Sem sample preparation method for micro-nano sample topography characterization

Abstract

The application provides a SEM sample preparation method for micro-nano sample morphology characterization. In the SEM sample preparation method, at least one of acetone, ethanol and methanol is used as a solvent, the solvent is a low-tension, low-boiling-point, high-vapor-pressure and low-viscosity liquid, the included angle between the conductive substrate and the horizontal plane is 15-45 degrees, the specific solvent such as acetone, ethanol and methanol is used to achieve the effect of rapid evaporation, and the dispersed liquid is added to the surface of the conductive substrate which is placed at an angle of 15-45 degrees, so that the micro-nano sample can be uniformly distributed on the conductive substrate, the coffee ring effect is avoided, and the uniformity and integrity of the surface structure of the micro-nano sample are ensured. This method reduces the aggregation of micro-nano sample particles, improves the surface quality of the micro-nano sample, is suitable for high-resolution morphology observation, and can present clearer and finer micro-nano structures in SEM and AFM characterization, thereby helping to accurately analyze the structural characteristics of the micro-nano sample.

Description

Technical Field

[0001] This invention belongs to the field of surface morphology analysis technology, and particularly relates to a SEM sample preparation method for characterizing the morphology of micro and nano samples. Background Technology

[0002] Scanning electron microscopy (SEM) sample preparation is of great significance in scientific research, especially in fields such as nanomaterials, surface science, microstructure analysis, and materials characterization. SEM sample preparation not only helps researchers gain a deeper understanding of the microscopic morphology, structural properties, and compositional distribution of materials, but also provides reliable data support for subsequent experiments and research. Micro- and nanostructures directly affect the physical and chemical properties of materials. By precisely controlling micro- and nanostructures, researchers can adjust the properties of materials to suit specific application requirements.

[0003] Currently, water is commonly used as a solvent in SEM sample preparation for characterizing the morphology of micro and nano samples. However, when water is used as a solvent, a strong coffee ring effect often occurs during the evaporation process, causing micro and nano sample particles to move towards the edge of the substrate and deposit, resulting in uneven distribution of micro and nano samples. This affects the subsequent analysis of the microscopic morphology and structural characteristics of micro and nano samples during SEM characterization. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a SEM sample preparation method for characterizing the morphology of micro-nano samples. It uses liquids such as acetone, ethanol, and methanol, which have low surface tension, low boiling point, high vapor pressure, and low viscosity, as solvents. These solvents have high volatility at room temperature, a rapid evaporation rate, and low surface tension. When the dispersion is dropped onto the surface of a conductive substrate, it evaporates rapidly, causing solvent molecules to leave quickly. The remaining micro-nano samples leave traces on the surface. Because acetone, ethanol, and methanol evaporate very quickly, the intermolecular forces do not yet cause the micro-nano samples to aggregate, thus maintaining a uniform distribution of the micro-nano samples.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a SEM sample preparation method for characterizing the morphology of micro / nano samples, comprising the following steps:

[0007] Micro- and nano-sized samples are dispersed in a solvent to obtain a dispersion.

[0008] The conductive substrate is placed at an angle of 15° to 45° with the horizontal plane.

[0009] The dispersion is dropped onto the surface of a tilted conductive substrate. After the solvent evaporates, the SEM sample is prepared and then subjected to SEM testing.

[0010] The solvent includes at least one of acetone, ethanol, and methanol.

[0011] Preferably, before adding the dispersion droplets to the surface of the tilted conductive substrate, the conductive substrate is further subjected to plasma cleaning.

[0012] Preferably, the mass fraction of the micro-nano sample in the dispersion is 0.01~0.0001%.

[0013] Preferably, the micro / nano sample includes any one of SiO2 nanospheres, graphene oxide nanosheets, MOF, and MXene-TiO2.

[0014] Preferably, if the micro / nano sample is SiO2 nanospheres, the solvent is acetone;

[0015] If the micro / nano sample is graphene oxide nanosheets, the solvent is ethanol;

[0016] If the micro / nano sample is a MOF, the solvent is acetone;

[0017] If the micro / nano sample is MXene-TiO2, the solvent is acetone.

[0018] Preferably, the diameter of the SiO2 nanospheres is 50~500 nm.

[0019] The diameter of the graphene oxide nanosheets is 0.1~6 μm.

