A calibration device and method for secondary electron yield measurements

Abstract

The application discloses a kind of calibration device and method of secondary electron yield measurement, it is related to secondary electron emission phenomenon and its application field;The calibration device includes: electron excitation source, Faraday cup, collecting electrode, beam measuring instrument and mobile terminal;Electron excitation source emits electron;Collecting electrode collects the secondary electron generated under the irradiation of electron that is injected by electron through hole of the sample to be measured;Beam measuring instrument measures the electron beam current that is transmitted by Faraday cup when Faraday cup is below electron excitation source and all covers electron through hole, and measures the current of secondary electron and the current that is transmitted through the sample to be measured;Mobile terminal obtains secondary electron calibration yield according to the secondary electron yield that is calculated according to the current of secondary electron and the current that is transmitted through the sample to be measured, and the correction factor that is calculated from the current of secondary electron and electron beam current;The application realizes accurate measurement of secondary electron yield by carrying out the calibration of secondary electron yield according to correction factor.

Description

TECHNICAL FIELD

[0001] The present application relates to the secondary electron emission phenomenon and its application field, in particular to a kind of calibration device and method of secondary electron yield measurement. BACKGROUND

[0002] Secondary electron emission phenomenon occurs in many scenarios, and secondary electron yield is usually used to characterize the strength of secondary electron emission. In the field of microanalysis and weak signal detection, it is necessary to improve the secondary electron yield to improve the performance of related instruments and equipment. In the scenarios such as spacecraft operating in space environment, high-voltage power transmission engineering equipment and large particle accelerator, it is necessary to reduce the secondary electron yield to reduce the adverse effects of secondary electrons. Therefore, it is necessary to carry out research on secondary electron emission phenomenon, especially the research on secondary electron yield regulation.

[0003] The key to the research on secondary electron yield regulation lies in the accurate measurement of secondary electron yield. There are three kinds of current test methods: collector method, sample bias method and charge derivation method. Compared with the other two methods, the collector method has strong universality and is suitable for the measurement of all materials. At the same time, the test process is relatively simple, reliable and high-precision, so it has been paid more and more attention and used. However, the influence of the collection efficiency of the collector itself on the final result is often ignored in the use process of the method, which leads to inaccurate measurement of secondary electron yield. Therefore, how to realize accurate measurement of secondary electron yield is very important. SUMMARY

[0004] The purpose of the present application is to provide a kind of calibration device and method of secondary electron yield measurement, by the secondary electron yield calibration according to correction coefficient, realize accurate measurement of secondary electron yield.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] A kind of calibration device of secondary electron yield measurement, the calibration device includes: electron excitation source, Faraday cup, collector, beam current measuring instrument and mobile terminal;

[0007] The Faraday cup is connected with the electron excitation source;

[0008] The collector is an electron collection device with a cover-shaped structure with electron through holes, and the cover is arranged around the sample to be measured;

[0009] The beam current measuring instrument is connected with the Faraday cup, the collector, the sample to be measured and the mobile terminal respectively;

[0010] The electron excitation source is used to emit electrons;

[0011] The collecting electrode is configured to collect secondary electrons generated by the sample under irradiation of electrons incident through the electron through-hole;

[0012] The beam measuring instrument is configured to:

[0013] measure the electron beam current transmitted through the Faraday cup when the Faraday cup is positioned below the electron excitation source and covers the electron through-hole completely;

[0014] measure the current of the secondary electrons and the current transmitted through the sample;

[0015] The mobile terminal is configured to:

[0016] calculate the secondary electron yield according to the current of the secondary electrons and the current transmitted through the sample;

[0017] calculate the correction coefficient according to the current of the secondary electrons and the electron beam current;

[0018] obtain the calibrated secondary electron yield according to the correction coefficient and the secondary electron yield.

[0019] Optionally, the beam measuring instrument comprises a single-channel measuring instrument and a double-channel measuring instrument;

[0020] The single-channel measuring instrument is connected to the Faraday cup and the mobile terminal respectively, and the double-channel measuring instrument is connected to the collecting electrode, the sample and the mobile terminal respectively;

[0021] The single-channel measuring instrument is configured to measure the electron beam current transmitted through the Faraday cup and transmit the electron beam current to the mobile terminal;

[0022] The double-channel measuring instrument is configured to measure the current of the secondary electrons and the current transmitted through the sample and transmit the current of the secondary electrons and the current transmitted through the sample to the mobile terminal.

[0023] Optionally, the single-channel measuring instrument is a single-channel picoammeter, and the double-channel measuring instrument is a double-channel picoammeter.

