Method for preparing hexagonal boron nitride single photon source

Abstract

This invention provides a method for fabricating a hexagonal boron nitride single-photon source, applicable to the field of quantum communication technology. The method includes: preparing a sapphire substrate; sputtering a solid boron thin film onto a first substrate and a third substrate; stacking the first substrate carrying the solid boron thin film onto a second substrate in a heating furnace to grow a first hexagonal boron nitride single-crystal thin film; plasma treating the first hexagonal boron nitride single-crystal thin film; and stacking the third substrate onto the second substrate and placing it in a heating furnace to grow a second hexagonal boron nitride single-crystal thin film, wherein the first hexagonal boron nitride single-crystal thin film is located between the second and third substrates. Large-scale fabrication of a single-photon source is achieved on the hexagonal boron nitride single-crystal thin film through plasma treatment, and efficient passivation protection of the single-photon source in the first hexagonal boron nitride single-crystal thin film is achieved by using an in-situ capping layer for secondary growth of the second hexagonal boron nitride single-crystal thin film.

Description

Technical Field

[0001] This invention relates to the field of quantum communication technology, and in particular to a method for preparing a hexagonal boron nitride single-photon source. Background Technology

[0002] Quantum emitters in solid-state systems have become a key element driving numerous cutting-edge quantum technology applications, including quantum communication, quantum computing, quantum network architecture, and quantum sensing. As the cornerstone of quantum information technology, single-photon sources provide an indispensable foundational resource for the realization of these technologies. With the deepening of research, the scope of single-photon emitters (SPEs) is no longer limited to the initial single-atom or single-molecule forms, but has been successfully expanded to various solid-state materials such as diamond, point defects in silicon carbide, semiconductor quantum dots, and carbon nanotubes.

[0003] Recently, two-dimensional (2D) materials have attracted much attention in the scientific community due to their superior ability to support specific spatial photonic devices (SPEs) and their inherent advantages in device integration and optical coupling efficiency. However, most SPEs in 2D transition metal dichalcogenides (TMDs) unfortunately only function properly at low temperatures, which undoubtedly limits their widespread application at room temperature. Against this backdrop, hexagonal boron nitride (h-BN), a 2D layered material with a structure similar to graphene, has successfully demonstrated its ability to support high-brightness, room-temperature stable, and strongly linearly polarized SPEs thanks to localized point defects within its wide bandgap of approximately 6 eV. Furthermore, the excellent chemical and thermal stability exhibited by h-BN provides strong assurance for the long-term stable operation of the SPEs. These remarkable properties make h-BN-based quantum emitters an ideal choice for integrating quantum photonic devices.

[0004] Quantum emitters in h-BN often originate from randomly formed defects during their growth process or when peeled from bulk crystals. Typically, these emitters require no further processing or only a simple thermal annealing process to achieve stabilization. However, this randomness leads to the ubiquitous and spatially disordered distribution of emitters, accompanied by low density and inhomogeneous optical properties. To overcome this challenge, researchers have explored and employed various post-processing methods, such as ion / electron irradiation, focused ion beam (FIB) treatment, plasma etching, femtosecond laser ablation, and atomic force microscopy (AFM) tip nanoindentation, aiming to create high-density and uniformly characterized quantum emitters. Among these methods, plasma processing technology stands out due to its ability to generate optically active defects on a large scale, its high scalability, and its ease of operation.