[0020] The diameter of the MOF is 1~6 μm:

[0021] The diameter of the MXene-TiO2 is 0.2~10 μm.

[0022] Preferably, the conductive substrate is a silicon wafer with gold plating on its surface.

[0023] Preferably, the plasma cleaning control process is as follows: gas pressure is 0.1~10 Pa, gas flow rate is 5~50 sccm, gas source is one or more of O2, Ar, and N2; cleaning time is 10~20 min, cleaning temperature is 30~50℃, and power is 50~150W.

[0024] Preferably, the dispersion is dropped onto the surface of the inclined conductive substrate to spread the dispersion evenly on the conductive substrate surface, and then the dispersion is dropped onto the conductive substrate surface. After the solvent evaporates, the SEM sample preparation is completed and the SEM test is performed.

[0025] The volume of the dispersion added each time is 0.5~50 μL.

[0026] The SEM sample preparation method for characterizing the morphology of micro-nano samples of the present invention has the following advantages compared with the prior art:

[0027] 1. The SEM sample preparation method for characterizing the morphology of micro-nano samples of the present invention uses at least one of acetone, ethanol, and methanol as the solvent. These solvents are liquids with low surface tension, low boiling point, high vapor pressure, and low viscosity. These solvents have high volatility at room temperature, a fast evaporation rate, and low surface tension. When the dispersion is dropped onto the surface of the conductive substrate, it evaporates rapidly, causing the solvent molecules to leave quickly, leaving traces of the remaining micro-nano sample on the surface. Because the evaporation rate of acetone, ethanol, and methanol is very fast, the intermolecular interaction forces have not yet caused the micro-nano sample to aggregate. This can maintain the uniform distribution of the micro-nano sample, which is convenient for analyzing the micro-morphology and structural characteristics of the micro-nano sample during SEM characterization.

[0028] 2. The SEM sample preparation method for micro / nano sample morphology characterization of the present invention, with a conductive substrate at an angle of 15-45° to the horizontal plane, has significant advantages in the field of micro / nano sample morphology characterization. By using specific solvents such as acetone, ethanol, and methanol to achieve rapid evaporation, and combining this with the method of adding the dispersion droplets to the surface of the conductive substrate placed at a 15-45° angle, the micro / nano sample can be uniformly distributed on the conductive substrate, avoiding the coffee ring effect and ensuring the uniformity and integrity of the micro / nano sample surface structure. This method reduces the aggregation of micro / nano sample particles, improves the surface quality of micro / nano samples, and is suitable for high-resolution morphology observation. Especially in characterization methods such as SEM and AFM, it can reveal clearer and finer micro / nano structures, which helps in the accurate analysis of the structural characteristics of micro / nano samples. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram of adding a dispersion solution when the silicon wafer is tilted at 15-45° for gold plating;

[0031] Figure 2 This is a photograph of a dispersion solution being dropped onto a gold-plated silicon wafer.

[0032] Figure 3 The image shows SEM images of dispersions with concentrations of 1 / 100000 and 1 / 1000000 obtained by using ethanol as a solvent in Example 1, after being dropped onto an inclined conductive substrate.

[0033] Figures 4-5 To use acetone or ethanol respectively according to the method in Example 2 Figures 4-5 SEM images at different magnifications after a dispersion with a concentration of 1 / 100,000 was dropped onto an inclined conductive substrate using ethanol (left side) and acetone (right side) as solvents.

[0034] Figure 6 SEM images from different perspectives after a 1 / 100000 concentration dispersion, obtained by using acetone as a solvent according to the method in Example 3, was dropped onto an inclined conductive substrate.

[0035] Figure 7 To use acetone or ethanol according to the method in Example 4 ( Figure 7 SEM image of a 1 / 100000 concentration dispersion obtained by adding it dropwise to an inclined conductive substrate using ethanol (left side) and acetone (right side) as solvents.

[0036] Figure 8 SEM images at different magnifications after a 1 / 100000 concentration dispersion, obtained by using water as a solvent according to the method in Comparative Example 1, is dropped onto an inclined conductive substrate.

[0037] Figure 9 The image shows a SEM image of a conductive substrate with a 5° angle to the horizontal plane, after the dispersion droplet is added to the conductive substrate with a 5° tilt angle, following the method in Comparative Example 2.

