Ion barrier film micro-channel plate, manufacturing method thereof and application in image enhancement tube
By covering hexagonal boron nitride on the microchannel plate as an ion barrier film, the problems of short life and poor performance of vacuum optoelectronic devices are solved, and longer working life and better imaging quality are achieved.
Patent Information
- Application Number
- CN202411284594.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2025-02-07
AI Technical Summary
The working life of vacuum optoelectronic devices is short, especially the third-generation image reinforcement tube, which has a device life of less than 100 hours and poor performance, mainly due to the damage to the photocathode film by residual water gas cations in the microchannel plate.
A layer of hexagonal boron nitride (hBN) is covered with electron incident surface of the microchannel plate as an ion barrier film. A single layer of hexagonal boron nitride is grown by chemical vapor deposition method, and it is fixed to the microchannel plate by wet transfer process .
It effectively improves the working life of vacuum optoelectronic devices, improves imaging quality, and realizes ultra-fast time resolution and transient capture.
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Figure CN119400674A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of optoelectronic imaging devices and preparation thereof, and in particular relates to an ion barrier membrane microchannel plate and a preparation method and application thereof, and an image intensifier tube. Background Art
[0002] Photoelectric imaging devices generate initial photoelectric signals based on the photoelectric effect. In practical application, they are divided into two directions, namely solid-state photoelectric devices and vacuum photoelectric devices. These two types of photoelectric devices have adopted completely different technical routes with the development of the semiconductor industry and have been adopted in their respective applicable application fields. Solid-state photoelectric devices, such as charge-coupled devices (CCDs) and complementary metal oxide semiconductor devices (CMOS), are used in many fields such as digital cameras, smart phones and scientific research instruments and equipment. Their advantages are large-scale integrated production and long life, but their disadvantages are that they cannot effectively collect signals in weak light applications. Vacuum photoelectric devices, such as image intensifier tubes (ii) and X-ray image converters, can effectively collect signals in weak light imaging environments and are often used in night vision observation, ultraviolet imaging and scientific research camera equipment. The advantages of vacuum photoelectric devices are that they can extend the human eye's field of view and have strong weak light noise resistance, but their complex preparation and short device life limit their use. In order to achieve complementary advantages, a scientific research-level ultrafast imaging camera architecture has been developed that uses vacuum photoelectric devices in conjunction with solid-state photoelectric devices, namely, intensified charge-coupled cameras (ICCDs) and intensified complementary metal oxide semiconductor cameras (ICMOS). The coordinated use of devices can certainly combine the technical advantages of both, but the improvement of the performance and life of vacuum optoelectronic devices also urgently requires technological improvements.
[0003] The core of vacuum photoelectric devices consists of three parts: photocathode film (PC), microchannel plate (MCP) and phosphor screen (PS); based on the external photoelectric effect, the photocathode film generates photoelectrons after being irradiated with electromagnetic radiation in the working band and emits photoelectrons into the vacuum with a certain probability. The microchannel plate can amplify the weak initial photoelectron signal emitted into the vacuum by 1000 to 10000 times. The amplified photoelectrons bombard the phosphor screen under the action of direct current high voltage (DCHV) to convert the vacuum current signal into a light signal again. The quality factor of vacuum photoelectric devices is an indicator for evaluating the performance of its device, such as photosensitive working band (Work Wavelength), quantum efficiency (QE), response time (RT), gain factor and working life. Although these quality factors are critical, the working life is particularly important, and the working life is generally limited by the working life of the photocathode film; the direction of the photoelectrons emitted by the photocathode film is opposite to the direction of the electric field to achieve accelerated escape of the photoelectrons. In addition to the reconstruction and evaporation of the heated surface atoms of the photocathode film during operation, the residual gas cations in the vacuum photoelectric device, such as H + 、H3O +The fundamental reason that limits the working life of vacuum optoelectronic devices is that the surface of the photocathode film is bombarded by electric fields, causing it to decompose and fail. During the preparation process of vacuum optoelectronic devices, each part of the material will be fully degassed at high temperature, but the microchannel plate itself is a capillary bundle with an aperture of 2 to 20 um. Its inner surface will be wetted by water molecules based on the capillary effect and it is difficult to remove the adsorbed gas molecules. In addition to conventional high-temperature degassing, the microchannel plate will also use high-speed electron flushing of the microchannel before being integrated into the vacuum optoelectronic device. However, this method can only further reduce the gas residue and cannot completely remove the residual water and gas.
