Preparation method of transmission electron microscopy samples suitable for in-situ compression experiments

Abstract

This invention provides a method for preparing transmission electron microscopy (TEM) samples suitable for in-situ compression experiments. The method involves mechanically thinning the sample for in-situ compression experiments and cutting it into a special convex shape. This convex shape is then attached to half a molybdenum ring and placed in an ion thinner to achieve direct thinning of the sample edges. Furthermore, this invention departs from the traditional dual-gun mode, employing a single-gun mode for ion thinning. This overcomes the interference of sputtering phenomena present in the dual-gun mode and results in a larger and more uniform thin area. This method is also applicable to the preparation of TEM samples from biomineralized materials. Biomineralized materials are fragile; this invention avoids the disadvantages of traditional thinning methods, conveniently preparing TEM samples with larger thin areas and better quality by directly thinning at the sample edges. This method has significant reference value for the preparation of TEM samples for in-situ compression experiments.

Description

Technical Field

[0001] This invention relates to the field of transmission electron microscopy (TEM) sample preparation technology, specifically a method for preparing TEM samples suitable for in-situ compression experiments. Background Technology

[0002] Transmission electron microscopy (TEM) is an indispensable characterization tool for studying the microstructure and evolution of materials. It plays a crucial role in revealing the underlying mechanisms behind macroscopic properties and promoting independent research and development and product upgrading in my country. TEM can observe and study the internal microstructure and crystal defects of materials, linking morphological information with structural information; it also enables dynamic observation, studying the movement and interaction of crystal defects such as dislocations under stress.

[0003] In-situ compression experiments using transmission electron microscopy (TEM) are an important experimental technique that enables in-situ study of the microstructure of materials at the atomic scale. This allows for in-situ observation of structural changes during sample deformation, effectively correlating microstructural changes with mechanical behavior in real time. Through in-situ compression experiments combined with electron microscopy, many unique physicochemical phenomena and properties of materials not present at room temperature and pressure can be discovered. In-situ compression experiments require a probe to contact a thin region of the sample to allow for observation of changes before and after probe contact under TEM; therefore, a thin region at the sample edge is necessary. Currently, the commonly used TEM sample preparation method for in-situ compression experiments is focused ion beam cutting (FIB). However, FIB sample preparation is costly, has limited thin region width, is time-consuming, and is difficult to preserve. Uncovering the potential properties of materials through in-situ compression experiments is essential; therefore, finding a low-cost method for preparing in-situ compressed samples would be a breakthrough, facilitating faster and more convenient in-situ compression experiments.

[0004] Traditional thinning methods for transmission electron microscopy (TEM) samples used in in-situ compression experiments include: first, grinding with sandpaper; then, using a pitter to create a pit in the center of the sample (this step aims to reduce the time required for subsequent ion thinning); finally, placing the cleaned, pitted sample into an ion thinner for further thinning. In recent years, research on biomineralized materials has become increasingly popular. However, biomineralized materials, similar to hard and brittle materials, exhibit high hardness and brittleness. Traditional thinning methods for biomineralized materials are prone to breakage during the pitting step, while mechanical thinning struggles to reduce the sample size to below 10 μm. Even with 7000# sandpaper, samples below 20 μm are easily ground to pieces. Without the pitting step, directly attaching a sample with a thickness of approximately 20 μm onto a molybdenum ring and placing it into the ion thinner is extremely time-consuming due to the sample's thickness. This increases the burden on the ion thinner and requires constant observation of the sample during the thinning process, making it a very time-consuming and labor-intensive task for the operator. Furthermore, traditional thinning methods often result in non-uniform thin regions with many sharp edges, and these regions are not large enough to produce good thin areas, directly affecting the observation results of transmission electron microscopy (TEM). Therefore, it is urgent to develop a convenient and rapid method for preparing high-quality TEM samples. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing transmission electron microscopy (TEM) samples suitable for in-situ compression experiments. The TEM samples prepared by this method have a large thin-area area and high quality, and can be applied to in-situ compression experiments.