[0038] Figure 10 The image shows a SEM image of a conductive substrate with a 60° angle to the horizontal plane, after the dispersion droplets were added to the conductive substrate with a 60° tilt angle, as described in Comparative Example 2. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0040] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0041] This invention provides a SEM sample preparation method for characterizing the morphology of micro / nano samples, comprising the following steps:

[0042] S1. Disperse the micro / nano sample in a solvent to obtain a dispersion;

[0043] S2. Place the conductive substrate at an angle of 15~45° with the horizontal plane.

[0044] S3. Add the dispersion droplets onto the surface of the tilted conductive substrate, wait for the solvent to evaporate, complete the SEM sample preparation, and perform SEM testing.

[0045] The solvent includes at least one of acetone, ethanol, and methanol.

[0046] The SEM sample preparation method for characterizing the morphology of micro-nano samples of the present invention uses at least one of acetone, ethanol, and methanol as the solvent. These solvents are liquids with low surface tension, low boiling point, high vapor pressure, and low viscosity. These solvents have high volatility at room temperature, a fast evaporation rate, and low surface tension. When the dispersion droplets are added to the surface of the conductive substrate, they evaporate rapidly, causing the solvent molecules to leave quickly, leaving traces of the remaining micro-nano samples on the surface. Because the evaporation rate of acetone, ethanol, and methanol is very fast, the intermolecular interaction forces have not yet caused the micro-nano samples to aggregate. This maintains the uniform distribution of the micro-nano samples, which is convenient for analyzing the micro-morphology and structural characteristics of the micro-nano samples during SEM characterization.

[0047] If water is used as a solvent, a strong coffee ring effect will occur during the evaporation process. This is because water has a high surface tension, and the evaporation rate is slower in the center of the dispersion, while the solvent at the edge of the dispersion evaporates faster, causing particles to move towards the edge and deposit, resulting in uneven distribution of micro and nano samples.

[0048] Furthermore, the conductive substrate of the present invention has an angle of 15 to 45° with the horizontal plane. When the dispersion is dropped onto the conductive substrate, the angle of 15 to 45° allows the dispersion to spread along the surface of the conductive substrate. Compared with the flat method (i.e., the angle is 0°), the tilt angle can promote the dispersion to spread more widely on the surface of the conductive substrate, avoiding the dispersion from concentrating in a small area.

[0049] The reason for adding the dispersion dropwise to the surface of a conductive substrate tilted at an angle of 15-45° is that the preparation process is simpler and faster than traditional methods such as spin coating and tableting, without damaging the sample, and the resulting sample is more uniform. The principle is as follows: It controls the balance between gravity and capillary action. The gravitational component drives the flow of the dispersion. When the conductive substrate is tilted, gravity is no longer perpendicular to the surface, but decomposes into two components: a component perpendicular to the surface, which keeps the dispersion in close contact with the conductive substrate; and a component parallel to the surface, which is the main driving force for the liquid to flow downwards along the tilted surface of the conductive substrate. The larger the angle, the larger the parallel component, and the stronger the driving force. The 15-45° angle range provides a suitable gravitational drive.

[0050] 1. Assist and guide capillary spreading: Utilize gravity to give the dispersion a clear downward direction, guiding the dispersion to flow and spread steadily and controllably downward along the surface of the conductive substrate.

[0051] 2. Ensure coverage speed and uniformity: Sufficient to drive the dispersion to uniformly cover the entire silicon wafer surface within a few seconds (using low viscosity and high wettability such as acetone or ethanol) under the synergy of capillary action, forming a relatively uniform thin liquid film layer.

[0052] 3. Avoid problems caused by excessive flow rate: Prevent uneven film thickness, particle erosion, agglomeration, and uncontrolled volatilization caused by excessively fast dispersion flow rate.

[0053] 4. An angle of 15~45° can also mitigate the "coffee ring effect" to some extent: When tilted at 15~45°, the dispersion front advances uniformly, and the solvent evaporation front remains parallel to the contact line (the contact line refers to the interface between the solid, gas, and liquid phases, i.e., the boundary between the dispersion, the conductive substrate, and the air). However, horizontally adding the dispersion can cause the contact line to pin, and the micro / nano sample will be pulled outward to form a ring-shaped aggregate.

