A sample preparation method for secondary ion mass spectrometry analysis of porous materials and its use

Abstract

The application provides a sample preparation method for analyzing secondary ion mass spectrum analysis of a porous material and application thereof, and the sample preparation method comprises the following steps: preparing a sheet sample from a sample to be detected, then taking two sheet samples, contacting the detection surfaces of the two sheet samples oppositely and applying pressure, maintaining the pressure, releasing the pressure, and optionally taking one of the two sheet samples as a test sample; placing a hollow metal sheet at a hollow part of a secondary ion mass spectrum sample stage, placing the detection surface of the test sample opposite to the hollow metal sheet and flattening the test sample, and completing the sample preparation. The method provided by the application does not damage the pore structure of the surface of the porous material, can obviously improve the secondary ion mass spectrum signal of the porous material, obviously improves the detection repeatability, the mass spectrum signal can be repeated after multiple tests, and is beneficial to the secondary ion mass spectrum analysis of the porous material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary ion mass spectrometry, and particularly relates to a sample preparation method for secondary ion mass spectrometry analysis of a porous material and application thereof. BACKGROUND

[0002] The secondary ion mass spectrometry (SIMS) analysis of a porous material usually causes various problems due to the unique physical structure of the porous material, high porosity, large specific surface area and low density. Because the SIMS test requires an atomically flat surface, the surface of the porous material has a large height difference and a suspended structure, which greatly affects the secondary ion yield. On the other hand, due to the low-density hole structure of the surface, the lower signal will also be detected when the surface mass spectrum signal is detected, further causing poor reproducibility and poor interpretability of the collected mass spectrum signal. Usually, for the analysis of such samples, the conventional method is to test a small piece of sample (for example, 5*5mm in size) fixed on a conductive tape, but experiments show that when the thickness of the selected film is relatively thick (greater than 2mm), the sample has very poor conductivity, which causes the effective secondary ion mass spectrum signal to be unable to be obtained; if the sample thickness is reduced, such as less than 1mm, the thin sheet sample preparation method has high difficulty and low success rate. When the less than 1mm thick sheet is fixed on the conductive tape, although the mass spectrum signal can be detected, the double peak / abnormal peak phenomenon still occurs, and the reproducibility is poor, that is, the mass spectrum signal cannot be repeated in multiple tests, and the secondary ion mass spectrum signal of the porous material itself cannot be obtained.

[0003] CN112229699A discloses a sample preparation method for dynamic secondary ion mass spectrometry (D-SIMS) analysis, which is particularly suitable for testing a sample to be tested with a face side length of not more than 200μm. The preparation method is as follows: the adhesive tape is attached to a flat carrier; the mold has two open ends, the open end part of one end is folded to attach the mold material to the adhesive tape, the sample to be tested and the casting material are put in through the other open end, the test surface of the sample to be tested is attached to the adhesive tape, and the carrier material is obtained; the carrier material is heated, and the heating temperature is not less than the melting point of the casting material; after the casting material is melted, the height of the liquid casting material is higher than that of the sample to be tested; after heating is completed, the mold is removed; the carrier and the adhesive tape are removed, and the sample to be tested is embedded in the casting material, and the sample preparation is completed. The sample prepared by the method has high sample preparation success rate, and the analysis accuracy and precision are greatly improved, and the problem of inaccurate D-SIMS analysis results and easy introduction of pollution in the past is overcome. However, it still belongs to the adhesive tape sample preparation method and is difficult to be used in the detection of porous materials.

[0004] Therefore, how to provide a sample preparation method capable of being used in the secondary ion mass spectrometry analysis of a porous material has become a problem to be solved. SUMMARY

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a sample preparation method for secondary ion mass spectrometry analysis of porous materials and its application. The method provided by this invention does not damage the pore structure of the porous material surface, significantly improves the secondary ion mass spectrometry signal of the porous material, and significantly enhances detection repeatability. Multiple tests yield reproducible mass spectrometry signals, which is beneficial for the secondary ion mass spectrometry analysis of this type of porous material.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a sample preparation method for secondary ion mass spectrometry analysis of porous materials, the sample preparation method comprising the following steps:

[0008] The sample to be tested is prepared into a sheet sample. Then, two sheet samples are taken, their test surfaces are brought into contact and pressure is applied and maintained. After the pressure is released, one of the sheets is randomly selected as the test sample.

