A secondary electron emission performance parameter testing device and testing method

Abstract

The invention discloses a secondary electron emission performance parameter testing device and a testing method. The device comprises a spherical electron collector, which is composed of a spherical collecting electrode, a spherical suppressing electrode and a spherical grounding electrode from the outside to the inside; the spherical electron collector is fixed on an electron collector fixing device in a vacuum chamber, an incident electron hole is arranged above the spherical electron collector, and an electron gun muzzle enters the interior of the spherical electron collector through the incident electron hole, and a sample stage inlet and outlet hole is arranged below the spherical electron collector; a sample stage lifting and rotating device comprises a magnetic fluid controller installed outside the vacuum chamber, a screw transmission mechanism in the vacuum chamber and a gear rotating mechanism connected thereto, the sample stage is connected to the gear rotating mechanism, and the sample stage enters the interior of the spherical electron collector from the opening below the spherical electron collector; the magnetic fluid controller drives the sample stage to move up and down and rotate through the screw transmission mechanism and the gear rotating mechanism connected thereto; one side of the sample stage is used to place the sample to be tested, and the other side fixes the primary electron collector.

Description

Technical Field

[0001] The invention relates to the field of solid material surface physical property testing, and in particular to a testing device and a testing method for secondary electron emission performance parameters of metal, semiconductor and insulator materials. Background Art

[0002] The phenomenon that electrons with a certain energy bombard the surface of a solid material, causing electrons inside the material to be emitted from the surface of the material, is called secondary electron emission of the material.

[0003] The secondary electron emission performance parameters of the material include the secondary electron emission coefficient δ, the secondary electron energy spectrum d(E) and the spatial angular distribution f(θ) of the secondary electrons. These parameters are mainly related to the energy E and angle β of the incident electrons. The electrons bombarding the surface of the material are called the primary electron current I p The power density of the primary electron flow is related to E and the electron beam spot area S. The electrons emitted from the surface of the material are called the secondary electron flow I s , the secondary electron emission coefficient δ of a material is usually defined as I s with I p When δ is less than 1, it means that the secondary electron suppression effect occurs. This effect can solve the problem of micro-discharge on the surface of spacecraft, the problem of electron cloud on the inner surface of circular accelerator, and the reliability and life of high-power microwave vacuum devices. When δ is greater than 1, it means that the secondary electron multiplication effect occurs. This effect is widely used in the field of electron multipliers. For example, the double-chip microchannel plate detector uses the secondary electron cascade multiplication effect on the surface of the material, and the gain can reach 10 7 ; As large-scale high-energy physics experiments place increasingly higher demands on detection devices, such as microchannel plate photomultiplier tubes (MCP-PMTs), it is particularly important to study the performance of secondary electron multiplication materials used in detectors. The secondary electrons emitted from the surface of a material present a certain distribution in energy, which is called the secondary electron energy spectrum curve d(E), including the elastic scattering electron peak, inelastic scattering electron peak, true secondary electron peak, Auger electron peak, etc. of the primary electrons. The principles of most surface analysis instruments are related to the secondary electron energy spectrum of the material, such as the Auger electron peak used in the Auger electron spectrometer and the true secondary electron peak used in the scanning electron microscope. By testing the secondary electron energy spectrum curve, many physical problems related to material properties can be solved. The secondary electrons emitted from the surface of a material have a certain spatial angular distribution. Testing the distribution of secondary electrons in space is of great significance for improving the existing secondary electron emission theory.

[0004] Secondary electron emission performance test equipment is a useful tool for obtaining secondary electron emission performance parameters of materials. The core part of the equipment is the secondary electron collector (including the collector and two layers of grids). Existing equipment usually uses spherical, cylindrical or hemispherical secondary electron collectors. The defect of the spherical secondary electron collector is that it is impossible to test the spatial angular distribution of secondary electrons; the defect of the cylindrical secondary electron collector is that when testing the secondary electron energy spectrum, there is an angle between the direction of the electric field lines between the two layers of grids and the trajectory of the secondary electrons, resulting in inaccurate secondary electron energy spectrum test results; in addition, when testing the spatial angular distribution of secondary electrons, it is necessary to constantly adjust the position of the sample stage, which is easy to cause a change in the area S of the primary incident electron beam spot, affecting the primary electron flow power density, and thus affecting the test results. The defect of the hemispherical secondary electron collector is that when the primary electron incident angle is large, the secondary electrons cannot be completely collected, resulting in large errors in the test results. Summary of the invention

[0005] In order to overcome the shortcomings of secondary electron collectors in the prior art, the purpose of the present application is to provide a testing device and method for the secondary electron emission performance parameters of solid materials, so that the testing process is simple and the secondary electrons are fully collected, and can be used to accurately measure the secondary electron emission coefficient, secondary electron energy spectrum and secondary electron spatial angular distribution of the material at different incident electron flow power densities and incident angles.