[0005] Maintaining good emission stability is a core element for the successful implementation of SPE applications. However, h-BN-based SPEs often encounter flickering and even quenching problems in practical testing and applications. Therefore, developing effective suppression and passivation techniques to enhance emitter stability has become an urgent task. In this regard, researchers have delved into the flickering and quenching mechanisms of h-BN-based SPEs and continuously explored various treatment methods to improve their stability. Some studies have shown that emitters based on thicker h-BN layers exhibit higher stability, suggesting that luminescence flickering may be related to chemical reactions between the h-BN emitter and surface impurities or adsorbed molecules. Similarly, some studies attribute flickering to photochemical reactions triggered by oxygen adsorption on the h-BN surface. Although the specific mechanisms of flickering and quenching in h-BN-based SPEs remain controversial, the industry has reached a consensus: isolating the h-BN emitter from the environment can significantly improve its stability. Based on this consensus, researchers have tried various isolation methods. For example, researchers have significantly improved emitter stability by spin-coating a polymethyl methacrylate (PMMA) film onto the surface of h-BN, effectively isolating the sample from the environment. Other researchers have used transfer technology to coat the upper and lower surfaces of h-BN with another layer of h-BN as a protective layer; this method significantly suppressed emitter quenching, extending its lifetime half-life by two orders of magnitude. Furthermore, researchers have used atomic layer deposition (ALD) to grow an Al₂O₃ layer on h-BN, achieving effective passivation and significantly reducing substrate-induced spectral diffusion.

[0006] However, it is worth noting that two-dimensional h-BN materials possess atomically flat and dangling-bond-free surfaces, making them ideal protective layers for emitters. However, covering the emitter by transferring an h-BN film is not the optimal choice, as the peeling and transfer process inevitably introduces contamination and damage, potentially creating electron traps and affecting emitter stability. Therefore, exploring a simple, effective, and contamination-free method that can perfectly cover the h-BN surface to protect the emitter is particularly urgent. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the technical problem of introducing additional contamination during the passivation protection process of hexagonal boron nitride emitters by covering with other material films or transferring h-BN, embodiments of the present invention provide a method for preparing a hexagonal boron nitride single-photon source. This method achieves large-scale preparation of single-photon sources on h-BN single-crystal thin films through plasma processing. In-situ capping layer secondary growth of h-BN single-crystal thin films achieves efficient passivation protection for the underlying single-photon source. The prepared single-photon source exhibits high brightness, high purity, room temperature operation, and stable luminescence properties, and the preparation cost is low.

[0009] (II) Technical Solution

[0010] To address the aforementioned technical problems, embodiments of the present invention propose a method for preparing a hexagonal boron nitride single-photon source.

[0011] According to a first aspect of the present invention, a method for fabricating a hexagonal boron nitride single-photon source is provided, comprising: preparing three single-sided polished sapphire substrates, respectively serving as a first substrate, a second substrate, and a third substrate; sputtering and depositing a first solid boron thin film on the polished surface of the first substrate; stacking a second substrate on the surface of the first solid boron thin film to obtain a first stack, wherein the first solid boron thin film is in contact with the polished surface of the second substrate; processing the first stack under a nitrogen atmosphere according to first process parameters to convert the first solid boron thin film into a first hexagonal boron nitride single-crystal thin film; peeling the first substrate from the first stack to obtain a second substrate carrying the first hexagonal boron nitride single-crystal thin film; and placing the second substrate carrying the first hexagonal boron nitride single-crystal thin film... The substrate is placed in a radio frequency plasma generator for processing to controllably introduce a single photon source into the first hexagonal boron nitride single crystal film; a second solid boron film is sputtered and deposited on the polished surface of the third substrate; the third substrate is stacked on the surface of the first hexagonal boron nitride single crystal film into which the single photon source is introduced to obtain a second stack, wherein the first hexagonal boron nitride single crystal film into which the single photon source is introduced is in contact with the second solid boron film; the second stack is processed in a nitrogen atmosphere according to the second process parameters to convert the second solid boron film into the second hexagonal boron nitride single crystal film; and the third substrate is peeled off from the second stack to obtain a second substrate carrying the first and second hexagonal boron nitride single crystal films, which serves as the hexagonal boron nitride single photon source.

[0012] In some exemplary embodiments, the method further includes annealing the second substrate carrying the first hexagonal boron nitride single crystal film and the second hexagonal boron nitride single crystal film.

[0013] In some exemplary embodiments, preparing three single-sided polished sapphire substrates includes sequentially immersing the sapphire substrates in acetone, isopropanol, and ethanol for ultrasonic cleaning and then drying them with nitrogen.

[0014] In some exemplary embodiments, the thicknesses of the first solid boron film and the second solid boron film are related to the sputtering deposition time; the deposition time of the first solid boron film is 5 min to 60 min; and the deposition time of the second solid boron film is 5 min to 60 min.

