In-situ integration method of rare earth doped two-dimensional material on lithium niobate micro-nano structure surface

Abstract

The present application relates to the technical fields of integrated photonics and two-dimensional material device manufacturing, and particularly relates to a method for in-situ integration of a lithium niobate micro-nano structure surface rare earth doped two-dimensional material, comprising: pretreating a lithium niobate micro-nano structure substrate; depositing a sub-nanometer metal layer by high-vacuum magnetron sputtering, with the thickness of the sub-nanometer metal layer being less than 1 nm; annealing at a low temperature in an inert atmosphere at 200-250 DEG C to form a nano anchoring layer; depositing a main metal film on the surface of the nano anchoring layer and introducing a rare earth doping element; constructing a pre-reaction layer by pre-reaction at a low temperature of 400-500 DEG C; and completing the conversion of the main metal film to a crystalline two-dimensional transition metal chalcogenide and solidifying the rare earth luminescent center and structure coating by high-temperature crystallization at 700-850 DEG C. The method has the advantages of realizing low-damage in-situ integration of a lithium niobate micro-nano structure, uniform and controllable rare earth doping, and excellent two-dimensional material crystallization; and can efficiently prepare high-performance near-infrared luminescence heterojunction devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated photonics and two-dimensional material device manufacturing, and particularly relates to an in-situ integration method of a lithium niobate micro-nano structure surface rare earth doped two-dimensional material. BACKGROUND

[0002] The lithium niobate photon platform is considered as the core material for realizing the next generation of multifunctional integrated photon chips due to its excellent electro-optic, acousto-optic and nonlinear optical coefficients. However, its indirect band gap semiconductor characteristics result in extremely low intrinsic light emission efficiency, which is a key bottleneck for building a fully functional lithium niobate photon integrated circuit (PIC). The prior art proposes two solutions: 1. Directly doping rare earth ions (such as Er 3+ ) into the lithium niobate lattice, which can realize light emission, but has problems such as low doping concentration, ion clustering, and increased non-radiative loss leading to passive device performance degradation; 2. Heterogeneous integration of III-V semiconductor lasers through wafer bonding technology, which faces challenges such as complex process, high production cost and difficult thermal management, making it difficult to meet the needs of large-scale integration applications.

[0003] Two-dimensional transition metal chalcogenides (such as MoS2) as emerging direct band gap semiconductor gain media, by introducing rare earth ions (such as Er 3+ ,Yb 3+ ), can realize high-efficiency light emission in the near-infrared communication band, providing a new technical path to solve the lithium niobate light emission bottleneck. However, high-quality integration of such materials onto lithium niobate microcavities faces a fundamental technical contradiction: the high-temperature process (usually ≥ 850℃) required for traditional two-dimensional material sulfuration far exceeds the thermal budget (usually ≤ 600℃) of lithium niobate micro-nano structures, which easily leads to irreversible phase changes, surface decomposition, microcavity structure cracking, and interface adhesion reduction of lithium niobate.

[0004] Specifically, the direct growth of rare earth doped MoS2 onto the surface of lithium niobate (LN) microdisks mainly faces two technical obstacles:

[0005] 1. Thermal sensitivity barrier: the conventional sulfuration temperature (≥ 800℃) of Mo to MoS2 will cause phase changes, stress cracking and morphology collapse of LN thin film / microdisk; in addition, the thermal expansion coefficients of LN and two-dimensional materials do not match, which is particularly prominent during rapid heating, making it difficult to maintain the integrity of the microcavity structure.

[0006] 2. High temperature compatibility and interface bonding difficulty: the conventional epitaxy or transfer integration route of two-dimensional materials either exceeds the LN thermal budget due to high process temperature, or affects the device performance due to the introduction of exogenous contamination and residual stress; and the sputtering-sulfuration process for growing rare earth doped MoS2 directly on the LN substrate has problems such as uncontrollable interface chemical reaction, insufficient film adhesion and poor long-term reliability of the device.

