A single crystal thin film and a method of manufacturing and using the same

Abstract

This invention provides a single-crystal thin film, its preparation method, and its application. The single-crystal thin film of this invention comprises a substrate layer, an isolation layer, and a lithium tantalate niobate thin film layer sequentially stacked; the lithium tantalate niobate thin film layer comprises LiTa. x Nb 1‑x O3, where 0 < x < 1. The single-crystal thin film of the present invention can achieve flexible optimization of the performance parameters of the thin film material while maintaining the suitability of the single-crystal thin film for optoelectronic and integrated photonic device applications.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and integrated photonic devices, and in particular to a single-crystal thin film, its preparation method, and its application. Background Technology

[0002] Single-crystal thin films are primarily targeted at the field of high-performance integrated optoelectronic devices, and are widely used in next-generation communication technologies, quantum information processing, high-precision sensing, and artificial intelligence hardware. For example, in 5G or 6G communication systems, their excellent surface acoustic wave (SAW) properties can be used in high-frequency broadband filters and RF front-end devices, enabling miniaturization and high-density integration of signal processing. In integrated photonics, single-crystal thin films are core materials for high-speed electro-optic modulators, nonlinear frequency converters, and optical waveguide devices. In the field of quantum information, their unique electro-optic and nonlinear properties support the development of devices such as single-photon sources and quantum entangled light sources. Furthermore, the thin-film nature of single-crystal thin films also makes them valuable in miniature infrared detectors, acoustic sensors, and low-power microelectromechanical systems (MEMS).

[0003] In existing technologies, lithium niobate (LiNbO3, LN) and lithium tantalate (LiTaO3, LT) crystals are widely used in single-crystal thin films due to their excellent piezoelectric, ferroelectric, and nonlinear optical properties. However, although pure LN crystals have high nonlinear optical coefficients, they have a low threshold for resistance to optical damage and are prone to performance degradation due to photorefractive effects, limiting their application in high-power laser devices. On the other hand, while pure LT crystals have strong resistance to optical damage, their nonlinear optical properties are relatively weak, making it difficult to meet the requirements for efficient frequency conversion.

[0004] Therefore, developing a single-crystal thin film and establishing a fabrication method compatible with existing semiconductor processes has become crucial for promoting the development of next-generation integrated optoelectronic devices. Summary of the Invention

[0005] This invention provides a single-crystal thin film that allows for flexible optimization of the thin film material performance parameters while maintaining its suitability for optoelectronic and integrated photonic device applications.

[0006] This invention provides a method for preparing a single-crystal thin film, which can prepare the above-mentioned single-crystal thin film. This single-crystal thin film can achieve flexible optimization of the performance parameters of the thin film material while maintaining its suitability for optoelectronic and integrated photonic device applications.

[0007] This invention provides an optoelectronic device with wide integration applications.

[0008] A first aspect of the present invention provides a single-crystal thin film, comprising a substrate layer, an isolation layer, and a lithium tantalate niobate thin film layer sequentially stacked.

[0009] The lithium tantalate / niobate thin film layer includes LiTa x Nb 1-x O3, where 0 < x < 1.

[0010] The single-crystal thin film described above, wherein the thickness of the lithium tantalate niobate thin film layer is 5 nm to 10 μm; and / or,

[0011] The surface roughness Ra of the lithium tantalate niobate thin film layer is <0.3 nm; and / or,

[0012] The difference between the maximum and minimum thickness of the lithium tantalate niobate thin film layer, TTV < 50 nm.

[0013] The single-crystal thin film described above, wherein the substrate layer is selected from silicon, quartz, silicon carbide, silicon nitride, or sapphire; and / or,

[0014] The thickness of the substrate layer is 0.1~1mm; and / or,

[0015] The material of the insulating layer is selected from at least one of silicon dioxide, silicon oxynitride, silicon nitride, aluminum oxide, and aluminum nitride; and / or,

[0016] The thickness of the isolation layer is 10nm~15μm.

[0017] The single-crystal thin film as described above further includes a trap layer located between the substrate layer and the isolation layer;

[0018] The trap layer is made of at least one of polycrystalline silicon, amorphous silicon, or polycrystalline germanium.

[0019] In the single-crystal thin film described above, the thickness of the trap layer is 300~5000 nm.

[0020] A second aspect of the present invention provides a method for preparing a single-crystal thin film, comprising:

[0021] A single-crystal thin film is obtained by bonding a lithium tantalate niobate thin film to a bonding substrate.

[0022] The bonding substrate includes a substrate layer and an isolation layer that are stacked in a sub-layer configuration, and the lithium tantalate niobate thin film layer is disposed close to the isolation layer.

[0023] The preparation method described above, wherein the bonding process between the lithium tantalate niobate thin film layer and the bonding substrate includes:

[0024] Ion implantation was performed on a lithium tantalate niobate donor wafer to obtain an intermediate consisting of a lithium tantalate niobate thin film layer and a residual layer.

[0025] The intermediate is bonded to the bonding substrate, and the lithium tantalate niobate thin film layer is placed close to the isolation layer to obtain a single crystal thin film precursor.

[0026] The single-crystal thin film precursor is subjected to a first heat treatment and a second heat treatment in sequence to obtain the single-crystal thin film.

[0027] The temperature of the first heat treatment is lower than the temperature of the second heat treatment.

[0028] The preparation method described above further includes, prior to the bonding process, surface activation treatment of the intermediate and the bonding substrate using plasma.

[0029] In the preparation method described above, the dose of implanted ions in the ion implantation treatment is 1 × 10⁻⁶. 16 ~3×10 17 ions / cm 2 The energy of the injected ions is 30 keV to 5 MeV; and / or,

[0030] The temperature of the first heat treatment is 180~300℃; and / or,

[0031] The temperature of the second heat treatment is 301~600℃.

[0032] A third aspect of the present invention provides an optoelectronic device comprising the above-described single-crystal thin film.

[0033] This invention involves depositing a lithium tantalate niobate thin film layer in a single-crystal thin film, and using LiTa as the lithium tantalate niobate thin film layer. x Nb 1-x The tunable composition of O3 with 0 < x < 1 enables the synergistic optimization of performance and interlayer matching in single-crystal thin film structures, taking into account the adjustment requirements of nonlinear optical performance, resistance to optical damage and birefringence of single-crystal thin films, thereby improving the stability, design flexibility and integrated application value of single-crystal thin films in optoelectronic and integrated photonic devices. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the stacked structure of a single-crystal thin film in some embodiments of the present invention;

[0036] Figure 2This is a schematic diagram of the stacked structure of a single-crystal thin film in some other embodiments of the present invention;

[0037] Figure 3 This is a flowchart illustrating the preparation process of single-crystal thin films in some embodiments of the present invention.