[0004] Alkali-ladder photocathode films can work at 10 -7 In a vacuum environment of 1000 mbar, the reverse bombardment of ionized cations from residual water vapor in the microchannel plate will degrade the performance of vacuum photoelectric devices, but the second-generation and super-second-generation compact image intensifier tubes corresponding to this type of photocathode film still have a lifespan of several thousand hours. However, the third-generation image intensifier tubes based on III-V semiconductors such as GaAs (doped with Zn), GaN (doped with Mg), GaAsP, InGaAs, and InGaAsP have to work at 10 -10 In a vacuum environment of mbar, it has a higher electron beam current and quantum efficiency than the second-generation image intensifier tube; but the reverse bombardment of the residual gas in the microchannel plate by the water vapor cations ionized by high-speed electrons will destroy the negative electron affinity Cs / O or Cs / F activation layer on the surface of the photocathode film, greatly reducing the photoelectric efficiency within 48 hours, resulting in the device life of the third-generation image intensifier tube being less than 100 hours, and its excellent performance cannot be fully utilized.
[0005] In view of this, the idea of covering the electron incident surface of the microchannel plate with an ion barrier film to improve the life of the third-generation image intensifier tube was proposed; initially, Al2O3 or SiO2 precursors were used to prepare the corresponding porous films with the assistance of porogens. This method has achieved certain results, but the films are brittle and easy to break, with a wide pore size distribution and low yield. After the graphene preparation technology matured, attempts were made to use graphene as an ion barrier film; although graphene is conductive and has a high Young's modulus, the characteristic of the carbon material itself is that it is easy to adsorb other impurities, which is not conducive to further improving the performance of vacuum optoelectronic devices. Summary of the invention
[0006] In order to overcome the shortcomings of short life and poor performance of optoelectronic devices, the present invention provides an ion barrier membrane microchannel plate, a manufacturing method and application thereof, and an image intensifier tube.
[0007] The inventive concept of the present invention:
[0008] The present invention utilizes a novel ion barrier film, namely hexagonal boron nitride (hBN), which acts as both an electron permeation film and a water vapor cation barrier film; firstly, a single layer of hexagonal boron nitride is grown on the surface of a copper single crystal by chemical vapor deposition (CVD), and a microchannel plate is prepared for standby use; then, the hexagonal boron nitride is transferred to the electron incident side surface of the microchannel plate by a classical wet transfer process and fixed. The novel ion barrier film microchannel plate is used in second-generation, super second-generation, third-generation and super third-generation image intensifier tubes, which can effectively increase the working life of vacuum photoelectric devices, improve the imaging quality of vacuum photoelectric devices, and realize ultrafast time resolution and transient capture of vacuum photoelectric devices.