[0054] The SEM sample preparation method for micro / nano sample morphology characterization of this invention has significant advantages in the field of micro / nano sample morphology characterization. By using specific solvents such as acetone, ethanol, and methanol to achieve rapid evaporation, and combining this with the method of adding the dispersion droplets onto the surface of a conductive substrate placed at an angle of 15-45°, the micro / nano sample can be uniformly distributed on the conductive substrate, avoiding the coffee ring effect and ensuring the uniformity and integrity of the micro / nano sample surface structure. This method reduces the aggregation of micro / nano sample particles, improves the surface quality of micro / nano samples, and is suitable for high-resolution morphology observation. Especially in characterization methods such as SEM and AFM, it can reveal clearer and finer micro / nano structures, which helps in the accurate analysis of the structural characteristics of micro / nano samples.

[0055] In some embodiments, the conductive substrate is further subjected to plasma cleaning before the dispersion droplets are added to the surface of the tilted conductive substrate.

[0056] In some embodiments, the mass fraction of the micro-nano sample in the dispersion is 0.01~0.0001%. The micro-nano sample is dispersed in the solvent, and the solution is ultrasonically treated using an ultrasonic processor to help the micro-nano sample be completely dispersed in the solution.

[0057] In some embodiments, the micro / nano sample includes any one of SiO2 nanospheres, graphene oxide nanosheets, MOF (metal-organic framework material), and MXene-TiO2.

[0058] Specifically, the MOF (metal-organic framework material) is ZIS (zinc indium sulfide ZnIn2S4), and its preparation method is as follows:

[0059] 1 mL of 1 mM ZnCl2 aqueous solution, 1 mL of 2 mM InCl3 aqueous solution, and 1 mL of 4 mM thioacetamide aqueous solution were added to a mixed solvent (2.5 mL of ethylene glycol and 7.5 mL of DMF). The mixture was heated at 160°C for 12 hours. The product was washed alternately by centrifugation with deionized water and ethanol. The product was dried overnight in a vacuum drying oven at 60°C to obtain MOF (metal-organic framework) ZIS.

[0060] In some embodiments, the preparation method of MXene-TiO2 is as follows:

[0061] S1. Add 2g LiF to 40mL of 9M hydrochloric acid and stir continuously for 30 minutes to obtain an etchant; gradually add 2g MAX powder (specifically Ti3AlC2) to the above etchant over 5 minutes and react at 35℃ for 24 hours to obtain a mixture;

[0062] S2. Washing with deionized water: Wash the mixture obtained in step 1) with deionized water by centrifugation (3500 rpm, 10 min each time) multiple times; after each wash, measure the pH of the supernatant until the pH of the supernatant is ≥5, remove the supernatant as waste by dumping, and collect the lower precipitate.

[0063] S3, Ethanol Sonication: Add ethanol to the precipitate obtained in step 2), sonicate for 60 min, centrifuge (10000 rpm, 10 min), remove the supernatant as waste by pouring, and collect the lower precipitate.

[0064] S4. Collect MXene: Add deionized water to the precipitate obtained in step S3, sonicate for 20 min, centrifuge at 3500 rpm for 3 min, observe the dark green supernatant, collect the supernatant, freeze dry to obtain powdered MXene;

[0065] S5. Preparation of TiO2-MXene: The powdered MXene obtained in step S4 is placed in a muffle furnace and calcined at 400℃ for 30 min to obtain TiO2-MXene.

[0066] In some embodiments, if the micro / nano sample is SiO2 nanospheres, the solvent is acetone;

[0067] In some embodiments, if the micro / nano sample is graphene oxide nanosheets, the solvent is ethanol;

[0068] In some embodiments, if the micro / nano sample is a MOF and the solvent is acetone;

[0069] In some embodiments, if the micro / nano sample is MXene-TiO2, the solvent is acetone.

[0070] For different micro / nano samples, appropriate solvents should be selected. Even acetone and ethanol, both low-tension, low-boiling-point, high-vapor-pressure, and low-viscosity liquids, have different effects on the dispersion of different materials. For example, for SiO2 nanospheres, acetone exhibits a much better dispersion effect than ethanol. Compared to ethanol, acetone has a lower boiling point and a faster evaporation rate. Rapidly evaporating acetone can be removed from the interparticle spaces more quickly, greatly shortening the time window during which particles may re-aggregate due to capillary forces in a moist state. Ethanol evaporates slowly and has a long residual time, making particles more easily pulled together and aggregated by strong capillary forces in the later stages of solvent evaporation. However, for graphene oxide nanosheets, the more polar ethanol is required as a solvent.

