Ultrafast and efficient electron detector based on nanopolycrystalline boron nitride

Abstract

The present invention relates to the field of electron detectors. Disclosed is an ultrafast and efficient electron detector based on nanopolycrystalline boron nitride, the ultrafast and efficient electron detector comprising a nanopolycrystalline boron nitride scintillator, a light guide and a photomultiplier tube, wherein the nanopolycrystalline boron nitride scintillator and the photomultiplier tube are respectively connected to the front end and the rear end of the light guide, and a nanopolycrystalline boron nitride material of the nanopolycrystalline boron nitride scintillator is prepared by using a sapphire single crystal wafer as a substrate, using NH3 and BCl3 or NH3 and BF3 as source gases, and performing epitaxial growth in a chemical vapor deposition furnace. In the present invention, the nanopolycrystalline boron nitride scintillator has a short electron decay time and a high scintillation light yield, and, when applied to the electron detector, can achieve ultrafast and efficient electron radiation detection. The electron detector of the present invention can be used for secondary electron and backscattered electron detection in electron beam inspection systems, thereby providing a new option for electron beam inspection technology.

Description

Ultrafast and efficient electron detectors based on nanocrystalline boron nitride Technical Field

[0001] This invention relates to the field of electronic detectors, and more particularly to an ultrafast and efficient electronic detector based on nanocrystalline boron nitride. Background Technology

[0002] Semiconductor wafer inspection technology is a crucial step in ensuring the quality and performance of semiconductor devices. It encompasses not only the detection of physical defects on the wafer surface but also the precise measurement of critical dimensions. Electron beam inspection technology plays an irreplaceable role in this field due to its high precision and high resolution. For example, electron beam defect inspection (EBI) equipment can detect the defect status of semiconductor wafers in real time, particularly electrical defects in internal circuitry. Critical dimension scanning electron microscopy (CD-SEM) enables the monitoring of key process parameters by measuring critical dimensions from electron beam microscopic images.

[0003] In these electron beam detection systems, the electron detector converts secondary electron or backscattered electron signals into visible light signals for detection. Electron scintillators are key components for achieving efficient electron detection, requiring the following characteristics: high light yield to ensure sufficient signal strength, short decay time for rapid signal response, low afterglow to avoid image trailing, and excellent radiation resistance to maintain long-term stability. Currently, the commonly used electron scintillator material is YAG:Ce (Ce-doped Y3Al5O3). 12 YAG:Ce scintillators and YAP:Ce (Ce-doped YAlO3) single crystals are widely used due to their relatively simple preparation processes and low cost. However, most YAG:Ce scintillators used to date suffer from excessively long decay times and high afterglow, which limits their performance in certain fast and high-precision applications. YAP:Ce scintillators, with their rapid decay capability of approximately 30 ns, can improve electron detection efficiency. Nevertheless, the continuous exploration and development of new electron scintillators remains of great significance in order to further advance electron beam detection technology and expand its applications. Summary of the Invention

[0004] In view of the above background technology, the present invention provides an ultrafast and efficient electronic detector based on nanocrystalline boron nitride and a method for preparing nanocrystalline boron nitride, which has a shorter decay time and higher luminous efficiency compared with existing YAP:Ce scintillators.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A first aspect of the present invention provides an ultrafast and efficient electronic detector based on nanocrystalline boron nitride, comprising a nanocrystalline boron nitride scintillator, a photoconductor, and a photomultiplier tube, wherein the nanocrystalline boron nitride scintillator and the photomultiplier tube are respectively connected to the front end and the rear end of the photoconductor; wherein,

[0007] The nanocrystalline boron nitride scintillator is used to receive electron irradiation and generate nanosecond-level ultrafast high-brightness scintillation emission by utilizing the carrier confinement effect of its nanocrystalline structure under electron excitation.

[0008] The nanocrystalline boron nitride scintillator is made of sapphire single crystal wafer as substrate, using NH3 and BCl3 or NH3 and BF3 as raw material gases, and is epitaxially grown in a vertical chemical vapor deposition furnace.

[0009] The light guide is used to transmit the scintillation light to the photomultiplier tube;

[0010] The photomultiplier tube is used to receive the scintillation light transmitted through the light guide and record photon information.