[0015] In some exemplary embodiments, the first process parameters include the following process steps: adjusting the nitrogen gas flow to 400 sccm and maintaining it; raising the temperature inside the heating furnace to the first target growth temperature at a heating rate not exceeding 5°C / min, with the first target growth temperature not exceeding 1600°C; or raising the temperature inside the heating furnace to 1600°C at a heating rate not exceeding 5°C / min, and then raising it to the first target growth temperature at a rate not exceeding 2°C / min, with the temperature held at the first target growth temperature for 1 min to 120 min; lowering the temperature of the furnace tubes to 500°C at a cooling rate not exceeding 3°C / min; and allowing it to cool naturally to room temperature.

[0016] In some exemplary embodiments, the second process parameters include the following process steps: adjusting the nitrogen gas flow to 400 sccm and maintaining it; raising the temperature inside the heating furnace to the second target growth temperature at a heating rate not exceeding 5°C / min, with the second target growth temperature not exceeding 1600°C; or raising the temperature inside the heating furnace to 1600°C at a heating rate not exceeding 5°C / min, and then raising it to the second target growth temperature at a rate not exceeding 2°C / min; holding at the second target growth temperature for 1 min to 30 min; lowering the furnace tube temperature to 500°C at a cooling rate not exceeding 3°C / min; and allowing it to cool naturally to room temperature.

[0017] In some exemplary embodiments, the first target growth temperature is 1350℃-1750℃; the second target growth temperature is 1350℃-1650℃; and the second target growth temperature is lower than the first target growth temperature.

[0018] In some exemplary embodiments, the plasma processing parameters for placing the second substrate carrying the first hexagonal boron nitride single crystal thin film into the radio frequency plasma generator are as follows: the plasma processing atmosphere includes at least one of argon, oxygen, nitrogen, hydrogen, methane, and ammonia; the plasma processing time is 1 min to 20 min; and the plasma processing power is 20 W to 250 W.

[0019] In some exemplary embodiments, the method of peeling the first substrate from the first stack includes purging with nitrogen; and the method of peeling the third substrate from the second stack includes purging with nitrogen.

[0020] In some exemplary embodiments, during the annealing process, the annealing atmosphere includes one of air, oxygen, nitrogen, or argon; the annealing temperature is 700°C-900°C; the annealing time is 30 min-60 min; and the rate of temperature rise and fall does not exceed 10°C / min.

[0021] (III) Beneficial Effects

[0022] As can be seen from the above technical solution, the method for preparing a hexagonal boron nitride single-photon source provided by the embodiments of the present invention has at least the following beneficial effects:

[0023] Large-scale single-photon sources were fabricated on h-BN single-crystal thin films using plasma processing technology. In-situ capping layer secondary growth of h-BN single-crystal thin films was used to achieve efficient passivation protection of the underlying single-photon source. The fabricated single-photon source has the characteristics of high brightness, high purity, room temperature operation and stable luminescence properties, and the fabrication cost is low. Attached Figure Description

[0024] The above-described features, other objects, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0025] Figure 1 The schematic diagram illustrates a process flow diagram of a method for preparing a hexagonal boron nitride single-photon source according to an embodiment of the present invention;

[0026] Figure 2 A schematic diagram illustrating the growth structure of a hexagonal boron nitride capping layer according to an embodiment of the present invention is shown.

[0027] Figure 3 This schematic diagram illustrates the surface morphology of a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention using atomic force microscopy.

[0028] Figure 4 A schematic diagram illustrating the Raman scattering spectrum of a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention is shown.

[0029] Figure 5 The schematic diagram illustrates the photoluminescence scanning image of a single photon source in a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention;

[0030] Figure 6 This schematic diagram illustrates the test results of the second-order correlation characteristics of a single photon source in a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention.

[0031] Figure 7 The emission spectrum-time correlation diagram of a single photon source in a first hexagonal boron nitride single crystal thin film structure according to an embodiment of the present invention is illustrated schematically.

