A secondary ion extraction device for secondary ion mass spectrometry

Abstract

The application belongs to the technical field of mass spectrometers, in particular to a secondary ion extraction device for secondary ion mass spectrometry, which comprises a sample table, an extraction cone shell and a five-ring deceleration focusing system arranged in sequence from bottom to top, the extraction cone shell is internally provided with an ion extraction system, a sample is placed on the sample table, the ion extraction system comprises an extraction electrode, a front ground electrode, a single lens electrode and a rear ground electrode arranged in sequence from bottom to top, and each electrode is connected and separated by an insulating ring; the five-ring deceleration focusing system comprises a middle-aperture metal shielding shell, four ring electrodes and a differential electrode sheet arranged in sequence from bottom to top, and the four ring electrodes, the metal shielding shell and the ring electrodes, and the ring electrodes and the differential electrode sheet are connected and separated by insulating rings. The application can extract secondary ions from the surface of the sample, has a compact structure, a small volume and ensures optical microscopic imaging compatibility.

Description

Technical Field

[0001] This invention belongs to the field of mass spectrometry analysis technology, specifically a secondary ion extraction device for secondary ion mass spectrometry. Background Technology

[0002] Mass spectrometry instruments, characterized by high resolution, high sensitivity, and high throughput, are currently widely used in atmospheric environmental monitoring, food testing, industrial processes, and scientific analysis. Conventional mass spectrometry analysis techniques provide the mass-to-charge ratio and intensity information of a single sample, enabling qualitative and quantitative detection of analytes. Mass spectrometry imaging technology is used in chemical, biological, and pharmaceutical research to analyze the distribution and concentration of different molecules in a sample. Its basic principle is to bombard the sample surface with a focused laser or ion beam. The resulting secondary ions are collected by an ion extraction cone and transported by an ion transport system before entering the mass spectrometer for analysis.

[0003] Mass spectra at different spatial coordinates can be acquired by scanning with a laser / ion beam or moving the sample stage. After data processing, the spatial coordinates and intensity information of different molecules on the surface can be obtained. Ion extraction systems play a crucial role in mass spectrometry. First, they improve sensitivity: a well-designed ion extraction system can increase the extraction efficiency of secondary ions by improving the angle and energy divergence, and reduce the influence of ion beam eccentricity at different sites. Second, they improve mass resolution: in high-field extraction, inconsistent target surface roughness leads to changes in the tip electric field, reducing mass resolution. Finally, they increase the field of view: ion extraction systems are important for large-field imaging.

[0004] The patent application CN105572216A, published on May 11, 2016, entitled "A Novel Time-of-Flight Secondary Ion Mass Spectrometer," discloses a mass spectrometer including a secondary ion extraction system. This secondary ion extraction system consists of two parallel, coaxially arranged electrodes, each with a DC voltage applied at a specific ratio. The electrode closer to the sample is a planar electrode, while the electrode further away is a conical electrode, which is grounded. This type of secondary ion extraction system has low extraction efficiency, a simple design, and lacks microscopic imaging technology, making it impossible to observe changes on the sample surface. Summary of the Invention

[0005] To address the issues of low-field extraction having a small impact on the deflection of the primary ion beam but low extraction efficiency and difficulty in matching the extraction system with TOF (Time-of-Flight mass spectrometry), the present invention aims to provide a secondary ion extraction device for secondary ion mass spectrometry.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention includes a sample stage, an extraction cone shell, and a five-ring deceleration focusing system arranged sequentially from bottom to top. The extraction cone shell houses an ion extraction system. A sample is placed on the sample stage. The ion extraction system, located above the sample, includes an extraction electrode, a front ground electrode, a single-lens electrode, and a rear ground electrode arranged sequentially from bottom to top. The extraction electrode, front ground electrode, single-lens electrode, and rear ground electrode are connected and separated by insulating rings. The five-ring deceleration focusing system is used for decelerating and focusing secondary ions. It includes a metal shielding shell with a central opening, four ring electrodes, and a differential electrode plate arranged sequentially from bottom to top. The four ring electrodes, the metal shielding shell and the ring electrodes, and the ring electrodes and the differential electrode plate are connected and separated by insulating rings.

[0008] Wherein: the single lens electrode consists of three hollow cylinders, which are uniformly arranged along the circumferential direction between the front ground electrode and the rear ground electrode, and a voltage is applied between the three hollow cylinders.

[0009] The single-lens electrode is a hollow cylinder, which is evenly divided into an even number of lobes along the circumference, with a gap between adjacent lobes, and a voltage is applied to each lobe individually.

[0010] The axial center lines of the extraction electrode, the front ground electrode, the single lens electrode, the rear ground electrode, the metal shielding shell, the four circular electrodes, and the differential electrode sheet are collinear.

[0011] The extraction electrode, front ground electrode, single lens electrode, rear ground electrode, metal shielding shell, four circular electrodes, and differential electrode sheet each have through holes with collinear axial center lines.

