Immersion lens in secondary ion mass spectrometer and method for focusing secondary ions

Abstract

The present invention relates to an immersion lens in a secondary ion mass spectrometer and a method for focusing secondary ions. The immersion lens is arranged in the secondary ion mass spectrometer, and includes a substrate disk, a first electrode assembly and an insulating mounting assembly. The substrate disk is used as a second electrode, and a mounting groove is arranged on the substrate disk, and the mounting groove is used to mount the first electrode assembly; the substrate disk is connected to a positive voltage, and the first electrode assembly is connected to a negative voltage, or the substrate disk is connected to a negative voltage, and the first electrode assembly is connected to a positive voltage, and an arc electric field is generated between the two electrodes. The method bombards the sample surface with a primary ion beam through an ion incident hole on the substrate disk, so that secondary ions escape from the sample surface, and the secondary ions are deflected by the arc electric field between the two electrodes, so that the secondary ions are focused on one point. The present invention has a simple structure, collects secondary ions to the greatest extent, obtains a stronger ion beam signal, facilitates subsequent collection and analysis, and can achieve dual focusing of ion energy and ion direction.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary ion mass spectrometers, and in particular to an immersion lens in a secondary ion mass spectrometer and a method for focusing secondary ions. Background Art

[0002] Secondary ion mass spectrometry (SIMS) is one of the most widely used techniques in surface analysis. It has high sensitivity (the lowest detectable concentration reaches ppm or even ppb), high resolution (about 10 -9 ) and low detection limit (absolute detection limit 10 -13 -10 -19 It can be used to detect the isotope abundance ratios of all elements including hydrogen, analyze the composition and molecular structure of unknown compounds in the sample, obtain sample surface information, perform line scanning analysis, generate three-dimensional images of ion distribution, and perform micro-area imaging and depth profile analysis of specific elements.

[0003] The immersion lens is a lens used to focus the secondary beam in SIMS. It is named because the sample surface is immersed in the electric field of the lens. The potential distribution curve starts from the sample surface. After the secondary ions leave the sample surface, they enter the electric field of the immersion lens under the action of the electric field. Due to the particularity of the lens electric field structure and the control of the movement path of the secondary ions in the secondary ion mass spectrometer, the existing immersion lens process and structure are complicated and cannot meet the unique ion focusing requirements in the secondary ion mass spectrometer. Summary of the invention

[0004] Based on this, an object of the present invention is to provide an immersion lens in a secondary ion mass spectrometer and a method for focusing secondary ions, which are used in a vacuum environment and can effectively focus secondary ions leaving the sample surface.

[0005] In a first aspect, an immersion lens in a secondary ion mass spectrometer according to the present invention is arranged in the secondary ion mass spectrometer, comprising:

[0006] A substrate disc, a first electrode assembly and an insulating mounting assembly, wherein the substrate disc is used as a second electrode, and a mounting groove is provided on the substrate disc, and the mounting groove is used to mount the first electrode assembly; the substrate disc is used to connect a positive voltage, and the first electrode assembly is used to connect a negative voltage, or the substrate disc is used to connect a negative voltage, and the first electrode assembly is used to connect a positive voltage;

[0007] The first electrode assembly includes a cylindrical electrode and metal rings fixed on both sides of the cylindrical electrode. The cylindrical electrode and the metal rings are fixed in the mounting groove through the insulating mounting assembly.

[0008] Furthermore, the insulating mounting assembly includes a ceramic washer, which is arranged under the metal ring and is used to separate the metal ring from the substrate disk, while leaving a gap between the cylindrical electrode and the substrate disk.

[0009] Furthermore, the mounting groove is three connected circular grooves, which match the shapes of the cylindrical electrode, the metal ring and the ceramic gasket. The diameter of the circular groove is larger than the diameter of the cylindrical electrode and the metal ring, so that there is a radial gap and they do not contact each other.

[0010] Furthermore, the ceramic gasket comprises an annular ceramic, and the upper end surface of the annular ceramic abuts against the lower end surface of the metal ring.