[0011] Furthermore, the surface of the nanocrystalline boron nitride scintillator is coated with a layer of metallic aluminum with a thickness of 50-60 nm using magnetron sputtering technology.

[0012] Furthermore, the electron detector also includes a Faraday cage device installed at the front end of the nanocrystalline boron nitride scintillator for secondary electron detection in the electron beam detection system.

[0013] Furthermore, the nanocrystalline boron nitride scintillator has a circular hole at its center, forming a ring structure for backscattered electron detection in an electron beam detection system.

[0014] Furthermore, the optical guide is any one of silica optical fiber, glass optical fiber, or plastic optical fiber.

[0015] Furthermore, the nanocrystalline boron nitride scintillator is prepared by the following method, which includes the following steps: ：

[0016] S1. Select sapphire single crystal with low lattice matching degree with boron nitride as substrate, and select aluminum polar surface which is easy to nucleate as growth surface.

[0017] S2. Use a graphite fixture to fix the substrate, and place the graphite fixture and the substrate together in a vertical chemical vapor deposition furnace. After evacuation, use lateral heating to reach the reaction temperature.

[0018] S3, NH3 and BCl3, or NH3 and BF3 raw material gas are introduced into the furnace, and N2 is used as the carrier gas;

[0019] S4. After venting, maintain a constant gas flow rate and temperature; finally, turn off the power and cool down. The boron nitride / sapphire is cooled to room temperature and taken out of the furnace. The boron nitride automatically falls off to obtain nano-polycrystalline boron nitride material.

[0020] S5. Cut the nano-polycrystalline boron nitride material to a preset size according to the detector requirements to obtain a nano-polycrystalline boron nitride scintillator.

[0021] Furthermore, step S5 of the method for preparing the nano-polycrystalline boron nitride scintillator further includes depositing a layer of metallic aluminum with a thickness of 50-60 nm on the surface of the nano-polycrystalline boron nitride material using magnetron sputtering, and then cutting it to a preset size.

[0022] Furthermore, in step S2 of the method for preparing the nanocrystalline boron nitride scintillator, after vacuuming, lateral heating is used to reach a reaction temperature of 1300–1600°C.

[0023] Furthermore, in step S3 of the method for preparing the nano-polycrystalline boron nitride scintillator, the gas volume ratio of the raw material gases NH3 and BCl3, or NH3 and BF3, is controlled at 1.2 to 1.5:1.

[0024] Furthermore, in step S4 of the preparation method of the nano-polycrystalline boron nitride scintillator (1), the temperature is maintained at 1300-1600℃ after ventilation and kept at that temperature for 240-360 minutes.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Compared with YAP:Ce single crystal, the nanocrystalline boron nitride of this invention has a shorter emission decay time and a faster response speed. This fast response characteristic helps to reduce image blurring during electron beam imaging, thereby further improving image quality.

[0027] 2. Compared with YAP:Ce single crystal, the nano-polycrystalline boron nitride film of the present invention exhibits higher luminescence efficiency, with a maximum luminescence quantum yield of up to 39.8%. Therefore, the nano-polycrystalline boron nitride film of the present invention has excellent luminescence characteristics.

[0028] 3. In this invention, a boron nitride scintillator prepared by vertical chemical vapor deposition is applied to an electron detector. Because the nanocrystalline boron nitride scintillator has a short electron decay time and high scintillation light yield, the electron detector based on nanocrystalline boron nitride constructed in this invention can achieve ultrafast and efficient electron detection. The electron detector of this invention can be applied to the detection of secondary electrons and backscattered electrons in electron beam detection systems, providing a new option for electron beam detection technology. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the structure of the nano-polycrystalline boron nitride electron scintillator detector of Embodiment 1 of the present invention;

[0030] Figure 2 is a schematic diagram and imaging comparison diagram of the electron detector based on nanocrystalline boron nitride that can be used for secondary electron detection according to Embodiment 2 of the present invention.

[0031] Figure 3 is a schematic diagram and imaging comparison diagram of the electron detector based on nanocrystalline boron nitride that can be used for backscattered electron detection according to Embodiment 3 of the present invention.

[0032] Figure 4 shows a physical image, growth diagram, and installation diagram of the nano-polycrystalline boron nitride of Embodiment 4 of the present invention.