[0012] The four annular electrodes are arranged from bottom to top as annular electrode A, annular electrode B, annular electrode C, and annular electrode D. The metal shielding shell and annular electrode B are grounded respectively. Positive voltages are applied to annular electrode A and annular electrode D respectively, and negative voltages are applied to annular electrode C.

[0013] The lower part of the extraction cone shell is a hollow frustum, and the upper part is a hollow cylinder. Both the upper and lower ends of the extraction cone shell are open structures.

[0014] The metal shielding shell has a disc-shaped structure with a central opening at the bottom and an open structure at the top.

[0015] The advantages and positive effects of this invention are as follows:

[0016] 1. This invention enables secondary ion extraction from the sample surface, has a compact structure and small size, and ensures compatibility with optical microscopy imaging.

[0017] 2. The present invention can apply different voltages to a single lens electrode, so that the ion beam is concentrated in the central region of the extraction cone, thereby improving the extraction efficiency.

[0018] 3. The present invention also optimizes the extraction technology route, which enables ions to be decelerated and cooled better, and to be extracted into the transmission system more efficiently.

[0019] 4. This invention has minimal impact on the deflection of the primary ion beam, high extraction efficiency, and easy matching between the extraction system, ion transport system, and TOF.

[0020] 5. This invention can solve the attenuation problem of photoionization mass spectrometers during long-term use, and has broad application prospects in the field of in-situ online mass spectrometry technology. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Wherein: 1 is the sample stage, 2 is the sample, 3 is the secondary ion beam, 4 is the extraction cone shell, 5 is the insulating ring, 6 is the single lens electrode, 7 is the rear ground electrode, 8 is the front ground electrode, 9 is the extraction electrode, 10 is the circular electrode A, 11 is the circular electrode B, 12 is the circular electrode C, 13 is the circular electrode D, 14 is the metal shielding shell, and 15 is the differential electrode sheet. Detailed Implementation

[0023] The invention will now be described in further detail with reference to the accompanying drawings.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0028] like Figure 1 As shown, the present invention includes a sample stage 1, an extraction cone shell 4, and a five-ring deceleration focusing system arranged sequentially from bottom to top. An ion extraction system is housed inside the extraction cone shell 4. A sample 2 is placed on the sample stage 1. The ion extraction system is located directly above the sample 2 and includes an extraction electrode 9, a front ground electrode 8, a single-lens electrode 6, and a rear ground electrode 7 arranged sequentially from bottom to top. These electrodes are connected and separated by insulating rings 5. The five-ring deceleration focusing system is used for decelerating and focusing secondary ions. It includes a metal shielding shell 14 with a central opening, four ring electrodes, and a differential electrode plate 15 arranged sequentially from bottom to top. The four ring electrodes, the metal shielding shell 14 and the ring electrodes, and the ring electrodes and the differential electrode plate 15 are connected and separated by insulating rings 5. The metal shielding shell 14 provides shielding protection to prevent voltage penetration to the front end. The voltage applied to each ring electrode is determined by the target voltage and can be determined through simulation.

[0029] The single-lens electrode 6 has a length of 6-10 mm and consists of three hollow cylinders evenly arranged circumferentially between the front ground electrode 8 and the rear ground electrode 7. A voltage is applied between the three hollow cylinders. Alternatively, the single-lens electrode 6 can be a single hollow cylinder, which is evenly divided into an even number of lobes circumferentially, with a gap between adjacent lobes. A voltage is applied to each lobe individually. In this embodiment, the single-lens electrode 6 is a hollow cylinder divided into four equal lobes, forming a quarter ring. There is a 1 mm gap between adjacent lobes of the quarter ring, and a voltage is applied to each lobe individually. The material is stainless steel with a thickness of 1-3 mm. Dividing the single-lens electrode 6 into four lobes for individual voltage application allows for focusing and flexible voltage adjustment, correcting the eccentricity of the secondary ion beam 3, aligning the secondary ions with the center of the extraction cone, and maximizing signal intensity.

[0030] In this embodiment, the extraction electrode 9, the front ground electrode 8, the single lens electrode 6, the rear ground electrode 7, the metal shielding shell 14, the four annular electrodes, and the differential electrode plate 15 are all collinear in axial direction. Each of the extraction electrode 9, the front ground electrode 8, the single lens electrode 6, the rear ground electrode 7, the metal shielding shell 14, the four annular electrodes, and the differential electrode plate 15 has a through-hole with its axial center line collinear. The through-hole in the center facilitates the uniform extraction of secondary ion currents into the transmission system.

[0031] In this embodiment, the lower part of the extraction cone shell 4 is a hollow frustum, close to the target surface of the sample 2, and the upper part of the extraction cone shell 4 is a hollow cylinder. Both the upper and lower ends of the extraction cone shell 4 are open structures. The axial centerline of the extraction cone shell 4 is collinear with the axial centerlines of the extraction electrode 9, the front ground electrode 8, the single lens electrode 6, the rear ground electrode 7, the metal shielding shell 14, the four circular electrodes, and the differential electrode plate 15.