[0007] In summary, the prior art restricts the application of high-performance light-emitting devices based on LN microcavities, and therefore there is an urgent need for a stable process that can realize the in-situ, uniform and controllable integration of rare earth doped MoS2 on LN microdisks. SUMMARY

[0008] To solve the above problems, the present application provides an in-situ integration method of rare earth doped two-dimensional material on the surface of lithium niobate micro-nano structure.

[0009] The first object of the present application is to provide an in-situ integration method of rare earth doped two-dimensional material on the surface of lithium niobate micro-nano structure, comprising the following steps:

[0010] S1. Pretreating the lithium niobate micro-nano structure substrate;

[0011] S2. Depositing a sub-nanometer metal layer on the surface of the pretreated substrate by high vacuum magnetron sputtering, and the thickness of the sub-nanometer metal layer is less than 1 nm; annealing at 200-250℃ in an inert atmosphere to form a nanometer anchoring layer;

[0012] S3. Depositing a main metal film on the surface of the nanometer anchoring layer and introducing a rare earth doping element;

[0013] S4. Constructing a pre-reaction layer by low temperature pre-reaction at 400-500℃; and completing the conversion of the main metal film to a crystalline two-dimensional transition metal chalcogenide and solidifying the rare earth luminescent center and structure coating by high temperature crystallization at 700-850℃.

[0014] Preferably, the process parameters of high vacuum magnetron sputtering in step S2 are as follows: sputtering power 5-10 W, cavity pressure 1-3 mTorr Ar atmosphere, deposition time 5-30 s, and the sub-nanometer metal layer is at the level of sub-monolayer to several atomic layers to realize uniform coverage of the substrate surface.

[0015] Preferably, the inert atmosphere is high-purity Ar or N2, and the annealing time is 5-10 min; the sub-nanometer metal layer is a sub-nanometer Mo layer or a sub-nanometer W layer; and the nanometer anchoring layer is a molybdate or tungstate transition phase.

[0016] Preferably, the sub-nanometer metal layer is a sub-nanometer Mo layer or a sub-nanometer W layer; and the main metal film and the sub-nanometer metal layer correspond in material to a Mo film or a W film, and the thickness is 3-30 nm.

[0017] In step S3, the main metal film is deposited by high vacuum direct current or radio frequency magnetron sputtering, and the process parameters are as follows: sputtering power 20-60 W, Ar flow rate 15-25 sccm, and cavity pressure 1-3 mTorr.

[0018] Preferably, the rare earth doping element includes at least one of Er 3+ , Yb 3+ , Tm 3+ , Eu 3+ , and the doping atom percentage is 0.1-5 at%; the rare earth doping element is introduced by at least one of co-sputtering, step-by-step sputtering or thermal evaporation doping.

[0019] Preferably, when the rare earth doping element is introduced by co-sputtering, the metal target is co-targeted with a rare earth target or a rare earth oxide target to complete uniform doping of the rare earth element while depositing the main metal film;

[0020] When the rare earth doping element is introduced by step-by-step sputtering, a rare earth layer or a rare earth oxide layer with a thickness of 0.5-1 nm is sputtered after the main metal film is deposited;

[0021] When the rare earth doping element is introduced by thermal evaporation doping, a rare earth halide film is deposited on the surface of the main metal film by thermal evaporation process, and the doping of the rare earth element is realized through subsequent sulfidation or selenization.

[0022] Preferably, the low-temperature pre-reaction in step S4 is low-temperature pre-sulfidation or pre-selenization, which is carried out in a mixed gas atmosphere with a volume ratio of H2 to Ar being 1:9, and the holding time is 10-15 min; the pre-reaction layer is amorphous or nanocrystalline MoS x or WS x (x>2) with a loose porous structure;

[0023] The high-temperature crystallization is treated by a tube furnace in stages or by chemical vapor deposition.

[0024] Preferably, when the high-temperature crystallization is treated by a tube furnace in stages, the tube furnace is heated to 800-850℃ at a heating rate of ≤10℃ / min, and the holding time is 15-30 min;

[0025] When the high-temperature crystallization is treated by chemical vapor deposition, a sulfur-containing gas or a selenium-containing gas and a rare earth source are introduced at 700-750℃, and the holding time is 15-30 min.