[0006] In order to achieve the above-mentioned various invention purposes, the testing device of the present invention comprises:

[0007] A vacuum system, including a vacuum pump for providing and maintaining a vacuum environment, a vacuum testing device for detecting the vacuum degree, and a vacuum chamber used as a cavity;

[0008] An electron beam generating system, comprising an electron gun installed in a vacuum chamber through a flange interface for generating a continuous or pulsed electron beam, and an electron gun controller outside the vacuum chamber;

[0009] The spherical electron collector is fixed on the electron collector fixture in the vacuum chamber. It includes three spherical structures, from outside to inside: a spherical collector, a spherical suppressor and a spherical grounding electrode. The upper opening is used as the incident electron hole. The electron gun muzzle enters the spherical electron collector from the upper opening. The lower opening of the spherical electron collector is used as the sample stage entrance and exit hole. The function of the spherical suppressor is to test the secondary electron energy spectrum. An electric field needs to be applied to the spherical suppressor. The spherical grounding electrode can ensure that the sample is in an equipotential zone to improve the test accuracy. When testing the relationship between the secondary electron emission coefficient and the incident electron power density, and the secondary electron emission coefficient and the incident electron angle, the secondary electron flow is equal to the sum of the currents measured on the spherical collector, the spherical suppressor and the spherical grounding electrode. When testing the spatial angular distribution of secondary electrons and the energy spectrum of secondary electrons, the current measured on the spherical collector is the secondary electron flow.

[0010] A weak signal measurement system, comprising a current meter or a current-voltage amplifier connected to a spherical collecting electrode, a spherical suppressing electrode, a spherical grounding electrode and a sample stage respectively;

[0011] The sample stage lifting and rotating device comprises a magnetic fluid controller with a dial installed outside the vacuum chamber, a screw transmission mechanism inside the vacuum chamber and a gear rotating mechanism connected thereto. The sample stage is connected to the gear rotating mechanism and enters the interior of the spherical electron collector from the opening below the spherical electron collector. The magnetic fluid controller drives the sample stage to move up and down and rotate a specific angle. The sample stage lifting and rotating device can control the height and rotation angle of the sample stage. The sample to be tested can be placed on one side of the sample stage to ensure good electrical contact between the sample and the sample stage. A primary electron collector is fixed on the other side, and its height and rotation angle are controlled by the sample stage lifting and rotating device, so that the size of the primary electron flow can be tested.

[0012] The sample surface potential neutralization system includes a surface potential detection device, a device for eliminating positive surface potential and a device for eliminating negative surface potential. The device for eliminating positive surface potential adopts an electron gun in an electron beam generating system, and the device for eliminating negative surface potential adopts a positive ion neutralization gun, which are installed in a vacuum chamber.

[0013] The electron collector fixing device is used to fix the spherical electron collector to ensure good electrical contact and electrical isolation of the three spherical structures from each other.

[0014] The spherical collector is isolated by a number of strip-shaped ceramic rings to form a plurality of annular collectors, and each annular collector is insulated from each other; the collector material is oxygen-free high-conductivity copper or stainless steel; the spherical collector has two observation windows symmetrically arranged along the central axis, and a rotating baffle is arranged outside the observation window.

[0015] The spherical suppressor electrode is made of a stainless steel mesh with an opening rate of 70% to 98% and has a high electron transmittance.

[0016] The spherical grounding electrode is made of a stainless steel mesh with an opening rate of 70% to 98% and has a high electron transmittance.

[0017] The primary electron collector is a Faraday cup with an inverted cone structure, made of stainless steel or oxygen-free high-conductivity copper, with an opening size of 10mm to 25mm. It is fixed below the sample stage and has good electrical contact with the sample stage.

[0018] The electron collector fixture has a hole in the middle, through which the sample stage can move up and down; the electron collector fixture has three annular grooves, which can respectively fix the spherical collector, the spherical suppressor and the spherical grounding electrode; the main material of the electron collector fixture is ceramic, and the three annular grooves are plated with metal materials and are electrically isolated from each other; small holes are provided at the bottom of the annular grooves, through which the spherical collector, the spherical suppressor and the spherical grounding electrode can be connected with wires.

[0019] The sample stage lifting and rotating device can send the sample stage into the spherical structure, and the height of the sample stage is adjustable; the center position of the sample stage, the axis of the spherical structure and the direction of the incident electron beam coincide with each other; the sample stage lifting and rotating device adjusts the rotation angle of the sample stage by rotating the gear structure; the sample stage is made of oxygen-free high-conductivity copper material or stainless steel material to ensure good electrical contact between the sample above the sample stage and the primary electron collector below the sample stage; there are metal leads at the bottom of the sample stage leading to the outside, which can test the current or voltage signal of the sample stage.

