Method for measuring thickness of metal oxide film based on SKPFM

Abstract

The invention provides a method for measuring the thickness of a metal oxide film based on SKPFM. The method belongs to the technical field of metal oxide thickness measurement, and comprises the following steps: embedding a to-be-measured sample into epoxy resin, and ensuring that the to-be-measured sample is completely sealed and cured; carrying out grinding and polishing treatment on the vertical direction of the metal oxide film to be detected of the cured sample to be detected; scanning the surface potential at the junction of the sample and the epoxy resin through SKPFM; and the thickness of the metal oxide film is calculated by analyzing and processing the surface potential distribution data. The surface electromotive force is measured through the SKPFM, the thickness of the oxidation film can be rapidly and accurately measured, the method has the advantages of being non-destructive, high in precision, easy to operate, wide in adaptability and the like, a brand new means is provided for detection of the thickness of the oxidation film of a metal material, and the method can be used for laboratory research and can also be used for detecting the thickness of the oxidation film of the metal material. The device can also be used as a quality control tool in the actual production process.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal oxide thickness measurement, and in particular relates to a method for measuring the thickness of a metal oxide film based on SKPFM. Background Art

[0002] In the manufacturing and application process of metal materials, especially in the fields of aerospace, nuclear energy, petrochemicals, etc., metal materials are easily oxidized to form oxide films under high temperature and complex service environments. The thickness and structure of these oxide films have a direct impact on material performance and service life. Accurately measuring and controlling the thickness of the oxide film is crucial to optimizing the protective performance of metal materials and extending their service life. It can guide the design of metal materials, the optimization of production processes, and maintenance during use. Therefore, the measurement of oxide film thickness is of great significance for improving production efficiency and product quality, reducing production costs and material waste.

[0003] Traditional methods for measuring oxide film thickness mainly include X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). These methods can accurately measure the thickness of oxide films at the nanometer level to a certain extent, but they also have some significant disadvantages. For example, XPS requires the sample to be irradiated with high-energy photons in a vacuum environment, which may cause damage to the oxide film of some samples and affect the measurement results; TEM requires ultra-thin slice preparation of the sample, which is complicated to operate and has a certain degree of destructiveness to the sample; ellipsometers have high requirements on the surface state of the sample and can only measure transparent or translucent film layers, and the measurement accuracy of opaque metal oxide films is limited. In addition, these methods usually require expensive instruments and complex pretreatment, which is time-consuming and costly, and cannot meet the needs of fast and convenient measurement of oxide film thickness in actual production processes. Summary of the invention

[0004] To solve the above problems, the present invention provides a method for measuring the thickness of metal oxide films based on SKPFM. By measuring the surface electromotive force through SKPFM, the thickness of the oxide film can be measured quickly and accurately. This method has the advantages of non-destructiveness, high precision, simple operation and wide adaptability. It provides a new means for detecting the thickness of oxide films of metal materials. It can not only be used for laboratory research, but also as a quality control tool in the actual production process, providing a scientific basis for material selection, process optimization and product reliability, and helping to promote the development of materials science and surface analysis technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for measuring the thickness of a metal oxide film based on SKPFM, comprising: embedding a sample to be tested into epoxy resin to ensure that the sample to be tested is completely sealed and cured; grinding and polishing the vertical direction of the metal oxide film to be tested of the cured sample to be tested; scanning the surface potential at the interface between the sample and the epoxy resin by SKPFM; and calculating the thickness of the metal oxide film by analyzing and processing surface potential distribution data.

[0007] Furthermore, the grinding and polishing treatment includes: grinding the sample to be tested in a manner of gradually increasing the mesh number, using at least 5000 mesh sandpaper for the final grinding, and when using the same mesh sandpaper for grinding, the grinding time does not exceed 5 minutes, the pressing force does not exceed 3N, and after there are no scratches on the surface, use a 0.5-1.5um diamond polishing spray to polish the surface to a scratch-free mirror state, and then use a silica suspension with a particle size of 0.02-0.06um for suspension polishing for 15 minutes.