[0024] Optionally, the electron excitation source adopts an electron gun.

[0025] Optionally, the collecting electrode is made of metal.

[0026] Optionally, the collecting electrode has a spherical, hemispherical or cylindrical shape.

[0027] Optionally, the calibration device further comprises a sample stage, and the sample stage is configured to place the sample.

[0028] Optionally, the sample stage is made of metal.

[0029] A calibration method of secondary electron yield measurement, the method adopts the calibration device of secondary electron yield measurement described above, and the method comprises:

[0030] Obtaining the electron beam current, the secondary electron current and the current transmitted through the sample to be measured; the electron beam current is the current of the electron beam transmitted through the Faraday cup when the Faraday cup is below the electron excitation source and all the electron through holes are covered; the electron through holes are arranged on the collecting electrode of the cover-shaped structure; the secondary electron current is the current corresponding to the secondary electrons generated by the sample to be measured under the irradiation of the electrons incident through the electron through holes and collected by the collecting electrode;

[0031] Calculating the secondary electron yield according to the secondary electron current and the current transmitted through the sample to be measured;

[0032] Calculating a correction coefficient according to the secondary electron current and the electron beam current;

[0033] Obtaining the secondary electron calibration yield according to the correction coefficient and the secondary electron yield.

[0034] According to the specific embodiments provided by the present application, the following technical effects are disclosed:

[0035] The present application provides a calibration device and method of secondary electron yield measurement, by arranging the collecting electrode and the Faraday cup, the electron beam current, the secondary electron current and the current transmitted through the sample to be measured are measured respectively, and the correction coefficient is calculated according to the secondary electron current and the electron beam current, so that in the calculation of the secondary electron yield, the self collection efficiency of the collecting electrode is considered, and finally the secondary electron calibration yield is calculated, so as to realize the accurate measurement of the secondary electron yield. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 The structural diagram of the calibration device of secondary electron yield measurement provided by the embodiments of the present application is shown in the figure.

[0038] Figure 2 The comparison diagram of the results before and after calibration provided by the embodiments of the present application is shown in the figure.

[0039] Symbol explanation:

[0040] Electron excitation source-1, Faraday cup-2, collecting electrode-3, sample stage-4, beam current measuring instrument-5, mobile terminal-6, single-channel picoammeter-7, dual-channel picoammeter-8, sample to be tested-9, secondary electron-10. Detailed Implementation

[0041] 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.

[0042] The purpose of this invention is to provide a calibration device and method for measuring secondary electron yield, which achieves accurate measurement of secondary electron yield by calibrating the secondary electron yield based on a correction coefficient.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] like Figure 1 As shown, this embodiment of the invention provides a calibration device for secondary electron yield measurement. The calibration device includes: an electron excitation source 1, a Faraday cup 2, a collecting electrode 3, a beam current measuring instrument 5, and a mobile terminal 6.

[0046] The Faraday cup 2 is connected to the electron excitation source 1; the collecting electrode 3 is an electron collecting device with a cover-shaped structure having electron through holes, and is placed around the sample 9 to be tested.

[0047] The beam measuring instrument 5 is connected to the Faraday cup 2, the collecting electrode 3, the sample to be tested 9, and the mobile terminal 6, respectively.

[0048] Electron excitation source 1 is used to emit electrons; wherein, electron excitation source 1 can be an electron gun.

[0049] The collecting electrode 3 is used to collect secondary electrons 10 generated by the sample 9 under the irradiation of electrons incident through the electron aperture. Specifically, the collecting electrode 3 is made of metal. The shape of the collecting electrode 3 can be spherical, hemispherical, or cylindrical. In practical applications, the collecting electrode 3 can be a hemispherical collecting electrode 3 made of 304 stainless steel and connected to one channel of the dual-channel picoammeter 8 via a BNC wire.

[0050] The beam current measuring instrument 5 is used to measure the electron beam current transmitted through the Faraday cup 2 when the Faraday cup 2 is below the electron excitation source 1 and the electron aperture is completely blocked.

[0051] The beam current meter 5 is also used to measure the current of the secondary electrons 10 and the current of the transmission through the sample 9 under test.

[0052] The mobile terminal 6 is used to calculate the secondary electron yield according to the current of the secondary electrons 10 and the current of the transmission through the sample 9 under test, and to calculate the correction coefficient according to the current of the secondary electrons 10 and the electron beam current;

[0053] The mobile terminal 6 is also used to obtain the secondary electron calibration yield according to the correction coefficient and the secondary electron yield.

