magnetron sputtering system, equipment model: AJA International Orion 8, function: deposit aluminum oxide (Al2O3) protective layer. Solvothermal reaction kettle, equipment model: Parr Instrument 5000 series, function: synthesize lead sulfide (PbS) nanoparticles. Spin coating / dip coating system, equipment model: SUSS MicroTec Gamma 8, function: coat nano-silica layer. Annealing furnace, equipment model: Thermo Scientific Lindberg Blue M, function: annealing treatment (inert gas atmosphere).

[0013] Through the multi-level structure design and the synergistic effect of functional components, this composite modified material solves the contradiction among the corrosion resistance, optoelectronic performance and environmental safety of lithium niobate wafers. The following is an in-depth analysis of its core mechanism: Anti-corrosion passivation matrix mechanism: silicon nitride / SiO2 multi-layer composite layer, Stress buffering mechanism: silicon nitride (Si3N4, hardness 8.5 - 9.0) and SiO2 (thermal expansion coefficient 0.5×10 -6 / °C) are alternately deposited to form a gradient structure. Through the gradual transition of the difference in thermal expansion coefficients, the interfacial stress concentration is reduced, preventing film cracking. Chemical corrosion inhibition: The dense crystal structure of Si3N4 (density 3.2 g / cm 3 ) can block the penetration of H + / OH - ions, and the corrosion rate in sulfuric acid solution with pH = 2 is reduced by 98% compared with pure lithium niobate. ALD titanium dioxide passivation layer: Defect filling effect: The TiO2 film (thickness ≤ 80 nm) deposited by ALD technology fills the surface grain boundary defects with atomic precision, reducing the interfacial state density from 10 12 cm -2 eV -1 to 10 10 cm -2 eV -1, reducing the carrier recombination rate. Energy band matching optimization: The conduction band position of TiO2 (-4.2 eV) and lithium niobate (-4.0 eV) form a stepped energy band structure, suppressing the reverse recombination of photo-generated electron-hole pairs and enhancing the quantum efficiency. Magnetron sputtering alumina protective layer: Mechanical strengthening effect: The nano-indentation hardness of the Al2O3 layer (thickness ≤ 10 nm) reaches 15 GPa, and the friction coefficient is 0.2, which can reduce the surface wear rate to 1 / 20 of the unmodified wafer. Chemical inert barrier: The dissolution rate of the dense amorphous structure of Al2O3 in a NaOH solution with pH = 12 is <0.1 nm / h, forming a dynamic passivation film. Functional enhancement material mechanism: Lead sulfide nanoparticles, quantum confinement effect: PbS particles with a size of 5-10 nm (bandgap 0.41 eV) are restricted by the exciton Bohr radius (18 nm) at a wavelength of 1550 nm, resulting in a significant quantum size effect, and the light absorption coefficient is increased to 10 5 cm -1 . Surface plasmon resonance: The local surface plasmon resonance (LSPR) peak position of PbS is matched to the 1550 nm communication band through size regulation, reducing the optical waveguide loss from 1.0 dB / cm to 0.15 dB / cm. Nano-silica auxiliary layer: Optical field regulation effect: 20-50 nm SiO2 particles (refractive index 1.46) form a graded refractive index layer on the surface of lithium niobate (refractive index 2.2), reducing the surface roughness from 10 nm to 2 nm by suppressing Rayleigh scattering. Stress release network: Nano-silica with a high specific surface area (≥200 m 2 / g) absorbs more than 60% of the thermal stress through a three-dimensional interpenetrating network structure, preventing the functional layer from peeling off. Environmental safety control mechanism: Lead ion stabilization, amphiphilic molecule encapsulation: Silane coupling agents (such as KH-570) and perfluoropolyether surfactants form a C-F / Si-O composite passivation layer on the surface of PbS, making the lead dissolution rate <0.1 ppm in a 72-hour water immersion test. Lattice anchoring effect: Ti in the ALD-TiO2 layer 40 and Pb 20 form Ti-O-Pb bonds through ion exchange, fixing lead ions in the TiO2 lattice. Process collaborative optimization: Low-temperature step deposition: The stepped temperature design of PECVD (250 °C) → ALD (175 °C) → magnetron sputtering (125 °C) makes the lattice distortion rate of lithium niobate <0.1%, maintaining its intrinsic electro-optic coefficient (r 33 ≈30.8 pm / V). Solvothermal method for controllable synthesis: 1-Octadecyl-3-methylimidazolium chloride template guides the preferential growth of PbS along the (200) crystal plane, obtaining monodisperse nanoparticles (PDI < 0.1). This material system realizes lithium niobate wafers for 5G optical waveguides (loss < 0.2 dB / cm) and quantum devices (interface state density 10 9 cm-2 eV- 1 ) in the breakthrough application.

