Use of a periodic multilayer film in the preparation of a scanning electron microscope proficiency testing sample

Abstract

The application provides application of a periodic multilayer film in preparation of a scanning electron microscope detection capability verification sample; the periodic multilayer film comprises Ti layers, TiN layers and CrN layers. The periodic multilayer film comprising the Ti layers, the TiN layers and the CrN layers is simple in structure, easy for electron microscope users of different professions to understand, and can make up for the deficiency that the existing scanning electron microscope detection capability verification sample has a professional background limitation on professional knowledge of a tester, and is more universal. Under the scanning electron microscope, the atomic number contrast difference of Ti and TiN is small, the atomic number contrast difference of TiN and CrN is large, and a certain scanning electron microscope test and analysis capacity basis is required to completely distinguish the morphology contrast difference, so that the detection capability of a laboratory can be verified.

Description

Technical Field

[0001] This invention belongs to the field of proficiency testing technology, and particularly relates to the application of a periodic multilayer film in the preparation of proficiency testing samples for scanning electron microscopy. Background Technology

[0002] Scanning electron microscopes (SEMs) are precision instruments for high-resolution microscopic morphology analysis. Due to their large depth of field, high resolution, and intuitive imaging, they are widely used in life sciences, physics, chemistry, forensics, earth sciences, materials science, and industrial production. Many research institutions, quality inspection agencies, and R&D departments of enterprises in China possess a considerable number of SEMs. However, the results of SEM microscopic structure observations are significantly affected by experimental methods, conditions, and operator skills. Therefore, strengthening the analytical and testing capabilities of laboratories in related fields and urging them to maintain and improve their analytical abilities and testing standards is crucial.

[0003] Currently, most SEM proficiency testing samples require specific professional knowledge and lack universal applicability. Examples include observing the secondary electron morphology of pearlitic structures in metallic materials and the cleavage and dimple morphology of impact fracture surfaces in metallic materials. Operators without materials science expertise often struggle to identify these morphologies, thus hindering broader comparisons of analytical capabilities between SEM laboratories. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an application of a periodic multilayer film in the preparation of scanning electron microscope (SEM) proficiency testing samples. This periodic multilayer film is a versatile SEM proficiency testing sample used to evaluate the capabilities of SEM users.

[0005] This invention provides an application of periodic multilayer films in the preparation of samples for scanning electron microscopy detection capability verification;

[0006] The periodic multilayer film includes a Ti layer, a TiN layer, and a CrN layer.

[0007] This invention employs a periodic multilayer film comprising Ti, TiN, and CrN layers. Its simple structure is easily understood by electron microscope users from various specialties, overcoming the limitations of existing scanning electron microscope (SEM) verification samples that require specialized background knowledge from the testing personnel, thus offering greater universality. Under an SEM, the atomic number contrast difference between Ti and TiN is relatively small, while the atomic number contrast difference between TiN and CrN is significant. Completely distinguishing these morphological contrast differences requires a certain level of SEM testing and analysis skills, thus enabling the verification of a laboratory's testing capabilities.

[0008] In this invention, the total thickness of the periodic multilayer film is 3–5 μm, and the modulation period is 500–1500 nm. Preferably, the periodic multilayer film has four periods, with each period comprising at least three layers. In this invention, in each modulation period of the periodic multilayer film, the number of at least one of the Ti, TiN, and CrN layers is ≥2.

[0009] In this invention, the scanning electron microscope (SEM) is applicable to mainstream SEM brands and models such as Thermo Fisher, Hitachi, Zeiss, JEOL, and Tescan. It is suitable for comparing the detection capabilities of SEM laboratories with different models and professional backgrounds.

[0010] The periodic multilayer film described in this invention is prepared by the following method:

[0011] Periodic multilayer films are deposited on a stainless steel substrate by magnetron sputtering.

[0012] More specifically: in a nitrogen atmosphere, using Ti and Cr targets, periodic multilayer films are deposited on a stainless steel substrate.

[0013] This invention achieves variations in film thickness and arrangement period by controlling the coating parameters of magnetron sputtering. The stainless steel and coating used are stable and resistant to corrosion, resulting in uniform and stable samples that meet the requirements for laboratory proficiency testing.

[0014] The stainless steel substrate is used after polishing and ultrasonic cleaning.

[0015] The surface of the multilayer film is provided with a TiN protective layer. Resin thermal bonding is then used after coating.

[0016] The temperature for hot mounting is 165–175°C, and the hot mounting time is 380–420 seconds.

[0017] In this invention, the resin hot-mounting process further includes:

[0018] The samples were water-polished with 180-mesh, 600-mesh, and 1200-mesh SiC sandpaper, respectively. Then, they were polished with 9μm, 3μm, 1μm, and 50nm polishing solutions, respectively. After polishing, the samples were cleaned with alcohol and dried.

[0019] The application provided by this invention requires participants to observe the morphology of multilayer films on metal surfaces in a laboratory setting. Specifically, the imaging position must be correct, the complete cycle of the film layer must be observed, the film interface must be clearly reflected, and the interface location must be correctly marked. The quantitative results can be obtained by counting the periodic structures.