[0009] Place the test surface of the sample onto the cutout area of ​​the secondary ion mass spectrometry sample stage and flatten it to complete the sample preparation.

[0010] The above method utilizes the "mirror contact compression method," which involves placing the test surfaces of two samples in relative contact to form a "mirror contact" structure for pressure application. This method effectively compacts the sample without damaging the pore structure on the surface of the porous material, avoiding interference from the lower layer of the porous material. Furthermore, the contact between the test surfaces prevents the introduction of additional contamination, significantly improving the secondary ion mass spectrometry signal of the porous material. It also significantly enhances detection repeatability, allowing for reproducible mass spectrometry signals from multiple tests, which is beneficial for the secondary ion mass spectrometry analysis of this type of porous material.

[0011] Preferably, the thickness of the sheet sample is 0.5-1 cm, such as 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm or 1 cm, but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0012] Preferably, the size of the sheet-like sample does not exceed 1cm × 1cm.

[0013] Preferably, the applied pressure is 10-30 MPa, such as 10 MPa, 15 MPa, 20 MPa, 25 MPa or 30 MPa, but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0014] Preferably, the pressurization process is a uniform pressurization.

[0015] Preferably, the time for the pressure maintaining is 0.5-2 min, for example, 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, 1.6 min, 1.7 min, 1.8 min, 1.9 min or 2 min, etc., but not limited to the above listed values, other values not listed in the above range are also applicable.

[0016] The above pressure applying and pressure maintaining process can effectively ensure the flatness of the test surface of the test sample, the pore structure is not damaged, the surface density is higher, and the test sample is more compact, thereby effectively improving the detection repeatability.

[0017] Preferably, the thickness of the test sample is not higher than 1 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, etc., but not limited to the above listed values, other values not listed in the above range are also applicable.

[0018] Preferably, the thickness of the test sample is 0.2-0.8 mm.

[0019] Preferably, the instruments and tools used in the sample preparation method are cleaned.

[0020] In another aspect, the application also provides the use of the sample preparation method as described above in the secondary ion mass spectrometric analysis of porous materials.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] The application provides a sample preparation method for the secondary ion mass spectrometric analysis of porous materials, which utilizes the "mirror contact pressing method" to press two test surfaces of test samples into contact with each other to form a "mirror contact" structure, so as to effectively compact the test sample without damaging the pore structure of the porous material, avoid the interference of the lower layer signal of the porous material, and prevent the introduction of additional pollution due to the contact between the test surfaces, thereby significantly improving the secondary ion mass spectrometric signal of the porous material and the detection repeatability, and the mass spectrometric signal can be repeated after multiple tests, which is conducive to the secondary ion mass spectrometric analysis of the porous material. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the sample sheet in Examples 1-5;

[0024] Figure 2 is a schematic diagram of the mirror contact pressing method in Examples 1-5;

[0025] Figure 3 is a schematic diagram of the structure of the sample after pressing in Examples 1-5;

[0026] Figure 4 is a secondary ion mass spectrum of the sample obtained in Example 1 at different positions;

[0027] Figure 5 is a comparison result of the secondary ion mass spectrum of the sample obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be further illustrated by specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0029] The instruments and tools used in the following methods are cleaned.

[0030] Example 1

[0031] This embodiment provides a sample preparation method for secondary ion mass spectrometry analysis of porous materials, and the specific steps are as follows:

[0032] 1. Use a clean blade to remove two sample slices of 5x5mm and similar size and shape (polyethylene foam, such as Figure 1 as shown in the following example).

[0033] 2. Press the sample using the "mirror contact pressing method" (see Figure 2 ): Place one of the sample slices (sample A) in the center of the lower mold cavity of a clean tablet press mold, with the test surface facing up. Carefully place the other sample slice (sample B) on top of sample A, ensuring that the test surface is in contact with the test surface of sample A, forming a "mirror contact" structure.