[0014] In summary, the beneficial effects of the present invention are as follows: excellent corrosion resistance and chemical stability: Through the multi-layer composite structure design, the present invention provides excellent corrosion protection for lithium niobate wafers, which can effectively resist the erosion of high-temperature, high-humidity and chemical corrosion environments. This beneficial effect is mainly due to the following three key components and their synergistic effects: Silicon nitride / SiO2 multi-layer composite layer: This layer alternately deposits silicon nitride (Si3N4) and silicon dioxide (SiO2) by plasma-enhanced chemical vapor deposition (PECVD) technology, and the single-layer thickness is controlled at 50-100 nm. Silicon nitride has high hardness (Mohs hardness 8.5-9.0), excellent chemical stability (resistant to strong acid and strong alkali corrosion) and low thermal expansion coefficient (2.5×10 -6 / °C), which can effectively resist external erosion. Silicon dioxide, with its high transparency (refractive index 1.46), low dielectric constant (3.9) and good insulation (breakdown field strength > 10 7 V / cm), relieves the interface stress and prevents film cracking or peeling caused by the difference in thermal expansion coefficient. Experimental data show that after the lithium niobate wafers modified by the present invention are immersed in sulfuric acid solution with pH = 2 and sodium hydroxide solution with pH = 12 for 240 h, the surface morphology has no obvious change, and the optical performance attenuation is less than 5%, which is far better than that of unmodified wafers (serious surface corrosion, attenuation > 50%). Atomic layer deposition (ALD) titanium dioxide passivation film: Titanium dioxide (TiO2), with its high refractive index (2.4-2.6), excellent chemical stability (resistant to acid and alkali corrosion) and wide bandgap (3.2 eV) characteristics, is deposited by ALD technology to form a uniform film with a thickness ≤ 80 nm. This film has atomic-level precision, can effectively fill surface micro-defects and reduce the interface state density. The C-V test results show that the interface state density decreases from 10 12 cm -2 eV -1 to 10 10 cm -e eV -1, significantly reducing charge trapping and leakage phenomena and enhancing the stability of the device in harsh environments. Magnetron sputtered alumina layer: Alumina (Al2O3) serves as the outermost protection with a thickness controlled at ≤10 nm, having high hardness (Mohs hardness 9.0) and excellent wear and corrosion resistance. The Al2O3 layer deposited by magnetron sputtering technology further enhances the mechanical strength and chemical stability of the surface. Corrosion resistance tests show that after adding the Al2O3 layer, the performance degradation of the wafer in acidic and alkaline environments is further reduced to <2%, demonstrating excellent protection ability. The cascade design of the above multi-layer structure makes full use of the advantages of each material to form a dual physical and chemical barrier, enabling the lithium niobate wafer to maintain stable performance in extreme environments. This effect not only solves the problem of insufficient corrosion resistance of traditional single protective layers but also significantly extends the service life of the device. Significantly improved optoelectronic performance: By introducing functional enhancement materials, the present invention significantly improves the optoelectronic performance of the lithium niobate wafer, making its application in optical waveguides and optoelectronic integrated devices more competitive. The specific improvements are reflected in the following aspects: Lead sulfide (PbS) nanoparticles: PbS nanoparticles, with their narrow bandgap (0.41 eV), high absorption coefficient (>10 5 cm -1 in the IR region), and excellent infrared response characteristics, are synthesized by solvothermal method (particle size 5 - 10 nm), showing quantum size effects and being able to effectively adjust the energy band structure and improve the light absorption efficiency. Optical performance tests show that the light loss of the modified wafer at a wavelength of 1550 nm is reduced to 0.15 dB / cm, far lower than 1.0 dB / cm of the unmodified wafer and 0.5 dB / cm of the traditional SiO2 cladding. This improvement is crucial for the requirements of low-loss optical waveguides in 5G communication. Nanoscale silicon dioxide (SiO2): Nanoscale SiO2 (particle size 20 - 50 nm, specific surface area ≥200 m 2 / g) It is uniformly coated on the surface through spin coating or dip coating techniques. Due to its high transparency and low refractive index (1.46) characteristics, it significantly improves the surface smoothness (RMS roughness is reduced from 10 nm to 2 nm), reduces light scattering loss, and further optimizes the optical performance. The test results show that the reduction of light loss is closely related to the addition of nano-SiO2. Surface modification optimization: The PbS nanoparticles are directionally modified by silane coupling agents (such as 3-methacryloxypropyltrimethoxysilane) and perfluoropolyether surfactants, which not only improves their dispersibility and stability in solvents, avoids agglomeration, but also ensures the uniformity and long-term stability of the functional layer. This modification enables the optoelectronic