[0038] Figure label:

[0039] 1: Lithium tantalate niobate thin film layer;

[0040] 2: Isolation layer;

[0041] 3: Substrate layer;

[0042] 4: Trap layer;

[0043] 5: Lithium tantalate niobate donor wafer;

[0044] 6: Residual mass layer. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the absence of conflict, the following embodiments and features can be combined with each other.

[0046] In the fields of optoelectronic devices and integrated photonics, functional crystalline thin films are commonly used in applications such as electro-optic modulation, frequency conversion, surface acoustic wave filtering, and high-sensitivity sensing. These devices often require the fabrication of multilayer thin-film structures on silicon-based or other heterogeneous substrates to meet the requirements of miniaturization, low power consumption, and high-density integration. In these systems, the substrate layer not only provides mechanical support but also works with the upper functional thin film to form a stable optical and electrical operating environment; the isolation layer provides electrical insulation, optical field confinement, and interface buffering; while the uppermost functional crystalline thin film layer directly determines the device's nonlinear response, electro-optic conversion efficiency, and resistance to environmental interference. Therefore, the structural design and heterogeneous integration of single-crystal thin-film materials have become a crucial foundation for realizing high-performance optoelectronic devices.

[0047] In existing technologies, functional crystals such as lithium niobate and lithium tantalate, and their thin films, are widely used in the aforementioned scenarios. They primarily rely on the electro-optic effect, nonlinear optical effect, and birefringence of the functional crystals themselves to achieve electro-optic modulation, frequency conversion, and filtering functions. Typically, these thin films are grown directly on a substrate or formed into thin-film device structures through deposition, epitaxy, bonding, etc., to work in conjunction with waveguides, electrodes, and other optical units. However, these functional crystals often have fixed compositions. Once the parameters of the functional crystal are determined, the balance between its nonlinear optical performance, resistance to light damage, and birefringence is difficult to readjust. This makes it difficult for the same type of functional crystal to simultaneously meet different application requirements such as high power, high efficiency, and high stability. For example, some functional crystals, although possessing high nonlinear response, are prone to performance degradation under strong light irradiation; others, while having good stability, struggle to meet the requirements for efficient frequency conversion in single-crystal thin films.

[0048] In view of this, how to achieve flexible adjustment of the performance of single-crystal thin films while maintaining the structural advantages of single-crystal thin films has become an urgent technical problem to be solved. The inventors discovered in their research that introducing tantalum and niobium elements into single-crystal thin films can reserve adjustment space for performance optimization of single-crystal thin films, and at the same time provide a structural basis for subsequent compatible integration with integrated photonic devices.

[0049] A first aspect of the present invention provides a single-crystal thin film, comprising a substrate layer, an isolation layer, and a lithium tantalate niobate thin film layer sequentially stacked.

[0050] The lithium tantalate niobate thin film layer includes lithium tantalate niobate, the chemical formula of which is LiTa. x Nb 1-x O3, where 0 < x < 1.

[0051] Specifically, such as Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a single-crystal thin film in some embodiments of the present invention. The single-crystal thin film of the present invention is constructed in a bottom-up stacked structure, wherein the substrate layer 3 serves as the basic support layer of the overall structure, providing mechanical support, heat conduction channels, and a process substrate for subsequent processing; the isolation layer 2 is disposed between the substrate layer 3 and the lithium tantalum niobate thin film layer 1, and is used to achieve electrical insulation, interface buffering, and optical field confinement; the lithium tantalum niobate thin film layer 1 serves as the uppermost functional single-crystal layer, directly participating in electro-optic modulation, nonlinear frequency conversion, acousto-optic coupling, or sensing response.

[0052] By setting the functional layer to LiTa x Nb 1-xBy creating a lithium tantalate-niobate solid solution single-crystal thin film in the form of O3, and ensuring that the component parameter x satisfies 0 < x < 1, the basic crystal characteristics of lithium niobate single-crystal thin films for integrated photonic devices can be maintained. This allows for continuous adjustment of the crystal composition, refractive index characteristics, resistance to optical damage, birefringence, and nonlinear response by introducing tantalum. Thus, the material properties are no longer limited to a single fixed chemical composition, but rather achieve a designable performance window within the same crystal system. In the formula, Li represents lithium, Ta represents tantalum, Nb represents niobium, O3 represents the oxygen octahedral framework, x represents the mole fraction of Ta in the B-site cation, and 1-x represents the mole fraction of Nb at the corresponding position. When x is between 0 and 1, it indicates that the single-crystal thin film is not pure lithium niobate or pure lithium tantalate, but rather a solid solution single-crystal system between the two.

[0053] The reaction mechanism lies in the fact that changes in the local bonding environment of Ta-O and Nb-O in lithium tantalum niobate alter the polarization response, electronic band structure, and photorefractive defect behavior of the lithium tantalum niobate unit cell. This results in a single-crystal thin film exhibiting different comprehensive properties compared to pure LiNbO3 or pure LiTaO3 in terms of refractive index, electro-optic coefficient, nonlinear coefficient, and resistance to laser-induced damage. This compositional approach can alleviate the difficulty of balancing high nonlinear response with high stability and strong damage resistance in existing single-crystal thin films at the material source. For example, appropriately increasing the Ta content typically helps improve the stability of the single-crystal thin film under strong illumination conditions and reduces photorefractive distortion or performance drift, while retaining a certain proportion of Nb helps the single-crystal thin film maintain superior electro-optic and nonlinear conversion capabilities. This makes the single-crystal thin film more suitable for applications such as high-power integrated optics, on-chip frequency doubling, narrow linewidth modulation, and high-stability sensing.