[0034] 3. Pressing: Apply pressure, gently place the upper mold head of the mold in the center of the tablet press, and apply pressure smoothly and slowly, with a pressure of 20 MPa. The pressure should be uniform during the pressing process to avoid impact.

[0035] 4. Pressure holding: Hold the target pressure for 1 minute.

[0036] 5. Pressure release and removal: Slowly release the pressure and carefully open the mold. At this time, the two sample slices will be tightly attached due to the pressure (thickness 0.5 mm).

[0037] 6. Separate the samples: Carefully take out the pressed "mirror contact" structure from the mold with tweezers. The two pieces of the sample will usually separate more easily. Optionally, one piece (sample A) is used as the test sample (pressed sample, higher surface density, becomes more compact, as shown in Figure 3 ).

[0038] 7. Fix the sample on the SIMS sample stage using the back fixation method: Place the test sample to be tested face down on the hollowed-out part of the sample stage, and press the back of the test sample with a metal aluminum block to ensure that the surface of the test sample is flat and in good contact with the sample stage. It is necessary to ensure that the sample is fixed firmly and does not shake.

[0039] 8. After the sample is prepared, it can be sent into the SIMS cavity for testing after vacuumizing.

[0040] The results of detecting different positions of the sample are shown in Figure 4 , which shows that the images of different positions of the same porous material sample are highly consistent, indicating that the method of the present application has high repeatability.

[0041] Example 2

[0042] The present embodiment provides a sample preparation method for analyzing the secondary ion mass spectrum of a porous material, and the specific steps are as follows:

[0043] 1. Use a clean blade to take off two pieces of sample slices with a size of 1x1 cm and a thickness of 1 cm (as shown in Figure 1 ).

[0044] 2. Press the sample using the "mirror contact pressing method" (see Figure 2 ): Place one of the sample pieces (sample A) in the center of the lower mold cavity of a clean tablet press mold, with the test surface facing up. Carefully cover the other sample piece (sample B) on top of sample A, ensuring that the test surface of sample B is in contact with the test surface of sample A, forming a "mirror contact" structure.

[0045] 3. Pressing: Apply pressure, gently place the upper mold head of the mold in the center of the tablet press, and apply pressure smoothly and slowly, with a pressure of 30 MPa. The pressure should be uniform during the pressing process to avoid impact.

[0046] 4. Pressure holding: Hold the target pressure for 0.5 minutes.

[0047] 5. Pressure release and removal: Slowly release the pressure and carefully open the mold. At this time, the two pieces of the sample will be tightly attached due to the pressure (thickness 0.8 mm).

[0048] 6. Separate the samples: Carefully take out the pressed "mirror contact" structure from the mold with tweezers. The two pieces of the sample will usually separate more easily. Optionally one piece (sample A) is used as the test sample (the pressed sample, the surface density is higher, becomes more compact, the schematic diagram is as shown in Figure 3 ).

[0049] 7. Fix the sample on the SIMS sample stage with the back fixed method: Place the test sample to be tested face to face with the hollow part of the sample stage, and press the back of the test sample with a metal aluminum block to ensure that the surface of the test sample is flat and in good contact with the sample stage. It is necessary to ensure that the sample is fixed firmly and does not shake.

[0050] 8. After the sample is prepared, it can be sent into the SIMS cavity for testing after vacuumizing.

[0051] Example 3

[0052] This embodiment provides a sample preparation method for analyzing the secondary ion mass spectrum of porous materials, and the specific steps are as follows:

[0053] 1. Use a clean blade to take off two pieces of sample slices with a size of 5x5mm and a thickness of 0.5cm (as shown in Figure 1 ).

[0054] 2. Press the sample using the "mirror contact pressing method" (see Figure 2 ): Place one piece of sample (sample A) in the center of the lower mold cavity of the clean tablet pressing mold, with the test surface facing up. Carefully cover the other piece of sample (sample B) on top of sample A, ensuring that its test surface is in contact with the test surface of sample A, forming a "mirror contact" structure.