performance to remain consistent in multiple tests with excellent repeatability. With the above improvements, the light loss of the present invention at a wavelength of 1550 nm is less than 0.2 dB / cm, far superior to traditional materials, and significantly enhances the application potential of lithium niobate wafers in photonic integrated circuits and infrared detectors. Excellent environmental safety: Aiming at the potential environmental risks posed by lead-containing materials, the present invention achieves excellent environmental safety through multiple strategies, ensuring the sustainability of the materials in practical applications: Stabilization of PbS nanoparticles: Through the modification of silane coupling agents and perfluoropolyether surfactants, a dense organic-inorganic composite protective layer is formed on the surface of PbS nanoparticles, significantly reducing the dissolution rate of lead ions. Environmental safety tests show that the lead dissolution rate of the modified wafer is less than 0.1 ppm, far lower than the international environmental safety standard (EPA standard: 5 ppm for drinking water). This result proves the effectiveness of the modification strategy. Environmentally friendly process: The solvents (such as ethanol, chlorobenzene) and precursors (such as trimethylaluminum) selected during the preparation process are all low-toxic or non-toxic substances, and the process temperature is controlled at 150 - 400 °C, avoiding the generation of hazardous waste caused by high-temperature treatment. The emissions of waste gas and waste liquid meet the requirements of green manufacturing, further reducing the potential impact on the environment. These measures not only eliminate the environmental risks of lead-containing materials, but also provide a solid guarantee for the popularization and application of the present invention, making it still competitive under the background of increasingly strict environmental protection regulations. Low-temperature and high-efficiency preparation process: The present invention adopts a series of low-temperature and high-efficiency preparation techniques, significantly reducing production costs and energy consumption, while improving the controllability and production efficiency of the process: PECVD-ALD-magnetron sputtering step deposition process: This process integrates the preparation processes of silicon nitride / SiO2 multi-layer composite layers (deposition temperature 200 - 300 °C), titanium dioxide passivation films (deposition temperature 150 - 200 °C), and alumina layers (deposition temperature 100 - 150 °C) into a step process, with the overall temperature controlled at 150 - 300 °C, far lower than the traditional high-temperature CVD process (>500 °C). The low-temperature process not only reduces the damage of thermal stress to lithium niobate wafers, but also reduces energy consumption, and is suitable for large-scale production.Solvothermal Synthesis of PbS Nanoparticles: PbS nanoparticles are synthesized by a low-temperature (150 °C) solvothermal method with short reaction time (<1 h), high yield (>90%), and easy control of particle size and morphology. Compared with traditional high-temperature synthesis processes, this method reduces energy consumption by about 50% and has a simple process, facilitating industrial promotion. Spin-Coating - Annealing Forming Process: The spin-coating technique ensures the uniformity of the functional layer. The annealing temperature is controlled at 300 - 400 °C for only 30 - 60 min, significantly reducing energy consumption compared with traditional high-temperature sintering processes (>600 °C). In addition, cooling in an inert gas after annealing avoids oxidation and contamination, further improving the material quality. The low-temperature and high-efficiency characteristics of the above processes not only reduce production costs (expected to save 30% - 40% compared with traditional processes) but also improve production efficiency, laying an economic foundation for the application of this invention in high-tech fields. Wide Application Prospects: Due to its excellent properties, the composite modified material of this invention shows wide application prospects, especially suitable for the following high-tech fields: 5G Optical Waveguides: In 5G communication, optical waveguides require low loss, high stability, and environmental resistance. The characteristics of optical loss <0.2 dB / cm, corrosion resistance >240 h, and a two-order-of-magnitude reduction in interface state density provided by this invention fully meet the high-performance requirements of 5G optical waveguides, providing reliable support for high-speed communication. Quantum Integrated Device Encapsulation: Quantum devices have extremely high requirements for the optical and electrical properties of materials. The composite modified material of this invention reduces interface defects through a passivation layer, improving quantum efficiency and device stability, and is particularly suitable for the fields of quantum optics and integrated photonics. Other Fields: This invention can also be extended to fields such as infrared detectors, electro-optical modulators, and surface acoustic wave filters that require high-performance optoelectronic materials. Its versatility and high reliability give it broad potential in the future optoelectronic market.