[0054] By selecting x, for example, in one possible embodiment x could be 0.3, the corresponding chemical formula of lithium tantalate niobate is LiTa. 0.3 Nb 0.7 O3, at which point the single-crystal thin film can balance a high nonlinear optical coefficient and a good resistance to optical damage threshold; in another possible embodiment, x can be 0.7, corresponding to the chemical formula of lithium tantalate niobate, LiTa. 0.7 Nb 0.3 O3 further balances the stability and optical performance of the single-crystal thin film. Based on the above composition adjustment, it can be seen that the tantalum-niobium ratio can be pre-designed according to the target device's requirements for modulation efficiency, frequency conversion efficiency, photodamage suppression capability, or environmental stability in different application scenarios, thereby improving the adaptability of the same type of single-crystal thin film to various optoelectronic applications.

[0055] In the single-crystal thin film of this invention, the distribution ratio of tantalum and niobium elements directly affects the physicochemical properties of the single-crystal thin film. By adjusting the x-value, the nonlinear optical coefficient, anti-optical damage threshold, and birefringence properties of the single-crystal thin film can be controlled. For example, when the chemical formula of lithium tantalate niobate is LiTa... 0.3 Nb 0.7 In the O3 stage, compared to pure LN crystals, the introduction of tantalum allows single-crystal thin films to maintain a high nonlinear coefficient while improving the resistance to optical damage threshold. This makes them suitable for fabricating frequency conversion devices with high incident light power and short wavelengths, combining high conversion efficiency and high stability. When the chemical formula of lithium tantalate niobate is LiTa... 0.7 Nb 0.3 O3 can improve the nonlinear optical coefficient of single-crystal thin films while maintaining a high resistance to light damage threshold and low birefringence performance, thereby improving the nonlinear conversion efficiency of optoelectronic devices.

[0056] This invention, by adjusting the ratio of tantalum and niobium in lithium tantalum niobate, allows the single-crystal thin film to adapt to the performance requirements of different application scenarios. Simultaneously, the substrate layer 3 and the isolation layer 2 provide mechanical support and functional optimization for the single-crystal thin film, thereby improving the integration and stability of optoelectronic devices incorporating the single-crystal thin film. The single-crystal thin film of this invention fills the performance gap between pure LN and pure LT, providing flexibility and performance optimization space for the design of optoelectronic devices.

[0057] In some embodiments of the present invention, the thickness of the lithium tantalate niobate thin film layer 1 is 5 nm to 10 μm. The thickness of the lithium tantalate niobate thin film layer 1 determines the distribution of the optical field in the lithium tantalate niobate thin film layer 1, the coupling efficiency with the electric field, and the nonlinear interaction length. When the thickness of the lithium tantalate niobate thin film layer 1 is controlled within the above range, the single crystal thin film can form sufficient optical field confinement and electric field interaction strength, and can also adapt to the mode design of different optoelectronic devices.

[0058] Furthermore, in some embodiments of the present invention, the surface roughness Ra of the lithium tantalate niobate thin film layer 1 is <0.3 nm, indicating that the surface of the lithium tantalate niobate thin film layer 1 is in a near-atomic smooth state, which can significantly reduce the scattering loss of optoelectronic devices in waveguide propagation and reduce random reflection and mode perturbation of light on the surface of the lithium tantalate niobate thin film layer 1.

[0059] Meanwhile, in some embodiments of the present invention, the difference between the maximum and minimum thickness of the lithium tantalate niobate thin film layer 1, TTV, is controlled to be below 50 nm, which can make the thickness distribution of the lithium tantalate niobate thin film layer 1 more uniform and keep the effective refractive index, phase matching conditions and modulation response consistent at different positions.

[0060] Therefore, the thickness, surface roughness, and TTV of the lithium tantalum niobate thin film layer 1 work synergistically to enable the lithium tantalum niobate thin film layer 1 to simultaneously possess designable mode constraint capability, low transmission loss, and excellent in-plane uniformity, thereby improving the overall performance and long-term reliability in electro-optic modulation, frequency conversion, and integrated photonic devices.

[0061] This invention does not strictly limit the specific material of the substrate layer 3, as long as it can provide sufficient flatness, mechanical strength, and thermal stability for the upper structure. In some embodiments of this invention, the material of the substrate layer 3 is selected from silicon, quartz, silicon carbide, silicon nitride, or sapphire. In one possible embodiment, silicon is selected as the substrate layer 3. Because silicon has a mature wafer manufacturing system, low cost, and good large-area processing consistency, it is beneficial for the single-crystal thin film to be compatible with existing CMOS (Complementary Metal-Oxide-Semiconductor) processes, microelectronic interconnect processes, and silicon photonics processes, enabling subsequent waveguides, electrodes, resonant cavities, and packaging structures to be integrated on the same platform. In another possible embodiment, sapphire can be selected as the substrate layer 3. Sapphire has high thermal stability and good optical transmittance characteristics, and can be used in working scenarios with high requirements for thermal drift control or light transmission. Silicon carbide substrates are also suitable for high-power or high-heat-flux working environments due to their high thermal conductivity. The thickness of substrate layer 3 can be determined based on material specifications and the mechanical strength requirements of optoelectronic devices. For example, a conventional semiconductor substrate layer 3 thickness range can be used to ensure that it is not prone to warping or cracking during bonding, thinning, photolithography, and etching processes. It should be understood that the selection of substrate layer 3 is closely related to the type of subsequent devices, thermal expansion matching, and manufacturing costs, and therefore can be adjusted according to specific product solutions.

[0062] In some embodiments of the present invention, when the thickness of the substrate layer 3 is 0.1~1mm, the thermal resistance of the lithium tantalum niobate thin film layer 1 can be reduced while ensuring the strength of the substrate material, warpage control and the feasibility of subsequent thinning processing, thereby optimizing the overall size of the optoelectronic device and improving the integration adaptability of the optoelectronic device.

[0063] The present invention does not strictly limit the specific material of the isolation layer 2, and materials commonly used in the art for the isolation layer 2 can be selected. In some embodiments of the present invention, when the material of the isolation layer 2 is selected from at least one of silicon dioxide, silicon oxynitride, silicon nitride, aluminum oxide, and aluminum nitride, the dielectric constant, stress matching, and thermal conductivity can be adjusted according to the requirements of different optoelectronic devices, thereby reducing defects caused by lattice and thermal expansion mismatch in single-crystal thin films.