[0009] The technical solution adopted by the present invention to solve the technical problem is:
[0010] An ion barrier film microchannel plate and a manufacturing method thereof, used for ultrafast imaging vacuum photoelectric devices of low-light-level night vision tubes, comprising the following steps:
[0011] Step 1, preparation of hexagonal boron nitride;
[0012] In order to obtain high-quality single-layer hexagonal boron nitride, chemical vapor deposition (CVD) is used. The atomically flat catalyst molds used in the preparation process include Cu(110) or Cu(111), Ni(111), Pt(111), etc. The typical temperature for growing high-quality hexagonal boron nitride on the Cu(111) surface is 1050°C; the gas sources used are generally BCl3 and NH3, or directly using N and B homologous sources such as cycloborazine (B3N3H6), NH3-B x wait;
[0013] Step 2, microchannel plate preparation;
[0014] The preparation of the microchannel plate involves a complex production process. The microchannel plate (φ20 mm) mentioned in this patent is purchased from the market;
[0015] Step 3, wet transfer of hexagonal boron nitride to the microchannel plate;
[0016] The hexagonal boron nitride was wet-transferred to the electron incident surface of the microchannel plate. First, polymethyl methacrylate (PMMA) was covered on the surface of the prepared hexagonal boron nitride. Then, the Cu (111) catalytic template was etched away using an ammonium persulfate (APS) solution. The hexagonal boron nitride transferred to the polymethyl methacrylate was immersed in deionized water for multiple cleanings. Then, the hexagonal boron nitride surface was bonded to the electron incident surface of the microchannel plate and dried. Finally, the polymethyl methacrylate was removed by spraying an acetone solution multiple times. Thus, a novel ion barrier membrane microchannel plate was prepared.
[0017] Step 4: vacuum packaging tube making test;
[0018] The ion barrier membrane microchannel plate was used in a third-generation image intensifier tube for further performance testing.
[0019] The electron trajectory and electron transmittance in the ion barrier membrane were simulated using CARSINO, an electron trajectory simulation software in solid materials based on the Monte Carlo method.
[0020] The beneficial effects of the present invention are:
[0021] A method for manufacturing an ion barrier membrane microchannel plate uses a single layer of hexagonal boron nitride as an electron transmission material for the electron incident surface of the microchannel plate. The purpose is to utilize its graphene-like honeycomb structure. The covalent bond length of 0.145nm between its B atoms and N atoms can effectively transmit photoelectrons. Because it is non-conductive, photoelectrons will only be scattered at a small angle when they hit its atomic skeleton and will not be dispersed, which can effectively improve the imaging quality. After years of development, single-layer hexagonal boron nitride has achieved wafer-level size growth, which can meet large-area size requirements.
[0022] A method for manufacturing an ion barrier membrane microchannel plate uses a single layer of hexagonal boron nitride as a barrier membrane material for residual water vapor cations in the microchannel plate, the purpose of which is to utilize its high mechanical strength and high in-plane thermal conductivity; the high mechanical strength and resistance to breakage are conducive to production integration and improving yield; the high in-plane thermal conductivity can timely dissipate the heat generated by the bombardment of water vapor cations, facilitating the cooling of the electron incident surface.
[0023] An ion barrier film microchannel plate can increase the working life of a third-generation image intensifier tube and improve its imaging quality; it can also be compatible with second-generation and super-second-generation image intensifier tubes to improve the quality of their vacuum photoelectric devices. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a flow chart of a method for manufacturing a novel ion barrier membrane microchannel plate according to an embodiment of the present invention;
[0025] Figure 2 is a simulation diagram of electron transmission trajectories of hexagonal boron nitride at different gate voltages in an embodiment of the present invention; Figure 2 a Gate voltage 100V, Figure 2 bGate voltage 200V, Figure 2 cGate voltage 500V, Figure 2 dGate voltage 700V;
[0026] Figure 3 is amorphous aluminum oxide ( Figure 3 a) and silicon dioxide ( Figure 3 b) porous membrane, and graphene ( Figure 3 c) and hexagonal boron nitride ( Figure 3d) Simulation diagram of electron transmission trajectory at the same gate voltage of 300V;
[0027] Figure 4 This is a simulation diagram of the electron transmission trajectory of hexagonal boron nitride at a gate voltage of 400V in an embodiment of the present invention ( Figure 4 a) and electron transmittance diagram ( Figure 4 b). DETAILED DESCRIPTION
[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0029] Embodiment 1
[0030] An ion barrier membrane microchannel plate and a method for manufacturing the same Figure 1 As shown, the preparation process includes the following steps:
[0031] Step 1, preparation of hexagonal boron nitride;
[0032] In order to obtain high-quality single-layer hexagonal boron nitride, chemical vapor deposition (CVD) is used for preparation. The atomically flat catalytic molds used in the preparation process include Cu (110) or Cu (111), Ni (111), Pt (111), etc.