[0071] The advantage of choosing a liquid with low surface tension, low boiling point, high vapor pressure, and low viscosity as a solvent is that it will not leave residue on the silicon wafer after drying, ensuring the purity and uncontaminated nature of the test sample and preventing any impact on the imaging of the micro / nano sample morphology. Conversely, using polymers (including polyvinylpyrrolidone, sodium carboxymethyl cellulose, and polyvinylidene fluoride) as solvents results in the polymers not volatile after drying, leaving residue on the conductive substrate. This leads to a decrease in overall conductivity and significantly impacts the imaging quality of SEM.

[0072] In some embodiments, the diameter of the SiO2 nanospheres is 50~500 nm:

[0073] The diameter of graphene oxide nanosheets ranges from 0.1 to 6 μm.

[0074] The diameter of MOFs is 1~6 μm:

[0075] The diameter of MXene-TiO2 is 0.2~10 μm.

[0076] In some embodiments, the conductive substrate is a gold-plated silicon wafer (i.e., a gold-plated silicon wafer). The specific gold-plated silicon wafer is not the only material that can be selected; any material with a smooth surface and a certain degree of conductivity can be used as the substrate.

[0077] In some embodiments, the plasma cleaning control process is as follows: the gas pressure is 0.1~10 Pa, the gas flow rate is 5~50 sccm, the gas source is one or more of O2, Ar, and N2; the cleaning time is 10~20 min, the cleaning temperature is 30~50℃, and the power is 50~150W.

[0078] Specifically, after removing a 5mm x 5mm (i.e., both length and width are 5mm) square gold-plated silicon wafer from the encapsulated film, it is cleaned using a plasma cleaner to obtain a clean, smooth surface with good wettability.

[0079] The reason for using gold-plated silicon wafers as the substrate and cleaning them with plasma:

[0080] Gold-plated silicon wafers possess extremely high electrical conductivity, providing stable and uniform conductivity in experiments. This is crucial for studying the electrical properties of micro- and nano-sized samples (such as charge transport and conductivity measurements). Secondly, gold-plated silicon wafers exhibit excellent chemical stability, resisting reactions with substances in the air (such as oxygen and moisture). Therefore, they provide a relatively stable surface unaffected by environmental factors, avoiding the problem of silicon surface oxidation. The chemical inertness of gold makes it difficult for it to react with substances in solution, especially in the dispersion of micro- and nano-sized samples. The gold surface exhibits minimal adsorption of solvents and micro- and nano-sized samples, which helps achieve uniform distribution of these samples. Commercially available gold-plated silicon wafers are typically bonded to an encapsulated thin film using an adhesive. After removing the film, residual adhesive or other organic substances may remain, potentially affecting the results of subsequent experiments. To ensure a clean, flat surface free of organic impurities, plasma cleaning is usually employed. Plasma cleaning involves inducing a discharge in a gas atmosphere to generate reactive particles such as active ions, electrons, and free radicals. These active particles react with the silicon wafer surface, removing contaminants, residual adhesive, and organic matter. In addition, plasma treatment can enhance the wettability of gold-plated silicon wafers, allowing ethanol solutions to spread better on the wafer surface, thus ensuring uniform distribution of micro / nano samples.

[0081] In some embodiments, the dispersion is dropped onto the surface of an inclined conductive substrate to spread the dispersion evenly on the conductive substrate surface, and then the dispersion is dropped onto the conductive substrate surface. After the solvent evaporates, the SEM sample preparation is completed and the SEM test is performed.

[0082] The volume of the dispersion added each time is 0.5~50 μL.

[0083] Take 0.5~50 μL of dispersion twice with a pipette. Tilt the cleaned gold-plated silicon wafer at 15~45° and drop the dispersion from the top of the silicon wafer. The dispersion will quickly spread over the entire silicon wafer. Then quickly drop the second dispersion. After the dispersion has completely evaporated, you can perform SEM testing.

[0084] Furthermore, a single drop volume of 2.5 μL ensures that the dispersion covers the entire substrate without causing uneven distribution of the solution on the silicon wafer. Adding too much solution may cause it to aggregate on the surface and become uneven at the edges, while adding too little may fail to cover the entire substrate. By adding 2.5 μL in two separate drops, the spreading and evaporation process of the dispersion can be more precisely controlled. The first drop of 2.5 μL partially covers the silicon wafer surface, while the second drop of 2.5 μL further smooths and evenly distributes the solution, ensuring that the micro / nano samples are uniformly distributed on the substrate surface.