[0064] In some embodiments of the present invention, when the thickness of the isolation layer 2 is 10 nm to 15 μm, the low interface loss of the optoelectronic device can be further reduced, the coupling efficiency of the optoelectronic device can be improved, and the insulation isolation and mechanical buffering can be enhanced. Thus, the material and thickness of the substrate layer 3 and the isolation layer 2 are synergistically matched, which can improve the stability of the single crystal thin film structure, the yield of optoelectronic devices, and the compatibility with integrated photonic platforms, thereby ensuring its suitability for applications such as electro-optic modulation, frequency conversion, and high-sensitivity sensing.

[0065] In some embodiments of the present invention, the single-crystal thin film further includes a trap layer, the material of which includes at least one of polycrystalline silicon, amorphous silicon, or polycrystalline germanium. Figure 2 This is a schematic diagram of the stacked structure of a single-crystal thin film in other embodiments of the present invention, such as... Figure 2 As shown, trap layer 4 is located between substrate layer 3 and isolation layer 2. The addition of trap layer 4 between substrate layer 3 and isolation layer 2 allows it to participate in the layered structure construction as an interface functional layer. Due to the presence of grain boundaries, disordered structures, or defect states within polycrystalline silicon, amorphous silicon, or polycrystalline germanium, these structures can provide numerous trap centers to capture free carriers that may arise at the interface between the substrate and isolation layer 2, suppressing charge accumulation and the formation of parasitic conductive channels. Trap layer 4, by adjusting the interface charge distribution with substrate layer 3 and isolation layer 2, weakens defect-induced scattering and absorption, thereby improving the electrical insulation and optical stability of the single-crystal thin film. Furthermore, trap layer 4 can also buffer the lattice and thermal stress differences between substrate layer 3 and isolation layer 2, making the lithium tantalate niobate thin film layer 1 less prone to interface degradation during subsequent optoelectronic device operation. Thus, the entire single-crystal thin film structure maintains the excellent photoelectric response of the functional thin film while improving the consistency, long-term reliability, and stability of the optoelectronic device under high power or high frequency operating conditions.

[0066] In some embodiments of the present invention, when the thickness of the trap layer 4 is 300~5000nm, it can be matched according to the requirements of optoelectronic devices for carrier trapping, interface buffering and stress release. On the one hand, it provides a charge trapping and buffering channel, and on the other hand, it maintains the interface continuity with the substrate and the isolation layer 2, thereby reducing the impact of defect propagation and interface mismatch on the upper lithium tantalate niobate film. This enables the single crystal film to obtain a more stable electrical environment, lower loss and higher optoelectronic device consistency in electro-optic modulation, frequency conversion and high-sensitivity sensing applications, thereby improving integration reliability and long-term working stability.

[0067] A second aspect of the present invention provides a method for preparing a single-crystal thin film, comprising:

[0068] The lithium tantalate niobate thin film layer 1 is bonded to the bonding substrate to obtain a single crystal thin film;

[0069] The bonding substrate includes a substrate layer 3 and an isolation layer 2 that are stacked in a sub-layer configuration, and a lithium tantalate niobate thin film layer 1 is disposed close to the isolation layer 2.

[0070] By bonding the lithium tantalum niobate thin film layer 1 to the bonding substrate, the structural stability of the single-crystal thin film can be enhanced. Simultaneously, the isolation layer 2 weakens the electrical and thermal disturbances of the substrate layer on the lithium tantalum niobate thin film layer. By placing the lithium niobate thin film layer 1 close to the isolation layer 2, the mode field confinement and electric field modulation capabilities can be enhanced, allowing the lithium tantalum niobate thin film layer 1 to achieve a more stable photoelectric response while maintaining single-crystal integrity. The synergistic effect of these structures improves the uniformity, interface flatness, and optoelectronic device consistency of the lithium tantalum niobate thin film layer 1 while ensuring bonding reliability, thereby meeting the requirements of high-performance optoelectronic devices for low loss, high stability, and integrability.

[0071] In this invention, the lithium tantalate niobate composition in the lithium tantalate niobate thin film layer 1 is adjustable, which can realize flexible optimization and heterogeneous integration of single crystal thin film performance, and realize customized optimization of optoelectronic device performance.

[0072] In some embodiments of the present invention, bonding the lithium tantalate niobate thin film layer 1 to the bonding substrate includes:

[0073] Ion implantation was performed on a lithium tantalate niobate donor wafer to obtain an intermediate comprising a lithium tantalate niobate thin film layer 1 and a residual layer.

[0074] The intermediate is bonded to the bonding substrate, and the lithium tantalate niobate thin film layer 1 is brought close to the isolation layer 2 to obtain a single crystal thin film precursor.

[0075] The single-crystal thin film precursor is subjected to a first heat treatment and a second heat treatment in sequence to obtain a single-crystal thin film.

[0076] The temperature of the first heat treatment is lower than the temperature of the second heat treatment.

[0077] Specifically, the lithium tantalate niobate donor wafer is a single-crystal LiTa. x Nb 1-x O3 wafers, where 0 < x < 1. Ion implantation can form a lithium tantalate niobate thin film layer 1 and a residual layer within the lithium tantalate niobate donor wafer; then, the intermediate is bonded to the bonding substrate, with the lithium tantalate niobate thin film layer 1 close to the isolation layer 2, to obtain a single-crystal thin film precursor; during the first heat treatment of the single-crystal thin film precursor, ions in the lithium tantalate niobate thin film layer 1 aggregate into bubbles and expand, causing the residual layer to peel off from the intermediate, achieving low-cost, high-precision transfer of the lithium tantalate niobate thin film layer 1; the second heat treatment can repair the lattice damage of the lithium tantalate niobate thin film layer 1 caused by ion implantation, and also strengthen the bonding strength between the lithium tantalate niobate thin film layer 1 and the bonding substrate, improving the stability of the single-crystal thin film.

[0078] This invention employs ion implantation to precisely control the thickness of the lithium tantalate niobate thin film layer 1, ensuring its structural integrity and surface smoothness while maximizing the preservation of the original single-crystal characteristics and optoelectronic properties of the lithium tantalate niobate donor wafer. Simultaneously, the lower first heat treatment temperature gently drives ion aggregation and bubbling, achieving non-destructive peeling of the excess layer and preventing high temperatures from directly causing film cracking, damage, or bonding failure. The higher second heat treatment temperature repairs lattice defects in lithium tantalate niobate introduced during ion implantation and enhances the stability of the single-crystal thin film.

[0079] The above preparation method can take into account the thickness control of lithium tantalum niobate thin film layer 1, surface flatness, interfacial bonding strength and process compatibility, thereby improving the yield, uniformity and long-term reliability of single crystal thin film.