[0008] Furthermore, when scanning the sample with SKPFM, the same probe is used throughout the process and the scanning is repeated under the same environmental conditions. If the surface potential changes by no more than 3mv, the surface is considered stable and subsequent experiments can be carried out.

[0009] Furthermore, the distance between the surface potential measurement area and the boundary is greater than 5 mm.

[0010] Furthermore, the measurement area is based on the boundary and extends at least 5 um toward the epoxy resin side and the metal sample side respectively.

[0011] Furthermore, the potential distribution data is considered valid if it has the following characteristics: an M peak; minimum potentials on both sides of the M peak; and the minimum potential on the epoxy resin side is lower than the minimum potential on the metal side.

[0012] Furthermore, the thickness of the metal oxide film is calculated as follows: the distance corresponding to the highest potential of the vertex of the M peak close to the metal side and the lowest potential close to the metal side minus the distance corresponding to the potentials of the two vertices of the M peak is subtracted to obtain the thickness of the metal oxide film.

[0013] The beneficial effects brought by the technical solution provided by the embodiment of the present invention include:

[0014] 1. Compared with TEM or XPS, the present invention uses SKPFM to scan and analyze the surface potential at the interface between the sample and the epoxy resin, which can quickly and accurately measure the thickness of the oxide film.

[0015] 2. The measuring method provided by the present invention has the advantages of non-destructiveness, high precision, simple operation and wide adaptability, and provides a new means for detecting the oxide film thickness of metal materials.

[0016] 3. The solution provided by the present invention can not only be used for laboratory research, but also can be used as a quality control tool in the actual production process, providing a scientific basis for material selection, process optimization and product reliability, and helping to promote the development of materials science and surface analysis technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of the structure of a cured sample provided in an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of surface potential detection provided by an embodiment of the present invention;

[0020] Figure 3 The morphology and surface potential map of the interface between the epoxy resin and the sample to be tested provided in Example 1 of the present invention, a is the morphology map, and b is the surface potential map;

[0021] Figure 4 A metal oxide film thickness test position diagram provided in Example 1 of the present invention;

[0022] Figure 5 for Figure 4 Surface potential diagram at a1 in the figure;

[0023] Figure 6 This is a SEM image of the same sample to be tested after fib processing provided in Example 1 of the present invention.

[0024] Reference numerals: 1, PVC tube; 2, epoxy resin; 3, sample to be tested; 4, SKPFM probe. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The embodiment of the present invention provides a method for measuring the thickness of a metal oxide film based on SKPFM, comprising:

[0027] S1. Embed the sample to be tested in epoxy resin to ensure that the sample to be tested is completely sealed and cured.

[0028] like Figure 1As shown, the sample is first pre-treated: the sample is encapsulated in a PVC tube with a diameter of 20 to 25 mm using a mixture of epoxy resin: dibutyl phthalate: ethylenediamine pentahydrate = 100:7:10, and air-dried and cured in the air.

[0029] Grinding and polishing treatment includes: grinding the sample in a gradually increasing mesh size, using at least 5000 mesh sandpaper for final grinding, using the same mesh sandpaper for grinding, the grinding time does not exceed 5 minutes, the pressing force does not exceed 3N, and after the surface is free of scratches, use a diamond polishing spray with a particle size of 0.5-1.5um to polish the surface to a scratch-free mirror state, and then use a silica suspension with a particle size of 0.02-0.06um for suspension polishing for 15 minutes to remove surface stress. Make the organization scanned by SKPFM clearer. It should be vacuum sealed before the experiment.

[0030] The sample to be tested is a metal with an oxide film.

[0031] S2. Grinding and polishing the vertical direction of the metal oxide film to be tested of the solidified sample to be tested.