[0006] This invention is implemented as follows:

[0007] A method for preparing transmission electron microscopy samples suitable for in-situ compression experiments includes the following steps:

[0008] (1) The sample was mechanically polished with sandpaper to reduce its thickness to slightly less than 100 μm;

[0009] (2) The sample in step (1) is pre-cut, and one side edge of the pre-cut sample has a crown-shaped arc protrusion structure;

[0010] (3) Continue to mechanically polish the sample in step (2) with sandpaper until the sample thickness is about 20 μm, for example, 19-21 μm or 20-22 μm;

[0011] (4) Cut the molybdenum ring in half along the axial tangent, and attach the sample from step (3) to half of the molybdenum ring, with the coronal arc protrusion of the sample protruding outside the axial tangent of the half molybdenum ring.

[0012] (5) Place the sample on the sample holder of the ion thinning instrument, so that one side of the clamp on the sample holder holds half of the molybdenum ring, and the coronal arc-shaped protrusion of the sample is located at the center of the clamp.

[0013] (6) Place the sample into the ion thinner and align the ion beam in the ion thinner so that the ion beam is just aligned with the coronal arc-shaped protrusion on the sample.

[0014] (7) Set the ion thinner to single gun mode, adjust the voltage and ion gun angle, set the thinning time, and make the ion gun spray argon ion beam to bombard the coronal arc-shaped protrusion structure on the sample.

[0015] (8) After the thinning time is over, observe whether there is any change in the shape of the coronal arc-shaped protrusion. If there is no change, increase the thinning time until the shape of the coronal arc-shaped protrusion is observed to change.

[0016] (9) Adjust the ion gun angle to 3°, single gun mode, voltage 4keV, purge impurities on the sample surface for 3 minutes, and then remove the sample.

[0017] Preferably, the sample is a biomineralized material.

[0018] Preferably, in step (7), the voltage is adjusted to 5keV and the ion gun angle is 5°.

[0019] Preferably, the maximum protrusion length of the coronal arc-shaped protrusion structure of the sample that extends beyond the tangent of half of the molybdenum ring does not exceed 1 / 6 of the inner diameter of the molybdenum ring.

[0020] Preferably, the angle between the line connecting the highest and lowest points of the coronal arc-shaped protrusion and the tangent of the molybdenum ring axis does not exceed 30°.

[0021] Preferably, in step (5), one side of the clamp on the sample holder clamps the center of the outer edge of half of the molybdenum ring.

[0022] Preferably, in step (1), 1000#, 2000#, and 3000# metallographic sandpaper are used to mechanically polish both sides of the sample in sequence.

[0023] Preferably, in step (3), 3000#, 5000# and 7000# metallographic sandpaper are used to mechanically polish both sides of the sample in sequence.

[0024] Preferably, when the sample thickness is 90-100 μm, it is polished with 3000# metallographic sandpaper; when the sample thickness is reduced to 70-90 μm, it is polished with 5000# metallographic sandpaper; when the sample thickness is reduced to less than 70 μm, it is polished with 7000# metallographic sandpaper.

[0025] Preferably, in step (4), the sample is attached to half of the molybdenum ring with the sample AB glue and the glue is allowed to dry completely on a heating table at 40°C.

[0026] The present invention has the following beneficial effects:

[0027] 1. This invention changes the traditional sample adhesion method and thinning mode. The ion beam only thins the coronal arc-shaped protrusion extending beyond the tangent of half of the molybdenum ring. Because the forces on the edge and core differ during mechanical thinning, the sample edge is thinner than the core. That is, the coronal arc-shaped protrusion is thinner than the center of the sample during mechanical thinning, making ion beam thinning more advantageous and improving efficiency. With the sample adhered to half of the molybdenum ring, there is no obstruction from the surrounding rings, allowing all argon ion beams to reach the sample edge, resulting in a larger thin area in the transmission electron microscope sample.

[0028] 2. By changing the traditional dual-gun mode to a single-gun mode for ion thinning, the interference of sputtering phenomenon present in the dual-gun mode can be overcome, and the area of ​​the thinned sample is larger and more uniform.

[0029] 3. This invention improves the position of the thin region of the sample, which is beneficial for in-situ compression experiments in transmission electron microscopy. Traditional in-situ compression experiments use FIB cutting technology to obtain transmission electron microscopy samples, which are costly, have limited thin region width, and are not easy to preserve.

[0030] 4. The present invention also improves the shape of the sample pre-thinning, improves the way the sample is held by the ion thinning instrument fixture, and adjusts the parameters of the ion thinning instrument. These improvements enable the thinning to obtain a high-quality, large-area thin region. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure in this invention where the sample is attached to half of a molybdenum ring.