[0033] Figure 5 is a result of the cross-sectional structure of nano-polycrystalline boron nitride captured by transmission electron microscopy in Example 5 of the present invention.

[0034] Figure 6 shows the results of a comparative analysis of the nanocrystalline boron nitride scintillator and the commercial YAP:Ce scintillator under the same excitation conditions in Example 6 of the present invention.

[0035] In the figure: 1-Nano polycrystalline boron nitride scintillator; 2-Optical guide; 3-Photomultiplier tube; 4-Faraday cage; 5-Circular hole. Detailed Implementation

[0036] 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, and 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.

[0037] Example 1: Ultrafast and High-Efficiency Electron Detector Based on Nanocrystalline Boron Nitride

[0038] This embodiment provides the ultrafast and efficient electronic detector based on nanocrystalline boron nitride according to the present invention. As shown in Figure 1, an ultrafast and efficient electronic detector based on nanocrystalline boron nitride includes a nanocrystalline boron nitride scintillator 1, a photoconductor 2, and a photomultiplier tube 3. The nanocrystalline boron nitride scintillator 1 and the photomultiplier tube 3 are respectively connected to the front end and the rear end of the photoconductor 2; wherein,

[0039] The nano-polycrystalline boron nitride scintillator 1 is rapidly grown by high-temperature chemical vapor deposition and is used to receive electron irradiation and generate nanosecond-level ultrafast high-brightness scintillation under electron excitation by utilizing the carrier confinement effect of its nano-polycrystalline structure.

[0040] Optical guide 2 is used to transmit scintillation light to photomultiplier tube 3. Specifically, optical guide 2 is one of quartz optical fiber, glass optical fiber or plastic optical fiber.

[0041] The photomultiplier tube 3 is used to receive the scintillation light transmitted through the light guide 2 and record photon information.

[0042] During operation, the nanocrystalline boron nitride scintillator 1 generates scintillating light after receiving electron irradiation, and the light guide 2 transmits the scintillating light to the photomultiplier tube 3. After receiving the scintillating light signal, the photomultiplier tube 3 records the photon information and then reads it out.

[0043] To prevent charge accumulation on the surface of the nanocrystalline boron nitride scintillator 1 due to electron impacts, in this embodiment, a 50-60 nm thick layer of metallic aluminum is deposited on the surface of the nanocrystalline boron nitride scintillator 1 using magnetron sputtering technology. This layer of metallic aluminum not only effectively prevents charge accumulation but also acts as a reflective layer, reflecting the backpropagating scintillating light, thereby improving the light output capability of the scintillator. Furthermore, in this embodiment, the nanocrystalline boron nitride scintillator 1 can be cut to a preset size according to the requirements of the electron detector.

[0044] Because the nanocrystalline boron nitride scintillator 1 has a short decay time and high light yield, combined with the matching back-end design of the light guide 2 and photomultiplier tube 3, the electronic detector of the present invention can achieve faster time resolution and higher detection efficiency.

[0045] Example 2: An electron detector based on nanocrystalline boron nitride that can be used for secondary electron detection.

[0046] Based on Example 1, this example provides a modified electron detector that can be used for secondary electron detection in an electron beam detection system.

[0047] Figures 2a and 2b are schematic diagrams of the structure and imaging comparison of the secondary electron detector based on nanocrystalline boron nitride in this embodiment, respectively. As shown in Figure 2a, based on Embodiment 1, the electron detector for secondary electron detection in this embodiment also includes a Faraday cage device installed at the front end of the nanocrystalline boron nitride scintillator 1. Since secondary electrons have relatively weak energy, they are easily deflected by an electric field. During the operation of the secondary electron detector, the voltage-applied Faraday cage attracts and accelerates scattered secondary electrons from all directions. Once these accelerated electrons strike the nanocrystalline boron nitride scintillator 1, they cause it to emit light. The resulting scintillating light is then transmitted through the light guide 2 and finally collected and recorded by the photomultiplier tube 3. Because the nanocrystalline boron nitride of this invention has faster and more efficient electron scintillation performance, compared with existing secondary electron detectors, using a secondary electron detector based on nanocrystalline boron nitride can significantly shorten the time for scanning and acquiring images of electronic signals, thereby achieving faster and more efficient detection of samples (see Figure 2b).