[0080] It should be understood that the above examples are for demonstration purposes only and are not limiting. The specific types of implanted ions, heat treatment temperature, holding time and bonding method can be adapted and adjusted according to the target film thickness, optoelectronic device type and equipment conditions, as long as high-quality transfer of lithium tantalate niobate film layer 1 from the donor wafer to the bonding substrate can be achieved.

[0081] In some embodiments, prior to the first heat treatment, the single-crystal thin film precursor is further subjected to an annealing treatment at a temperature of <180°C. The annealing treatment promotes the hydroxyl polymerization reaction at the bonding interface of the single-crystal thin film precursor, thereby significantly improving the bonding strength, which is sufficient to withstand the subsequent peeling process of the residual layer.

[0082] This invention does not specifically limit the implanted ions used in ion implantation; any commonly used implanted ions in the art can be used. For example, the implanted ion can be at least one of hydrogen ions, helium ions, nitrogen ions, oxygen ions, and argon ions. By selecting different implanted ions, the removal precision of the excess layer can be improved. When x < 0.5 in the lithium tantalate niobate donor wafer, the niobium content is relatively high, making helium ion implantation more suitable. This is because the Nb-O bond is weaker, and hydrogen ion implantation would result in the presence of OH groups. - The trapping effect; when x > 0.5, the tantalum content is higher, making it more suitable for hydrogen ion implantation with higher ionization efficiency.

[0083] The present invention does not particularly limit the method for preparing the bonding substrate, and can use any method commonly used in the art for preparing the bonding substrate. For example, when preparing the bonding substrate, the material of the isolation layer 2 can be deposited onto the substrate layer 3 by deposition, and the deposition method can be one of chemical vapor deposition (CVD), physical vapor deposition (PVD), or magnetron sputtering.

[0084] In some embodiments, when a trap layer 4 is also included between the substrate layer 3 and the isolation layer 2, at least one of polycrystalline silicon, amorphous silicon, and polycrystalline germanium can be deposited on the substrate layer 3 by deposition. Alternatively, the substrate surface can be etched or ion implantation can be performed directly into the substrate to introduce structural damage, thereby forming a trap layer 4 on the surface of the substrate layer 3. Then, a dense and stable isolation layer 2 can be prepared on the surface of the trap layer 4 by deposition or oxidation processes, which can improve the interfacial bonding force and achieve electrical and optical isolation.

[0085] In some implementations, prior to ion implantation, the surface of the lithium tantalate niobate donor wafer is cleaned using a standard RCA cleaning process to ensure that the lithium tantalate niobate donor wafer is free of particles, organic matter, and metal contamination.

[0086] After the residual layer is stripped, the surface of the lithium tantalate niobate thin film layer 1 will be relatively rough. In some embodiments, chemical mechanical polishing can be used to thin and planarize the lithium tantalate niobate thin film layer 1 to obtain an atomically smooth surface.

[0087] In some implementations, the lithium tantalate niobate donor wafer is a double-sided polished, X-cut lithium tantalate niobate single crystal.

[0088] This is a flowchart illustrating the preparation process of single-crystal thin films in some embodiments of the present invention, such as... Figure 3 As shown, the preparation process of the single-crystal thin film of the present invention may include the following steps:

[0089] According to the application requirements, the material of the substrate layer 3 is selected, and a first deposition process is performed on the surface of the substrate layer 3 to obtain the trap layer 4. Then, a second deposition process is performed on the surface of the trap layer 4 to obtain the isolation layer 2. The isolation layer 2, the trap layer 4, and the substrate layer 3 together form a bonding substrate.

[0090] Meanwhile, the lithium tantalate niobate donor wafer 5 is subjected to ion implantation to obtain an intermediate including a lithium tantalate niobate thin film layer 1 and a residual layer 6.

[0091] The intermediate was then bonded to the bonding substrate to obtain a single-crystal thin film precursor.

[0092] The single-crystal thin film precursor is subjected to a first heat treatment to peel off the residual layer 6, followed by a second heat treatment to obtain the single-crystal thin film.

[0093] In some embodiments of the present invention, prior to the bonding process, the intermediate and the bonding substrate are further subjected to surface activation treatment using plasma.

[0094] Specifically, the intermediate and the bonding substrate are typically placed separately in a plasma treatment chamber. Oxygen plasma, argon plasma, nitrogen plasma, hydrogen plasma, or a combination thereof are used to treat the surfaces of the intermediate and the bonding substrate to be bonded. This introduces hydroxyl groups, dangling bonds, or weakly roughened active sites into the surfaces, thereby increasing the surface energy and enhancing the interfacial affinity for subsequent direct or assisted bonding. The power, gas flow rate, treatment time, and chamber pressure during plasma treatment can be adjusted according to the material surface condition. For example, the treatment power can be controlled within a range suitable for avoiding over-etching, and the treatment time should be sufficient to form a uniformly activated lithium tantalate-niobate thin film without damaging the crystal quality of the film.

[0095] By simultaneously performing surface activation on the intermediate and the bonding substrate before bonding, the interface to be bonded on the intermediate and the bonding substrate can achieve higher cleanliness on a macroscopic level and form more stable chemical adsorption conditions on a microscopic level. This is beneficial for the gradual enhancement of interfacial bonding during subsequent heat treatment, ultimately obtaining a single-crystal thin film structure containing substrate layer 3, isolation layer 2, and lithium tantalate niobate thin film layer 1.

[0096] Based on the above processing method, this application utilizes plasma to activate the surfaces of the intermediate and the bonding substrate, thereby improving bonding success and interface consistency without significantly increasing process complexity. Since the intermediate surface typically contains a damaged layer from ion implantation, adsorbed contaminants, and some inactive groups, while the bonding substrate surface may also contain trace amounts of organic residues and inert terminal groups, plasma can remove weakly bound contaminants and rebuild surface chemical activity through the synergistic effect of physical bombardment and chemical reaction, thus reducing the interface energy barrier required for initial bonding between the intermediate and the bonding substrate. Furthermore, the activated surfaces are more likely to form a uniform initial adhesion upon contact. Subsequently, during the first and second heat treatments, interface moisture removal, bond rearrangement, and expansion are more thorough, thereby improving the bonding strength between the lithium tantalum niobate thin film layer 1 and the isolation layer 2, and improving the thickness uniformity and subsequent processing stability of the large-area lithium tantalum niobate thin film layer 1. It should be understood that the above examples are merely illustrative and not limiting. Without departing from the concept of this application, the type of plasma, processing conditions, and activation sequence can be adaptively adjusted according to the specific material system and equipment conditions.