[0015] In summary, through innovative multi-layer composite structure and functional enhancement material design, this invention has achieved a comprehensive improvement in the corrosion resistance, optoelectronic properties, environmental safety, preparation process, and application prospects of lithium niobate wafers. Specifically, its corrosion resistance and chemical stability are significantly enhanced through the synergistic effect of the silicon nitride / SiO2 multi-layer composite layer, titanium dioxide passivation film, and alumina layer; the optoelectronic properties are greatly improved by the introduction of lead sulfide nanoparticles and nano-silica; environmental safety is ensured through modification strategies and green processes; the low-temperature and high-efficiency preparation process reduces costs and improves efficiency; the wide application prospects provide new solutions for high-tech fields. These beneficial effects not only solve the contradictions of surface degradation, optoelectronic property decline of lithium niobate wafers, and environmental risks of lead-containing materials but also provide strong material support for the development of cutting-edge technologies such as 5G communication and quantum optics, with remarkable innovation and practical value. Description of the Drawings

[0016] Figure 1It is the scanning electron microscope image of the thin film prepared in Example 1.

[0017] Figure 2 It is the scanning electron microscope demonstration image of the silicon nitride / SiO2 multilayer composite layer prepared in Example 1.

[0018] Figure 3 It is the transmission electron microscope image of the lead sulfide nanoparticles prepared in Example 1.

[0019] Figure 4 It is the scanning electron microscope image of the composite modified material prepared in Example 1. Detailed implementation manners

[0020] The present invention will be described in detail below through specific examples. However, the uses and purposes of these exemplary embodiments are only used to illustrate the present invention, and do not constitute any form of limitation to the actual protection scope of the present invention, nor limit the protection scope of the present invention thereto. For parameter ranges not mentioned, intermediate values are selected. At the same time, for mass percentages or weight percentages not clearly stated or mentioned, it generally refers to the final concentration after addition. In addition, for possible unmentioned components or process parameter conditions, it is generally defaulted that the conventional operations of those skilled in the art can be adopted to achieve.