[0026] Preferably, the pretreatment in step S1 comprises: sequentially ultrasonic cleaning the substrate with deionized water, acetone and anhydrous ethanol, each time for 5-10 min; after cleaning, drying the substrate with high-purity nitrogen; and activating the dried substrate with UV-O3 or Ar plasma, at an activation power of 50-100 W for 3-10 min.

[0027] The lithium niobate micro-nano structure substrate is a lithium niobate microdisk resonant cavity, a micro-ring resonant cavity, a microsphere resonant cavity or an optical waveguide structure.

[0028] The second object of the application is to provide a lithium niobate / rare earth doped two-dimensional transition metal chalcogenide heterojunction light-emitting device, which is prepared by an in-situ integration method of a lithium niobate micro-nano structure surface rare earth doped two-dimensional material; the integrated structure is a core-shell or gradient chimeric microstructure, which can generate near-infrared light emission near 1530 nm under 980 nm pumping.

[0029] Compared with the prior art, the application can achieve the following beneficial effects:

[0030] (1) Revolutionary thermal compatibility: through the interface engineering of Mo atomic layer pre-bonding and interface passivation, the lithium niobate microcavity can withstand the high-temperature vulcanization process that is traditionally sufficient to damage it, solving the fundamental obstacle of hetero-integration.

[0031] (2) Excellent interface stability: the chemically bonded interface layer causes a qualitative change in the adhesion of the thin film, significantly improving the mechanical strength and environmental stability of the device, and significantly prolonging the service life.

[0032] (3) Excellent light-emitting performance: the unique heterostructure formed by staged temperature control vulcanization, through the dual effects of "photonic localization" and "energy sensitization", together enhances the light-emitting efficiency and gain of rare earth ions to a new height, laying the foundation for realizing low-threshold laser.

[0033] (4) High process compatibility and universality: the whole process is compatible with existing micro-nano processing technology and is suitable for wafer-level manufacturing. This technical route can be easily extended to WS2, MoSe2 and other two-dimensional materials, as well as Nd 3+ , Tm 3+ and other rare earth ions, realizing wide-spectrum sheet light emission from visible to near-infrared. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a process flow chart of an in-situ integration method of a lithium niobate micro-nano structure surface rare earth doped two-dimensional material according to an embodiment of the application.

[0035] Figure 2Fig. 1 is a schematic diagram of a sub-nanometer metal layer pre-bonding and interface passivation process according to an embodiment of the present application; (a) sub-nanometer Mo atomic layer is deposited on a lithium niobate surface; (b) a stable, chemically bonded nano-anchor layer is formed after low-temperature annealing.

[0036] Figure 3 Fig. 2 is a comparison of optical microscope images of a lithium niobate microdisk and a comparative example (without pre-bonding treatment) after vulcanization; in the figure, the microdisk structure in region A is complete and the film is uniformly covered, while the lithium niobate film in region B of the comparative example is cracked at the edge and the film is peeled off.

[0037] Figure 4 Fig. 3 is a Raman spectrum test result according to an embodiment of the present application.

[0038] Figure 5 Fig. 4 is a photoluminescence (PL) spectrum of an Er-doped MoS2 / LNOI-based lithium niobate microdisk resonant cavity under 980 nm pumping according to an embodiment of the present application.

[0039] Reference signs:

[0040] 1. substrate;

[0041] 2. nano-anchor layer;

[0042] 3. main Mo film;

[0043] 4. MoS2 film. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0045] In order to make the objects, technical solutions, and advantages of the present application clearer, further detailed descriptions will be given below in combination with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not constitute a limitation on the present application.