[0020] The specific working principle of the present invention is:

[0021] Since the spherical collector structure is an ideally symmetrical hollow conductor, the incident electron beam can be incident vertically to the center of the sample stage. Rotate the sample stage so that the primary electron collector faces the direction of the incident electron beam. Through the metal lead on the sample stage, it can be led to an external small ammeter to test the size of the primary electron current. Rotate the sample stage so that the sample on the sample stage faces the direction of the incident electron beam. The secondary electrons generated after the primary electron bombards the sample are collected by the spherical collector, spherical suppressor and spherical grounding electrode. By testing the size of the secondary electron current on the spherical collector, spherical suppressor and spherical grounding electrode, the relationship between the secondary electron emission coefficient of the material and the incident electron power density, incident energy and incident angle can be calculated; by testing the secondary electron current intensity on each annular collector that constitutes the spherical collector, the secondary electron spatial angular distribution of the material can be calculated; by applying different bias voltages on the spherical suppressor and testing the size of the secondary electron current on the spherical collector, the secondary electron energy spectrum of the material can be calculated.

[0022] Another object of the present invention is to propose a method for testing secondary electron emission performance parameters. To achieve this object, the present application discloses a method for measuring secondary electron performance parameters using the above-mentioned secondary electron measurement device, the method comprising the following steps:

[0023] (1) Place the fluorescent screen on the sample stage;

[0024] (2) Turn on the vacuum equipment to evacuate the vacuum chamber to the working environment and adjust the position of the sample stage to an appropriate height;

[0025] (3) Turn on the electron gun and preheat it;

[0026] (4) Output the electron beam, open the observation window baffle, observe the position and size of the light spot on the fluorescent screen, adjust the electron gun parameters or the sample stage lifting height, record the electron beam spot size through the circular scale on the sample stage, and determine the electron gun controller parameters and sample stage position parameters corresponding to different electron beam power densities;

[0027] (5) Take the fluorescent screen out of the vacuum chamber, place the sample to be tested on the sample stage, evacuate to the working environment, and adjust the position of the sample stage and the output parameters of the electron gun according to the parameters obtained in step (4); when the set electron beam power density is reached, stop adjusting and proceed to step (6);

[0028] (6) The sample position is fixed and the spatial angular distribution of secondary electrons can be obtained by measuring the secondary electron currents on each annular collector.

[0029] (7) By changing the voltage on the spherical suppressor electrode and testing the secondary electron current on the spherical collector electrode, the secondary electron energy spectrum of the sample can be tested;

[0030] (8) By measuring the secondary electron currents on the spherical collecting electrode, the spherical suppressor electrode and the spherical grounding electrode and the primary electron current on the primary electron collector, the secondary electron emission coefficient under different incident electron energies and power densities can be tested. By using the sample stage lifting and rotating device to adjust the sample rotation angle, the secondary electron emission coefficient under different incident angles can be tested.

[0031] The advantages of the present invention compared with the prior art are:

[0032] 1. Comprehensive testing functions: Conventional testing technology can only test the change of the secondary electron emission coefficient of the material with the incident electron energy, but cannot test the change of the secondary electron emission coefficient with the incident electron flow power density; the present application uses two observation windows on the spherical collecting electrode and a fluorescent screen to first determine the size of the incident electron beam area S, and uses the sample stage lifting device and adjusts the electron gun parameters to change the size of S, thereby changing the primary electron flow power density, and can test the secondary electron emission coefficient of the material under different incident electron power densities; uses the sample stage lifting and rotating device to adjust the sample rotation angle, and tests the secondary electron emission coefficient of solid materials with an incident angle range of 0° to 85°; by adjusting the spherical suppressor potential, secondary electrons of a specific energy can be filtered out, and the secondary electron energy spectrum of the material can be tested; by testing the current or voltage signals on each collecting electrode, the spatial angular distribution of the secondary electrons of the material can be obtained through simple calculations.

[0033] 2. The test process is simple: When the cylindrical collector tests the angular distribution of secondary electrons, the position of the sample stage needs to be changed for each angle tested, which will change the incident electron beam spot area S and affect the test results. In the present invention, the sample is sent into the spherical collector by the sample stage lifting and rotating device, and the sample height can be precisely controlled. When testing the spatial angular distribution of secondary electrons, the position of the sample stage remains unchanged. By testing the current on each layer of the collector, the spatial angular distribution of secondary electrons can be obtained through simple calculations.

[0034] 3. Accurate test results: When testing the secondary electron energy spectrum, the direction of the electric field between the two layers of spherical grids is parallel to the trajectory of the secondary electrons, making the secondary electron energy spectrum test results more accurate; the spherical collector structure can comprehensively collect the secondary electrons emitted by the material; the primary electron collector can test the size of the primary electron flow, and the size of the primary electron flow can also be tested by summing the sample current, the spherical collector current, the spherical suppressor current and the spherical grounding electrode current. Comparing the two methods can verify the accuracy of the primary electron flow test results, thereby ensuring the accuracy of measuring the secondary electron emission performance parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0036] Figure 1 It is a schematic diagram of the overall structure of the secondary electron emission performance testing device of the present invention;

[0037] Figure 2 yes Figure 1 A front view and a half-section view of the spherical collector structure shown in;

[0038] Figure 3 It is a schematic diagram of the positional relationship between the spherical collecting electrode and the sample to be tested in step 19 of the method of the present invention.