[0032] Figure 2 This is a schematic diagram of the structure of the clamp holding half of the edge of the molybdenum ring in this invention.

[0033] Figure 3 This is a graph showing the relationship between the direction of ions ejected by the ion gun and the sample under single-gun thinning mode and dual-gun thinning mode.

[0034] Figure 4 This is a schematic diagram of the working principle of the ion gun in single-gun mode; where ① the ion beam hits the upper surface of the sample; ② the ion beam hits the lower surface of the sample.

[0035] Figure 5 This is a schematic diagram of the working principle of the ion gun in dual-gun mode; where ①③ the ion beams hit the upper surface of the sample; ②④ the ion beams hit the lower surface of the sample.

[0036] Figure 6 This is a schematic diagram of the sample being placed in the PI95 rod in this invention.

[0037] Figure 7 These are schematic diagrams showing different structural shapes of the sample after pre-thinning.

[0038] Figure 8 This is a schematic diagram of different clamping methods for half of a molybdenum ring.

[0039] Figure 9 The image is a 400x TEM image in LOWMAG mode of the biogenic calcium carbonate nacre sample prepared for Comparative Example 1.

[0040] Figure 10 This is a TEM image of the biogenic aragonite calcium carbonate nacre sample prepared in Example 1, in LOWMAG mode at 400x magnification.

[0041] Figure 11 The image shows a TEM image of the biogenic aragonite calcium carbonate nacre sample prepared in Comparative Example 1 at LOWMAG mode × 8000 magnification.

[0042] Figure 12 This is a TEM image of the biogenic aragonite calcium carbonate nacre sample prepared in Example 1, magnified at LOWMAG mode × 8000.

[0043] Figure 13 and Figure 14 All images are Montage Image Viewer images at 8000x magnification of the biogenic aragonite calcium carbonate nacre sample prepared in Comparative Example 1.

[0044] Figure 15 and Figure 16 All images are Montage Image Viewer images at 8000x magnification of the bio-aragonite calcium carbonate nacre sample prepared in Example 1.

[0045] Figure 17 Load-displacement curves and images of in-situ compression experiments performed on the sample prepared in Example 1.

[0046] Figure 18 These are Montage Image Viewer images of the sample prepared in Example 2 at a magnification of 8000.

[0047] Figure 19 These are Montage Image Viewer images of the sample prepared in Example 3 at a magnification of 8000.

[0048] Figure 20These are Montage Image Viewer images of the sample prepared in Example 4 at a magnification of 8000.

[0049] Figure 21 These are Montage Image Viewer images of the sample prepared in Example 5 at a magnification of 8000.

[0050] Figure 22 These are Montage Image Viewer images of the sample prepared in Example 6 at a magnification of 8000. Detailed Implementation

[0051] The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments provided by this invention includes the following steps:

[0052] (1) Take a sample of appropriate size and glue it to the grinding table. Then, mechanically grind both sides of the sample on 1000#, 2000# and 3000# metallographic sandpaper in sequence. Place a smooth and flat glass plate under the sandpaper and grind on the sandpaper in a figure-eight pattern to achieve uniform thinning. Mechanically thin the sample to a thickness of slightly less than 100μm and then remove the sample.

[0053] (2) Wipe the residual adhesive on the sample surface with acetone, then rinse three times with anhydrous ethanol and deionized water in sequence. Pre-cut the mechanically thinned sample as follows: Figure 1 As shown, a sample 2 with a coronal arc-shaped protrusion structure 2-1 is obtained. The side of sample 2 opposite to the coronal arc-shaped protrusion structure 2-1 can be a semi-circular structure, or other regular or irregular structures. This regular or irregular structure needs to be subsequently attached to half of the molybdenum ring 1. After attaching sample 2 to half of the molybdenum ring 1, the coronal arc-shaped protrusion structure 2-1 protrudes beyond the outer side of the axial tangent of half of the molybdenum ring 1 (shown by the dotted line in the figure). Through trimming, the highest protrusion length of the coronal arc-shaped protrusion structure 2-1 does not exceed 1 / 6 of the inner diameter of the molybdenum ring, or in other words, the length d of sample 2 on the straight line perpendicular to the axial tangent of the inner diameter of the molybdenum ring does not exceed 2 / 3 of the inner diameter of the molybdenum ring. The angle θ between the line connecting the highest and lowest points of the coronal arc-shaped protrusion structure 2-1 and the axial tangent of the molybdenum ring 1 does not exceed 30°.