[0033] 1.1 Deposit a Cu film of several hundred nanometers on the surface of a 2-inch sapphire wafer; use a high-temperature post-treatment process at 1100°C and introduce a reducing atmosphere (such as H2, or a mixture of oxalic acid and H2) to eliminate the copper polycrystalline grain boundaries and recrystallize to form Cu (111);
[0034] 1.2 The gas sources used are generally BCl3 and NH3, or directly use N and B homologous sources such as cycloborazine (B3N3H6), NH3-B x wait;
[0035] The typical temperature for growing high-quality hexagonal boron nitride on 1.3Cu(111) surface by wall-heated CVD is 1050℃;
[0036] The above conditions will not apply to the growth of hexagonal boron nitride using other gas sources, catalytic templates or CVD heating methods.
[0037] Step 2, microchannel plate preparation;
[0038] Generally, the microchannel plate made of lead glass is prepared by a two-step filament forming and arranging process; the first filament forming forms a core layer glass filament, which is put into a high-temperature and high-pressure reactor together with the wall layer glass for hot pressing into a glass column; the second filament forming forms a core layer / wall layer heterogeneous glass filament, and the secondary filaments are arranged in a hexagonal shape and put into a high-temperature and high-pressure reactor again for hot pressing into a glass column; the glass column is chamfered, polished, cut, etched, and reduced to obtain a microchannel plate blank template; and then a secondary electron layer is deposited on the inner wall of the microchannel plate by further atomic layer deposition, and the microchannel plate electrode is evaporated;
[0039] The preparation of the microchannel plate involves a complex production process. The microchannel plate (φ20 mm) used in this patent is purchased from the market.
[0040] Step 3, wet transfer of hexagonal boron nitride to the microchannel plate;
[0041] Wet transfer of hexagonal boron nitride to the electron incident surface of the microchannel plate and fixation of the hexagonal boron nitride film while evaporating the microchannel plate electrode;
[0042] 3.1 First, polymethyl methacrylate (PMMA) is coated on the surface of the prepared hexagonal boron nitride, and then the Cu (111) catalytic template is removed by etching using an ammonium persulfate (APS) solution;
[0043] 3.2 The hexagonal boron nitride transferred to the polymethyl methacrylate is immersed in deionized water for multiple cleanings, and then the hexagonal boron nitride surface is bonded to the electron incident surface of the microchannel plate and dried;
[0044] 3.3 Finally, the polymethyl methacrylate is removed by spraying the acetone solution multiple times; thus, a new ion barrier membrane microchannel plate is obtained.
[0045] Step 4: vacuum packaging tube making test;
[0046] The ion barrier membrane microchannel plate can be used in the third generation image intensifier tube for further performance testing, such as working life, electronic gain, imaging quality, signal-to-noise ratio and other quality factors.
[0047] CARSINO simulates the electron trajectory and electron transmittance in ion barrier membranes:
[0048] The solid material electron trajectory simulation software CARSINO was used to simulate the electron transmittance of a single-layer hexagonal boron nitride acting as an ion barrier membrane, and the simulation data of the electron transmittance of hexagonal boron nitride at different gate voltages were collected; CARSINO was further used to simulate the electron transmittance of amorphous porous Al2O3 and SiO2 films and single or double-layer graphene films, and the differences in electron transmittance of different materials were compared.