[0097] In some embodiments, oxygen plasma is preferred for surface activation treatment of the bonding substrate to generate a hydroxylated surface and enhance hydrophilicity; nitrogen plasma is preferred for surface activation treatment of the lithium tantalate niobate thin film layer 1 to prevent oxidation damage to lithium tantalate niobate by oxygen plasma, while introducing nitrogen dangling bonds to enhance the bonding strength between the lithium tantalate niobate thin film layer 1 and the bonding substrate.

[0098] In some embodiments of the present invention, the dose of implanted ions in the ion implantation process is 1 × 10⁻⁶. 16~3×10 17 ions / cm 2 When the energy of the implanted ions is 30keV~5MeV, a lithium tantalate niobate thin film layer 1 and a residual layer 6 can be formed while ensuring the integrity of the lithium tantalate lattice. At the same time, the thickness of the lithium tantalate niobate thin film layer 1 can be controlled more precisely, and the uniformity between the interface of the lithium tantalate niobate thin film layer 1 and the residual layer 6 can be improved.

[0099] In some embodiments of the present invention, when the temperature of the first heat treatment is 180~300°C, the implanted ions can be gently driven to aggregate and form microbubbles and generate internal stress, thereby achieving a smooth peeling of the lithium tantalum niobate thin film layer 1 from the residual layer 6, while ensuring the integrity of the crystal structure of the lithium tantalum niobate thin film layer 1.

[0100] In some embodiments of the present invention, when the temperature of the second heat treatment is 301~600°C, the lattice damage caused by ion implantation in the lithium tantalum niobate thin film layer 1 can be repaired more fully while saving energy, thereby improving the crystal quality and photoelectric performance of the lithium tantalum niobate thin film layer 1, and further strengthening the bonding strength between the lithium tantalum niobate thin film layer 1 and the bonding substrate, so that the single crystal thin film has better stability.

[0101] By limiting the ion implantation dose, ion implantation energy, and the first and second heat treatment temperatures within the aforementioned ranges, the controllability of the residual layer 6 peeling, the integrity of the thin film crystal, and the stability of the bonding interface can be balanced. This results in a lithium tantalate niobate single-crystal thin film structure with uniform thickness, low surface roughness, and suitability for subsequent optoelectronic device integration, thereby improving the yield and long-term reliability of optoelectronic device fabrication.

[0102] A third aspect of the present invention provides an optoelectronic device comprising the above-described single-crystal thin film.

[0103] When the optoelectronic device includes the aforementioned single-crystal thin film, the substrate layer 3 can provide mechanical support and an integration foundation, the isolation layer 2 can achieve electrical insulation, optical field confinement, and interface buffering, and the lithium tantalum niobate thin film layer 1 can undertake electro-optic modulation, nonlinear response, or filtering functions. Since the lithium tantalum niobate thin film layer 1 includes LiTa... x Nb 1-x O3, with 0 < x < 1, allows for the optimization of nonlinear optical properties, birefringence characteristics, and resistance to optical damage through compositional adjustments. This enables optoelectronic devices to achieve a balance between efficiency and stability in modulation, frequency conversion, surface acoustic wave processing, or sensing applications. The stacked single-crystal thin-film structure also makes optoelectronic devices easier to integrate with silicon-based or other heterogeneous platforms, thereby improving interface bonding, process adaptability, and long-term reliability.

[0104] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0105] Example 1

[0106] The method for preparing the single-crystal thin film in this embodiment includes the following steps:

[0107] (1) Preparation of bonding substrate

[0108] (a) Prepare a silicon wafer with a thickness of 0.5 mm, fix the silicon wafer on the porous ceramic chuck of the polishing equipment, perform chemical mechanical polishing to remove residual polishing liquid and abrasive particles, and then dry it with nitrogen to obtain a smooth silicon wafer. Then perform RCA cleaning on the smooth silicon wafer to obtain substrate layer 3.

[0109] (b) Polysilicon (Poly Si) is deposited on substrate 3 by LPCVD at a temperature of 600°C and a thickness of 300 nm to form a trap layer 4. Silicon dioxide is deposited on trap layer 4 by LPCVD to form an isolation layer 2. The surface of isolation layer 2 is then chemically mechanically polished. The thickness of isolation layer 2 is 2 μm. After that, the surface of isolation layer 2 is RCA cleaned. Thus, a bonded substrate is obtained, which includes substrate 3, trap layer 4 and isolation layer 2 stacked sequentially from bottom to top.

[0110] (2) Preparation of intermediates

[0111] A 300μm thick, double-sided polished, X-cut lithium tantalate niobate single crystal wafer was selected as the lithium tantalate niobate donor wafer 5, wherein the chemical formula of lithium tantalate niobate is LiTa. 0.3 Nb 0.7 O3 was used to perform RCA cleaning on the lithium tantalate niobate donor wafer 5; then, argon ions were used to perform ion implantation on the lithium tantalate niobate donor wafer 5 to obtain an intermediate including a lithium tantalate niobate thin film layer 1 and a residual layer 6; during the ion implantation process, the dose of implanted ions was 3 × 10⁻⁶. 16 ions / cm 2 The energy of the implanted ions is 500 keV; the thickness of the lithium tantalate niobate thin film layer 1 is 1 μm.

[0112] (3) Preparation of single-crystal thin films

[0113] (a) The bonding substrate and the intermediate are placed in a plasma processing device, and the outer surface of the isolation layer 2 of the bonding substrate and the ion implantation surface of the lithium tantalate niobate thin film layer 1 of the intermediate are bombarded with a mixed plasma beam of O2 and Ar respectively to achieve surface activation treatment of the bonding substrate and the intermediate. The surface activation treatment time is 60s, wherein the volume ratio of O2 to Ar in the mixed plasma beam is 1:3. Then the intermediate and the bonding substrate are bonded to make the outer surface of the isolation layer 2 and the outer surface of the lithium tantalate niobate thin film layer 1 adhere to each other to obtain a single crystal thin film precursor.