[0032] Figure 8 The emission spectrum-time correlation diagram of a single photon source in a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention is illustrated schematically.

[0033] Figure 9This schematically illustrates the emission stability test results of a single-photon source in a first hexagonal boron nitride single-crystal thin film structure according to an embodiment of the present invention; and

[0034] Figure 10 The diagram illustrates the emission stability test results of a single-photon source in a hexagonal boron nitride capping structure according to an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] Figure 1 The schematic diagram illustrates a process flow diagram of a method for preparing a hexagonal boron nitride single-photon source according to an embodiment of the present invention.

[0037] like Figure 1 As shown, a method for preparing a hexagonal boron nitride single-photon source according to an embodiment of the present invention includes steps S101-S110.

[0038] In step S101, three single-sided polished sapphire substrates are prepared as the first substrate, the second substrate, and the third substrate, respectively.

[0039] For example, a 2-inch single-sided polished sapphire wafer is prepared as a sapphire substrate. The sapphire wafer is then ultrasonically cleaned in acetone, isopropanol, and ethanol sequentially, and dried with nitrogen gas. Optionally, the wafer is cleaned twice in each solvent, with each cleaning time lasting 30 minutes, and then dried with nitrogen gas of 99.9% purity.

[0040] In step S102, a first solid boron film is sputtered and deposited on the polished surface of the first substrate. The thickness of the first solid boron film is related to the sputtering deposition time, and optionally, the deposition time of the first solid boron film is 5 min to 60 min.

[0041] For example, a clean sapphire substrate is fixed with its polished surface facing out onto a sample holder, which is then placed on a rotatable heating furnace within the sputtering chamber; the vacuum pump is then turned on, reducing the vacuum level within the sputtering chamber to 5 × 10⁻⁶. -5Below Pa. The heating furnace is turned on for staged heating. When the substrate temperature reaches 1100℃-1410℃, the distance between the substrate and the boron sputtering target is adjusted to 7cm-11cm. The sample holder is turned on to rotate at 10r / min. The boron sputtering target inside the cavity is turned on to rotate at 15r / min. No gas needs to be introduced to maintain a high vacuum environment during this process. The krypton fluoride (KrF) excimer laser power supply is turned on, and the laser path is adjusted so that the laser beam is focused through the lens and exits through the transparent optical window. The laser pulse width is set to 20 ns, the frequency to 1-20 Hz, the energy of a single pulse to 200-700 mJ, the spot diameter to 4 mm, and the excitation voltage to 22 kV. The substrate temperature is maintained constant, and continuous sputtering deposition is performed for 5-60 minutes. After sputtering, the sample holder rotation and target rotation are stopped, the distance between the substrate and the boron sputtering target is restored to its maximum, and the substrate temperature is slowly reduced to room temperature to obtain a high-purity solid boron thin film. Optionally, the purity of the boron sputtering target is not less than 99.9%.

[0042] In step S103, a second substrate is stacked on the surface of the first solid boron film to obtain a first stack, wherein the first solid boron film is in contact with the polished surface of the second substrate.

[0043] In step S104, the first stack is processed under a nitrogen atmosphere according to the first process parameters to convert the first solid boron film into a first hexagonal boron nitride single crystal film.

[0044] In some exemplary embodiments, the first process parameters include the following process steps: adjusting the nitrogen gas flow to 400 sccm and maintaining it; raising the temperature inside the heating furnace to the first target growth temperature at a heating rate not exceeding 5°C / min, with the first target growth temperature not exceeding 1600°C; or raising the temperature inside the heating furnace to 1600°C at a heating rate not exceeding 5°C / min, and then raising it to the first target growth temperature at a rate not exceeding 2°C / min, with the first target growth temperature being 1350°C-1750°C, and holding at the first target growth temperature for 1 min-120 min; lowering the temperature of the furnace tubes to 500°C at a cooling rate not exceeding 3°C / min; and allowing it to cool naturally to room temperature.

[0045] In step S105, the first substrate is peeled off from the first stack to obtain a second substrate carrying the first hexagonal boron nitride single crystal film.