[0011] Furthermore, the ceramic gasket also includes a stepped circular ring-shaped ceramic, the upper ring of the stepped circular ring-shaped ceramic has a diameter larger than the lower ring of the stepped circular ring-shaped ceramic, the lower end surface of the upper ring of the stepped circular ring-shaped ceramic abuts against the upper end surface of the annular ceramic, the lower ring of the stepped circular ring-shaped ceramic abuts against the mounting groove surface in the substrate disk, and the metal ring is sleeved outside the upper ring of the stepped circular ring-shaped ceramic.

[0012] Furthermore, the two circular grooves in the mounting groove corresponding to the metal ring are in the shape of stepped grooves, which match the stepped ring-shaped ceramic.

[0013] Furthermore, it also includes a metal strip, a through hole is penetrated on one side of the substrate disk, an insulating component is arranged in the through hole, one end of the metal strip passes through the through hole and the insulating component in the through hole and contacts the metal ring on the same side of the through hole, and the other end is connected to the vacuum flange electrode outside the substrate disk.

[0014] Furthermore, the upper end of the cylindrical electrode is cylindrical, and the lower end is inclined inward, and the upper and lower ends of the cylindrical electrode are connected.

[0015] Furthermore, the insulating mounting assembly also includes screws, and the first electrode assembly is assembled and fixed by the screws passing through the stepped circular ring-shaped ceramic and the threaded holes of the substrate disk.

[0016] In a second aspect, the present invention further provides a method for focusing secondary ions in a secondary ion mass spectrometer, the method comprising the following steps:

[0017] Vertically placing an immersion lens as described in any one of the first aspects into a secondary ion mass spectrometer;

[0018] Putting a sample holder loaded with a sample into the secondary ion mass spectrometer and locating it on one side of the lower end surface of the substrate disk;

[0019] Connecting a positive voltage to the substrate disk and a negative voltage to the first electrode assembly, or connecting a positive voltage to the first electrode assembly and a negative voltage to the substrate disk;

[0020] The primary ion beam is bombarded on the sample surface through the ion entrance hole on the substrate disk, so that secondary ions escape from the sample surface. The secondary ions are deflected by the arc electric field between the two electrodes, so that the secondary ions are focused at a point on the side of the substrate disk away from the sample holder.

[0021] The present invention provides an immersion lens in a secondary ion mass spectrometer and a method for focusing secondary ions. A cylindrical electrode is insulated and arranged on a substrate disk electrode, and voltage is applied to the two electrodes to form an arc electric field, so that the secondary ions passing through the arc electric field are subjected to the same force and are finally focused on a point outside the immersion lens. The structure is simple, the ion optical path is easy to control, and the ion beam focusing effect is good, so that the secondary ions can be collected to the greatest extent, and a stronger ion beam signal can be obtained, which is convenient for subsequent collection and analysis, and finally can achieve dual focusing of ion energy and ion direction.

[0022] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of an immersion lens in a secondary ion mass spectrometer in an embodiment of the present invention;

[0024] Figure 2 It is a schematic structural diagram of a first electrode assembly of an immersion lens in a secondary ion mass spectrometer in an embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of assembling a first electrode assembly and an insulating mounting assembly of an immersion lens in a secondary ion mass spectrometer in an embodiment of the present invention;

[0026] Figure 4 is a cross-sectional schematic diagram of an immersion lens in a secondary ion mass spectrometer according to an embodiment of the present invention;

[0027] Figure 5 It is a schematic diagram of a power connection device of an immersion lens in a secondary ion mass spectrometer in an embodiment of the present invention;

[0028] Figure 6 A schematic diagram of ion trajectories of an immersion lens in a secondary ion mass spectrometer in an embodiment of the present invention;

[0029] Figure 7Schematic diagram of the potential distribution of an immersion lens in a secondary ion mass spectrometer according to an embodiment of the present invention. Description of the drawings:

[0031] 1. substrate disk; 11. mounting groove; 2. first electrode assembly; 21. cylindrical electrode; 22. metal ring; 3. insulating mounting assembly; 31. annular ceramic; 32. stepped annular ceramic; 4. cylindrical insulating ceramic; 5. metal strip. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0033] It should be clear that the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the embodiments of the present application.