[0049] In order to make the CARSINO simulation close to the actual application scenario of the ion barrier membrane and restore the physical process of electron penetration, the simulation setting parameters include material composition, density, thickness, electron energy, electron beam diameter, etc.; the first layer of the simulation structure is set as the ion barrier membrane, and the second layer is set as vacuum (Vacuum); the parameters are set specifically for the actual simulation instance. The vacuum condition is set to restore the ultra-high vacuum environment in which the ion barrier membrane and the microchannel plate actually work, and the vacuum layer thickness is set to 15nm, and the vacuum layer density is infinitely small; the vacuum layer setting is consistent for all simulation instances, and the horizontal dotted line in the simulation diagram is the cross section between the ion barrier membrane and the vacuum.
[0050] Figure 2 This is a simulation diagram of the electron transmission trajectory of hexagonal boron nitride under different gate voltages in the embodiment of the present invention. The density of the single-layer or double-layer hexagonal boron nitride simulation is set to 2.29g / cm 3 , thickness 0.7nm. Figure 2 a is the electron trajectory diagram obtained by simulating the gate voltage of 100V. It can be seen intuitively that there are no electrons at the interface between hexagonal boron nitride and the vacuum layer. Therefore, the electron transmittance is 0 under this gate voltage, and electrons cannot pass through hexagonal boron nitride. Figure 2 b Electron trajectory diagram obtained by simulating a gate voltage of 200V. The gate voltage of 200V is also the normal working gate voltage of the image intensifier tube without ion barrier film. In addition to normal backscattering and blocking of electrons, the electron transmittance is 65%. Figure 2 c The electron trajectory diagram obtained by simulating a gate voltage of 500V. This voltage is the saturation operating gate voltage of the image intensifier tube equipped with an ion barrier film. In addition to normal backscattering and blocking of electrons, the electron transmittance is 73%. Figure 2 d Electron trajectory diagram obtained by simulation with a gate voltage of 700V. The voltage is too high and the electron beam is saturated. In addition to normal backscattering and blocking of electrons, the high voltage causes a space charge effect, so the electron transmittance drops to 60%.
[0051] Figure 3 It is a diagram of electron transmission trajectories in ion barrier films of different materials at a gate voltage of 300V in an embodiment of the present invention. Figure 3 a and 3b are the electron transmission trajectories of amorphous aluminum oxide porous film and amorphous silicon dioxide porous film, respectively. The film thickness of both materials is set to 5 nm, and the density of porous aluminum oxide film is 1.9 g / cm 3 The density of porous silica membrane is 1.74 g / cm 3 ; From the simulation data, it can be seen that under this condition, the electron transmittance of the amorphous aluminum oxide porous membrane is 24%, and the electron transmittance of the amorphous silicon dioxide porous membrane is 30%. Most of the incident electrons in the two are backscattered or deviate from the far original diameter direction. Figure 3c and 3d are the electron transmission trajectories of single-layer or double-layer graphene and single-layer or double-layer hexagonal boron nitride, respectively. The film thickness of both materials is set to 0.7 nm, and the density of single-layer or double-layer graphene is 2.259 g / cm 3 ; Through simulation data, it can be known that the electron transmittance of single-layer or double-layer graphene under this condition is 65%, and the electron transmittance of single-layer or double-layer hexagonal boron nitride is 67%. Through the electron trajectory and electron transmittance data in the barrier film obtained by simulation, it can be concluded that the electron transmittance of amorphous aluminum oxide porous film and amorphous silicon dioxide porous film is comparable and both are relatively low; while the electron transmittance of single-layer or double-layer hexagonal boron nitride and single-layer or double-layer graphene is comparable and both are relatively high, and hexagonal boron nitride is slightly better than graphene at the same simulation film thickness. After analysis, it is believed that although the density of amorphous aluminum oxide porous membrane and amorphous silicon dioxide porous membrane is low, the thickness of the material used to prepare the amorphous membrane is large and the pores are irregular, resulting in a large electron backscattering cross-section, causing a large amount of electron backscattering loss; while single-layer or double-layer graphene and single-layer or double-layer hexagonal boron nitride have high density, but they are hexagonal planar crystals and have a small atomic layer thickness. The regular hexagonal planar structure and atomic layer thickness result in a small electron backscattering cross-section, resulting in a larger electron transmittance.