[0046] In some exemplary embodiments, the method of peeling the first substrate from the first stack includes purging with nitrogen.

[0047] For example, two overlapping substrates are placed in a custom-made marble holder to fix their position. The marble holder is then placed horizontally in the furnace tube of a high-temperature tubular furnace and slowly pushed into the center of the furnace tube. Flanges and rubber rings are used to seal both sides of the furnace tube. A vacuum pump is used to evacuate the pressure inside the furnace tube from one end of the furnace to below 1 Pa and maintain this pressure for 5-10 minutes. Then, the vacuum pump is turned off and nitrogen gas is introduced from the other end of the furnace tube to raise the pressure inside the furnace tube to atmospheric pressure. After repeating the evacuation-filling step 4-6 times, adjust the nitrogen flow rate to 400 sccm and maintain it. Then, increase the temperature inside the furnace to the growth target temperature (1350-1750℃) in stages at a heating rate not exceeding 5℃ / min. If the target temperature is higher than 1600℃, increase the temperature inside the furnace to 1600℃ in stages at a heating rate not exceeding 5℃ / min, and then increase it to the target temperature at a rate not exceeding 2℃ / min. Then, hold the temperature at the target temperature for 1-120 minutes. Next, reduce the furnace tube temperature to 500℃ at a cooling rate not exceeding 3℃ / min, and then allow it to cool naturally to room temperature. After removing the marble tray, use a nitrogen gun to purge between the first and second substrates to separate the two substrates. Finally, a high-quality hexagonal boron nitride two-dimensional atomic crystal is obtained on the second substrate.

[0048] In step S106, the second substrate carrying the first hexagonal boron nitride single crystal film is placed in a radio frequency plasma generator for processing, so as to controllably introduce a single photon source into the first hexagonal boron nitride single crystal film.

[0049] In some exemplary embodiments, the plasma processing parameters for placing the second substrate carrying the first hexagonal boron nitride single crystal thin film into the radio frequency plasma generator are as follows: the plasma processing atmosphere includes at least one of argon, oxygen, nitrogen, hydrogen, methane, and ammonia; the plasma processing time is 1 min to 20 min; and the plasma processing power is 20 W to 250 W.

[0050] For example, the second substrate with the obtained h-BN single-crystal thin film is placed into the chamber of an RF plasma generator. The chamber is then sealed, and a vacuum pump is used to evacuate the chamber pressure to below 0.5 Pa and maintain this pressure for 5 minutes. The vacuum pump is then turned off, and argon gas is introduced into the chamber to purge it. This evacuation-purging process is repeated 2-3 times. Depending on the desired treatment effect, gases such as argon, nitrogen, oxygen, hydrogen, methane, or ammonia are introduced into the chamber. The chamber pressure is adjusted to 20-150 Pa by regulating the gas flow rate and the tightness of the chamber bypass valve. The plasma excitation power is adjusted to 20-250 W. The plasma generator is then turned on, and the matching capacitor is adjusted so that the forward plasma power reaches the set excitation power, while the reverse power drops to 0. After the plasma glow in the chamber stabilizes, the h-BN single-crystal thin film on the second substrate is treated for 1-20 minutes. After treatment, the plasma generator power and gas valves are turned off, followed by the vacuum pump. The treated second substrate is then removed from the chamber.

[0051] In step S107, a second solid boron film is sputter-deposited on the polished surface of the third substrate. The thickness of the second solid boron film is related to the sputtering deposition time; the deposition time of the second solid boron film is 5 min to 60 min. Optionally, the method for depositing the second solid boron film is the same as the method for depositing the first solid boron film in step S102.

[0052] In step S108, a third substrate is stacked on the surface of the first hexagonal boron nitride single crystal thin film with a single photon source introduced to obtain a second stack, wherein the first hexagonal boron nitride single crystal thin film with a single photon source introduced to the second solid boron thin film is in contact.

[0053] In step S109, under a nitrogen atmosphere, the second stack is processed according to the second process parameters to convert the second solid boron film into a second hexagonal boron nitride single crystal film (capping layer).