[0039] Reference numerals

[0040] 1-spherical electron collector, 2-electron collector fixing device, 3-sample stage lifting and rotating device, 4-observation window, 5-rotating baffle, 6-spherical suppression electrode, 7-spherical grounding electrode, 8-sample to be tested, 9-sample stage, 10-rotating gear, 11-primary electron collector, 12-spherical suppression minimum current meter, 13-spherical grounding minimum current meter, 14-sample stage small current meter, 15-first collection minimum current meter, 16-second collection minimum current meter, 17-third collection minimum current meter, 18-fourth collection minimum current meter, 19-fifth collection minimum current meter, 20-sixth collection minimum current meter, 21-seventh collection Minimum ammeter, 22-eighth collecting minimum ammeter, 23-spherical collector ammeter, 24-first collecting electrode, 25-second collecting electrode, 26-third collecting electrode, 27-fourth collecting electrode, 28-fifth collecting electrode, 29-sixth collecting electrode, 30-seventh collecting electrode, 31-eighth collecting electrode, 32-first magnetic fluid controller, 33-second magnetic fluid controller, 34-ceramic insulating ring, 35-electron gun, 36-electron gun controller, 37-vacuum chamber, 38-neutralization gun control power supply, 39-positive ion neutralization gun, 40-potential detection device control power supply, 41-sample surface potential detection device, 42-vacuum equipment. DETAILED DESCRIPTION

[0041] The present application will be further described in detail below with reference to the accompanying drawings and embodiments, but is not limited thereto.

[0042] Reference Figure 1 and attached Figure 2 In this embodiment, a testing device for the secondary electron emission performance parameters of solid materials is provided, including: a vacuum system, an electron beam generating system, a spherical electron collector, a weak signal measurement system, a sample stage lifting and rotating device, and a sample surface potential neutralization system.

[0043] The vacuum system includes a vacuum chamber 37 and a vacuum device 42 for providing a vacuum environment for the vacuum chamber 37; the vacuum chamber 37 and the vacuum device 42 are connected by a valve; the vacuum device 42 may include a dry pump, a molecular pump and an ion pump as vacuum acquisition equipment, an ionization gauge and a resistance gauge as vacuum measurement equipment, and a vacuum needle valve plus a high-purity nitrogen pipeline as a charging device.

[0044] The electron beam generating system includes an electron gun 35 and an electron gun controller 36. The electron gun 35 is installed in a vacuum chamber 37 through a flange interface. By adjusting the electron gun controller 36, the electron gun 35 can output a continuous or pulsed electron beam with an energy of 0-10KeV, and the size and position of the beam spot can be adjusted individually.

[0045] The spherical electron collector is located inside the vacuum chamber 37, and includes a spherical electron collector 1 and an electron collector fixing device 2; the spherical electron collector 1 includes a three-layer spherical structure: a spherical collector, a spherical suppressor 6 and a spherical grounding electrode 7; the spherical collector is made of oxygen-free high-conductivity copper; the spherical suppressor 6 and the spherical grounding electrode 7 are made of a stainless steel mesh with an opening rate of 70% to 98%; the spherical collector in this embodiment is divided into eight parts by a ceramic insulating ring 34: a first collector 24, a second collector 25, a third collector 26, a fourth collector 27, a fifth collector 28, a sixth collector 29, a seventh collector 30 and an eighth collector 31; the third collector 26 is provided with two observation windows 4 symmetrically located along the central axis, and the diameter thereof is 20 mm to 80 mm; a rotating baffle 5 is provided outside the observation window 4, and the electron beam spot can be observed by opening the baffle 5, and the test can be performed by closing the baffle 5, so as to ensure that the secondary electrons are fully collected during the test. The upper opening of the spherical electron collector 1 is a primary electron beam entrance hole, and the lower opening is a sample stage entrance and exit hole; the neck length of the lower opening of the spherical electron collector 1 is 30 mm to 50 mm; the spherical electron collector 1 is installed on the electron collector fixture 2; the central opening of the electron collector fixture 2 is for the sample stage to move up and down, and three annular grooves are made outside the central hole for respectively fixing the spherical collector, the spherical suppressor 6 and the spherical grounding electrode 7; the spherical suppressor 6 is fixed in the middle annular groove on the electron collector fixture 2; the annular groove is plated with metal material to ensure good electrical contact with the spherical suppressor 6; a small hole is opened below the annular groove for connecting a small ammeter 12; the spherical grounding electrode 7 is fixed in the innermost annular groove on the electron collector fixture 2, and the annular groove is plated with metal material to ensure good electrical contact with the spherical grounding electrode 7; a small hole is opened below the annular groove for connecting a spherical grounding electrode small ammeter 13. In other embodiments, the spherical collector may not be layered, in which case the spatial angular distribution of secondary electrons cannot be tested, but the manufacturing cost can be reduced; in addition, the spherical collector may also be divided into more layers, so that when testing the spatial angular distribution of secondary electrons, the test accuracy is higher, but the cost is increased; therefore, the structure of the spherical collector may be specifically selected according to the test requirements.