[0046] The present application aims to provide a low-damage, controlled and batchable in-situ integration method of rare earth doped two-dimensional transition metal chalcogenides and lithium niobate micro-nano structures without destroying the integrity and quality factor (Q factor) of the LN micro disk structure: by combining Mo atomic layer pre-bonding passivation and two-stage temperature control sulfuration, a rare earth doped MoS2 light-emitting layer is constructed to realize near-infrared light emission near about 1.53 µm under 980 nm pumping, and the risk of brittle fracture of the LN micro disk in the subsequent high-temperature link is significantly reduced. The method has the characteristics of clear process window and can be extended to other rare earth / two-dimensional materials and other LN microcavity / waveguide structures.

[0047] The present application provides an in-situ integration method of a lithium niobate micro-nano structure surface rare earth doped two-dimensional material, which specifically comprises the following steps:

[0048] S1. Lithium niobate micro-nano structure substrate pretreatment; specifically including:

[0049] S11. Select a micro-nano processed LNOI (LN-on-insulator) lithium niobate micro-nano structure substrate, and sequentially use deionized water, acetone and anhydrous ethanol to ultrasonically clean the substrate, with each ultrasonic time controlled to be 5-10 min, so as to remove photoresist residues, particulate impurities and organic pollutants on the surface of the substrate through gradient cleaning;

[0050] The substrate is specifically a micro disk resonant cavity, a micro ring resonant cavity, a micro sphere resonant cavity or an optical waveguide structure; wherein the diameter of the micro disk resonant cavity is preferably 30-120 µm, and the edge needs to be smoothly treated to avoid stress concentration leading to edge collapse in the subsequent process.

[0051] S12. The cleaned substrate is blown dry with high-purity nitrogen to avoid film growth defects caused by water stains.

[0052] S13. Surface activation treatment is performed on the dried substrate, which removes residual organic groups on the surface of the substrate and introduces active sites such as hydroxyl groups to improve the interfacial wettability and bonding force of the subsequent metal layer and the substrate.

[0053] Specifically, UV-O3 or Ar plasma activation is used, with an activation power of 50-100 W and an activation time of 3-10 min.

[0054] S2. Deposition of sub-nanometer metal layer and low-temperature annealing to form a nano anchor layer; specifically including:

[0055] S21. Put the pretreated lithium niobate micro-nano structure substrate into a high-vacuum magnetron sputtering device, and deposit a sub-nanometer metal layer by using a direct current (DC) sputtering method.

[0056] Specifically, the sub-nanometer metal layer is selected from Mo layer or W layer, the sputtering power is controlled to be extremely low at 5-10 W, the cavity pressure is maintained at 1-3 mTorr in Ar atmosphere, the deposition time is 5-30 s, the thickness of the deposited metal layer is less than 1 nm, and the metal layer is in the level of "sub-monolayer to several atomic layers", so that the surface of the substrate is uniformly covered instead of forming a continuous thick film.

[0057] S22. The substrate after deposition of the sub-nanometer metal layer is transferred to an annealing furnace for low-temperature annealing treatment in an inert atmosphere (high-purity Ar or N2), the annealing temperature is 200-250℃, and the annealing time is 5-10 min; during the annealing process, the sub-nanometer metal layer and the Nb, O and Li atoms on the surface of the lithium niobate substrate undergo interdiffusion and interface reaction to form a stable, chemically bonded nano-anchoring layer of molybdate or tungstate transition phase;

[0058] The nano-anchoring layer prepared in this step has a triple core effect, i.e. stress buffering, chemical bonding and diffusion blocking; specifically, it includes: (1) heat shielding effect: blocking the direct erosion of sulfur / selenium vapor on the lithium niobate body in the subsequent high-temperature sulfidation / selenization process; (2) stress buffering effect: relieving the stress generated between lithium niobate and two-dimensional transition metal chalcogenide due to the mismatch of thermal expansion coefficients; (3) nucleation promotion effect: providing high-density, low-energy nucleation sites for the deposition of the subsequent main metal film, and inducing the preferential growth of two-dimensional material along the (100) crystal plane.

