Method for positioning nanoscale defects on surface of hard material based on atomic force microscope

Abstract

The invention relates to a method for positioning nanoscale defects on the surface of a hard material based on an atomic force microscope, which comprises the following steps: preparing a soft film on the surface of the hard material, and scanning the obtained surface-modified hard material through the atomic force microscope to determine the nanoscale defects on the surface of the hard material, and performing inelastic indentation on the soft film corresponding to the peripheral side of the nano-scale defect by using a nano indentation probe in an atomic force microscope to obtain a defect identifier, thereby completing the positioning of the nano-scale defect. According to the method, the soft film layer is prepared on the surface of the hard material, the soft film memorizes the morphology of the nanoscale defect on the surface of the hard material and does not influence the morphology of the original defect, and the existence of the soft film does not influence optical transmission, so that the atomic force microscope is not influenced to quickly find the position of the nanoscale defect; meanwhile, the mark with enough depth can be generated on the surface of the hard material, so that the precise positioning of the nanoscale defect on the surface of the hard material is effectively realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of defect positioning, and particularly to a method for positioning nanoscale defects on the surface of hard material based on an atomic force microscope. BACKGROUND

[0002] Atomic force microscope (AFM) indentation technology is one of the core means in the field of nanoscale characterization. Its significant feature is that the load application range is concentrated in the nanonewton (nN) to micronewton (μN) level. This load interval is designed due to the precise control ability of AFM on micro force, so that it can realize the characterization of the material surface under the condition of small mechanical disturbance. For relatively soft material systems such as polymer films, biological tissues and soft nanocomposites, the Young's modulus of such materials is usually low (generally in the order of kPa to MPa), and the intermolecular or interface binding force is weak. Under the action of low load of AFM indentation, the surface defects (such as micropores, cracks, local agglomerate boundaries, composition segregation areas, etc.) will produce significant plastic deformation or elastic recovery difference due to stress concentration effect. This deformation difference can be captured in real time by the contact mode or tapping mode of AFM: during the indentation process, the interaction force signal between the probe and the sample surface will change with the mechanical response of the defect area. Combined with the high-resolution scanning imaging function of AFM, the indentation position and the surface topography image can be directly superimposed to accurately identify the distribution characteristics of the defects.

[0003] However, for hard materials such as glass, silicon single crystal or diamond, the Young's modulus is high, the interatomic binding force is strong, and the crystal lattice structure is dense. The AFM indentation under low load is difficult to break through the elastic limit of the material. Even if the upper limit load of the order of μN is applied, the indentation depth generated is usually only sub-nanometer to several nanometers, which is far below the morphology resolution threshold of the instrument, and a recognizable indentation mark cannot be formed. In this case, nanoindentation can be considered. This technology uses a diamond probe to apply a larger load (usually in the order of millinewton) to generate a sufficient indentation to detect defects and provide quantitative material performance data such as hardness and elastic modulus. Although nanoindentation has advantages in large-load indentation marking and quantitative characterization of mechanical properties of hard materials, it has significant application limitations. First, it is a point measurement mode and cannot achieve continuous scanning imaging like AFM. If the defects on the surface of the material need to be fully screened, multiple tests need to be performed by moving the probe point by point, which is extremely inefficient and may affect the test results due to the mechanical interaction between the indentations. Second, for nanoindentation, the indentation size is usually in the micrometer to sub-micrometer range. For nanoscale defects on the surface (such as 100 nm or less of recesses, cracks and surface contamination), the indentation mark is easy to cover or damage the defects themselves, making it difficult to achieve accurate positioning and topography observation. Therefore, compared with nanoindentation, the core competitiveness of AFM lies in its high-resolution surface topography imaging capability at the atomic to nanoscale level, which clearly presents the spatial distribution of nanoscale defects.