[0046] The weak signal measurement system can test the electron flow size of the spherical collector, the spherical suppressor 6, the spherical grounding electrode 7 and the sample stage 9; the first collector minimum ammeter 15 is connected to the first collector 24, and can test the secondary electron flow on the first collector; the second collector minimum ammeter 16 is connected to the second collector 25, and can test the secondary electron flow on the second collector; the third collector minimum ammeter 17 is connected to the third collector 26, and can test the secondary electron flow on the third collector; the fourth collector minimum ammeter 18 is connected to the fourth collector 27, and can test the secondary electron flow on the fourth collector; the fifth collector minimum ammeter 19 is connected to the fifth collector 28, and can test the secondary electron flow on the fifth collector; the sixth collector minimum ammeter 20 is connected to the sixth collector 29, and can test the secondary electron flow on the sixth collector; the seventh collector minimum ammeter 21 is connected to the seventh collector 30, and can test the secondary electron flow on the seventh collector; The eight-collector small current meter 22 is connected to the eighth collector 31, and can test the secondary electron flow on the eighth collector; the spherical collector current meter 23 can test the secondary electron flow of the entire spherical collector; the spherical suppressor small current meter 12 is connected to the spherical suppressor 6, and can measure the electron flow of the spherical suppressor and change the DC bias on the spherical suppressor; the spherical grounded small current meter 13 is connected to the spherical grounding electrode 7, and can bias the spherical grounding electrode and test the electron flow on the grounding electrode; the sample stage small current meter 14 is connected to the sample stage 9, and can test the electron flow of the sample and the primary electron collector respectively; in this embodiment, the small current meter can be an electrostatic meter, which can test small currents with a test range of fA to mA, and can output DC bias with a range of 0-1000V; in other embodiments, the small current meter can be implemented by other methods of testing current or voltage, such as using a current-voltage amplifier, an oscilloscope method, or a pulse amplitude multi-channel analyzer test method.

[0047] The sample stage lifting and rotating device 3 includes a sample to be tested 8, a sample stage 9, a rotating gear 10 and a primary electron collector 11 located in a vacuum chamber, and a first magnetic fluid controller 32 for controlling the height of the sample stage and a second magnetic fluid controller 33 for controlling the rotation angle of the sample stage located outside the vacuum chamber; the sample stage 9 is a circular structure, and a scale ring is marked on the surface of the sample stage; the first magnetic fluid controller 32 is connected to the sample stage through a transmission mechanism, and the sample stage can be moved to enter the interior of the spherical collector; the second magnetic fluid controller 33 is provided with a dial, and the rotating gear 10 is controlled by the transmission mechanism to change the rotation angle of the sample stage, and the rotation angle is directly read from the dial. The sample stage lifting and rotating control device used in this embodiment has a program control function, and has the advantages of simple operation and high control accuracy when testing the secondary electron emission performance parameters.

[0048] The sample surface potential neutralization system can ensure that the surface potential of the sample 8 to be tested is maintained within the set threshold range, making the test results more accurate, and is usually used to test semiconductor and insulator materials with relatively large resistivity; the system includes a sample surface potential detection device 41, a potential detection device control power supply 40, a positive ion neutralization gun 39 and a neutralization gun control power supply 38; when testing samples with relatively large resistivity, the height of the sample stage is controlled by the sample stage lifting and rotating device 3 so that it is located at a suitable position directly below the spherical collector, and the sample surface potential is tested by the potential detection device 41. If the sample surface is positively charged, the electron gun 35 is used to output low-energy electrons to neutralize it; if the sample is negatively charged, the positive ion neutralization gun 39 is used to output low-energy ion beams to neutralize it; when the sample surface potential is within the set threshold range, it can be considered to be completely neutralized and subsequent tests can be performed. In this embodiment, a preferred neutralization method is provided, which uses an electron gun and a positive ion gun to neutralize the positive and negative potentials on the sample surface, respectively, and has the advantages of simple operation and high neutralization efficiency. In other embodiments, other methods can also be used to neutralize the sample surface potential, such as neutralizing the sample surface potential by applying a bias voltage to the sample.

[0049] Based on the above-mentioned device for measuring the secondary electron emission performance parameters of solid materials, this embodiment provides a method for measuring the secondary electron performance parameters, comprising the following steps:

[0050] (1) Place fluorescent material on the sample stage 9, adjust the electron gun controller 36 to make the electron gun 35 output an incident electron beam with energy E, open the rotating baffle 5 on the third collector 26, and observe through the observation window 4 whether the position of the electron beam spot is at the center of the sample stage scale ring.

[0051] (2) If the electron beam spot is not at the center of the sample stage 9, the incident direction of the electron beam can be adjusted so that it is located at the center of the sample stage 9, and the size of the electron beam spot size S can be tested using the scale ring on the surface of the sample stage.

[0052] (3) The height of the sample stage is adjusted by the first magnetic fluid controller 32, the change of the electron beam spot size S is observed, and the size of the electron beam spot at different positions and the corresponding power density E / S are recorded.

[0053] (4) Take out the fluorescent material, place the sample 8 to be tested on the sample table 9, and evacuate to the working pressure.