[0052] Figure 4 This is a simulation diagram of the electron transmission trajectory of hexagonal boron nitride at a gate voltage of 400V in an embodiment of the present invention ( Figure 4 a) By Figure 4 b Electron transmittance diagram shows that its electron transmittance reaches 83%.
Claims
1. A method for preparing an ion barrier membrane microchannel plate, characterized in that: The following steps are involved: Step 1, preparation of hexagonal boron nitride: Hexagonal boron nitride is grown on the atomically flat surface of the catalytic mold Cu (111) using chemical vapor deposition (CVD) to obtain hexagonal boron nitride. Step 2, microchannel plate preparation: The microchannel plate may be a purchased microchannel plate with a diameter of φ20 mm, which is prepared by a two-fold filamentation process; Step 3, wet transfer of hexagonal boron nitride to the microchannel plate: The hexagonal boron nitride is wet-transferred to the electron incident surface of the microchannel plate; while evaporating the microchannel plate electrode, the hexagonal boron nitride film is fixed to obtain the ion barrier film microchannel plate.
2. The method for preparing an ion barrier membrane microchannel plate according to claim 1, characterized in that: The step 1, preparation of hexagonal boron nitride, further comprises: The temperature for growing hexagonal boron nitride is 1050°C; the gas sources used are BCl3 and NH3, or B3N3H6, NH3-B x .
3. The method for preparing an ion barrier membrane microchannel plate according to claim 1, characterized in that: The atomically flat catalytic mold uses Cu(110), or Ni(111), or Pt(111) instead of Cu(111).
4. The method for preparing an ion barrier membrane microchannel plate according to claim 1, characterized in that: The Cu(111) is prepared by surface deposition and recrystallization. The preparation process is as follows: a Cu film of several hundred nanometers is deposited on the surface of a 2-inch sapphire wafer; a high temperature treatment process is used to pass a reducing atmosphere at 1100° C. to eliminate the copper polycrystalline grain boundaries. The reducing atmosphere is H2, or a mixture of oxalic acid and H2, and recrystallization forms Cu(111).
5. The method for preparing an ion barrier membrane microchannel plate according to claim 1, characterized in that: The step 3, wet transfer of hexagonal boron nitride to the microchannel plate, further comprises: First, polymethyl methacrylate (PMMA) is coated on the surface of hexagonal boron nitride, and the Cu (111) catalytic template is etched away using ammonium persulfate (APS) solution. Secondly, the hexagonal boron nitride transferred onto the polymethyl methacrylate is immersed in deionized water for cleaning; the hexagonal boron nitride surface is bonded to the electron incident surface of the microchannel plate and dried; Finally, the polymethyl methacrylate is removed by spraying an acetone solution, and an ion barrier membrane microchannel plate is obtained.
6. An ion barrier membrane microchannel plate, characterized in that: Including microchannel plate, ion barrier membrane; The ion blocking film is located on the electron incident surface of the microchannel plate and is attached and fixed; The ion barrier film is hexagonal boron nitride; The microchannel plate comprises a microchannel plate electrode and a secondary electron layer material located on the inner wall of the microchannel plate.
7. The ion barrier membrane microchannel plate according to claim 6, characterized in that: The microchannel plate electrode is deposited by atomic layer deposition or evaporation.
8. An application of an ion barrier membrane microchannel plate, characterized in that: Ion barrier membrane microchannel plates are used for performance testing in image intensifier tubes; It includes simulating the electron trajectory and electron transmittance in the ion barrier membrane based on the Monte Carlo method and using the solid material electron trajectory simulation software Carsino.
9. An image intensifier tube, comprising an ion barrier membrane microchannel plate, and the image intensifier tube is prepared by vacuum packaging.