[0055] 3. Pressing: Apply pressure, gently place the upper mold head of the mold in the center of the tablet press, and apply pressure smoothly and slowly, with a pressure of 10 MPa. The pressure process is uniform to avoid impact.

[0056] 4. Pressure holding: Hold at the target pressure for 2 minutes.

[0057] 5. Pressure release and removal: Slowly release the pressure, and carefully open the mold. At this time, the two pieces of sample will be tightly attached due to the pressure (thickness 0.2mm).

[0058] 6. Separate the samples: Carefully take out the pressed "mirror contact" structure from the mold with tweezers. The two pieces of the sample will usually separate more easily. Optionally one piece (sample A) is used as the test sample (the pressed sample, the surface density is higher, becomes more compact, the schematic diagram is as shown in Figure 3 ).

[0059] 7. Fix the sample on the SIMS sample stage by back fixation: Place the test sample with the surface to be tested facing the hollowed-out part of the sample stage, and press the back of the sample flat with a metal aluminum block to ensure that the surface to be tested is flat and in good contact with the sample stage. It is necessary to ensure that the sample is firmly fixed and does not move.

[0060] 8. After the sample is prepared, it can be sent into the SIMS cavity for testing after vacuum pumping.

[0061] Example 4

[0062] This example provides a sample preparation method for secondary ion mass spectrometry analysis of porous materials, the specific steps are as follows:

[0063] 1. Use a clean blade to remove two pieces of sample sheet with a size of 5x5 mm and a thickness of 0.8 cm (as shown in Figure 1 ).

[0064] 2. Use the "mirror contact pressing method" to press the sample (see Figure 2 ): Place one of the samples (sample A) in the center of the lower mold cavity of the clean tablet press mold, with the surface to be tested facing up. Carefully cover the other sample (sample B) on top of sample A, ensuring that the surface to be tested is in contact with the surface to be tested of sample A, forming a "mirror contact" structure.

[0065] 3. Pressing: Apply pressure, gently place the upper mold head of the mold in the center of the tablet press, and apply pressure smoothly and slowly, with a pressure of 40 MPa. The pressure should be uniform during the pressing process to avoid impact.

[0066] 4. Pressure holding: Hold at the target pressure for 25 s.

[0067] 5. Pressure release and removal: Slowly release the pressure and carefully open the mold. At this time, the two samples will be tightly attached due to the pressure (thickness 0.5 mm).

[0068] 6. Separate the samples: Carefully remove the "mirror contact" structure from the mold with tweezers. The two samples will usually be relatively easy to separate. Optionally, one of the samples (sample A) can be used as the test sample (the pressed sample, the surface density is higher and becomes more compact, as shown in Figure 3 ).

[0069] 7. Fix the sample on the SIMS sample stage by back fixation: Place the test sample with the surface to be tested facing the hollowed-out part of the sample stage, and press the back of the sample flat with a metal aluminum block to ensure that the surface to be tested is flat and in good contact with the sample stage. It is necessary to ensure that the sample is firmly fixed and does not move.

[0070] 8. After the sample is prepared, it can be sent into the SIMS cavity for vacuum pumping and testing.

[0071] The different positions of the sample were detected, and the effective mass spectrum signal could not be detected due to poor pressing effect.

[0072] Example 5

[0073] The embodiment provides a sample preparation method for secondary ion mass spectrum analysis of a porous material, and the specific steps are as follows:

[0074] 1. A clean blade is used to take off two sample slices with a size and shape similar to each other (for example, as shown in FIG. 1) with a size of 5*5 mm and a thickness of 0.8 cm. Figure 1

[0075] 2. The sample is pressed by using a “mirror contact pressing method” (see FIG. 2): one of the sample slices (sample A) is placed in the center of the lower die cavity of a clean tablet pressing mold, and the surface to be detected faces upward. The other sample slice (sample B) is carefully covered on the sample A, and the surface to be detected is ensured to be in contact with the surface to be detected of the sample A, so as to form a “mirror contact” structure. Figure 2

[0076] 3. Pressing: the upper die head of the mold is gently placed in the center of the tablet press, and the pressure is steadily and slowly applied. The pressure is 7 MPa, and the pressure process is uniform to avoid impact.