[0004] Therefore, how to realize accurate positioning of nanoscale defects on the surface of hard materials based on atomic force microscope indentation technology is a technical problem to be solved at present. SUMMARY

[0005] To solve the above technical problems, the present application provides a method for positioning nanoscale defects on the surface of hard materials based on atomic force microscope. In order to realize accurate positioning of nanoscale defects on the surface of hard materials by using atomic force microscope (AFM) indentation technology, a soft film layer is prepared on the surface of the hard material in a detour manner. The soft film has topographic memory for nanoscale defects on the surface of the hard material, i.e., it does not affect the topography of the original defects, and its existence does not affect optical transmission, thereby not affecting the atomic force microscope to quickly find the position of the nanoscale defects, and at the same time, a mark with sufficient depth can also be generated thereon. Therefore, the position of the nanoscale defect is found in the scanning range by using AFM, and then a non-elastic indentation is performed on the defect side by using a nanoindentation probe in AFM to obtain a defect mark, thereby effectively realizing accurate positioning of nanoscale defects on the surface of hard materials. Subsequently, the defect mark can be used to perform precise position cutting by using a focused ion beam to find the nanoscale defect.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for locating nanoscale defects on the surface of a hard material based on atomic force microscopy, the method comprising the following steps:

[0008] S1. Prepare a soft film on the surface of a hard material to obtain a surface-modified hard material;

[0009] S2. The surface-modified hard material described in step S1 is scanned using an atomic force microscope to determine the nanoscale defects on the surface of the hard material. Inelastic indentation is then performed on the soft film corresponding to the periphery of the nanoscale defects using a nanoindentation probe in the atomic force microscope to obtain defect identification and complete the localization of the nanoscale defects.

[0010] This invention aims to achieve precise localization of nanoscale defects on the surface of hard materials using AFM indentation technology. A soft thin film layer is fabricated on the surface of the hard material using a roundabout method. This soft film retains the morphology memory of the nanoscale defects on the hard material surface; that is, it does not affect the original defect morphology, and its presence does not affect optical transmission. Therefore, it does not hinder the rapid location of nanoscale defects using atomic force microscopy (AFM), while also creating sufficiently deep markings. Thus, the location of the nanoscale defect is found within the scanning range using AFM, and then inelastic indentation is performed around the defect using a nanoindentation probe in the AFM to obtain defect markings. This effectively achieves precise localization of nanoscale defects on the surface of hard materials. Subsequently, based on the defect markings, a focused ion beam can be used for precise location cutting to locate the nanoscale defects.

[0011] As a preferred technical solution of the present invention, the nanoscale defects include at least one of nano-contamination, nano-pits, or nano-cracks.

[0012] Preferably, the nanocontamination includes at least one of nanoparticles, nanofilms, nanolayers, or nanoclusters.

[0013] As a preferred technical solution of the present invention, the hard material in step S1 includes any one of hard glass sheet, single crystal silicon wafer or diamond film.

[0014] As a preferred technical solution of the present invention, the soft film material in step S1 includes soft metal.

[0015] It should be noted that the present invention does not impose specific requirements or special limitations on the preparation process of the soft thin film. Common preparation processes of soft metal thin films in the art are applicable to the present invention. Those skilled in the art can make adaptive selections and adjustments according to actual conditions. For example, the coating can be performed using a metal coating machine or by using ion beam induced chemical vapor deposition in a focused ion beam system.

[0016] Preferably, the soft metal includes at least one of platinum, gold, or silver.

[0017] As a preferred technical solution of the present invention, the thickness of the soft film in step S1 is 10nm~100nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, etc., preferably 10nm~50nm.

[0018] In this invention, by adjusting the thickness of the soft film to 10nm~50nm, a good balance between optical transmittance and sufficient depth of defect marking can be achieved. If the thickness of the soft film is too thin, the nanoindentation probe of the atomic force microscope will not be able to generate a sufficiently deep defect marking on the soft film, thus making subsequent precise cutting impossible. If the thickness of the soft film is too thick, the atomic force microscope will not be able to quickly locate the target nanoscale defect, and may even fail to accurately identify the defect. In addition, it will also make the film deposition time too long, affecting efficiency.