[0021] Example 1

[0022] Etching-resistant passivation matrix material: silicon nitride / SiO2 multilayer composite layer: 60 g (single layer thickness 75 nm), atomic layer deposition passivation thin film (titanium dioxide), and its structure is as Figure 1 shown: 25 g (thickness 50 nm), alumina layer: 5 g (thickness 8 nm).

[0023] Function-enhancing material: lead sulfide nanoparticles: 10 g (particle size 7 nm), nano-silica: 5 g (particle size 35 nm, specific surface area 250 m 2 / g).

[0024] Auxiliary components: silane coupling agent (3-methacryloxypropyltrimethoxysilane): 3 g, perfluoropolyether surfactant (perfluoropolyether carboxylic acid): 1 g.

[0025] Preparation method: deposition of silicon nitride / SiO2 multilayer composite layer, and it is as Figure 2 shown: method: plasma enhanced chemical vapor deposition (PECVD); parameters: temperature 250 °C, gas source SiH4, radio frequency power 150 W. Deposition of titanium dioxide passivation thin film: method: atomic layer deposition (ALD); parameters: deposition temperature 175 °C, precursor is tetrakis(dimethylamino)titanium (TDMAT). Deposition of alumina layer: method: magnetron sputtering; parameters: using Al target, deposition temperature 125 °C. Synthesis of lead sulfide nanoparticles, and its structure is as Figure 3Shown as follows: Method: Solvothermal method. Steps: Mix lead oxide and 1-octadecyl-3-methylimidazolium chloride in a mass ratio of 1:4, and degas at 110 °C for 2 h under argon protection. Dissolve sulfur and N,N-dimethylformamide in a weight ratio of 1:3, and perform ultrasonic treatment at 80 °C for 30 min. Heat the lead precursor to 150 °C and inject the sulfur precursor solution at a rate of 2 mL / s, with a lead-to-sulfur molar ratio of 1.05:1. After the reaction, quench with ice water, centrifuge at 9000 rpm, and disperse the final product in chlorobenzene with a solid content of 10 mg / mL. Coating of the functional layer: Disperse PbS nanoparticles in 7 times the weight of ethanol, and add a silane coupling agent and a perfluoropolyether surfactant. Coat nanosilica on the surface of the alumina layer by spin coating, and dry at a temperature of 100 °C. Annealing treatment: Temperature 350 °C, time 45 min, and cool to room temperature in an argon atmosphere. The scanning electron micrograph of the outer surface of the finally prepared composite modified material is as shown in Figure 4 shown.

[0026] Example 2

[0027] Same as Example 1, but the silicon nitride / SiO2 multilayer composite layer is adjusted to 50 g, and the other components are adjusted accordingly to keep the total mass 100 g.

[0028] Example 3

[0029] Same as Example 1, but the silicon nitride / SiO2 multilayer composite layer is adjusted to 70 g, and the other components are adjusted accordingly to keep the total mass 100 g.

[0030] Example 4

[0031] Same as Example 1, but the atomic layer deposition passivation film is adjusted to 20 g, and the other components are adjusted accordingly to keep the total mass 100 g.

[0032] Example 5

[0033] Same as Example 1, but the atomic layer deposition passivation film is adjusted to 30 g, and the other components are adjusted accordingly to keep the total mass 100 g.

[0034] Example 6

[0035] Same as Example 1, but the lead sulfide nanoparticles are adjusted to 5 g, and the other components are adjusted accordingly to keep the total mass 100 g.

[0036] Example 7

[0037] Same as Example 1, but the lead sulfide nanoparticles are adjusted to 15 g, and the other components are adjusted accordingly to keep the total mass 100 g.

[0038] Example 8

[0039] Same as Example 1, but the nano-silica is adjusted to 3 g, and the other components are adjusted accordingly to maintain a total mass of 100 g.

[0040] Example 9

[0041] Same as Example 1, but the nano-silica is adjusted to 8 g, and the other components are adjusted accordingly to maintain a total mass of 100 g.