[0054] In some exemplary embodiments, the second process parameters include the following process steps: adjusting the nitrogen gas flow to 400 sccm and maintaining it; raising the furnace temperature to the second target growth temperature at a rate not exceeding 5°C / min, with the second target growth temperature not exceeding 1600°C; or raising the furnace temperature to 1600°C at a rate not exceeding 5°C / min, and then raising it to the second target growth temperature at a rate not exceeding 2°C / min, with the second target growth temperature held at that temperature for 1 min to 30 min; lowering the furnace tube temperature to 500°C at a rate not exceeding 3°C / min; and allowing natural cooling to room temperature. Optionally, the second target growth temperature is 1350°C to 1650°C; and the second target growth temperature is lower than the first target growth temperature.

[0055] In step S110, the third substrate is peeled off from the second stack to obtain a second substrate carrying the first and second hexagonal boron nitride single-crystal thin films, which serves as a hexagonal boron nitride single-photon source. Optionally, the method for peeling the third substrate off from the second stack includes purging with nitrogen gas.

[0056] For example, the polished surfaces of the third and second substrates are stacked face-to-face. A solid boron thin film and a plasma-treated h-BN single crystal thin film are located between the two substrates. The two stacked substrates are placed in a custom-made marble holder to fix their position. Then, the marble holder is placed horizontally in the furnace tube of a high-temperature tubular furnace and slowly pushed into the center of the furnace tube. Flanges and rubber rings are used to seal both sides of the furnace tube. A vacuum pump is used to evacuate the pressure inside the furnace tube from one end of the furnace to below 1 Pa and maintain this pressure for 5-10 minutes. Then, the vacuum pump is turned off and nitrogen gas is introduced from the other end of the furnace tube to raise the pressure inside the furnace tube to atmospheric pressure. After repeating the evacuation-filling step 4-6 times, adjust the nitrogen flow rate to 400 sccm and maintain it. Then, increase the temperature inside the furnace to the target growth temperature (1350-1650℃, with the secondary growth temperature slightly lower than the primary growth temperature) in stages at a heating rate not exceeding 5℃ / min. If the target temperature is higher than 1600℃, increase the temperature inside the furnace to 1600℃ in stages at a heating rate not exceeding 5℃ / min, and then increase it to the target temperature at a rate not exceeding 2℃ / min. Then, hold the temperature at the target temperature for 1-30 minutes. Next, decrease the furnace tube temperature to 500℃ at a cooling rate not exceeding 3℃ / min, and then allow it to cool naturally to room temperature. After removing the marble support, use a nitrogen gun to purge between the third and second substrates to separate the two substrates. Finally, in-situ growth of h-BN single crystal thin films on the h-BN-based single photon source is achieved on the second substrate.

[0057] In this embodiment of the invention, a large-scale single-photon source is fabricated on an h-BN single-crystal thin film using a plasma processing technique. An in-situ capping layer is used to grow a second hexagonal boron nitride single-crystal thin film to achieve efficient passivation protection of the single-photon source in the first hexagonal boron nitride single-crystal thin film. The fabricated single-photon source exhibits high brightness, high purity, room temperature operation, and stable luminescence properties, and the fabrication cost is low.

[0058] To further improve the quality of hexagonal boron nitride single crystal thin films, in Figure 1 Based on the method shown, it may further include annealing the second substrate carrying the first hexagonal boron nitride single crystal thin film and the second hexagonal boron nitride single crystal thin film.

[0059] Optionally, during the annealing process, the annealing atmosphere includes one of air, oxygen, nitrogen, or argon; the annealing temperature is 700℃-900℃; the annealing time is 30min-60min; and the rate of temperature rise and fall does not exceed 10℃ / min.

[0060] Figure 2 A schematic diagram of the growth structure of a hexagonal boron nitride capping layer according to an embodiment of the present invention is shown.

[0061] like Figure 2 As shown, in the hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention, the single photon source is covered by a second hexagonal boron nitride single crystal thin film.

[0062] Figure 3 The schematic diagram illustrates the surface morphology of the hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention via atomic force microscopy.