[0019] As a preferred technical solution of the present invention, the area corresponding to the periphery in step S2 is a circular area with a radius of 0.1μm to 100μm centered on the nanoscale defect, such as 0.1μm, 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, etc.

[0020] As a preferred technical solution of the present invention, the depth of the defect marking in step S2 is 5nm~50nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, preferably 5nm~25nm.

[0021] In this invention, by adjusting the depth of the defect marker to 5nm~50nm, a better marking effect can be obtained and the SEM imaging contrast is more obvious. If the depth of the defect marker is too shallow, the SEM imaging contrast will not be obvious.

[0022] As a preferred technical solution of the present invention, in step S2, with the position of the nanoscale defect as the center of symmetry, the defect identifier includes at least one set of symmetric identifiers.

[0023] As a preferred technical solution of the present invention, in step S2, with the location of the nanoscale defect as the center, the defect identifier includes at least one set of asymmetric identifiers.

[0024] In this invention, defect markers can be symmetrically or asymmetrically arranged, with the aim of being easily identifiable during focused ion beam cutting.

[0025] Preferably, the nanoindentation probe comprises a diamond probe.

[0026] As a preferred technical solution of the present invention, the method includes the following steps:

[0027] S1. Prepare a soft film with a thickness of 10nm~50nm on the surface of a hard material to obtain a surface-modified hard material;

[0028] S2. Using an atomic force microscope, the surface-modified hard material described in step S1 is scanned to determine the nanoscale defects on the surface of the hard material. The nanoscale defects include at least one of nano-contamination, nano-pits, or nano-cracks. Inelastic indentation is performed on the soft film corresponding to the periphery of the nanoscale defect using a nano-indentation probe in the atomic force microscope. The periphery corresponds to a circumferential region with a radius of 0.1 μm to 100 μm centered on the nanoscale defect, resulting in a defect marker with a depth of 5 nm to 25 nm, thus completing the localization of the nanoscale defect.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] This invention aims to achieve precise localization of nanoscale defects on the surface of hard materials using AFM indentation technology. A soft thin film layer is fabricated on the surface of the hard material using a roundabout method. This soft film retains the morphology memory of the nanoscale defects on the hard material surface; that is, it does not affect the original defect morphology, and its presence does not affect optical transmission. Therefore, it does not hinder the rapid location of nanoscale defects using atomic force microscopy (AFM), while also creating sufficiently deep markings. Thus, the location of the nanoscale defect is found within the scanning range using AFM, and then inelastic indentation is performed around the defect using a nanoindentation probe in the AFM to obtain defect markings. This effectively achieves precise localization of nanoscale defects on the surface of hard materials. Subsequently, based on the defect markings, a focused ion beam can be used for precise location cutting to locate the nanoscale defects. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the method for locating nanoscale defects on the surface of hard materials based on atomic force microscopy according to the present invention.

[0032] Figure 2 This is a schematic diagram of the atomic force microscope of the present invention used to locate defects on hard materials.

[0033] Figure 3 This is a SEM image of the defect markers formed on a soft thin film using the atomic force microscope of this invention.

[0034] Figure 4This is a cross-sectional SEM image of the section after being cut by focused ion beam cutting in Embodiment 1 of the present invention.

[0035] Among them, 1-hard material, 2-soft material, 3-nanoscale defect, 4-defect mark, 5-position of inelastic indentation defect mark, 6-position of nanoparticles on the surface of hard glass sheet. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0037] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0038] Figure 1 This invention illustrates a flowchart of a method for locating nanoscale defects on the surface of hard materials using atomic force microscopy, the method comprising the following steps:

[0039] S1. Prepare a soft film on the surface of a hard material to obtain a surface-modified hard material;

[0040] S2. The surface-modified hard material described in step S1 is scanned using an atomic force microscope to determine the nanoscale defects on the surface of the hard material. Inelastic indentation is then performed on the soft film corresponding to the periphery of the nanoscale defects using a nanoindentation probe in the atomic force microscope to obtain defect identification and complete the localization of the nanoscale defects.