[0054] (5) Under a certain incident electron beam energy, the height of the sample stage 9 is changed, and the rotating baffle 5 on the third collector 26 is closed. The currents on the spherical collector, the spherical suppressor and the spherical grounding electrode are respectively measured by the spherical collector current meter 23, the spherical suppression minimum current meter 12 and the spherical grounding minimum current meter 13. The sum of the currents is used as the secondary electron current I of the material under different incident electron power densities.s .

[0055] (6) The sample stage is rotated by the second magnetic fluid controller 33 so that the primary electron collector faces the incident electron beam, and the primary electron current size I can be tested. p , according to I s with I p The ratio of δ~(E / S) is used to test the secondary electron emission coefficient of the material under different incident electron power densities.

[0056] (7) Repeat steps (1)-(4), adjust the position of the sample stage 9 so that it is located at the center of the spherical collector, and use the spherical suppressor minimum ammeter 12 to change the DC bias △U on the spherical suppressor 6. Secondary electrons with energy d(E) lower than e△U are filtered out by the spherical suppressor, and secondary electrons with energy d(E) higher than e△U can pass through the spherical suppressor to reach the spherical collector.

[0057] (8) Using the spherical collector current meter 23, the secondary electron current I on the spherical collector under different bias voltages △U is measured. s , get I s The integral spectrum of ~e△U.

[0058] (9) According to the secondary electron current I under different bias voltages s The size of the incident electron energy is calculated by calculating the differential spectrum to obtain the secondary electron energy spectrum curve I under a certain incident electron energy. s ~d(E).

[0059] (10) Repeat steps (1)-(4) and adjust the second magnetic fluid controller 33 so that the sample stage 9 is in a horizontal position (β=0°).

[0060] (11) Turn on the electron gun 35 to output an electron beam with energy E, which bombards the sample 8 to be tested.

[0061] (12) The currents on the spherical collector, spherical suppressor and spherical grounding electrode are measured respectively by using the spherical collector current meter 23, the spherical suppressor minimum current meter 12 and the spherical grounding minimum current meter 13. The sum of the currents is taken as the secondary electron current I of the material. s I s (β=0°).

[0062] (13) Adjust the second magnetic fluid controller 33, rotate the sample stage, and change the incident electron beam angle to △β∈(0°,85°).

[0063] (14) The currents on the spherical collector, spherical suppressor and spherical grounding electrode are measured by using the spherical collector current meter 23, the spherical suppressor minimum current meter 12 and the spherical grounding minimum current meter 13 respectively, and the sum of the currents is taken as the secondary electron current I s(△β); repeat step (13).

[0064] (15) Using the primary electron collector 11 to test the primary electron current size I p .

[0065] (16) According to I s (△β) and I p The ratio of can be used to test the relationship between the secondary electron emission coefficient of the material and the incident electron angle δ~△β.

[0066] (17) Adjust the first magnetic fluid controller 32, move the sample stage 9 with the sample 8 to be tested to the bottom of the spherical collecting pole, with the sample surface at a distance L from the center of the sphere, turn on the electron gun 35, and output an electron beam with energy E to bombard the sample 8 to be tested.

[0067] (18) Use a small ammeter connected to the mth collector (i.e., the mth annular collector) to measure the secondary electron current I on the mth collector. 2,m .

[0068] (19) In the spherical coordinate system, since the secondary electron emission coefficient is isotropic in the φ direction and only differs in the θ direction, the angular distribution formula of the secondary electron emission coefficient can be set as f(θ). It can be seen that the secondary current intensity collected on the first layer of the collector is: For the convenience of mathematical calculation, the function F(θ) can be constructed so that its derivative is: F'(θ) = f(θ)sinθ, θ k It is the angle between the line from any position of the lower edge of the kth layer collector to the secondary electron emission point and the normal of the sample surface. There is a formula: Where k = 0, 1, 2, ..., m, R is the radius of curvature of the spherical collector, L is the distance from the sample surface to the center of the sphere (when the sample stage is below the center of the sphere, the value is positive, otherwise it is negative), m is the number of collector layers (here m = 8), θ p is the angle between the line connecting any position on the upper edge of the first collector and the center of the sphere and the axis of the center of the sphere, and dθ is the central angle corresponding to each layer of the collector.

[0069] (20) It can be seen that the current measured on the mth collector is: I 2,m =2πI1[F(θ m )-F(θ m-1 )]. Similarly, to facilitate mathematical calculations, the constructor F(θ m ), so that its derivative is: F'(θ m )=f(θ m )sinθ m ,θ mIt is the angle between the line from any position of the lower edge of the mth layer collector to the secondary electron emission point and the normal direction of the sample surface.

[0070] (21) Assume the function: G(θ) = F(θ) - F(θ0), we can know:

[0071] (22) According to the I measured in (18) 2,m There are m sets of data in total. After fitting, we can get the function G(θ).

[0072] (23) By taking the derivative of the function G(θ), that is, according to G'(θ) = [F(θ) - F(θ0)]' = F'(θ) = f(θ)sinθ, the spatial angular distribution function of the secondary electrons can be obtained: In this embodiment, when testing the spatial angular distribution of secondary electrons, the sample position remains unchanged, ensuring that the incident electron beam power density is consistent, the measurement results are accurate, and the operation is simple.