[0114] (b) The single-crystal thin film precursor is placed in an annealing furnace and subjected to a first heat treatment at 250°C for 3 hours to remove the residual layer 6; then the single-crystal thin film precursor is subjected to a second heat treatment at 500°C for 2 hours, and finally chemical mechanical polishing is performed to obtain a single-crystal thin film; wherein the surface roughness of the lithium tantalate niobate thin film layer 1 is 0.3 nm and the TTV is 40 nm.

[0115] Example 2

[0116] The preparation method of the single-crystal thin film in this embodiment is basically the same as that in Example 1, except that:

[0117] (1) Preparation of bonding substrate

[0118] (b) The thickness of substrate 3 is 0.5 mm.

[0119] (c) Amorphous silicon (trap layer 4) is deposited on substrate 3 using LPCVD.

[0120] The thickness of the isolation layer 2 is 2 μm.

[0121] (2) Preparation of intermediates

[0122] The chemical formula of lithium tantalate niobate is LiTa. 0.7 Nb 0.3 O3;

[0123] Helium ions were used to implant lithium tantalate niobate donor wafer 5 to obtain an intermediate comprising a lithium tantalate niobate thin film layer 1 and a residual layer 6; the ion implantation dose was 4 × 10⁻⁶ ions. 16 ions / cm 2 The energy of the implanted ions is 350 keV; the thickness of the lithium tantalate niobate thin film layer 1 is 500 nm.

[0124] (3) Preparation of single-crystal thin films

[0125] (b) The single-crystal thin film precursor is placed in an annealing furnace and subjected to a first heat treatment at 220°C for 3 hours to remove the residual layer 6; then the single-crystal thin film precursor is subjected to a second heat treatment at 500°C for 2 hours, and finally chemical mechanical polishing is performed to obtain a single-crystal thin film; wherein the surface roughness of the lithium tantalate niobate thin film layer 1 is 0.2 nm and the TTV is 40 nm.

[0126] Comparative Example 1

[0127] The preparation method of the single-crystal thin film in this comparative example includes the following steps:

[0128] (1) Preparation of bonding substrate

[0129] (a) A silicon wafer with a thickness of 0.5 mm is fixed on a porous ceramic chuck of a polishing equipment and chemically mechanically polished to remove residual polishing liquid and abrasive particles. Then, it is dried with nitrogen to obtain a smooth silicon wafer. The smooth silicon wafer is then subjected to RCA cleaning to obtain a substrate layer.

[0130] (b) Polysilicon (Poly Si) is deposited on the substrate using LPCVD at a temperature of 600°C and a thickness of 1 μm to form a trap layer. Silicon dioxide is deposited on the trap layer using LPCVD to form an isolation layer. The surface of the isolation layer is then chemically mechanically polished to a thickness of 1 μm. The surface of the isolation layer is then RCA cleaned. Thus, a bonded substrate is obtained comprising a substrate layer, a trap layer, and an isolation layer stacked sequentially from bottom to top.

[0131] (2) Preparation of intermediates

[0132] A lithium niobate wafer with a thickness of 250 μm was selected and subjected to chemical mechanical polishing (CMP) and RCA cleaning. Then, argon ions were used to implant the lithium niobate wafer to obtain an intermediate lithium niobate thin film layer and a residual layer. The ion implantation dose was 3 × 10⁻⁶ ions. 16 ions / cm 2 The energy of the implanted ions is 400 keV; the thickness of the lithium niobate thin film is 1 μm.

[0133] (3) Preparation of single-crystal thin films

[0134] (a) The bonding substrate and the intermediate are placed in a plasma processing device, and the outer surface of the isolation layer of the bonding substrate and the ion implantation surface of the lithium niobate thin film layer of the intermediate are bombarded by a mixed plasma beam of O2 and Ar, respectively, to achieve surface activation treatment of the bonding substrate and the intermediate. The surface activation treatment time is 60s, wherein the volume ratio of O2 to Ar in the mixed plasma beam is 1:3; then the intermediate and the bonding substrate are bonded to make the outer surface of the isolation layer and the outer surface of the lithium niobate thin film layer adhere to each other to obtain a single crystal thin film precursor.

[0135] (b) The single crystal thin film precursor is placed in an annealing furnace and subjected to a first heat treatment at 200°C for 3 hours to remove the excess material layer; then the single crystal thin film precursor is subjected to a second heat treatment at 500°C for 1 hour, and finally chemical mechanical polishing is performed to obtain the single crystal thin film.

[0136] Comparative Example 2

[0137] The preparation method of the single-crystal thin film in this comparative example is basically the same as that in Comparative Example 1, except that:

[0138] (1) Preparation of bonding substrate

[0139] (b) Polysilicon (Poly Si) was deposited on the substrate using LPCVD at a temperature of 600°C and a thickness of 500 nm to form a trap layer. Silicon dioxide was deposited on the trap layer using LPCVD to form an isolation layer. The surface of the isolation layer was then chemically and mechanically polished to a thickness of 5 μm. The surface of the isolation layer was then RCA cleaned. Thus, a bonded substrate consisting of a substrate layer, a trap layer, and an isolation layer stacked sequentially from bottom to top was obtained.

[0140] (2) Preparation of intermediates

[0141] A lithium tantalate wafer with a thickness of 400 μm was selected and subjected to chemical mechanical polishing (CMP) and RCA cleaning. Then, a lithium niobate wafer was ion-implanted using helium ions to obtain an intermediate lithium niobate thin film layer and a residual layer. The ion implantation dose was 4 × 10⁻⁶ ions. 16 ions / cm 2 The energy of the implanted ions is 225 keV; the thickness of the lithium tantalate thin film is 1 μm.

[0142] (3) Preparation of single-crystal thin films

[0143] (b) The single crystal thin film precursor is placed in an annealing furnace and subjected to a first heat treatment at 220°C for 3 hours to remove the excess material layer; then the single crystal thin film precursor is subjected to a second heat treatment at 600°C for 1 hour, and finally chemical mechanical polishing is performed to obtain the single crystal thin film.

[0144] Performance testing

[0145] Referring to the "chemical bonding method" mentioned in the "Theoretical method" section of the paper "Dielectric properties of lithium niobate–tantalate crystals" published by D. Xue et al. in Solid State Communications (July 26, 2002, DOI: 10.1016 / s0038-1098(00)00243-x), the second-order nonlinear optical coefficient d of the single-crystal thin film in the examples and comparative examples of this invention was calculated. 33 (Unit: pm / V) and resistance to light damage threshold (Unit: MW / cm) 2 The test results are shown in Table 1.