[0054] Specifically, the beam current meter 5 comprises a single-channel meter and a double-channel meter. The single-channel meter can be a single-channel picoammeter 7, and the double-channel meter can be a double-channel picoammeter 8.

[0055] The single-channel meter is connected with the Faraday cup 2 and the mobile terminal 6 respectively, and the double-channel meter is connected with the collector 3, the sample 9 under test and the mobile terminal 6 respectively.

[0056] The single-channel meter is used to measure the electron beam current transmitted through the Faraday cup 2 and transmit the electron beam current to the mobile terminal 6.

[0057] The double-channel meter is used to measure the current of the secondary electrons 10 and the current of the transmission through the sample 9 under test, and transmit the current of the secondary electrons 10 and the current of the transmission through the sample 9 under test to the mobile terminal 6.

[0058] As an optional implementation, the calibration device further comprises a sample table 4, the sample table 4 is used to place the sample 9 under test, and the material of the sample table 4 is a metal material. The material of the sample table 4 can be selected as 304 stainless steel, is located below the collector 3, and is connected with another channel of the double-channel picoammeter 8 through a BNC line.

[0059] In actual application, the electron gun, i.e. the electron excitation source 1, is located directly above the sample table 4, the Faraday cup 2 is below the electron gun and can be moved to be directly below the electron gun. The collector 3 is located above the sample table 4 and covers the sample table 4 completely. The single-channel picoammeter 7 is connected with the Faraday cup 2, the double-channel picoammeter 8 is connected with the collector 3 and the sample table 4, and sends data to the mobile terminal 6 (such as a computer) for processing. The picoammeter can communicate with the computer through IEE-488 or RS-232. The Faraday cup 2 is connected with the single-channel picoammeter 7 through a BNC line.

[0060] The electron gun is used to generate electrons, and the generated electrons are the excitation source of the secondary electrons 10 as incident electrons. The Faraday cup 2 can be moved to be directly below the electron gun to receive the electrons generated by the electron gun. The Faraday cup 2 is connected to the electron gun by a screw rod and can be moved to or away from the position directly below the electron gun, and when moved to the position directly below, the incident electron beam can be transmitted.

[0061] The computer is connected to the single-channel picoammeter 7 and the double-channel picoammeter 8 through a GPIB card, is responsible for data acquisition and processing, and finally realizes the calibration of the secondary electron yield through data processing.

[0062] Embodiment 2

[0063] The embodiment of the present application provides a calibration method for secondary electron yield measurement, which adopts the calibration device for secondary electron yield measurement in the embodiment 1, and the method comprises the following steps:

[0064] The electron beam current, the current of the secondary electrons, and the current transmitted through the sample to be measured are obtained; the electron beam current is the current of the electron beam transmitted through the Faraday cup when the Faraday cup is below the electron excitation source and all the electron through holes are covered; the electron through holes are arranged on the collector of the cover-shaped structure; the current of the secondary electrons is the current of the secondary electrons generated by the sample to be measured under the irradiation of the electrons incident through the electron through holes.

[0065] The secondary electron yield is calculated according to the current of the secondary electrons and the current transmitted through the sample to be measured.

[0066] The correction coefficient is calculated according to the current of the secondary electrons and the electron beam current.

[0067] The secondary electron calibration yield is obtained according to the correction coefficient and the secondary electron yield.

[0068] The comparison results of the secondary electron calibration yield obtained by the calibration method for secondary electron yield measurement provided by the present application and the secondary electron yield without calibration are shown in Figure 2 .

[0069] In practical application, the specific process of the calibration method can also be as follows:

[0070] ①Move the Faraday cup to be directly below the electron gun.

[0071] ②Turn on the single-channel picoammeter and run the acquisition program in the computer.

[0072] ③Set the working parameters of the electron gun, mainly including the acceleration voltage, the cathode current and the grid voltage, and wait for a period of time until the reading of the single-channel picoammeter basically does not change any more, at this time the electron gun is in a stable working state.

[0073] 4. Turn on the double-channel picoammeter and run the acquisition program in the computer.

[0074] 5. Move the Faraday cup away from directly below the electron gun.

[0075] 6. Record the value of the double-channel picoammeter; calculate the secondary electron yield according to the formula.

[0076] Specifically, the current of the secondary electrons I s and the current I t transmitted through the sample to be measured are obtained. Then the secondary electron yield δ is calculated:

[0077]

[0078] 7. Adjust the accelerating voltage of the electron gun until the value of the current transmitted through the sample is zero, and record the value of the double-channel picoammeter at this time, i.e. the current of the secondary electrons I′ s and the current I′ t transmitted through the sample to be measured after adjustment.