[0073] (24) Turn off the electron gun controller 36, turn off the vacuum device 42, fill the vacuum chamber 37 with dry nitrogen, open the device to take out the sample 8 to be tested, and turn off the device.

[0074] In the above test process, when calculating the secondary electron emission coefficient δ, it is necessary to find the primary electron current I p In addition to using the primary electron collector to directly test the size, the spherical collector current meter 23 can also be used to test the secondary electron current I on the spherical collector. s , use the sample stage small ammeter 14 to test the sample current I sample , use the spherical suppression minimum current meter 12 to test the spherical suppression current I sup , use the spherical grounding electrode small current meter 13 to test the spherical grounding electrode current I gnd , by I s +I sample +I sup +I gnd The size of the electron current is obtained by comparing it with I p By comparison, the accuracy of the two methods in testing the primary electron current can be verified, thereby ensuring the accuracy of testing the secondary electron emission performance parameters.

[0075] It should be noted that the method for measuring the secondary electron emission performance parameters of solid materials provided in this embodiment includes measuring the secondary electron emission coefficient under different incident electron power densities, the relationship between the secondary electron spatial angular distribution and the incident electron energy and power density, the relationship between the secondary electron energy spectrum and the incident electron energy, and the relationship between the secondary electron emission coefficient and the incident electron angle; in specific applications, the order of measuring these four parameters can be changed at will, or only some of the parameters can be measured.

[0076] This application proposes a new technical solution that can accurately test the secondary electron emission coefficient, secondary electron energy spectrum and secondary electron spatial angular distribution of materials under different incident electron power densities, laying a foundation for in-depth research on the secondary electron emission performance of materials. This application provides a test device that can measure the secondary electron emission performance parameters of materials. The device adopts a spherical collector structure to ensure the accuracy of the measurement results.

[0077] The above contents are further detailed descriptions of the present application in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the inventive concept of the present application.

Claims

1. A secondary electron emission performance parameter testing device, characterized in that: include An electron beam generating system is connected to the vacuum chamber via a flange interface, and includes an electron gun in the vacuum chamber and an electron gun controller outside the vacuum chamber; The spherical electron collector includes three mutually insulated spherical structures, which are, from outside to inside, a spherical collecting electrode, a spherical suppressing electrode and a spherical grounding electrode; the spherical electron collector is fixed on an electron collector fixing device in a vacuum chamber, and an upper opening is used as an incident electron hole, through which the electron gun muzzle enters the interior of the spherical electron collector, and a lower opening of the spherical electron collector is used as a sample stage inlet and outlet hole; A weak signal measurement system, comprising an ammeter or a current-voltage amplifier connected to the spherical collector, the spherical suppressor, the spherical grounding electrode and the sample stage, respectively, for collecting currents of the spherical collector, the spherical suppressor, the spherical grounding electrode and the sample stage; The sample stage lifting and rotating device includes a magnetic fluid controller installed outside the vacuum chamber, a screw transmission mechanism inside the vacuum chamber and a gear rotating mechanism connected thereto, the sample stage is connected to the gear rotating mechanism, and the sample stage enters the spherical electron collector from the opening below the spherical electron collector; The magnetic fluid controller drives the sample stage to move up and down and rotate through a screw transmission mechanism and a gear rotation mechanism connected thereto; one side of the sample stage is used to place the sample to be tested, and the other side is used to fix the primary electron collector; The sample surface potential neutralization system comprises a surface potential detection device, a surface positive potential elimination device and a surface negative potential elimination device.

2. The secondary electron emission performance parameter testing device according to claim 1, characterized in that: The spherical suppression electrode is made of a stainless steel mesh with an opening rate of 70% to 98%; the spherical grounding electrode is made of a stainless steel mesh with an opening rate of 70% to 98%.

3. The secondary electron emission performance parameter testing device according to claim 1, characterized in that: The electron collector fixing device has a hole in the middle for the sample stage to move up and down; the electron collector fixing device has three annular grooves for respectively fixing the spherical collector, the spherical suppressor and the spherical grounding electrode; the bottom of the annular grooves has small holes for the wires connected to the spherical collector, the spherical suppressor and the spherical grounding electrode to pass through.

4. The secondary electron emission performance parameter testing device according to claim 1, characterized in that: The primary electron collector is a Faraday cup with an inverted cone structure.

5. The secondary electron emission performance parameter testing device according to claim 1, characterized in that: The spherical collector is isolated by a plurality of strip-shaped ceramic rings to form a plurality of annular collectors, and each annular collector is insulated from each other; the weak signal measurement system is connected to each annular collector through an ammeter or a current-voltage amplifier to collect the current of each annular collector.