[0041] Figure 2 A schematic diagram of the atomic force microscope of the present invention being used to locate defects in hard materials is shown. Figure 3 The figure shows a SEM image of the defect markings formed on a soft film by the atomic force microscope of the present invention. As can be seen from the figure, the defect markings obtained after inelastic indentation have a certain depth.

[0042] The atomic force microscope used in the specific embodiments of this invention is manufactured by Bruker, model DIMENSIONICON, and the nanoindentation probe is a diamond probe.

[0043] Example 1

[0044] This embodiment provides a method for locating nanoscale defects on the surface of a hard material using atomic force microscopy. The method uses a hard glass slide containing nanoparticles (50 nm in diameter) on its surface.

[0045] S1. A Pt metal thin film with a thickness of 30 nm is prepared on the surface of a hard glass sheet using a metal coating machine to obtain a hard glass sheet with a surface-modified Pt metal thin film.

[0046] S2. Using an atomic force microscope, the nanoparticles on the surface of the hard glass slide modified with Pt metal film are identified by scanning. Inelastic indentation is performed on the Pt metal film corresponding to the periphery of the nanoparticle (the circumferential area within a radius of 25 μm centered on the nanoparticle) using a diamond probe in the atomic force microscope to obtain a set of symmetrical defect markers with a depth of 15 nm (the set of defect markers is located on the same straight line as the nanoparticle), thus completing the localization of the nanoparticles.

[0047] After locating the nanoparticles, a 50 nm thick protective layer was deposited on the surface of the Pt metal film. Then, a focused ion beam was used to cut along the line where the defect marker and the nanoparticle were located to find the nanoparticles.

[0048] Figure 4 The figure shows a cross-sectional SEM image of the section after being cut by focused ion beam cutting in Embodiment 1 of the present invention. As can be seen from the figure, from bottom to top, there are hard glass sheets, Pt metal films and protective layers. In the Pt metal film, the left-hand depression 5 is the location of the inelastic indentation defect. The left and right edges of the depression will be slightly raised, and then to the right, the adjacent protrusion 6 on the right is the location of the nanoparticles on the surface of the hard glass sheet.

[0049] The method in this embodiment can accurately identify the location of nanoparticles on the surface of a hard glass sheet.

[0050] Example 2

[0051] This embodiment provides a method for locating nanoscale defects on the surface of hard materials using atomic force microscopy. The method uses a silicon single-crystal wafer with nano-recesses (80 nm wide and 20 nm deep) on its surface.

[0052] S1. A Pt metal thin film with a thickness of 50 nm is prepared on the surface of a silicon single crystal wafer using a metal coating machine to obtain a silicon single crystal wafer with a surface-modified Pt metal thin film.

[0053] S2. The surface of the silicon single crystal wafer modified with Pt metal film is scanned by atomic force microscopy to determine the nano-depressions on the surface of the silicon single crystal wafer. Inelastic indentation is performed on the Pt metal film corresponding to the periphery of the nano-depression (the circumferential area within a radius of 50 μm centered on the nano-depression) using a diamond probe in atomic force microscopy to obtain a set of symmetrical defect markers with a depth of 25 nm (the set of defect markers is located on the same straight line as the nano-depression), thus completing the localization of the nano-depression.

[0054] After locating the nano-depressions, a 50 nm thick protective layer was prepared on the surface of the Pt metal thin film. Then, a focused ion beam was used to cut along the line where the defect marker and the nano-depression were located to find the nano-depressions.

[0055] The method in this embodiment can accurately identify the location of nano-depressions on the surface of silicon single wafers.