[0020] The periodic multilayer film comprising Ti, TiN, and CrN layers used in this invention offers excellent tunability, allowing for adjustment of the film thickness and arrangement period as needed. This effectively prevents premature leakage of sample structure during proficiency testing. The periodic multilayer film, including Ti, TiN, and CrN layers, provides excellent uniformity and stability as a verification sample, meeting the requirements for long-term transportation. The total thickness of this periodic multilayer film is 3–5 μm, observable on both low-resolution tungsten filament electron microscopes and high-resolution field emission electron microscopes, thus expanding the range of proficiency testing laboratories that can participate in its application. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the multilayer film used in the application of this invention;

[0022] Figure 2 This is a morphology image of a multilayer film sample under an electron microscope with a tungsten filament in an embodiment of the present invention.

[0023] Figure 3 This is a field emission electron microscope (FEM) image of a multilayer film sample from an embodiment of the present invention. Detailed Implementation

[0024] To further illustrate the present invention, the application of a periodic multilayer film provided by the present invention in the preparation of scanning electron microscope detection capability verification samples is described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0025] Example 1

[0026] (1) After ultrasonically cleaning the polished stainless steel substrate with acetone and ethanol, a periodic multilayer film is deposited on the stainless steel substrate using a magnetron sputtering device. The film thickness and periodic structure can be adjusted according to actual needs. In this patent specification, the sample was prepared using a Hauzer Flexicoat 850 DC magnetron sputtering device. Ti and Cr targets were used in a nitrogen atmosphere. The nitrogen layer deposition time for the Ti / TiN / CrN film was set to 18 min, 52 min, and 28 min, respectively, and the surface TiN protective layer deposition time was 85 min. To ensure the uniformity of the coating thickness, during sample preparation, the fixed position of different samples in the magnetron sputtering coating device cavity should be kept as consistent as possible with the distance from the target material.

[0027] (2) After coating, the sample was heat-mounted with resin. To ensure the sample was level, a metallographic mounting butterfly clip was used to fix it. The mounting parameters were: heating temperature 170℃, heating time 400s, and cooling time 300s. After mounting, the sample was wet-polished with 180-grit, 600-grit, and 1200-grit SiC sandpaper, respectively. Then, the sample was polished with 9μm, 3μm, 1μm, and 50nm polishing solutions, respectively. After polishing, the sample was cleaned with alcohol and dried. The sample preparation was then complete.

[0028] (3) Therefore, the design verification result is "the complete cycle of the film layer can be observed, the film interface can be clearly reflected, and the interface position is correctly marked." The verification result design is reasonable, reflects the testing and analysis capabilities of the scanning electron microscope laboratory, and is also simple and easy to operate. Figure 2 As shown in Figure 3, the dark area above the stainless steel substrate can be distinguished as two films, each with a thickness of 200–300 nm. The lighter-colored film above the dark film is a CrN layer, with a thickness of approximately 500–600 nm. This is mainly due to the higher atomic number of Cr, resulting in a larger number of backscattered electrons, thus making this area brighter. These three thin films form one cycle. Moving upwards, a new three-layer film combination repeats, for a total of four repetitions. The uppermost dark film layer is a TiN protective layer. The ability to distinguish these four repetitions demonstrates that the laboratory possesses basic scanning electron microscope observation skills. Accurate imaging of the two films in the dark area requires strong instrument operation capabilities.

[0029] As demonstrated by the above embodiments, the periodic multilayer film comprising Ti, TiN, and CrN layers used in this invention exhibits excellent tunability. The film thickness and arrangement period can be adjusted according to requirements, effectively preventing premature leakage of the sample structure during proficiency testing. The periodic multilayer film comprising Ti, TiN, and CrN layers, as a verification sample, demonstrates excellent uniformity and stability, meeting the requirements for long-term transportation. The total thickness of this periodic multilayer film is 3–5 μm, observable on both low-resolution tungsten filament electron microscopes and high-resolution field emission electron microscopes, thus expanding the range of laboratories participating in proficiency testing.

[0030] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Application of a periodic multilayer film in the preparation of samples for scanning electron microscopy (SEM) capability verification; The periodic multilayer film includes a Ti layer, a TiN layer, and a CrN layer.

2. The application according to claim 1, characterized in that, The total thickness of the periodic multilayer film is 3–5 μm, and the modulation period is 500–1500 nm.

3. The application according to claim 1, characterized in that, In each modulation cycle of the periodic multilayer film, the number of at least one of the Ti, TiN, and CrN layers is ≥2.

4. The application according to claim 1, characterized in that, The surface of the multilayer film is provided with a TiN protective layer.

5. The application according to claim 1, characterized in that, The periodic multilayer film is prepared by the following method: Periodic multilayer films are deposited on a stainless steel substrate by magnetron sputtering.

6. The application according to claim 5, characterized in that, The specific process of depositing a periodic multilayer film on a stainless steel substrate by magnetron sputtering is as follows: In a nitrogen atmosphere, a periodic multilayer film is deposited on a stainless steel substrate using Ti and Cr targets.

7. The application according to claim 5, characterized in that, The stainless steel substrate is used after polishing and ultrasonic cleaning.

8. The application according to claim 5, characterized in that, Resin thermal bonding is used after coating; The temperature for hot mounting is 165–175°C, and the hot mounting time is 380–420 seconds.

9. The application according to claim 8, characterized in that, Resin heat-setting also includes: The samples were water-polished with 180-mesh, 600-mesh, and 1200-mesh SiC sandpaper, respectively. Then, they were polished with 9μm, 3μm, 1μm, and 50nm polishing solutions, respectively. After polishing, the samples were cleaned with alcohol and dried.

10. The application according to claim 1, characterized in that, The scanning electron microscopes include ThermoFisher, Hitachi, Zeiss, JEOL, or Tescan.

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