[0085] Specifically, such as Figure 1As shown, it illustrates the process of adding a dispersion liquid when the gold-plated silicon wafer is tilted at 15-45°.

[0086] like Figure 2 The image shown is a physical photograph of a dispersion liquid being dropped onto a gold-plated silicon wafer.

[0087] The following specific embodiments further illustrate the SEM sample preparation method for characterizing the micro / nano sample morphology of the present invention. This section further describes the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0088] In the following examples and comparative examples, the gold-plated silicon wafers were purchased from Harbin Tebo Technology Co., Ltd., and their size was 5mm × 5mm (i.e., both the length and width were 5mm).

[0089] SiO2 nanospheres were purchased from Jiangsu Yuante New Materials Technology Co., Ltd., with diameters ranging from 50 to 500 nm.

[0090] The graphene oxide nanosheets were purchased from Sanya Hanxi Graphene Technology Research Institute Co., Ltd., with diameters ranging from 0.1 to 6 μm.

[0091] MOF (metal-organic framework material) is ZIS (zinc indium sulfide ZnIn2S4), prepared by the same method as above, with a diameter of 1~6 μm;

[0092] The preparation method of MXene-TiO2 is the same as above, and its diameter is 0.2~10 μm.

[0093] In the following examples and comparative examples, the plasma cleaning process is controlled as follows: gas pressure is 2 Pa, gas flow rate is 10 sccm, gas source is Ar; cleaning time is 10 min, cleaning temperature is 30℃, and power is 80W.

[0094] Example 1

[0095] This embodiment provides a SEM sample preparation method for characterizing the morphology of micro / nano samples, including the following steps:

[0096] S1. Disperse graphene oxide sheets in ethanol to obtain a dispersion; the mass fraction of graphene oxide sheets in the dispersion is 1 / 100000 or 1 / 1000000.

[0097] S2. Perform plasma cleaning on the conductive substrate (specifically, a gold-plated silicon wafer);

[0098] The plasma-cleaned conductive substrate is placed at an angle of 40° to the horizontal plane.

[0099] S3. Add 2.5 μL of dispersion to the surface of the tilted conductive substrate (add the dispersion from the highest point of the conductive substrate). At this time, the dispersion will quickly cover the entire silicon wafer. Then add another 2.5 μL of dispersion to the surface of the conductive substrate. After the solvent evaporates, the SEM sample preparation is complete, and SEM testing is performed.

[0100] like Figure 3 As shown, it is a SEM image of a conductive substrate placed at an incline after dispersions with concentrations of 1 / 100000 and 1 / 1000000 were obtained by using ethanol as a solvent in accordance with the method in Example 1.

[0101] from Figure 3 It can be seen that the graphene oxide is evenly dispersed and no coffee rings are present.

[0102] Example 2

[0103] This embodiment provides a SEM sample preparation method for characterizing the morphology of micro / nano samples, including the following steps:

[0104] S1. Disperse SiO2 nanospheres in acetone (or ethanol) to obtain a dispersion; the mass fraction of SiO2 nanospheres in the dispersion is 1 / 100000.

[0105] S2. Perform plasma cleaning on the conductive substrate (specifically, a gold-plated silicon wafer);

[0106] The plasma-cleaned conductive substrate is placed at an angle of 40° to the horizontal plane.

[0107] S3. Add 2.5 μL of dispersion to the surface of the tilted conductive substrate (add the dispersion from the highest point of the conductive substrate). At this time, the dispersion will quickly cover the entire silicon wafer. Then add another 2.5 μL of dispersion to the surface of the conductive substrate. After the solvent evaporates, the SEM sample preparation is complete, and SEM testing is performed.

[0108] like Figures 4-5 As shown, these are SEM images at different magnifications after a dispersion with a concentration of 1 / 100000 was obtained by using acetone or ethanol as solvents according to the method in Example 2 and then dropped onto an inclined conductive substrate.

[0109] Figures 4-5 The left side of the image shows ethanol as the solvent, and the right side shows acetone as the solvent.