[0042] Example 10

[0043] Same as Example 1, but the silane coupling agent is adjusted to 2 g, and the other components are adjusted accordingly to maintain a total mass of 100 g.

[0044] Example 11

[0045] Same as Example 1, but the silane coupling agent is adjusted to 5 g, and the other components are adjusted accordingly to maintain a total mass of 100 g.

[0046] Example 12

[0047] Same as Example 1, but the perfluoropolyether surfactant is adjusted to 0.5 g, and the other components are adjusted accordingly to maintain a total mass of 100 g.

[0048] Example 13

[0049] Same as Example 1, but the perfluoropolyether surfactant is adjusted to 1.5 g, and the other components are adjusted accordingly to maintain a total mass of 100 g.

[0050] Example 14

[0051] Same as Example 1, but the annealing temperature is adjusted to 300 °C.

[0052] Example 15

[0053] Same as Example 1, but the annealing temperature is adjusted to 400 °C.

[0054] Comparative Example 1

[0055] Do not use the silicon nitride / SiO2 multi-layer composite layer (0 g), and the other components are the same as in Example 1 and the proportions are adjusted to maintain a total mass of 100 g.

[0056] Comparative Example 2

[0057] Do not use the atomic layer deposition passivation thin film (0 g), and the other components are the same as in Example 1 and the proportions are adjusted to maintain a total mass of 100 g.

[0058] Comparative Example 3

[0059] Do not use the alumina layer (0 g), and the other components are the same as in Example 1 and the proportions are adjusted to maintain a total mass of 100 g.

[0060] Comparative Example 4

[0061] Lead sulfide nanoparticles were not used (0 g), and the remaining components were the same as in Example 1 and the proportions were adjusted to maintain a total mass of 100 g.

[0062] Comparative Example 5

[0063] Nanosilica was not used (0 g), and the remaining components were the same as in Example 1 and the proportions were adjusted to maintain a total mass of 100 g.

[0064] Comparative Example 6

[0065] Silane coupling agent was not used (0 g), and the remaining components were the same as in Example 1 and the proportions were adjusted to maintain a total mass of 100 g.

[0066] Comparative Example 7

[0067] Perfluoropolyether surfactant was not used (0 g), and the remaining components were the same as in Example 1 and the proportions were adjusted to maintain a total mass of 100 g.

[0068] Comparative Example 8

[0069] Annealing treatment was not carried out, and the remaining steps and components were the same as in Example 1.

[0070] It should be reminded that the total mass of all examples and comparative examples is 100 g.

[0071] Optical property test

[0072] Purpose: To measure the optical loss of the composite modified material at a wavelength of 1550 nm and evaluate its optical properties in optical waveguide applications. Method: Using an optical waveguide loss measurement system, a 1550 nm laser source was used to measure the propagation loss of light in the waveguide, with the unit of dB / cm. Equipment: 1550 nm laser source, optical waveguide coupling system, optical power detector. Test steps: Sample preparation: The composite modified material was coated on a lithium niobate wafer according to the formula and process of the example or comparative example. System setup: Using a 1550 nm laser source, light was injected into the waveguide through the coupling system, and the detector recorded the output light intensity. Measurement: Record the input light intensity and output light intensity, and calculate the propagation loss. The formula is: where L is the waveguide length (cm).

[0073] Corrosion resistance test

[0074] Purpose: To evaluate the corrosion resistance of materials in acidic and alkaline environments. Method: Acid-base immersion tests were conducted using sulfuric acid solution with pH = 2 and sodium hydroxide solution with pH = 12. The immersion time was 240 h. Corrosion resistance was evaluated by changes in surface morphology and attenuation of optical properties. Equipment: Optical microscope, optical property testing system. Test procedure: Sample preparation: The same as for optical property testing. Immersion: Place the samples in solutions with pH = 2 and pH = 12 respectively, and immerse for 240 h while maintaining a constant temperature (25 °C). Observation: Use SEM or optical microscope to observe the morphological changes on the surface of the samples after immersion. Performance testing: Re-measure the optical properties after immersion and calculate the percentage change in loss:

[0075] Environmental safety test

[0076] Purpose: To measure the lead dissolution rate and evaluate the environmental safety of lead-containing materials. Method: The immersion method was used. The samples were placed in distilled water, and samples were taken regularly. Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the lead content. Equipment: ICP-MS. Constant temperature water bath test procedure: Sample preparation: The same as above. Immersion: Immerse the samples in distilled water for 72 h at a temperature of 25 °C. Sampling: Take samples once every 24 h, for a total of 3 times. Analysis: Use ICP-MS to measure the lead concentration (unit: ppm) of each sample taken, and calculate the average dissolution rate. Interface performance test

[0077] Purpose: To measure the interface state density and evaluate the quality of the interface between the material and the lithium niobate wafer. Method: Capacitance-voltage (C-V) tests were conducted. A metal-insulator-semiconductor (MIS) structure was prepared, and the insulating layer was a composite modified material. Equipment: LCR meter. Vacuum evaporation system Test procedure: Sample preparation: Deposit a composite modified material as the insulating layer on the lithium niobate wafer, and then evaporate a metal electrode (such as aluminum) to form an MIS structure. C-V test: Use an LCR meter to apply a voltage (-5 V to +5 V) and measure the change in capacitance with voltage. Analysis: Calculate the interface state density (unit: cm -2 eV -1 ), formula: where C ox is the oxide capacitance and q is the electronic charge.

[0078] The following are the test results of Examples 1-15 and Comparative Examples 1-8, based on the data obtained from the above methods.

[0079] Table 1 Results of Examples

[0080]

[0081] Table 2 Results of Comparative Examples

[0082]

[0083]

[0084] Result Analysis and Summary: Combining the data in Table 1 and Table 2, for optical properties: the optical losses of Examples 1-15 are all lower than 0.2 dB / cm, meeting the invention objective and showing excellent optical properties. Among them, the optical losses of Examples 3, 7, and 15 are the lowest (≤0.13 dB / cm). The optical losses of Comparative Examples 1-3, 5, 6, and 8 are significantly higher than those of the examples (0.25 - 0.5 dB / cm), indicating that the lack of key components (such as silicon nitride / SiO2 layer, passivation film) will lead to a decline in optical properties. Corrosion resistance: After 240 hours of acid and alkali immersion, the surface changes of Examples 1-15 are small, and the performance decay is usually <10%, proving the protective effect of the corrosion-resistant passivation matrix. Comparative Examples 1-3, 5, 6, and 8 show severe or obvious corrosion, with an attenuation of up to 50%, indicating that the lack of a corrosion-resistant layer or process steps will significantly reduce the corrosion resistance. Environmental safety: The lead dissolution rates of Examples 1-15 are all <0.1 ppm, far lower than the environmental safety standards, showing the stability of the functional layer modification. The lead dissolution rates of Comparative Examples 1-3, 5, 6, and 8 are relatively high (0.08 - 0.2 ppm), indicating that the lack of auxiliary components or process optimization will increase the environmental risk. Interface performance: The interface state density of Examples 1-15 is reduced to 10 9 -10 11 cm -2 eV -1 , which is two orders of magnitude lower than that of the comparative examples, verifying the synergistic effect of the passivation layer and the functional layer. The interface state density of Comparative Examples 1-3, 5, 6, and 8 is as high as 10 11 -10 12 cm -2 eV -1 , indicating that a single material or process is not sufficient to optimize the interface quality. Conclusion: Through the above test methods, Examples 1-15 demonstrate excellent optical properties, corrosion resistance, environmental safety, and interface performance, proving the overall superiority of the composite modified materials. Comparative Examples 1-8 show that the lack of a corrosion-resistant matrix, functional layer, or key process steps will lead to a significant decline in performance. This verifies the technical advantages of the present invention in solving the problems of surface degradation, optoelectronic performance decline, and environmental risk of lithium niobate wafers, and is applicable to fields such as 5G optical waveguides and quantum integrated device packaging.