[0077] 4. Pressure keeping: the target pressure is kept for 2.5 minutes.

[0078] 5. Pressure release and taking out: the pressure is slowly released, and the mold is carefully opened. At this time, the two sample slices are tightly attached due to the pressure (with a thickness of 0.5 mm).

[0079] 6. Separating the sample: the “mirror contact” structure after pressing is carefully taken out from the mold by using tweezers. The two sample slices are usually easy to separate. Optionally, one of the sample slices (sample A) is used as a test sample (the sample after pressing, the surface density is increased, and the sample becomes more compact, and a schematic diagram is shown in FIG. 3). Figure 3

[0080] 7. The sample is fixed on the SIMS sample table by using a back fixation method: the surface to be detected of the test sample is placed to face the hollow part of the sample table, and the surface to be detected is pressed flat by using a metal aluminum block on the back of the sample to be detected, so that the surface to be detected is ensured to be flat and in good contact with the sample table. It is necessary to ensure that the sample is fixed firmly and does not shake.

[0081] 8. After the sample is prepared, it can be sent into the SIMS cavity for vacuum pumping and testing.

[0082] ​​​The sample was detected at different positions, and effective mass spectrum signal could not be detected due to poor pressing effect.

[0083] Comparative Example 1

[0084] The present comparative example provides a sample preparation method (thin section sample preparation method) for analyzing secondary ion mass spectrum analysis of porous materials, and the specific steps are as follows:

[0085] The thin section less than 1 mm in thickness was slowly taken out directly with a blade and fixed on a conductive tape, and the sample was fixed on a secondary ion mass spectrum sample stage for direct secondary ion mass spectrum analysis.

[0086] The test results of the comparative example 1 are compared with the test results of the example 1 as shown in the following table. Figure 5 It can be found that although the mass spectrum signal can be measured by the comparative example method, the phenomenon of double peaks / abnormal peaks (as shown in the square in the middle of the figure) still occurs, and the repeatability is poor, that is, the mass spectrum signal is not repeated in multiple tests, and the secondary ion mass spectrum signal of the porous material itself cannot be obtained; while the method of the present application does not have the above problems, and has good repeatability. Figure 5

[0087] The applicant declares that the sample preparation method for analyzing secondary ion mass spectrum analysis of porous materials and its application of the present application are illustrated by the above examples, but the present application is not limited to the above examples, that is, it does not mean that the present application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

[0088] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0089] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined by any suitable method without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combination methods.​

Claims

1. A sample preparation method for secondary ion mass spectrometric analysis of a porous material, characterized by, The sample preparation method comprises the following steps: The sample to be tested is prepared into a sheet sample, and then two sheet samples are taken, the testing surfaces of which are contacted and pressed, and one of the two sheet samples is optionally taken as a test sample after pressure relief; The testing surface of the test sample is placed and flattened against the hollow part of the secondary ion mass spectrometry sample table, and the sample preparation is completed.

2. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized in that, The thickness of the sheet sample is 0.5-1 cm.

3. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized in that, The size of the sheet sample is not more than 1 cm*1 cm.

4. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized by, The pressure of the pressing is 10-30 MPa.

5. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized by, The pressure increasing process of the pressing is uniform speed.

6. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized by, The pressure maintaining time is 0.5-2 min.

7. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized by, The thickness of the test sample is not higher than 1 mm.

8. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 7, characterized in that, The thickness of the test sample is 0.2-0.8 mm.

9. The sample preparation method for secondary ion mass spectrometric analysis of a porous material according to claim 1, characterized by, The instruments and tools used in the sample preparation method are cleaned.

10. Application of the sample preparation method according to any one of claims 1-9 in secondary ion mass spectrometry analysis of porous materials.

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