[0059] S3. Deposition of main metal film and introduction of rare earth doping elements; specifically including:

[0060] S31. In a high-vacuum environment, a direct current (DC) or radio frequency (RF) magnetron sputtering method is used to deposit a main metal film on the surface of the nano-anchoring layer;

[0061] The main metal film is selected from Mo film or W film corresponding to the sub-nanometer metal layer, and the total thickness is 3-30 nm; the sputtering process parameters are controlled as follows: power 20-60 W, Ar flow rate 15-25 sccm, and cavity pressure 1-5 mTorr;

[0062] Preferably, the thickness of the main metal film is 5-15 nm, which can balance the crystalline quality and stress level of the thin film.

[0063] S32. The rare earth doping elements are introduced by any one or combination of the following methods, and the rare earth doping elements include at least one of Er 3+ , Yb 3+ , Tm 3+ , Eu 3+ , and the doping atomic percentage is controlled to be 0.1-5 at%, preferably 0.2-2 at%, to avoid ion clusters caused by high-concentration doping:

[0064] (1) Co-sputtering: co-target sputtering of a metal target (Mo target or W target) and a rare earth target (such as an Er target) or a rare earth oxide target (such as an Er2O3 target) is performed to uniformly dope the rare earth element while depositing the main metal film;

[0065] (2) Stepwise sputtering: after the main metal film is deposited, a rare earth layer or a rare earth oxide layer with a thickness of 0.5-1 nm is sequentially sputtered, and the rare earth ions can diffuse and solid-solve into the two-dimensional material lattice during the subsequent sulfidation or selenization process;

[0066] (3) Thermal evaporation doping: as an alternative to sputtering doping, a rare earth halide film is deposited on the surface of the main metal film using a thermal evaporation process, and the doping of the rare earth element is realized during the subsequent sulfidation or selenization process. This scheme can reduce the complexity of the equipment;

[0067] In this step, Er 3+ / Yb 3+ is co-doped. Yb 3+ is used to improve the absorption of 980 nm pump light, realize efficient energy transfer from Yb 3+ to Er 3+ , and further improve the luminescent efficiency of the rare earth-doped two-dimensional transition metal chalcogenide.

[0068] S4. Stage-wise temperature-controlled sulfidation or selenization treatment: the substrate on which the main metal film is deposited is pre-reacted at low temperature to form a pre-reaction layer, and then crystallized at high temperature to complete the conversion of the main metal film to a crystalline two-dimensional transition metal chalcogenide and solidify the rare earth luminescent center and structural coating. This realizes the controlled growth of the rare earth-doped two-dimensional transition metal chalcogenide while avoiding thermal damage to the lithium niobate micro-nano structure. Specifically, the following sub-steps are included:

[0069] S41. Low-temperature pre-sulfidation or pre-selenization (generate transition phase pre-reaction layer): place the lithium niobate micro-nano structure substrate on which the main metal film and the rare earth doping element are deposited into a tube furnace reaction chamber; first, introduce a mixed protective atmosphere of H2 and Ar, then raise the furnace temperature to 400-500°C and keep it for 10-15 min;

[0070] Specifically, the volume ratio of H2 to Ar is preferably 1:9, and the H2 proportion can be adjusted to control the reaction activity according to the size of the substrate;

[0071] In this stage, the surface layer of the main metal film (Mo or W film) preferentially reacts with the sulfur source or selenium source to form a non-stoichiometric amorphous or nanocrystalline transition phase metal sulfide or selenide pre-reaction layer (such as MoS x , WS xwherein x>2); the pre-reaction layer has a loose porous structure, which can not only serve as a fast channel for the inward diffusion of the sulfur source or selenium source and the outward migration of the metal source in the subsequent high-temperature stage, but also can absorb the interface stress by itself to avoid cracking of the substrate and the film due to the difference in the thermal expansion coefficient.