[0146] Table 1

[0147]

[0148] As can be seen from Table 1, the single-crystal thin film of the present invention achieves synergistic optimization of pure lithium niobate and pure lithium tantalate in two core properties: second-order nonlinear optical coefficient and anti-optical damage threshold.

[0149] First, compared with pure lithium niobate (Comparative Example 1), the second-order nonlinear optical coefficients of Examples 1 and 2 are -23.2 pm / V and -19.4 pm / V, respectively. Although slightly lower than the -26.5 pm / V of pure lithium niobate, they still maintain a high level of nonlinear optical coefficients, and the anti-optical damage thresholds reach 152.7 MW / cm², respectively. 2 and 198.3 MW / cm 2 This is far higher than the 115.6 MW / cm³ of pure lithium niobate. 2 This solves the problem of "high nonlinear optical coefficient but insufficient damage resistance" in pure lithium niobate; secondly, compared with pure lithium tantalate (Comparative Example 2), the optical damage resistance thresholds of Examples 1 and 2 are 152.7 MW / cm², respectively. 2 and 198.3 MW / cm 2 Although slightly lower than the 238.4 MW / cm³ of pure lithium tantalate. 2 However, it is still at a relatively high level. At the same time, the second-order nonlinear optical coefficients are -23.2pm / V and -19.4pm / V, respectively, which are significantly higher than the -16.1pm / V of pure lithium tantalate, thus solving the problem of "strong resistance to light damage but low nonlinear coefficient" of pure lithium tantalate.

[0150] The above reasons are as follows: The single-crystal thin film of the present invention contains lithium tantalate niobate. Tantalum ions and niobium ions belong to the same group VB, have similar ionic radii and chemical properties, and can achieve uniform substitution in any proportion in the crystal lattice to form a stable single-phase crystal structure. This substitution can not only suppress the photorefractive effect of pure lithium niobate by controlling the intrinsic defect concentration, photoconductivity and photorefractive sensitivity of lithium tantalate niobate crystal, and improve the anti-photodamage threshold, but also maintain a high nonlinear polarizability by retaining a certain proportion of lithium niobate. Thus, the single-crystal thin film of the present invention has both the high nonlinear optical performance of pure lithium niobate and the high anti-photodamage ability of pure lithium tantalate, solving the performance shortcomings of the two single materials.

[0151] Therefore, this invention, by controlling the tantalum-niobium composition in the single-crystal thin film, retains the high nonlinear optical properties of pure LN while introducing the high resistance to optical damage of pure LT. This eliminates the single performance weakness of the material and allows for flexible matching according to the specific needs of different application scenarios. Although the single performance index of the single-crystal thin film of this invention does not exceed the limit of pure LN or pure LT, it achieves synergistic optimization in terms of comprehensive performance. For example, in scenarios that balance conversion efficiency and high power stability, Example 1 can provide high nonlinear performance and significantly improved damage resistance. In scenarios with high power, long lifespan, and basic requirements for nonlinear efficiency, Example 2 can provide excellent damage resistance and nonlinear performance superior to pure LT. This achieves precise adaptation to different application needs and has a wider range of application scenarios and balanced performance advantages compared to two single materials.

[0152] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A single-crystal thin film, characterized in that, It includes a substrate layer, an isolation layer, and a lithium tantalate niobate thin film layer stacked sequentially; The lithium tantalate / niobate thin film layer includes LiTa x Nb 1-x O3, where 0 < x < 1.

2. The single-crystal thin film according to claim 1, characterized in that, The thickness of the lithium tantalate niobate thin film layer is 5 nm to 10 μm; and / or, The surface roughness Ra of the lithium tantalate niobate thin film layer is <0.3 nm; and / or, The difference between the maximum and minimum thickness of the lithium tantalate niobate thin film layer, TTV < 50 nm.

3. The single-crystal thin film according to claim 1 or 2, characterized in that, The substrate layer is made of silicon, quartz, silicon carbide, silicon nitride, or sapphire; and / or, The thickness of the substrate layer is 0.1~1mm; and / or, The material of the insulating layer is selected from at least one of silicon dioxide, silicon oxynitride, silicon nitride, aluminum oxide, and aluminum nitride; and / or, The thickness of the isolation layer is 10nm~15μm.

4. The single-crystal thin film according to any one of claims 1-3, characterized in that, The single-crystal thin film further includes a trap layer, which is located between the substrate layer and the isolation layer; The trap layer is made of at least one of polycrystalline silicon, amorphous silicon, or polycrystalline germanium.

5. The single-crystal thin film according to claim 4, characterized in that, The thickness of the trap layer is 300~5000nm.

6. A method for preparing a single-crystal thin film according to any one of claims 1-5, characterized in that, include: A single-crystal thin film is obtained by bonding a lithium tantalate niobate thin film to a bonding substrate. The bonding substrate includes a substrate layer and an isolation layer stacked sequentially, with the lithium tantalate niobate thin film layer disposed close to the isolation layer.

7. The preparation method according to claim 6, characterized in that, The bonding process between the lithium tantalate niobate thin film layer and the bonding substrate includes: Ion implantation was performed on a lithium tantalate niobate donor wafer to obtain an intermediate comprising a lithium tantalate niobate thin film layer and a residual layer. The intermediate is bonded to the bonding substrate, with the lithium tantalate niobate thin film layer close to the isolation layer, to obtain a single-crystal thin film precursor; The single-crystal thin film precursor is subjected to a first heat treatment and a second heat treatment in sequence to obtain the single-crystal thin film. The temperature of the first heat treatment is lower than the temperature of the second heat treatment.

8. The preparation method according to claim 7, characterized in that, Prior to the bonding process, the intermediate and the bonding substrate are surface activated using plasma.

9. The preparation method according to claim 7 or 8, characterized in that, In the ion implantation process, the dose of implanted ions is 1×10⁻⁶. 16 ~3×10 17 ions / cm 2 The energy of the injected ions is 30 keV to 5 MeV; and / or, The temperature of the first heat treatment is 180~300℃; and / or, The temperature of the second heat treatment is 301~600℃.

10. An optoelectronic device, characterized in that, Includes the single-crystal thin film according to any one of claims 1-5.

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