[0110] from Figures 4-5As can be seen, acetone solvent exhibits a much better dispersion effect than ethanol for SiO2 nanospheres. Compared with ethanol, acetone has a lower boiling point and a faster evaporation rate. The rapidly evaporating acetone can be removed from the particles more quickly, greatly shortening the time window during which the particles may re-aggregate due to capillary forces in a humid state. In contrast, ethanol evaporates slowly and has a long residual time, making the particles more likely to be pulled together and aggregate by strong capillary forces in the later stages of solvent evaporation.

[0111] Example 3

[0112] This embodiment provides a SEM sample preparation method for characterizing the morphology of micro / nano samples, including the following steps:

[0113] S1. Disperse MOF (specifically ZIS (zinc indium sulfide ZnIn2S4)) in acetone to obtain a dispersion; the mass fraction of MOF in the dispersion is 1 / 100000.

[0114] S2. Perform plasma cleaning on the conductive substrate (specifically, a gold-plated silicon wafer);

[0115] The plasma-cleaned conductive substrate is placed at an angle of 40° to the horizontal plane.

[0116] S3. Add 2.5 μL of dispersion to the surface of the tilted conductive substrate (add the dispersion from the highest point of the conductive substrate). At this time, the dispersion will quickly cover the entire silicon wafer. Then add another 2.5 μL of dispersion to the surface of the conductive substrate. After the solvent evaporates, the SEM sample preparation is complete, and SEM testing is performed.

[0117] like Figure 6 As shown, these are SEM images from different perspectives after a dispersion with a concentration of 1 / 100000, obtained by using acetone as a solvent according to the method in Example 3, is dropped onto an inclined conductive substrate.

[0118] from Figure 6 It can be seen that the MOF is evenly dispersed and no coffee rings appear.

[0119] Example 4

[0120] This embodiment provides a SEM sample preparation method for characterizing the morphology of micro / nano samples, including the following steps:

[0121] S1. Disperse MXene-TiO2 in acetone (or ethanol) to obtain a dispersion; the mass fraction of MXene-TiO2 in the dispersion is 1 / 100000;

[0122] S2. Perform plasma cleaning on the conductive substrate (specifically, a gold-plated silicon wafer);

[0123] The plasma-cleaned conductive substrate is placed at an angle of 40° to the horizontal plane.

[0124] S3. Add 2.5 μL of dispersion to the surface of the tilted conductive substrate (add the dispersion from the highest point of the conductive substrate). At this time, the dispersion will quickly cover the entire silicon wafer. Then add another 2.5 μL of dispersion to the surface of the conductive substrate. After the solvent evaporates, the SEM sample preparation is complete, and SEM testing is performed.

[0125] like Figure 7 As shown, it is a SEM image of a dispersion with a concentration of 1 / 100000 obtained by using acetone or ethanol as a solvent according to the method in Example 4, after being dropped onto a tilted conductive substrate.

[0126] Figure 7 The left side of the image shows ethanol as the solvent, and the right side shows acetone as the solvent.

[0127] from Figure 7 As can be seen, MXene-TiO2 exhibits significant aggregation when ethanol is used as the solvent, while no obvious aggregation occurs when acetone is used as the solvent.

[0128] Comparative Example 1

[0129] This comparative example provides a SEM sample preparation method for characterizing the morphology of micro and nano samples, including the following steps:

[0130] S1. Graphene oxide sheets are dispersed in water to obtain a dispersion; the mass fraction of graphene oxide sheets in the dispersion is 1 / 100000.

[0131] S2. Perform plasma cleaning on the conductive substrate (specifically, a gold-plated silicon wafer);

[0132] The plasma-cleaned conductive substrate is placed at an angle of 40° to the horizontal plane.

[0133] S3. Add 2.5 μL of dispersion to the surface of the tilted conductive substrate (add the dispersion from the highest point of the conductive substrate). At this time, the dispersion will quickly cover the entire silicon wafer. Then add another 2.5 μL of dispersion to the surface of the conductive substrate. After the solvent evaporates, the SEM sample preparation is complete, and SEM testing is performed.

[0134] like Figure 8 As shown, it is a SEM image at different magnifications after a dispersion with a concentration of 1 / 100000 was obtained by using water as a solvent according to the method in Comparative Example 1 and then dropped onto an inclined conductive substrate.