[0072] S42. High-temperature crystallization sulfuration or selenization (complete crystalline transformation and solidification of rare earth luminescent centers): adopt a tubular furnace staged treatment or chemical vapor deposition to realize the transformation of the main metal film into a crystalline rare earth-doped two-dimensional transition metal chalcogenide and solidify the rare earth luminescent centers and the structural coating; the specific process is as follows:

[0073] (1) Tubular furnace staged treatment: after the low-temperature pretreatment is completed, the temperature of the tubular furnace is raised to 800-850℃ at a controllable heating rate of ≤10℃ / min (to avoid stress concentration caused by rapid heating), and the temperature is kept at this temperature for 15-30min; during this process, the internal unreacted Mo or W atoms are fully reacted with sulfur or selenium through the transition phase pre-reaction layer to completely transform into a 2H phase two-dimensional material (such as MoS2, WS2 or MoSe2) with good crystallinity, and at the same time, the rare earth ions (Er 3+ , Yb 3+ , etc.) are effectively embedded in the two-dimensional material lattice (mainly occupying the metal atom sites or existing between the layers), realizing the solidification of the rare earth luminescent centers and the structural coating of the two-dimensional material;

[0074] (2) Chemical vapor deposition treatment: the substrate on which the main metal film and the rare earth-doped elements are deposited is placed in a chemical vapor deposition reaction chamber, and at a temperature of 700-750℃, sulfur-containing gas or selenium-containing gas (such as H2S, Se powder vapor) and rare earth source (such as rare earth organic compound vapor) are simultaneously introduced into the reaction chamber, and the temperature is kept for 15-30min; during this process, the main metal film reacts with the sulfur source or the selenium source to generate a two-dimensional transition metal chalcogenide, and at the same time, the rare earth ions provided by the rare earth source are doped into the two-dimensional material, realizing the sulfuration or selenization, the crystalline transformation, and the solidification and structural coating of the rare earth luminescent centers in one step;

[0075] In specific embodiments, taking the Mo system as an example, the internal Mo is fully reacted with the pre-formed MoS x channel and the sulfur to completely transform into a 2H phase MoS2 with good crystallinity. At the same time, the rare earth ions are effectively introduced into the MoS2 lattice, mainly occupying the Mo sites or existing between the layers. The finally formed film has a unique "core-shell" or "gradient embedded" microstructure, that is, the internal part is a high-quality crystalline MoS2, while the surface layer or the grain boundary is wrapped / embedded with MoS x phase.

[0076] S43. Furnace cooling and integrated structure forming: after the sulfuration or selenization reaction is completed, the heating device is turned off, and the protective atmosphere is maintained until the furnace temperature naturally cools to room temperature; after cooling, the sample is taken out to obtain an integrated structure of a rare earth doped two-dimensional transition metal chalcogenide and a lithium niobate micro-nano structure;

[0077] The integrated structure includes a lithium niobate micro-nano structure substrate and a rare earth doped two-dimensional transition metal chalcogenide layer covering the surface of the substrate; and has a core-shell or gradient chimeric microscopic feature in structure: the inside is a high-quality crystalline (2H phase crystalline) rare earth doped two-dimensional material, and the surface layer or the grain boundary is wrapped or inlaid with a transition phase metal sulfide or selenide, which ensures the luminescent performance of the rare earth doped two-dimensional material and improves the interface bonding force of the thin film and the substrate; at the same time, the lithium niobate micro-nano structure has no crystal phase damage, edge collapse and other defects, and maintains high Q factor optical performance.

[0078] Embodiment 1

[0079] This embodiment provides an in-situ integrated method of an Er doped MoS2 / LNOI based lithium niobate micro-disk resonant cavity, and a flow chart is shown as Figure 1 , and specifically includes the following steps:

[0080] S1. Select a LNOI based lithium niobate micro-disk resonant cavity with a diameter of 80 µm as a substrate 1, and sequentially clean it with deionized water, acetone and anhydrous ethanol for 8 min, dry it by nitrogen blowing, and then activate it by 100W Ar plasma for 5 min;

[0081] S2. Put the substrate 1 into a high vacuum magnetron sputtering device, deposit a Mo atomic layer by 5W direct current sputtering, the cavity pressure is 2mTorr Ar, the deposition time is 15s, and the thickness is ≤0.5nm; then anneal it at 230℃ under high-purity Ar atmosphere for 8 min to form a nanometer anchoring layer 2 of molybdate transition phase; and a principle diagram of the preparation process is shown as Figure 2 ;