6. A secondary electron spatial angular distribution testing method based on the secondary electron emission performance parameter testing device according to claim 1, the steps comprising: 1) Place the fluorescent material on the sample stage and adjust the electron gun controller so that the electron gun outputs an incident electron beam with an energy of E; 2) If the incident electron beam spot is not at the center of the sample stage, adjust the incident direction of the electron beam so that it is located at the center of the sample stage and measure the electron beam spot size S; 3) Adjust the height of the sample stage, observe the change of the electron beam spot size S, and record the size of the electron beam spot at different positions and the corresponding power density E / S; 4) Take out the fluorescent material, place the sample to be tested on the sample table, and evacuate to the working pressure; 5) Turn on the electron gun, output an electron beam with energy E, and bombard the sample to be tested; 6) Use the spherical collector, spherical suppressor and spherical grounding electrode to test the current on the spherical collector, spherical suppressor and spherical grounding electrode respectively, and the sum of their currents is the secondary electron current I s ; wherein the spherical collector is isolated by a plurality of strip-shaped ceramic rings to form a plurality of annular collectors, and each annular collector is insulated from each other; 7) Rotate the sample stage, change the incident electron beam angle to △β, and use the spherical collector, spherical suppressor and spherical grounding electrode to test the secondary electron current I s (△β); 8) Use the primary electron collector to test the primary electron current I of the incident electron beam p ; 9) According to I s (△β) and I p The ratio of the secondary electron emission coefficient of the test material and the relationship between the incident electron angle δ~△β; 10) Move the sample stage with the sample to be tested to the bottom of the spherical collector, with the sample surface at a distance L from the center of the sphere, turn on the electron gun, and output an electron beam with energy E to bombard the sample to be tested; 11) Using an ammeter connected to each annular collector, test the secondary electron current on the corresponding annular collector; 12) Let the angular distribution of the secondary electron emission coefficient be f(θ), the function G(θ) = F(θ) - F(θ0), and the derivative of F(θ) be: F'(θ) = f(θ) sinθ; 13) fitting the function G(θ) based on the current data of the m annular collectors measured; 14) Deriving the function G(θ), that is, according to G'(θ) = [F(θ) - F(θ0)]' = F'(θ) = f(θ)sinθ, we can obtain the spatial angular distribution of secondary electrons:

7. The method according to claim 6, characterized in that θ k The angle between the line from any position of the lower edge of the kth layer collector to the secondary electron emission point and the normal of the sample surface is: Where k = 0, 1, 2, ..., m, R is the radius of curvature of the spherical collector, L is the distance between the sample surface and the center of the sphere, when the sample stage is below the center of the sphere, the L value is positive, otherwise it is negative; m is the total number of annular collectors, θ p is the angle between the line connecting any position of the upper edge of the first collector and the center of the sphere and the axis of the center of the sphere, and dθ is the central angle corresponding to each annular collector.

8. A secondary electron energy spectrum curve testing method based on the secondary electron emission performance parameter testing device according to claim 1, the steps comprising: 1) Place the fluorescent material on the sample stage and adjust the electron gun controller so that the electron gun outputs an incident electron beam with an energy of E; 2) If the incident electron beam spot is not at the center of the sample stage, adjust the incident direction of the electron beam so that it is located at the center of the sample stage and measure the electron beam spot size S; 3) Adjust the height of the sample stage, observe the change of the electron beam spot size S, and record the size of the electron beam spot at different positions and the corresponding power density E / S; 4) Take out the fluorescent material, place the sample to be tested on the sample table, and evacuate to the working pressure; 5) Adjust the position of the sample stage so that it is located at the center of the spherical collector, and change the DC bias voltage △U on the spherical suppressor, so that the secondary electrons with energy d(E) lower than e△U are filtered out by the spherical suppressor, and the secondary electrons with energy d(E) higher than e△U can pass through the spherical suppressor to reach the spherical collector; 6) Using a spherical collector to measure the secondary electron current I on the spherical collector under different bias voltages △U s , get I s The integrated spectrum of ~e△U; 7) According to the secondary electron current I under different bias voltages s , calculate the differential spectrum to obtain the secondary electron energy spectrum curve I under a certain incident electron energy s ~d(E).

9. A secondary electron emission coefficient testing method based on the secondary electron emission performance parameter testing device according to claim 1, the steps comprising: 1) Place the fluorescent material on the sample stage and adjust the electron gun controller so that the electron gun outputs an incident electron beam with an energy of E; 2) If the incident electron beam spot is not at the center of the sample stage, adjust the incident direction of the electron beam so that it is located at the center of the sample stage and measure the electron beam spot size S; 3) Adjust the height of the sample stage, observe the change of the electron beam spot size S, and record the size of the electron beam spot at different positions and the corresponding power density E / S; 4) Take out the fluorescent material, place the sample to be tested on the sample table, and evacuate to the working pressure; 5) Under a certain incident electron beam energy, change the height of the sample stage, and use the spherical collector, spherical suppressor and spherical grounding electrode to test the current on the spherical collector, spherical suppressor and spherical grounding electrode respectively. The sum of the currents is the secondary electron current I s , I s as secondary electron flux of the material at different incident electron power densities; 6) Rotate the sample stage so that the primary electron collector faces the incident electron beam and measure the primary electron current size I p , according to I s with I p The ratio of δ~(E / S) is used to test the secondary electron emission coefficient of the material under different incident electron power densities.

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