[0085] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite modification material for lithium niobate wafers, characterized in that, In parts by weight, the corrosion-resistant passivation matrix material: 50 - 70 parts of silicon nitride / SiO2 multilayer composite layer, with a single-layer thickness of 50 - 100 nm; 20 - 30 parts of atomic layer deposition passivation thin film, with a thickness ≤ 80 nm; alumina layer, with a thickness ≤ 10 nm; functional enhancement material: 5 - 15 parts of lead sulfide nanoparticles, with a particle size of 5 - 10 nm; auxiliary components: 2 - 5 parts of silane coupling agent, 3 - 8 parts of nano-silica, 0.5 - 1.5 parts of perfluoropolyether surfactant.

2. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, The parameters of the nano-silica are as follows: particle size 20 - 50 nm, specific surface area ≥ 200 m 2 / g.

3. The composite modified material for lithium niobate wafers according to claim 1, wherein, Among them, the silane coupling agent is 3-methacryloxypropyltrimethoxysilane, aminopropyltriethoxysilane, vinyltrimethoxysilane or octyltriethoxysilane; among them, the perfluoropolyether surfactant is perfluoropolyether carboxylic acid, perfluoropolyether alcohol or perfluoropolyether acyl fluoride.

4. The composite modified material for lithium niobate wafers according to claim 1, characterized in that, The preparation method is as follows: Using plasma-enhanced chemical vapor deposition technology, silicon nitride and SiO2 layers are alternately deposited on the surface of a clean lithium niobate wafer; then, an atomic layer deposition technology is used to deposit a titanium dioxide passivation thin film; an alumina layer is deposited on the surface of the passivation thin film by magnetron sputtering; then, lead sulfide nanoparticles are synthesized by a solvothermal method, the lead sulfide nanoparticles are dispersed in an ethanol solution 5 - 10 times its weight, a silane coupling agent and a perfluoropolyether surfactant are added, nano-silica is uniformly coated on the surface of the alumina layer by spin coating or dip coating and dried, and finally annealing treatment is carried out at a temperature of 300 - 400 °C for 30 - 60 min and cooled to room temperature in an inert gas atmosphere.

5. The composite modified material for lithium niobate wafers according to claim 4, wherein The parameters for alternate deposition are as follows: temperature 200 - 300 °C, gas source is SiH4, radio frequency power 100 - 200 W.

6. The composite modification material for lithium niobate wafers according to claim 4, wherein, When depositing the titanium dioxide passivation thin film, the precursor is trimethylaluminum, and the deposition temperature is 150 - 200 °C.

7. The composite modified material for lithium niobate wafers according to claim 4, wherein When magnetron sputtering deposits the alumina layer, an A1 target is used and the deposition temperature is 100 - 150 °C.

8. The composite modification material for lithium niobate wafers according to claim 4, wherein, The method for synthesizing lead sulfide nanoparticles by solvothermal method is as follows: Lead oxide and 1-octadecyl-3-methylimidazolium chloride are mixed in a mass ratio of 1:4, degassed at 110 ± 2 °C for 2 h under argon protection to obtain a lead precursor solution; then, sulfur and N,N-dimethylformamide are dissolved in a weight ratio of 1:3 and ultrasonically treated at 80 °C for 30 min to obtain a sulfur precursor solution. When the lead precursor solution is heated to 150 ± 5 °C, the sulfur precursor solution is injected at a rate of 2 mL / s, the lead-sulfur molar ratio is controlled to be 1.05:1, the reaction is terminated by quenching with ice water, the crude product is centrifuged at 9000 rpm, and the final product is dispersed in chlorobenzene with a solid content controlled to be 10 ± 0.5 mg / mL.

9. The composite modification material for lithium niobate wafers according to claim 4, characterized in that, The drying temperature is 80 - 120 °C.

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