[0082] S3. Deposit a main Mo film 3 with a thickness of 10nm on the surface of the nanometer anchoring layer 2 by 40W RF magnetron sputtering, the Ar flow is 20sccm, and the cavity pressure is 3mTorr; synchronously co-sputter by an Er2O3 target, and control the Er doping atomic percentage to be 0.8at%;

[0083] S4: temperature-controlled sulfuration treatment in stages:

[0084] First stage: put the sample into a tube furnace, introduce a H2 / Ar mixed atmosphere (5 / 45sccm, volume ratio 1:9), the sulfur source temperature is 200℃, and first pre-sulfurate at 450℃ for 12 min;

[0085] Second stage: increase to 820℃ at a heating rate of 5℃ / min, high-temperature vulcanization for 20 min; after furnace cooling, Er-doped MoS2 film 4 is obtained, and the preparation of Er-doped MoS2 / LNOI-based lithium niobate micro-disk resonator is completed.

[0086] Figure 3 It is an optical microscope photo of the Er-doped MoS2 / LNOI-based lithium niobate micro-disk resonator after vulcanization, wherein the left photo is the overall morphology of the micro-disk, and the right photo is a local enlarged view; it can be observed from the photo that the micro-disk surface is completely covered by the uniform film layer without defects such as exposed bottom and holes; the edge of the micro-disk (the junction of regions A and B) maintains a smooth shape without edge collapse, cracks or film layer falling off; the film layer surface has no obvious protrusions and wrinkles, and presents a dense and flat appearance. The results prove that, by the sub-nanometer Mo layer anchoring and the stage temperature control vulcanization process in this embodiment, the thermal damage of the lithium niobate micro-disk in the high-temperature process is effectively avoided, and the good combination of the MoS2 film and the substrate is ensured, realizing the morphology integrity of the micro-nano structure.

[0087] Figure 4 It is the Raman spectrum test result, and it can be seen from the curve in the photo that the characteristic vibration peaks (E - 2g and A1g modes) of 2H phase MoS2 appear near ~400cm 1 , proving that the main metal film has been successfully converted into crystalline 2H phase MoS2; at the same time, the characteristic peak signal of the lithium niobate substrate in the red curve is covered by the signal of the MoS2 film, further proving the continuity and uniformity of the film layer; and the slight broadening of the characteristic peak (compared with the standard peak of pure MoS2), combined with the doping parameters in the foregoing, can indicate the lattice micro-strain caused by the Er element after doping. The results show that the vulcanization process in this embodiment realizes the crystalline growth of MoS2 and successfully completes the rare earth doping without damaging the crystal structure of the material.

[0088] The test results are shown in Figure 5 As shown in the photo, a strong PL peak appears near about 1530 nm under 980 nm pumping; there is no crack at the edge of the micro-disk, the microscope photo shows that the film layer is dense, the Raman spectrum is characteristic of 2H MoS2 with slight shift (strain / doping indication).

[0089] It should be understood that the various forms of the flow shown above can be reordered, added to, or deleted from. For example, the steps described in the present disclosure can be executed in parallel, in sequence, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, which is not limited herein.

[0090] The above detailed description does not limit the scope of the application. Various modifications, combinations, sub-combinations and alternatives can be made to the detailed description. Any modification, equivalent replacement and improvement etc. made within the spirit and principle of the application shall be included in the scope of the application.