[0063] like Figure 3 As shown, the hexagonal boron nitride thin film according to an embodiment of the present invention is distributed in a sheet-like stacked layer and has good surface roughness.

[0064] Figure 4 A schematic diagram of the Raman scattering spectrum of a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention is shown.

[0065] like Figure 4 As shown in the figure, E from h-BN 2g The characteristic peak spectra show that both the first and second hexagonal boron nitride single-crystal films possess excellent crystal quality. The Raman intensity of the second hexagonal boron nitride single-crystal film is significantly higher than that of the first hexagonal boron nitride single-crystal film, indicating that the h-BN film achieved a significant thickness increase after the second growth.

[0066] Figure 5 The diagram schematically illustrates a photoluminescence scan of a single-photon source in a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention.

[0067] like Figure 5 As shown in the figure, the luminous point circled by the marked square pattern is the single-photon source. From its density results, it can be seen that the surface density of the single-photon source exceeds 0.1 counts / μm², indicating that the h-BN capping layer growth structure can support a high surface density of single-photon sources.

[0068] Figure 6 The diagram illustrates the test results of the second-order correlation characteristics of a single photon source in a hexagonal boron nitride capping structure according to an embodiment of the present invention.

[0069] like Figure 6As shown, the second-order correlation of the hexagonal boron nitride capping layer according to the embodiment of the present invention is much less than 0.5 at the position of time zero, which indicates that the processed product is a single-photon source with high single-photon purity.

[0070] Figure 7 The diagram schematically illustrates the emission spectrum-time correlation of a single-photon source in a first hexagonal boron nitride single-crystal thin film structure according to an embodiment of the present invention.

[0071] like Figure 7 As shown, due to the lack of passivation effect from the second h-BN single-crystal thin film, the single-photon source exhibited obvious flickering or even quenching phenomena during the test.

[0072] Figure 8 The diagram schematically illustrates the emission spectrum-time correlation of a single-photon source in a hexagonal boron nitride capping layer growth structure according to an embodiment of the present invention.

[0073] like Figure 8 As shown, compared to Figure 7 The single-photon source in the structure of the first hexagonal boron nitride single crystal film does not cover the single-photon source in the structure of the second hexagonal boron nitride single crystal film. The single-photon source in the structure containing the second hexagonal boron nitride single crystal film (capping layer) showed significantly improved stability in the test and did not exhibit obvious flickering or quenching phenomena.

[0074] Figure 9 The diagram illustrates the emission stability test results of a single-photon source in a first hexagonal boron nitride single-crystal thin film structure according to an embodiment of the present invention.

[0075] like Figure 9 As shown, the emission stability test of the single-photon source in the first hexagonal boron nitride single-crystal thin film (without capping layer) structure according to an embodiment of the present invention was conducted by observing the single-photon source over a large area of ​​the sample using a wide-field fluorescence microscope, and the time distribution of all single-photon sources from the first emission to the last emission, i.e., the "lifetime", was statistically analyzed. It can be seen from the figure that the "lifetime" of most single-photon sources is near 0, indicating that they quench up shortly after emission, resulting in poor emission stability.

[0076] Figure 10 The diagram illustrates the emission stability test results of a single-photon source in a hexagonal boron nitride capping structure according to an embodiment of the present invention.

[0077] like Figure 10 As shown, compared to Figure 9 In the single-photon source structure where the first hexagonal boron nitride single-crystal thin film does not cover the second hexagonal boron nitride single-crystal thin film, the single-photon source in the h-BN capping structure, compared to the single-photon source in the uncapped structure, exhibits a significantly increased "lifetime" and markedly improved emission stability.