[0135] As can be seen from Figure 8, when water is used as a solvent, a strong coffee ring effect often occurs during the evaporation process. This is because water has a high surface tension, and the evaporation rate is slower at the center of the droplet, while the solvent at the edge of the droplet evaporates faster, causing the particles to move towards the edge and deposit.

[0136] Comparative Example 2

[0137] This comparative example provides a SEM sample preparation method for characterizing the morphology of micro and nano samples, including the following steps:

[0138] S1. Graphene oxide sheets are dispersed in ethanol to obtain a dispersion; the mass fraction of graphene oxide sheets in the dispersion is 1 / 100000.

[0139] S2. Perform plasma cleaning on the conductive substrate (specifically, a gold-plated silicon wafer);

[0140] The plasma-cleaned conductive substrate is placed at an angle of 5° (or 60°) to the horizontal plane.

[0141] S3. Add 2.5 μL of dispersion to the surface of the tilted conductive substrate (add the dispersion from the highest point of the conductive substrate). At this time, the dispersion will quickly cover the entire silicon wafer. Then add another 2.5 μL of dispersion to the surface of the conductive substrate. After the solvent evaporates, the SEM sample preparation is complete, and SEM testing is performed.

[0142] like Figure 9 As shown, it is a SEM image of the conductive substrate with an angle of 5° (less than 15°) to the horizontal plane, after the dispersion droplet is added to the conductive substrate with an inclination angle of only 5° according to the method in Comparative Example 2 (SEM comparison image of graphene oxide sheet on the upper and lower parts of silicon wafer).

[0143] like Figure 10 As shown, it is a SEM image of the conductive substrate with an angle of 60° (greater than 45°) to the horizontal plane, after the dispersion droplet is added to the conductive substrate with an inclination angle of 60° according to the method in Comparative Example 2 (SEM comparison image of graphene oxide sheet on the upper and lower parts of silicon wafer).

[0144] from Figure 9 As can be seen, when the tilt angle of the conductive substrate is less than 15° (specifically 5°), most of the graphene oxide nanosheets will be deposited on the upper part of the silicon wafer, and a certain degree of coffee rings will also be formed. The graphene oxide nanosheets are stacked together, while only a few graphene oxide nanosheets are dispersed on the lower part of the silicon wafer.

[0145] from Figure 10 As can be seen, when the tilt angle of the conductive substrate is greater than 45° (specifically 60°), only a small amount of graphene oxide nanosheets are distributed on the upper part of the silicon wafer, while agglomeration occurs on the lower part.

[0146] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0147] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A method for preparing a sample for SEM for micro-nano sample topography characterization, characterized in that, The method comprises the following steps: dispersing a micro-nano sample into a solvent to obtain a dispersion liquid; inclining an electrically conductive substrate, and the angle between the electrically conductive substrate and a horizontal plane is 40°; dropping the dispersion liquid onto the surface of the inclined electrically conductive substrate, and then volatilizing the solvent to complete SEM sample preparation and perform SEM testing; the solvent is ethanol; the micro-nano sample is graphene oxide nanosheet; the diameter of the graphene oxide nanosheet is 0.1-6 μm; the mass fraction of the micro-nano sample in the dispersion liquid is 0.01-0.0001%.

2. The SEM sample preparation method for micro-nano sample topography characterization of claim 1, wherein, Before the step of dropping the dispersion liquid onto the surface of the inclined electrically conductive substrate, the method further comprises the step of performing plasma cleaning on the electrically conductive substrate.

3. The SEM sample preparation method for micro-nano sample topography characterization of claim 1, wherein, the electrically conductive substrate is a silicon wafer plated with gold on the surface.

4. The SEM sample preparation method for micro-nano sample topography characterization of claim 2, wherein, the process of the plasma cleaning control is as follows: the gas pressure is 0.1-10 Pa, the gas flow is 5-50 sccm, the gas source is one or more of O2, Ar and N2, the cleaning time is 10-20 min, the cleaning temperature is 30-50℃, and the power is 50-150 W.

5. The SEM sample preparation method for micro-nano sample topography characterization of claim 1, wherein, dropping the dispersion liquid onto the surface of the inclined electrically conductive substrate, spreading the dispersion liquid on the surface of the electrically conductive substrate, then dropping the dispersion liquid onto the surface of the electrically conductive substrate again, and then volatilizing the solvent to complete SEM sample preparation and perform SEM testing; the volume of the dispersion liquid dropped each time is 0.5-50 μL.

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