Claims

1. An in-situ integration method for rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures, characterized in that: Includes the following steps: S1. Pretreatment of lithium niobate micro / nano structure substrate; S2. A sub-nanometer metal layer with a thickness of less than 1 nm is deposited on the pretreated substrate surface by high vacuum magnetron sputtering. The nano-anchoring layer is formed by low-temperature annealing in an inert atmosphere at 200~250℃; the sub-nano metal layer is a sub-nano Mo layer or a sub-nano W layer; the nano-anchoring layer is a molybdate or tungstate transition phase; S3. Deposit a main metal film on the surface of the nano-anchoring layer and introduce rare earth doping elements; the main metal film corresponds to the material of the sub-nano metal layer, and is a Mo film or a W film with a thickness of 3~30nm; S4. Staged temperature-controlled sulfidation or selenization treatment: A pre-reaction layer is constructed through a low-temperature pre-reaction at 400~500℃, wherein the pre-reaction layer is amorphous or nanocrystalline MoS2. x or WS x x>2, with a loose and porous structure; then, through high-temperature crystallization at 700~850℃, the main metal film is transformed into a crystalline two-dimensional transition metal chalcogenide, and the rare earth luminescent center and structural coating are solidified; the low-temperature pre-reaction is low-temperature pre-sulfidation or pre-selenization.

2. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 1, characterized in that: The process parameters for high-vacuum magnetron sputtering in step S2 are: sputtering power 5~10W, cavity pressure 1~3mTorrAr atmosphere, deposition time 5~30s, and the sub-nanometer metal layer is at the sub-monolayer to several atomic layer level to achieve uniform coverage of the substrate surface.

3. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 2, characterized in that: The inert atmosphere is high-purity Ar or N2, and the annealing time is 5-10 min.

4. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 1, characterized in that: In step S3, the main metal film is deposited by high vacuum DC or radio frequency magnetron sputtering with the following process parameters: sputtering power 20~60W, Ar flow rate 15~25sccm, and cavity pressure 1~3mTorr.

5. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 4, characterized in that: The rare earth doping element includes Er 3+ Yb 3+ Tm 3+ Eu 3+ At least one of the following, with a doping atomic percentage of 0.1~5 at%; the rare earth doping element is introduced by at least one of co-sputtering, step sputtering or thermal evaporation doping.

6. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 5, characterized in that: When the rare earth doping element is introduced by co-sputtering, the metal target and the rare earth target or the rare earth oxide target are co-sputtered, and the rare earth element is uniformly doped while the main metal film is deposited. When the rare earth doping element is introduced by step sputtering, a rare earth layer or rare earth oxide layer with a thickness of 0.5~1nm is sputtered after the main metal film is deposited. When the rare earth doping element is introduced by thermal evaporation doping, a rare earth halide film is deposited on the surface of the main metal film using a thermal evaporation process, and the rare earth element is doped through subsequent sulfidation or selenization processes.

7. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 1, characterized in that: The low-temperature pre-reaction in step S4 is carried out in a mixed atmosphere of H2 and Ar with a volume ratio of 1:9, and the holding time is 10-15 min. The high-temperature crystallization is performed using a tubular furnace in stages or chemical vapor deposition.

8. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 7, characterized in that: When the high-temperature crystallization is carried out in stages using a tube furnace, the tube furnace is heated to 800~850℃ at a heating rate of ≤10℃ / min and held for 15~30min. When the high-temperature crystallization is treated by chemical vapor deposition, sulfur-containing gas or selenium-containing gas and rare earth source are introduced at 700~750℃ and kept at this temperature for 15~30 minutes.

9. The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structures according to claim 1, characterized in that: The pretreatment in step S1 includes: firstly, ultrasonically cleaning the substrate sequentially with deionized water, acetone and anhydrous ethanol, each ultrasonic time being 5-10 min; after cleaning, drying with high-purity nitrogen; and then surface activation of the dried substrate using UV-O3 or Ar plasma, with an activation power of 50-100W and an activation time of 3-10 min. The lithium niobate micro / nano structure substrate is a lithium niobate microdisk resonant cavity, microring resonant cavity, microsphere resonant cavity, or optical waveguide structure.

10. A lithium niobate / rare earth-doped two-dimensional transition metal chalcogenide heterojunction light-emitting device, characterized in that: The in-situ integration method of rare earth-doped two-dimensional materials on the surface of lithium niobate micro / nano structure as described in claim 1 is used to prepare the material. The integrated structure is a core-shell or gradient interlocking microstructure, which can produce near-infrared emission of 1530 nm under 980 nm pumping.

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