[0032] In this embodiment, the metal shielding shell 14 has a disc-shaped structure made of stainless steel. The bottom center of the disc has an opening, and the top of the disc has an open structure.

[0033] In this embodiment, the four annular electrodes are arranged from bottom to top: annular electrode A10, annular electrode B11, annular electrode C12, and annular electrode D13. The metal shielding shell 14 and annular electrode B11 are grounded. Positive voltages are applied to annular electrodes A10 and D13, and a negative voltage is applied to annular electrode C12. Different magnitudes and polarities of voltages are applied to the five-ring deceleration focusing system. The secondary ion flow first passes through the single lens electrode 6 for deceleration and focusing, then passes through the negative voltage electrode to slightly accelerate the secondary ion flow, facilitating its passage through the aperture. Finally, a positive voltage is applied for secondary deceleration. The inner diameter of the annular electrodes can be large or small, ranging from 12mm to 20mm, while the outer diameter increases accordingly, ranging from 16mm to 25mm. In this embodiment, the inner diameters of annular electrodes A10, B11, C12, and D13 are the same as the diameter of the through-hole on the metal shielding shell 14.

[0034] The insulating ring 5 in this embodiment is made of PEek (polyether ether ketone). PEek has fewer exposed structures, which prevents signal degradation caused by charge accumulation.

[0035] In this embodiment, the extraction electrode 9, the front ground electrode 8, the single lens electrode 6, the rear ground electrode, the ring electrode, and the differential electrode sheet 15 are all made of stainless steel.

[0036] The working principle of this invention is as follows:

[0037] The secondary ion beam 3 emitted from the target surface of sample 2 passes through the cone opening of the extraction cone shell 4, sequentially through the extraction electrode 9, the single lens electrode 6, and the ground electrode, and is finally cooled and focused by the five-ring deceleration focusing system before entering the ion transport system. The ion extraction process and the ion transport process do not interfere with each other and do not affect the quality of optical imaging.

[0038] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, extensions, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A secondary ion extraction device for secondary ion mass spectrometry, characterized in that: The system includes a sample stage (1), an extraction cone shell (4), and a five-ring deceleration focusing system arranged sequentially from bottom to top. The extraction cone shell (4) contains an ion extraction system. A sample (2) is placed on the sample stage (1). The ion extraction system is located above the sample (2) and includes an extraction electrode (9), a front ground electrode (8), a single lens electrode (6), and a rear ground electrode (7) arranged sequentially from bottom to top. The extraction electrode (9), the front ground electrode (8), the single lens electrode (6), and the rear ground electrode (7) are connected and separated by insulating rings (5). The five-ring deceleration focusing system is used for deceleration focusing of secondary ions and includes a metal shield shell (14) with a central opening, four ring electrodes, and a differential electrode plate (15) arranged sequentially from bottom to top. The four ring electrodes, the metal shield shell (14), and the ring electrodes are connected and separated by insulating rings (5).

2. The secondary ion extraction device for secondary ion mass spectrometry according to claim 1, characterized in that: The single lens electrode (6) consists of three hollow cylinders, which are uniformly arranged along the circumferential direction between the front ground electrode (8) and the rear ground electrode (7), and a voltage is applied between the three hollow cylinders.

3. The secondary ion extraction device for secondary ion mass spectrometry according to claim 1, characterized in that: The single-lens electrode (6) is a hollow cylinder, which is evenly divided into an even number of lobes along the circumference, with a gap between adjacent lobes, and a voltage is applied to each lobe individually.

4. The secondary ion extraction device for secondary ion mass spectrometry according to claim 1, characterized in that: The axial center lines of the extraction electrode (9), the front ground electrode (8), the single lens electrode (6), the rear ground electrode (7), the metal shielding shell (14), the four circular electrodes and the differential electrode plate (15) are collinear.

5. The secondary ion extraction device for secondary ion mass spectrometry according to claim 1, characterized in that: The extraction electrode (9), the front ground electrode (8), the single lens electrode (6), the rear ground electrode (7), the metal shielding shell (14), the four circular electrodes and the differential electrode plate (15) each have through holes with collinear axial center lines.

6. The secondary ion extraction apparatus for secondary ion mass spectrometry according to claim 1, characterized in that: The four annular electrodes are arranged from bottom to top as annular electrode A (10), annular electrode B (11), annular electrode C (12) and annular electrode D (13). The metal shielding shell (14) and annular electrode B (11) are grounded respectively. Annular electrode A (10) and annular electrode D (13) are respectively applied with positive voltage, and annular electrode C (12) is applied with negative voltage.

7. The secondary ion extraction apparatus for secondary ion mass spectrometry according to claim 1, characterized in that: The lower part of the extraction cone shell (4) is a hollow frustum and the upper part is a hollow cylinder. Both the upper and lower ends of the extraction cone shell (4) are open structures.

8. The secondary ion extraction apparatus for secondary ion mass spectrometry according to claim 1, characterized in that: The metal shielding shell (14) has a disc-shaped structure with a hole in the center of the bottom and an open structure on the top.

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