[0056] Example 3

[0057] This embodiment provides a method for locating nanoscale defects on the surface of a hard material using atomic force microscopy. The method uses a hard glass slide with nanocracks (60 nm in length) on its surface.

[0058] S1. An Au metal thin film with a thickness of 30 nm is prepared on the surface of a hard glass sheet using a metal coating machine to obtain a hard glass sheet with surface-modified Au metal thin film.

[0059] S2. Using an atomic force microscope, the surface of the Au metal film modified with the hard glass plate is scanned to identify the nanocracks on the hard glass plate surface. Inelastic indentation is performed on the Au metal film corresponding to the periphery of the nanocrack (the circumferential area within a radius of 10 μm centered on the nanocrack) using a diamond probe in the atomic force microscope to obtain a set of symmetrical defect markers with a depth of 10 nm (the set of defect markers is located on the same straight line as the length direction of the nanocrack), thus completing the localization of the nanocrack.

[0060] After locating the nanocracks, a 50 nm thick protective layer was prepared on the surface of the Au metal thin film. Then, a focused ion beam was used to cut along the straight line containing the defect marker and the length direction of the nanocrack to find the nanocracks.

[0061] The method in this embodiment can accurately identify the location of nanocracks on the surface of a hard glass sheet.

[0062] Example 4

[0063] This embodiment provides a method for locating nanoscale defects on the surface of hard materials based on atomic force microscopy. The difference between this method and Embodiment 1 is that the thickness of the Pt metal film in step S1 is 80 nm, resulting in a defect marker with a depth of 40 nm. The remaining methods and parameters are consistent with Embodiment 1.

[0064] The method in this embodiment suffers from poor light transmittance due to the relatively thick Pt metal film, resulting in generally low accuracy in identifying the position of nanoparticles on the surface of a hard glass sheet.

[0065] Example 5

[0066] This embodiment provides a method for locating nanoscale defects on the surface of hard materials based on atomic force microscopy. The difference between this method and Embodiment 1 is that the thickness of the Pt metal film in step S1 is 100 nm, resulting in a defect marker with a depth of 20 nm. The remaining methods and parameters are consistent with Embodiment 1.

[0067] The method in this embodiment suffers from poor accuracy in identifying the position of nanoparticles on the surface of a hard glass sheet because the thickness of the Pt metal film is relatively large, which affects light transmittance.

[0068] Example 6

[0069] This embodiment provides a method for locating nanoscale defects on the surface of hard materials based on atomic force microscopy. The difference between this method and Embodiment 1 is that the thickness of the Pt metal film in step S1 is 8 nm, resulting in a defect marker with a depth of 3 nm. The remaining methods and parameters are consistent with Embodiment 1.

[0070] The method in this embodiment suffers from poor accuracy in identifying the position of nanoparticles on the surface of hard glass sheets because the Pt metal film is too thin to form a sufficiently deep defect marker, resulting in unclear SEM imaging contrast and making subsequent cutting processes impossible.

[0071] Example 7

[0072] This embodiment provides a method for locating nanoscale defects on the surface of hard materials based on atomic force microscopy. The difference between this method and Embodiment 1 is that the thickness of the Pt metal film in step S1 is 300 nm, resulting in a defect marker with a depth of 30 nm. The remaining methods and parameters are consistent with Embodiment 1.

[0073] The method in this embodiment is unable to identify the position of nanoparticles on the surface of the underlying hard glass sheet because the Pt metal film is too thick, thus making subsequent cutting processes impossible.

[0074] Comparative Example 1

[0075] This comparative example provides a method for locating nanoscale defects on the surface of hard materials based on atomic force microscopy. The method includes the following steps:

[0076] Nanoparticles on the surface of a hard glass slide were identified by scanning with an atomic force microscope. Inelastic indentation was then performed on the surface of the nanoparticles (the circumferential area within a radius of 50 μm centered on the nanoparticle) using a diamond probe in the atomic force microscope to locate the nanoscale defects.