[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0035] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar human bodies, and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0036] In addition, in the description of this application, unless otherwise specified, "multiple" means two or more. "And / or" describes the association relationship of the associated human bodies, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated human bodies before and after are in an "or" relationship.

[0037] In view of the technical problems in the background technology, an embodiment of the present invention provides an immersion lens in a secondary ion mass spectrometer. The immersion lens is arranged in the secondary ion mass spectrometer and is used in a vacuum environment. The immersion lens is used to focus the secondary ions leaving the sample surface, such as Figure 1 As shown, the immersion lens includes a substrate disk 1, a first electrode assembly 2 and an insulating mounting assembly 3. The substrate disk 1 is a solid circular metal plate used as a second electrode. The first electrode assembly and the second electrode are respectively connected to voltages to generate an electric field. The secondary ions are deflected and focused at a point outside the immersion lens by the electric field. The sample observation device and immersion lens of the secondary ion mass spectrometer are integrated on the substrate disk at the same time. The substrate disk is also provided with an ion entrance hole. The primary ion beam bombards the sample surface through the ion entrance hole. The secondary ions excited on the sample surface are deflected and focused by the electric field in the immersion lens. At the same time, the escape of ions on the sample surface can be observed by the sample observation device. After the secondary ions are focused by the immersion lens, they are collected. After passing through the energy analyzer and the mass analyzer, the ion distribution imaging of the micro area is realized at the ion detection end. The present invention can concentrate the primary ion beam, the secondary ion beam and the sample observation on the same side of the sample, that is, in all directions close to the side of the substrate disk.

[0038] Specifically, a mounting groove 11 is provided on the upper end surface of the substrate disk 1, and the mounting groove 11 is used to install the first electrode assembly 2. When the immersion lens is in use, the substrate disk 1 is connected to a positive voltage and the first electrode assembly 2 is connected to a negative voltage, or the substrate disk 1 is connected to a negative voltage and the first electrode assembly 2 is connected to a positive voltage, so that an arc electric field is generated between the substrate disk 1 and the first electrode assembly 2, so that the positive ions or negative ions passing through the arc electric field are deflected and focused on a point on the side of the substrate disk away from the sample holder.

[0039] like Figure 2 As shown, the first electrode assembly 2 includes a cylindrical electrode 21 and metal rings 22 fixed on both sides of the cylindrical electrode 21. The cylindrical electrode 21 and the metal ring 22 are fixed in the mounting groove 11 through the insulating mounting assembly 3. Optionally, the upper end of the cylindrical electrode 21 is cylindrical, and the lower end is inclined inward. The upper and lower ends of the cylindrical electrode 21 are connected so that secondary ions leaving the sample surface can pass through. Optionally, the total height of the cylindrical electrode 21 ranges from 10 to 20 mm, the inner diameter of the upper end ranges from 5 to 10 mm, the radial thickness ranges from 1 to 6 mm, and the diameter of the through hole in the middle of the lower end ranges from 3 to 8 mm.

[0040] The insulating mounting assembly 3 includes a ceramic washer, which is arranged under the metal ring 22 and is used to separate the metal ring 22 and the substrate disk 1, so that the metal ring 22 and the substrate disk 1 are insulated from each other, and at the same time a gap is left between the cylindrical electrode 21 and the substrate disk 1, so that they do not contact each other and can be connected to different voltages respectively, thereby generating an electric field.