[0032] The grinding and polishing treatment includes: grinding the sample to be tested in a manner of gradually increasing the mesh number, using at least 5000 mesh sandpaper for final grinding, and when the same mesh sandpaper is used for grinding, the grinding time does not exceed 5min, the pressing force does not exceed 3N, and after the surface is free of scratches, the surface is polished to a scratch-free mirror state with a diamond polishing spray with a particle size of 0.5-1.5um, and then suspended polishing is performed for 15min using a silica suspension with a particle size of 0.02-0.06um. The grinding and polishing treatment has a great influence on the surface morphology of the subsequently prepared samples. Specifically, the wear resistance of metal samples is good, and the wear resistance of epoxy resin is poor. During the grinding process, the abrasive is easily gathered at the interface between epoxy resin and metal matrix, and the degree of wear on metal oxide increases; on the other hand, the surface potentials of epoxy resin, metal oxide and metal matrix itself are different. Therefore, the present invention is based on the different wear resistance and surface potential of various materials during the grinding process, and the two are combined to calculate the thickness of metal oxide. In order to avoid excessive wear and tear, which would have a significant impact on the results, the grinding time, pressure and polishing method were limited. Otherwise, the measured data would be too messy to be analyzed and processed to obtain the metal oxide thickness to be measured in this application.

[0033] S3. Scan the surface potential at the interface between the sample and epoxy resin using SKPFM.

[0034] like Figure 2As shown, the surface state of the sample should be stable before scanning to eliminate the interference of humidity, temperature and probe. When scanning the sample with SKPFM, the same probe is used throughout the process and scanned repeatedly under the same environmental conditions. If the surface potential change does not exceed 3mv, the surface is considered stable and subsequent experiments can be carried out.

[0035] Specifically, the distance between the surface potential measurement area and the boundary is greater than 5 mm. The greater the distance between the measurement area and the boundary, the better the surface flatness of the sample to be measured, the greater the reduction of stress inhomogeneity, and the higher the accuracy of the measured metal oxide film. The measurement area is based on the boundary and extends at least 5 um to the epoxy resin side and the metal sample side to ensure that the detected surface main electromotive force can completely cover the range of the metal oxide film.

[0036] S4. Calculate the thickness of the metal oxide film by analyzing and processing the surface potential distribution data.

[0037] The potential distribution data is considered valid if it has the following characteristics: 1) it has an M peak; 2) both sides of the M peak have minimum potentials; 3) the minimum potential close to the epoxy resin side is lower than the minimum potential close to the metal side.

[0038] The thickness of the metal oxide film is calculated as follows:

[0039] The thickness of the metal oxide film is obtained by subtracting the distance corresponding to the potentials of the two vertices of the M peak from the distance corresponding to the highest potential of the vertex of the M peak close to the metal side and the lowest potential close to the metal side. The specific calculation method is described in Example 1.

[0040] In order to characterize the thickness of the metal oxide film, it is preferred in the present application to measure the thickness of the metal oxide film at least 5 locations and take the average value.

[0041] In order to further illustrate the present invention, the technical solutions protected by the present application are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0042] Example 1

[0043] The embodiment of the present invention provides a method for measuring the thickness of a metal oxide film based on SKPFM, comprising:

[0044] S1. Embed the sample to be tested in epoxy resin to ensure that the sample to be tested is completely sealed and cured. Pre-treat the sample first: use a mixture of epoxy resin: dibutyl phthalate: ethylenediamine pentahydrate = 100:7:10 to encapsulate the sample in a PVC tube with a diameter of 20 mm and air-dry and cure in the air.

[0045] S2. Grinding and polishing the vertical direction of the metal oxide film to be tested of the solidified sample to be tested.

[0046] The cured samples were polished with sandpapers of 500, 1000, 2000 and 5000 meshes. When the same sandpaper was used for polishing, the polishing time did not exceed 5 min, the pressing force did not exceed 3 N, and after the surface was free of scratches, a diamond polishing spray with a particle size of 1 um was used to polish the surface to a scratch-free mirror state, and then a silica suspension with a particle size of 0.04 um was used for suspension polishing for 15 min.