[0048] Example 3: An electron detector based on nanocrystalline boron nitride that can be used for backscattered electron detection

[0049] Based on Example 1, this example provides a modified electron detector that can be used for backscattered electron detection in an electron beam detection system.

[0050] Figures 3a and 3b are schematic diagrams of the structure and imaging comparison of the backscattered electron detector based on nanocrystalline boron nitride in this embodiment, respectively. As shown in Figure 3a, based on Embodiment 1, the electron detector of this embodiment, which can be used for backscattered electron detection, has a circular hole in the center of the nanocrystalline boron nitride scintillator 1, forming a ring structure. The purpose of this geometric arrangement is to allow the incident electron beam to directly reach the sample surface, thereby exciting backscattered electrons. Although the incident electron beam can simultaneously excite secondary electrons and backscattered electrons, the secondary electrons have lower energy and do not produce significant scintillation light after reaching the backscattered electron detector, while the high-energy backscattered electrons can effectively excite the scintillator to emit light. The light emitted by the scintillator is conducted through the light guide 2 and then collected and recorded by the photomultiplier tube 3. Since nanocrystalline boron nitride has faster and more efficient electron scintillation performance, compared with existing backscattered electron detectors, the backscattered electron detector based on nanocrystalline boron nitride in this embodiment can significantly shorten the time for scanning and acquiring images of electron signals, thereby achieving faster and more efficient detection of samples (see Figure 3b).

[0051] Example 4: Preparation method of nanocrystalline boron nitride scintillator in electronic detector

[0052] This embodiment provides a method for preparing the nanocrystalline boron nitride scintillator in the electronic detector described in Embodiments 1 to 3. In this embodiment, the nanocrystalline boron nitride is prepared by epitaxial growth using a 6-inch sapphire single-crystal wafer as a substrate and NH3 and BCl3 (or NH3 and BF3) as raw material gases in a vertical chemical vapor deposition furnace. The preparation method of the nanocrystalline boron nitride material includes the following steps:

[0053] S1. Select a 6-inch sapphire single crystal with low lattice matching degree with boron nitride as the substrate, and select the aluminum polar surface, which is easy to nucleate, as the growth surface.

[0054] In this embodiment, since the aluminum polar surface of sapphire has high surface energy, which is beneficial for adsorption and nucleation, the aluminum surface of the substrate is selected for the growth of nano-polycrystalline boron nitride.

[0055] S2. Use a graphite clamp to fix the substrate, and place the graphite clamp and the substrate together in a vertical chemical vapor deposition furnace. After evacuation, use lateral heating to reach the reaction temperature of 1500℃.

[0056] S3. The raw material gases NH3 and BCl3 (or NH3 and BF3) are fed into the furnace, and N2 is used as the carrier gas to allow the gas mixing reaction to rapidly generate boron nitride on the substrate and promote its continuous growth; S4. The gas flow rate is kept constant, and the gas volume ratio of raw material gases NH3 and BCl3 (or NH3 and BF3) is controlled at 1.2:1 to promote the formation of boron nitride; after the gas is introduced, the temperature is maintained at 1500℃ and held for 300 min. During this period, boron nitride grains nucleate on the sapphire substrate and gradually grow to form a nano-polycrystalline structure; finally, the power is turned off and the furnace is cooled to room temperature. The boron nitride is automatically detached, and the nano-polycrystalline boron nitride material of the present invention is obtained.

[0057] S5. A layer of aluminum with a thickness of 50-60 nm is deposited on the surface of the nano-polycrystalline boron nitride material by magnetron sputtering, and the nano-polycrystalline boron nitride material is cut to a preset size according to the requirements of the detector to obtain the nano-polycrystalline boron nitride scintillator of the present invention.

[0058] In this embodiment, aluminum not only effectively prevents charge accumulation, but also acts as a reflective layer to reflect the back-propagating scintillating light, thereby enhancing the light output capability of the scintillator.

[0059] S6. The cut nanocrystalline boron nitride scintillator is installed at the front end of the light guide to obtain the electronic detector based on nanocrystalline boron nitride of the present invention.