[0041] Optional, such as Figure 3 and Figure 4 As shown, the ceramic gasket includes an annular ceramic 31, the upper end face of the annular ceramic 31 abuts against the lower end face of the metal ring 22, so that the metal ring 22 is separated from the substrate disk 1. Optionally, the ceramic gasket may also include a stepped annular ceramic 32, the upper ring diameter of the stepped annular ceramic 32 is larger than the lower ring of the stepped annular ceramic 32, the lower end face of the upper ring of the stepped annular ceramic 32 abuts against the upper end face of the annular ceramic 31, the lower ring of the stepped annular ceramic 32 abuts against the mounting groove surface in the substrate disk 1, and the metal ring 22 is sleeved outside the upper ring of the stepped annular ceramic 32. The annular ceramic 31 and the stepped annular ceramic 32 are used together to effectively play a positioning role.

[0042] Correspondingly, the mounting groove 11 is three interconnected circular grooves, which match the shapes of the cylindrical electrode 21, the metal ring 22 and the ceramic gasket, and the mounting groove corresponding to the cylindrical electrode passes through the substrate disc. Preferably, the shape of the two circular grooves in the mounting groove 11 corresponding to the metal rings 22 on both sides is a stepped groove, so that the mounting groove 11 matches the stepped ring-shaped ceramic 32. Preferably, the diameter of the circular groove is larger than the diameter of the cylindrical electrode 21 and the metal ring 22, so that there is a radial gap between the circular groove and the cylindrical electrode and between the circular groove and the metal ring, and they do not contact each other. Optionally, the outer diameter of the two fixed metal rings 22 ranges from 10 to 15 mm, the radial thickness ranges from 1 to 5 mm, and the corresponding stepped groove diameter in the disc ranges from 15 to 25 mm.

[0043] Optionally, threaded holes are further provided in the two circular grooves in the mounting groove 11 corresponding to the metal ring 22 , and the insulating mounting assembly 3 further includes screws, which pass through the stepped annular ceramic 32 to assemble and fix the first electrode assembly 2 and the substrate disk 1 .

[0044] like Figure 5As shown, the immersion lens in the embodiment of the present invention further includes a metal strip 5, a through hole is provided on one side of the substrate disk 1, and an insulating component is provided in the through hole, so that the substrate disk 1 and the metal strip 5 are insulated from each other, one end of the metal strip 5 passes through the through hole and the insulating component in the through hole in turn to contact the metal ring 22 on the same side of the through hole, and the other end is connected to the vacuum flange electrode outside the substrate disk 1, so that the metal ring 22 of the first electrode assembly 2 can be applied with voltage through the metal strip 5, and because the substrate disk 1 and the metal strip 5 are insulated from each other, the substrate disk 1 can also be applied with a voltage different from that of the metal strip 5. In the embodiment of the present invention, the insulating component is a cylindrical insulating ceramic 4, and the cylindrical insulating ceramic 4 is laid in the through hole. Optionally, the voltage connected to the cylindrical electrode 21 and the substrate disk electrode ranges from 2 to 8 kV.

[0045] The materials of the substrate disk, cylindrical electrode, metal ring and metal strip are all non-magnetic materials and cannot be magnetized by the outside world.

[0046] The principle of the immersion lens of the present invention focusing the secondary ions leaving the sample surface is as follows Figure 6 and Figure 7 As shown, Figure 6 and Figure 7 The ion trajectory diagram and ion potential distribution diagram are shown under the immersion lens composed of the cylindrical electrode and the substrate disk electrode at different potentials, and the incident direction is parallel to the optical axis of the ion light path (hereinafter referred to as the axis). In a specific embodiment, Figure 6 As shown, the substrate disk electrode is connected to a positive voltage U a , connect negative voltage U to the cylindrical electrode b When the electric field is in the arc shape, an arc electric field will be generated between the two electrodes. There is an equipotential surface MN at the center of the electric field. Before and after the ions enter the electric field, Figure 6 Taking the ion trajectory points A, B, C, and D in the image as an example, all ions emitted from the sample surface are subject to the same effect when passing through the electric field. In theory, they are focused on a point outside the electric field of the immersion lens. The actual position of the intersection with the axis is related to many factors such as the electric field strength and ion energy. The specific process is as follows:

[0047] The sample with high voltage positive charge generates charged ions or ion clusters, uncharged atoms or atomic clusters under the bombardment of primary ions. There are positively charged ions with incident direction parallel to the axis at point A on the sample surface. Under the action of the electrostatic field, they move in the direction away from the positively charged sample (Z-axis direction), and then enter the electric field of the immersion lens. The charged ions move to point B and enter the arc electric field of the immersion lens. The ion trajectory is deflected toward the axis due to the action of the electric field force F perpendicular to the equipotential surface and pointing to the axis. In the electric field to the right of the electric field center plane MN, such as point C, the force F on the ions points to the direction away from the axis. However, in this part of the electric field, the ions have a relatively large speed due to the acceleration, so that the deflection of the ions away from the axis is much smaller than the deflection toward the axis in the electric field on the left. Therefore, in general, the ions are still deflected toward the axis when passing through the electric field between the substrate disk electrode and the cylindrical electrode, and finally intersect with the axis at point D.

[0048] The potential distribution of the immersion lens is shown in the figure Figure 7 As shown in the figure, the curve U(z) represents the potential of ions at different positions during their movement. a with U b are the voltages applied to the substrate disk electrode and the cylindrical electrode, respectively. The slope of the change in U(z) reflects that the electric field strength at different positions of the ions in the arc electric field is different, so the electric field force on the ions is also different.

[0049] During use of an immersion lens of a secondary ion mass spectrometer provided by the present invention, a primary ion source generates a primary ion beam with an energy of several keV, which continuously bombards a micro-area on a sample surface through an ion entrance hole on a substrate disk. Secondary ions sputtered from the sample surface enter an arc electric field formed between two electrodes in the immersion lens under the action of an electrostatic field. The trajectory of the secondary ions is deflected twice under the action of the arc electric field of the immersion lens. All secondary ions emitted from the sample surface are subjected to the same action when passing through this electric field, and are finally focused on a point on a side of the substrate disk away from the sample holder. Subsequently, the focused secondary ions are collected by a detection system through a dual-focusing ion optical system for subsequent analysis by a mass spectrometer.

[0050] The present invention also provides a method for focusing secondary ions in a secondary ion mass spectrometer, the method comprising the following steps:

[0051] vertically placing an immersion lens of any of the above embodiments into a secondary ion mass spectrometer;

[0052] Putting a sample holder loaded with a sample into the secondary ion mass spectrometer and locating it on one side of the lower end surface of the substrate disk;

[0053] Connecting a positive voltage to the substrate disk and a negative voltage to the first electrode assembly, or connecting a positive voltage to the first electrode assembly and a negative voltage to the substrate disk;

[0054] The primary ion beam is bombarded on the sample surface through the ion entrance hole on the substrate disk, so that secondary ions escape from the sample surface. The secondary ions are deflected by the arc electric field between the two electrodes, so that the secondary ions are focused at a point on the side of the substrate disk away from the sample holder.

[0055] In an optional embodiment, the method further comprises the following steps:

[0056] A metal strip is arranged through one side of the substrate disk, so that one end of the metal strip contacts the metal ring of the first electrode assembly, and the other end is connected to the vacuum flange electrode outside the substrate disk;

[0057] A positive voltage is connected to the cylindrical electrode through a vacuum flange electrode, or a negative voltage is connected to the cylindrical electrode through a vacuum flange electrode.

[0058] The present invention provides an immersion lens in a secondary ion mass spectrometer and a method for focusing secondary ions. A cylindrical electrode is insulated and arranged on a substrate disk electrode, and voltage is applied to the two electrodes to form an arc electric field, so that the secondary ions passing through the arc electric field are subjected to the same force and are finally focused on a point outside the immersion lens. The structure is simple, the ion optical path is easy to control, and the ion beam focusing effect is good, so that the secondary ions can be collected to the greatest extent, and a stronger ion beam signal can be obtained, which is convenient for subsequent collection and analysis, and finally can achieve dual focusing of ion energy and ion direction.