[0047] S3, scan the surface potential at the interface between the sample and epoxy resin by SKPFM, such as Figure 3 a and 3b.

[0048] S4. Calculate the thickness of the metal oxide film by analyzing and processing the surface potential distribution data.

[0049] Exemplarily, the embodiment of the present invention measures the surface potential, such as Figure 4 and 5 As shown, the electromotive force distribution data has the following characteristics: 1) it has an M peak; 2) both sides of the M peak have the lowest potential; 3) the lowest potential close to the epoxy resin side is lower than the lowest potential close to the metal side. The data of this embodiment is valid.

[0050] like Figure 5 The thickness of the metal oxide film is calculated as follows: the distance L1 corresponding to the vertex P0 of the M peak close to the metal side and the lowest potential P2 close to the metal side minus the distance L2 corresponding to the two vertices of the M peak is subtracted to obtain the thickness of the metal oxide film, that is, L1-L2 is the thickness of the metal oxide film.

[0051] In order to characterize the accuracy of the method for measuring the thickness of metal oxide film proposed in this application, the same sample was observed after being processed by FIB, and the thickness of the metal oxide film was measured, such as Figure 6 As shown, the oxide film is specifically divided into multiple rectangles with areas of S1, S2...Sn and a total length of Ln. The oxide film thickness is:

[0052] d=(S1+S2+…+Sn) / Ln=307nm

[0053] Data analysis is performed on the potential diagram to extract potential curves at a1, a2, a3, a4, and a5. Taking the potential curve at a1 as an example, the thickness of the oxide film at a1 is D1=2356-2040-10=306nm; then D=(D1+D2+D3+D4+D5) / =(306+304+310+312+295) / 5=305nm. It can be seen that the error between the thickness of the metal oxide film measured by the present application and the actual measurement data is extremely small within 1%, and can be used to measure the thickness of the metal oxide film.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring the thickness of a metal oxide film based on SKPFM, characterized in that: include: Embed the sample to be tested in epoxy resin to ensure that the sample to be tested is completely sealed and cured; Grinding and polishing the vertical direction of the metal oxide film to be tested of the solidified sample to be tested; The surface potential at the interface between the sample and epoxy resin was scanned by SKPFM; The thickness of the metal oxide film is calculated by analyzing and processing the surface potential distribution data.

2. The method according to claim 1, characterized in that The grinding and polishing treatment includes: grinding the sample to be tested in a manner of gradually increasing the mesh number, using at least 5000 mesh sandpaper for the final grinding, and when using the same mesh sandpaper for grinding, the grinding time shall not exceed 5 minutes, the pressing force shall not exceed 3N, and after there are no scratches on the surface, use a diamond polishing spray with a particle size of 0.5-1.5um to polish the surface to a scratch-free mirror state, and then use a silica suspension with a particle size of 0.02-0.06um for suspension polishing for 15 minutes.

3. The method according to claim 1, characterized in that When scanning the sample with SKPFM, the same probe is used throughout the process and the scan is repeated under the same environmental conditions. If the surface potential changes by no more than 3mv, the surface is considered stable and subsequent experiments can be carried out.

4. The method according to claim 1, characterized in that The distance between the surface potential measurement area and the boundary is greater than 5 mm.

5. The method according to claim 4, characterized in that The measurement area is based on the boundary and extends at least 5 um toward the epoxy resin side and the metal sample side respectively.

6. The method according to claim 1, characterized in that The potential distribution data is considered valid if it has the following characteristics: With M peak; The two sides of the M peak have the lowest potential; The lowest potential on the epoxy side is lower than the lowest potential on the metal side.

7. The method according to claim 6, characterized in that The thickness of the metal oxide film is calculated as follows: The thickness of the metal oxide film is obtained by subtracting the distance corresponding to the potentials of the two vertices of the M peak from the distance corresponding to the highest potential of the vertices of the M peak close to the metal side and the lowest potential close to the metal side.

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