[0077] The method in this comparative example does not include a Pt metal film, and the hard glass sheet is too rigid to form defect markings (depth is 0), making it impossible to accurately locate defects and thus impossible to perform subsequent cutting processes.

[0078] In summary, this invention aims to achieve precise localization of nanoscale defects on the surface of hard materials using AFM indentation technology. It employs a roundabout approach to prepare a soft thin film layer on the surface of the hard material. This soft film retains the morphological memory of the nanoscale defects on the hard material surface, meaning it does not affect the original defect morphology and its presence does not impede optical transmission. Therefore, it does not hinder the rapid location of nanoscale defects using atomic force microscopy (AFM), while simultaneously creating sufficiently deep markings. Thus, by using AFM to locate the nanoscale defects within the scanning range, and then performing inelastic indentation around the defects using nanoindentation probes in the AFM, defect markings are obtained. This effectively achieves precise localization of nanoscale defects on the surface of hard materials. Subsequently, based on the defect markings, focused ion beams can be used for precise location cutting to locate the nanoscale defects.

[0079] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for locating nanoscale defects on a surface of a hard material based on atomic force microscopy, characterized in that, The method comprises the following steps: S1, preparing a soft film on the surface of a hard material to obtain a surface-modified hard material; S2, scanning the surface-modified hard material in step S1 by an atomic force microscope to determine a nanoscale defect on the surface of the hard material, and performing a non-elastic indentation on the soft film corresponding to the side of the nanoscale defect by using a nanoindentation probe in the atomic force microscope to obtain a defect mark, and completing the positioning of the nanoscale defect.

2. The method of claim 1, wherein, The nanoscale defect comprises at least one of a nanoscale contamination, a nanoscale pit or a nanoscale crack. Preferably, the nanoscale contamination comprises at least one of a nanoparticle, a nanofilm, a nanolayer or a nanocluster.

3. The method according to claim 1 or 2, characterized in that, The hard material in step S1 comprises any one of a hard glass sheet, a single crystal silicon wafer or a diamond film.

4. The method according to any one of claims 1 to 3, characterized in that, The soft film material in step S1 comprises a soft metal. Preferably, the soft metal comprises at least one of platinum, gold or silver.

5. The method according to any one of claims 1 to 4, characterized in that, The thickness of the soft film in step S1 is 10 nm to 100 nm, preferably 10 nm to 50 nm.

6. The method according to any one of claims 1 to 5, characterized in that, The region corresponding to the side in step S2 is a circumferential region corresponding to a radius of 0.1 μm to 100 μm centered on the nanoscale defect.

7. The method according to any one of claims 1 to 6, characterized in that, The depth of the defect mark in step S2 is 5 nm to 50 nm, preferably 5 nm to 25 nm.

8. The method according to any one of claims 1 to 7, characterized in that, In step S2, the defect mark comprises at least one set of symmetric marks with the position of the nanoscale defect as a symmetric center.

9. The method according to any one of claims 1 to 7, characterized in that, In step S2, the defect mark comprises at least one set of asymmetric marks with the position of the nanoscale defect as a center.

10. The method according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: S1, preparing a soft film with a thickness of 10 nm to 50 nm on the surface of a hard material to obtain a surface-modified hard material; S2, scanning the surface-modified hard material in step S1 by an atomic force microscope to determine a nanoscale defect on the surface of the hard material, the nanoscale defect comprising at least one of a nanoscale contamination, a nanoscale pit or a nanoscale crack, and performing a non-elastic indentation on the soft film corresponding to the side of the nanoscale defect by using a nanoindentation probe in the atomic force microscope, the region corresponding to the side being a circumferential region corresponding to a radius of 0.1 μm to 100 μm centered on the nanoscale defect, to obtain a defect mark with a depth of 5 nm to 25 nm, and completing the positioning of the nanoscale defect.

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