[0060] Figure 4 shows a schematic diagram of the growth of the nano-polycrystalline boron nitride prepared using this embodiment, a physical diagram, and an installation schematic diagram. Figure 4a is a physical diagram of the nano-polycrystalline boron nitride, Figure 4b is a schematic diagram of the growth of the nano-polycrystalline boron nitride, and Figure 4c is an installation schematic diagram of the nano-polycrystalline boron nitride scintillator.

[0061] Example 5: Cross-sectional structural analysis of nanocrystalline boron nitride using transmission electron microscopy

[0062] The low lattice matching between sapphire and boron nitride, coupled with the micrometer-scale boron nitride film, often leads to the spontaneous detachment of the grown boron nitride film from the sapphire substrate. Cross-sectional structures were imaged using transmission electron microscopy (TEM), as shown in Figure 5. Figure 5a is a low-magnification TEM image, Figure 5b is a selected area electron diffraction pattern, and Figure 5c is a high-resolution TEM image.

[0063] Ideally, boron nitride should exhibit a layered structure. However, as shown in Figure 5a, the structure of the grown boron nitride film appears rather disordered in low-magnification TEM images. In Figure 5b, the selected area electron diffraction pattern reveals that it mainly grows along the c-axis, with the principal crystal plane being the (002) plane, exhibiting polycrystalline characteristics. Further analysis of the high-resolution TEM images reveals that the atomic arrangement of the grown boron nitride film is not uniform, and the lattice is distorted, forming a nanocluster structure (see Figure 5c). Within local regions at the nanoscale, boron nitride maintains an ordered layered structure, but overall exhibits polycrystalline properties, defined as a nanopolycrystalline (NP) structure. This structure is attributed, on the one hand, to the low lattice matching between the boron nitride layer and the sapphire substrate, leading to island-like growth; on the other hand, the use of a large reactive gas flow rate during growth accelerates the growth rate, resulting in uneven lattice arrangement and local distortion. Therefore, in this embodiment, nanopolycrystalline boron nitride (NPBN) was successfully grown by chemical vapor deposition.

[0064] Example 6: Comparative Analysis of Nanocrystalline Boron Nitride Scintillator and Commercial YAP:Ce Scintillator

[0065] Comparative analysis of electron beam imaging was performed on nanocrystalline boron nitride (NPBN) film scintillators and commercially available YAP:Ce single-crystal scintillators under the same excitation conditions. The results are shown in Figure 6. Figure 6a shows the emission time response of NPBN and YAP:Ce under the same excitation conditions; Figure 6b shows the comparison of emission quantum yield; Figures 6c and 6d are grayscale images of the scintillation emission of NPBN and YAP:Ce under 2MeV electron beam excitation, respectively; and Figures 6e and 6f are simulations of the electron penetration depth distribution of NPBN and YAP:Ce under 2MeV electron beam excitation, respectively.

[0066] As shown in the figure, the emission decay time of NPBN (9.4 ns) is significantly shorter than that of YAP:Ce (40.6 ns), exhibiting a faster time response. This rapid response characteristic helps reduce image blurring during electron beam imaging, further improving image quality (see Figure 6a). Furthermore, the emission peak wavelength of NPBN is around 385 nm, similar to that of YAP:Ce, thus eliminating the need for photomultiplier tubes with increased sensitivity in the long-wavelength region. Further luminescent quantum yield (PLQY) tests also confirmed that NPBN exhibits higher luminescent efficiency than YAP:Ce, with a maximum luminescent quantum yield as high as 39.8% (see Figure 6b). This strong luminescence originates from the carrier confinement effect caused by the nanopolycrystalline structure of boron nitride. The confinement of excited carriers by the structure leads to a greater tendency for radiative recombination, thereby enhancing luminescence. These results demonstrate the superior luminescent properties of NPBN.

[0067] To further visualize the electron scintillation light yield of NPBN, this example captures emission images of NPBN and YAP:Ce scintillators under electron beam excitation. When the electron beam (energy 2 MeV) strikes the scintillator perpendicularly, the generated light is first deflected at a 90° angle by a mirror and then captured by the camera. The emission images of the scintillator are captured while maintaining the same electron beam pulse frequency and camera integration time. Figures 6c and 6d show grayscale images of the scintillation emission of 100 μm thick NPBN and 500 μm thick YAP:Ce, respectively. As shown, under the same excitation conditions, compared to 500 μm thick commercial YAP:Ce, 100 μm thick NPBN exhibits higher contrast, i.e., higher scintillation light yield.