[0059] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An immersion lens in a secondary ion mass spectrometer, arranged in the secondary ion mass spectrometer, characterized in that: include: A substrate disc, a first electrode assembly and an insulating mounting assembly, wherein the substrate disc is used as a second electrode, and a mounting groove is provided on the upper end surface of the substrate disc, and the mounting groove is used to mount the first electrode assembly; the substrate disc is used to connect a positive voltage, and the first electrode assembly is used to connect a negative voltage, or the substrate disc is used to connect a negative voltage, and the first electrode assembly is used to connect a positive voltage; an arc electric field is generated between the first electrode assembly and the second electrode, so that secondary ions passing through the arc electric field are subjected to the same force and are finally focused on one point; The first electrode assembly includes a cylindrical electrode and metal rings fixed on both sides of the cylindrical electrode, and the cylindrical electrode and the metal rings are fixed in the mounting groove through the insulating mounting assembly; The insulating mounting assembly comprises a ceramic washer, which is arranged under the metal ring and used to separate the metal ring from the substrate disk, while leaving a gap between the cylindrical electrode and the substrate disk.

2. The immersion lens in a secondary ion mass spectrometer according to claim 1, characterized in that: The mounting groove is three interconnected circular grooves, which match the shapes of the cylindrical electrode, the metal ring and the ceramic gasket. The diameter of the circular groove is larger than the diameter of the cylindrical electrode and the metal ring, so that there is a radial gap between the circular groove and the cylindrical electrode and between the circular groove and the metal ring, and they do not contact each other.

3. The immersion lens in a secondary ion mass spectrometer according to claim 1, characterized in that: The ceramic gasket comprises an annular ceramic, and the upper end surface of the annular ceramic abuts against the lower end surface of the metal ring.

4. The immersion lens in a secondary ion mass spectrometer according to claim 3, characterized in that: The ceramic gasket also includes a stepped annular ceramic, the upper ring of which has a diameter larger than the lower ring of which, the lower end surface of the upper ring of which abuts against the upper end surface of the annular ceramic, the lower ring of which abuts against the mounting groove surface in the substrate disk, and the metal ring is sleeved outside the upper ring of the stepped annular ceramic.

5. The immersion lens in a secondary ion mass spectrometer according to claim 4, characterized in that: The two circular grooves in the installation groove corresponding to the metal ring are in the shape of stepped grooves, which match the stepped circular ring-shaped ceramic.

6. The immersion lens in a secondary ion mass spectrometer according to claim 1, characterized in that: It also includes a metal strip, a through hole is penetrated on one side of the substrate disk, an insulating component is arranged in the through hole, one end of the metal strip passes through the through hole and the insulating component in the through hole and contacts the metal ring on the same side of the through hole, and the other end is connected to the vacuum flange electrode outside the substrate disk.

7. The immersion lens in a secondary ion mass spectrometer according to claim 1, characterized in that: The upper end of the cylindrical electrode is cylindrical, and the lower end is inclined inwards, and the upper and lower ends of the cylindrical electrode are connected.

8. The immersion lens in a secondary ion mass spectrometer according to claim 5, characterized in that: The insulating mounting assembly further comprises screws, and the first electrode assembly is assembled and fixed with the threaded holes of the substrate disk by means of the screws passing through the stepped circular ring-shaped ceramic.

9. A method for focusing secondary ions in a secondary ion mass spectrometer, characterized in that: The following steps are involved: Vertically placing an immersion lens according to any one of claims 1 to 8 into a secondary ion mass spectrometer; Putting a sample holder loaded with a sample into the secondary ion mass spectrometer and locating it on one side of the lower end surface of the substrate disk; Connecting a positive voltage to the substrate disk and a negative voltage to the first electrode assembly, or connecting a positive voltage to the first electrode assembly and a negative voltage to the substrate disk; The primary ion beam is bombarded on the sample surface through the ion entrance hole on the substrate disk, so that secondary ions escape from the sample surface. The secondary ions are deflected by the arc electric field between the two electrodes, so that the secondary ions are focused at a point on the side of the substrate disk away from the sample holder.

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