[0079] 8. Move the Faraday cup back to directly below the electron gun and record the value of the single-channel current at this time, i.e. the beam current I′ p .

[0080] 9. Compare the collection electrode current recorded by the double-channel with the value of the single-channel to obtain the collection efficiency of the device, i.e. the correction factor:

[0081]

[0082] 10. Bring the correction factor into the secondary electron yield calculation formula to obtain the calibrated secondary electron emission yield δ′:

[0083]

[0084] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be mutually referred to.

[0085] The principles and implementation modes of the present application are described by applying specific examples in this paper. The above description of the embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A calibration device for secondary electron yield measurements, characterized by The calibration device comprises an electron excitation source, a Faraday cup, a collector, a beam current measuring instrument and a mobile terminal; The Faraday cup is connected with the electron excitation source; The collector is an electron collecting device in the form of a cover with electron through holes, and the cover is arranged around the sample to be measured; The beam current measuring instrument is connected with the Faraday cup, the collector, the sample to be measured and the mobile terminal respectively; The electron excitation source is used for emitting electrons; The collector is used for collecting secondary electrons generated by the sample to be measured under the irradiation of the electrons incident through the electron through holes; The beam current measuring instrument is used for: measuring the electron beam current transmitted through the Faraday cup when the Faraday cup is below the electron excitation source and covers all the electron through holes; measuring the current of the secondary electrons and the current transmitted through the sample to be measured; The mobile terminal is used for: calculating the secondary electron yield according to the current of the secondary electrons and the current transmitted through the sample to be measured; calculating the correction coefficient according to the current of the secondary electrons and the electron beam current; obtaining the calibrated secondary electron emission yield according to the correction coefficient and the secondary electron yield. Secondary electron yield δ: I s is the current of secondary electrons; I t is the current through the sample under test; Correction coefficient α: I′ s is the current of the adjusted secondary electrons; I′ p is the electron beam current; Calibrated secondary electron emission yield δ':

2. The calibration apparatus for secondary electron yield measurement according to claim 1, characterized in that, The beam current measuring instrument comprises a single-channel measuring instrument and a double-channel measuring instrument; The single-channel measuring instrument is connected with the Faraday cup and the mobile terminal respectively, and the double-channel measuring instrument is connected with the collector, the sample to be measured and the mobile terminal respectively; The single-channel measuring instrument is used for measuring the electron beam current transmitted through the Faraday cup and transmitting the electron beam current to the mobile terminal; The double-channel measuring instrument is used for measuring the current of the secondary electrons and the current transmitted through the sample to be measured and transmitting the current of the secondary electrons and the current transmitted through the sample to be measured to the mobile terminal.

3. The calibration apparatus for secondary electron yield measurement according to claim 2, characterized in that, The single-channel measuring instrument is a single-channel picoammeter, and the double-channel measuring instrument is a double-channel picoammeter.

4. The calibration apparatus for secondary electron yield measurement according to claim 1, wherein The electron excitation source adopts an electron gun.

5. The calibration device for secondary electron yield measurement of claim 1, wherein, The material of the collector is metal.

6. The calibration apparatus for secondary electron yield measurement according to claim 1, wherein The shape of the collector is spherical, hemispherical or cylindrical.

7. The calibration apparatus for secondary electron yield measurement according to claim 1, wherein The calibration device further comprises a sample table, and the sample table is used for placing the sample to be measured.

8. The calibration device for secondary electron yield measurement according to claim 7, characterized in that, The material of the sample table is metal.

9. A calibration method for secondary electronic yield measurement, characterized in that, The method adopts the calibration device for measuring the secondary electron yield according to any one of claims 1-8, and the method comprises: obtaining the electron beam current, the current of the secondary electrons and the current transmitted through the sample to be measured; the electron beam current is the current of the electron beam transmitted through the Faraday cup when the Faraday cup is below the electron excitation source and covers all the electron through holes; the electron through holes are arranged on the collector in the form of a cover; the current of the secondary electrons is the current corresponding to the secondary electrons generated by the collector under the irradiation of the electrons incident through the electron through holes; calculating the secondary electron yield according to the current of the secondary electrons and the current transmitted through the sample to be measured; calculating the correction coefficient according to the current of the secondary electrons and the electron beam current; obtaining the calibrated secondary electron yield according to the correction coefficient and the secondary electron yield.

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