[0068] Furthermore, this embodiment also used Casino software to simulate the penetration depth of the electron beam through NPBN and YAP:Ce scintillators under these conditions. The simulation results show that under these conditions, the electron beam can easily penetrate 100 μm thick NPBN and 500 μm thick YAP:Ce (see Figures 6e and 6f). NPBN maintains a high scintillation light output even at relatively thin thicknesses, which further confirms the great potential of NPBN as an electron scintillator.

[0069] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An ultrafast and efficient electron detector based on nanocrystalline boron nitride, characterized in that, The system includes a nanocrystalline boron nitride scintillator (1), a light guide (2), and a photomultiplier tube (3), wherein the nanocrystalline boron nitride scintillator (1) and the photomultiplier tube (3) are respectively connected to the front and rear ends of the light guide (2); wherein, The nano-polycrystalline boron nitride scintillator (1) is used to receive electron irradiation and generate nanosecond-level ultrafast high-brightness scintillation emission by utilizing the carrier confinement effect of its nano-polycrystalline structure under electron excitation. The nano-polycrystalline boron nitride scintillator (1) is made of sapphire single crystal wafer as substrate, using NH3 and BCl3 or NH3 and BF3 as raw material gases, and is epitaxially grown in a vertical chemical vapor deposition furnace. The light guide (2) is used to transmit the scintillation light to the photomultiplier tube (3); The photomultiplier tube (3) is used to receive the scintillation light transmitted through the light guide (2) and record photon information.

2. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 1, characterized in that, The surface of the nanocrystalline boron nitride scintillator (1) is coated with a layer of aluminum with a thickness of 50-60 nm using magnetron sputtering technology.

3. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 1, characterized in that, The electron detector also includes a Faraday cage device (4) installed at the front end of the nanocrystalline boron nitride scintillator (1) for secondary electron detection in the electron beam detection system.

4. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 1, characterized in that, The nanocrystalline boron nitride scintillator (1) has a circular hole (5) at its center, forming a ring structure for backscattered electron detection in an electron beam detection system.

5. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 1, characterized in that, The optical guide (2) is any one of quartz optical fiber, glass optical fiber or plastic optical fiber.

6. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 1, characterized in that, The nanocrystalline boron nitride scintillator (1) is prepared by the following method, which includes the following steps: ： S1. Select sapphire single crystal with low lattice matching degree with boron nitride as substrate, and select aluminum polar surface which is easy to nucleate as growth surface. S2. Use a graphite fixture to fix the substrate, and place the graphite fixture and the substrate together in a vertical chemical vapor deposition furnace. After evacuation, use lateral heating to reach the reaction temperature. S3, NH3 and BCl3, or NH3 and BF3 raw material gas are introduced into the furnace, and N2 is used as the carrier gas; S4. After venting, maintain a constant gas flow rate and temperature; finally, turn off the power and cool down. The boron nitride / sapphire is cooled to room temperature and taken out of the furnace. The boron nitride automatically falls off to obtain nano-polycrystalline boron nitride material. S5. Cut the nano-polycrystalline boron nitride material to a preset size according to the detector requirements to obtain a nano-polycrystalline boron nitride scintillator.

7. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 6, characterized in that, Step S5 of the method for preparing the nano-polycrystalline boron nitride scintillator (1) further includes depositing a layer of metallic aluminum with a thickness of 50-60 nm on the surface of the nano-polycrystalline boron nitride material using magnetron sputtering, and then cutting it to a preset size.

8. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 6, characterized in that, In step S2 of the preparation method of the nano-polycrystalline boron nitride scintillator (1), after vacuuming, it is heated laterally to a reaction temperature of 1300-1600℃.

9. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 6, characterized in that, In step S3 of the preparation method of the nano-polycrystalline boron nitride scintillator (1), the gas volume ratio of the raw material gas NH3 and BCl3, or NH3 and BF3, is controlled at 1.2 to 1.5:

1.

10. The ultrafast and efficient electron detector based on nanocrystalline boron nitride according to claim 6, characterized in that, In step S4 of the preparation method of the nano-polycrystalline boron nitride scintillator (1), the temperature is maintained at 1300-1600℃ after ventilation and kept at that temperature for 240-360 minutes.

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