[0078] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hexagonal boron nitride single-photon source, characterized in that, The method includes: Prepare three single-sided polished sapphire substrates, which will be used as the first substrate, the second substrate, and the third substrate, respectively; A first solid boron thin film is sputtered and deposited on the polished surface of the first substrate; A second substrate is stacked on the surface of the first solid boron film to obtain a first stack, wherein the first solid boron film is in contact with the polished surface of the second substrate; Under a nitrogen atmosphere, the first stack is processed according to the first process parameters to convert the first solid boron film into a first hexagonal boron nitride single crystal film. The first substrate is peeled off from the first stack to obtain a second substrate carrying the first hexagonal boron nitride single crystal film; The second substrate carrying the first hexagonal boron nitride single crystal film is placed in a radio frequency plasma generator for processing, so as to controllably introduce a single photon source into the first hexagonal boron nitride single crystal film. A second solid boron thin film is sputtered and deposited on the polished surface of the third substrate; The third substrate is stacked on the surface of the first hexagonal boron nitride single crystal thin film with a single photon source introduced to obtain a second stack, wherein the first hexagonal boron nitride single crystal thin film with a single photon source introduced to the second solid boron thin film is in contact. Under a nitrogen atmosphere, the second stack is processed according to the second process parameters to convert the second solid boron film into a second hexagonal boron nitride single crystal film; and The third substrate is peeled off from the second stack to obtain a second substrate that carries the first hexagonal boron nitride single crystal film and the second hexagonal boron nitride single crystal film, which serves as a hexagonal boron nitride single photon source; The first process parameter includes the following process steps: Adjust the nitrogen flow rate to 400 sccm and maintain it; The first target growth temperature is not higher than 1600℃, and the temperature inside the heating furnace is raised to the first target growth temperature at a heating rate of not more than 5℃ / min; or the first target growth temperature is higher than 1600℃, and the temperature inside the heating furnace is raised to 1600℃ at a heating rate of not more than 5℃ / min, and then raised to the first target growth temperature at a rate of not more than 2℃ / min. At the first target growth temperature, maintain the temperature for 1 min to 120 min; The furnace tube temperature is reduced to 500°C at a cooling rate not exceeding 3°C / min; and Cool naturally to room temperature; The second process parameters include the following process steps: Adjust the nitrogen flow rate to 400 sccm and maintain it; The second target growth temperature is not higher than 1600℃, and the temperature inside the heating furnace is raised to the second target growth temperature at a heating rate of not more than 5℃ / min; or the second target growth temperature is higher than 1600℃, and the temperature inside the heating furnace is raised to 1600℃ at a heating rate of not more than 5℃ / min, and then raised to the second target growth temperature at a rate of not more than 2℃ / min. At the second target growth temperature, maintain the temperature for 1 min to 30 min; The furnace tube temperature is reduced to 500°C at a cooling rate not exceeding 3°C / min; and Cool naturally to room temperature; The first target growth temperature is 1350℃-1750℃; The second target growth temperature is 1350℃-1650℃; and The second target growth temperature is lower than the first target growth temperature.

2. The method according to claim 1, characterized in that, The method further includes: The second substrate carrying the first hexagonal boron nitride single crystal film and the second hexagonal boron nitride single crystal film is annealed.

3. The method according to claim 1, characterized in that, The preparation of three single-sided polished sapphire substrates includes sequentially immersing the sapphire substrates in acetone, isopropanol, and ethanol for ultrasonic cleaning and then drying them with nitrogen.

4. The method according to claim 1, characterized in that, The thicknesses of the first and second solid boron films are related to the sputtering deposition time; The deposition time of the first solid boron film is 5 min-60 min; and The deposition time of the second solid boron film is 5 min to 60 min.

5. The method according to claim 1, characterized in that, The plasma processing parameters for placing the second substrate carrying the first hexagonal boron nitride single crystal thin film into the radio frequency plasma generator are as follows: The plasma treatment atmosphere includes at least one of argon, oxygen, nitrogen, hydrogen, methane, and ammonia. The plasma treatment time is 1 min-20 min; and The plasma processing power is 20W-250W.

6. The method according to claim 1, characterized in that, The method of peeling the first substrate from the first stack includes purging with nitrogen gas; and The method for peeling the third substrate from the second stack includes purging with nitrogen.

7. The method according to claim 2, characterized in that, During the annealing process, the annealing atmosphere includes one of air, oxygen, nitrogen, or argon. The annealing temperature is 700℃-900℃; The annealing time is 30-60 minutes; and The rate of temperature rise and fall shall not exceed 10℃ / min.

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