[0054] (3) Use a rubber to drag the sample and continue to polish it on the metallographic sandpaper. When the thickness of the sample is 90 - 100 μm, polish it with 3000# sandpaper; when the sample is thinned to a thickness of 70 - 90 μm, polish it with 5000# sandpaper; when the thickness of the sample is thinned to less than 70 μm, polish it with 7000# sandpaper; use 7000# sandpaper to polish until the thickness of the sample is polished to about 20 μm. Samples of different thicknesses are polished with sandpapers of different mesh numbers. The thinner the sample, the higher the mesh number of the sandpaper used, to prevent the sample from breaking during polishing due to too low mesh number of the sandpaper. The sample needs to be polished to about 20 μm because samples thicker than 20 μm are too thick, affecting the thinning effect, with a small and uneven thin area; while samples thinner than 20 μm are very thin, and it is difficult to control the thickness during mechanical thinning, and it is easy to grind the sample into pieces during mechanical thinning.

[0055] (4) Cut the molybdenum ring (a molybdenum ring with an outer diameter of 3 mm is selected in the embodiment of the present invention) in half along the symmetry axis, and the cut line is the axis tangent line; stick the sample on half of the molybdenum ring with a small amount of ab glue, so that after the sample is stuck on the molybdenum ring, the coronal arc-shaped convex structure on the sample protrudes outside the axis tangent line of half of the molybdenum ring, as Figure 1 shown. Then place the molybdenum ring on the pad paper, and let the sample wait for the glue to dry on the heating table at 40 °C in a relatively suspended setting.

[0056] Sticking the sample on half of the molybdenum ring is beneficial for subsequent ion thinning. After being placed in the ion thinner, without the hindrance of the other half of the molybdenum ring, all the ion beams can hit the edge part of the sample, enabling both the upper and lower surfaces of the sample to be bombarded by the ion beams to achieve a large-area and high-quality thin area.

[0057] (5) Place the sample on the loading table wall of the sample holder配套 to the ion thinner, open the clamp, and slide the arm forward to clamp the outer edge center of half of the molybdenum ring on one side, with the coronal arc-shaped convex structure part of the sample suspended, as Figure 2 shown, and the coronal arc-shaped convex structure part of the sample is located at the center position of the clamp, then close the clamp.

[0058] Placing the coronal arc-shaped convex structure part of the sample at the center position of the clamp enables the ion thinner after ion beam alignment to thin the coronal arc-shaped convex structure part. Due to different forces during the sample grinding process, the edge part is thinner than the core part, that is: the coronal arc-shaped convex structure part is thinner than the center part of the sample. Therefore, the thinning time can be shortened, and it is also beneficial for sample preparation of samples for observing the micron-level edge part.

[0059] (6) Align the ion beam in the ion thinner and place the sample in the ion thinner. When the ion beam is aligned with the coronal arc-shaped protrusion on the sample, set the ion thinner to single-gun mode, adjust the voltage (e.g., 5keV) and ion gun angle (e.g., 5°), and set the thinning time. Initially, set it to 0.5h and observe whether the shape of the coronal arc-shaped protrusion changes. If there is no change, increase the thinning time until a change in the shape of the coronal arc-shaped protrusion is observed. Then, adjust the ion gun angle to 3°, switch to single-gun mode, set the voltage to 4keV, purge impurities from the sample surface for 3 minutes, and remove the sample.

[0060] This invention employs a single-gun method to thin the sample, such as... Figure 3 As shown in (a); if the traditional dual-gun method is used to thin the sample, then as Figure 3 As shown in (b). That is, in single-gun mode, the ion gun can only thin from the side marked with a star (as indicated by the arrow in the figure), while in dual-gun mode, the ion gun can thin from either the side marked with a star or the opposite side. In other words, in dual-gun mode, a thin area can be thinned along the two arrow directions shown in the figure. This mode is subject to sputtering interference, and by comparison, it was found that the sample thin area thinned in single-gun mode is larger and more uniform.

[0061] Figure 4 and Figure 5 The working principles of the ion gun in single-gun and dual-gun modes are shown respectively. In the figure, ①-④ represent the working conditions of the ion gun during one rotation of the sample, which is also a cycle. In single-gun mode, the sample is bombarded twice by the argon ion beam during one rotation in the ion thinner, while in the traditional dual-gun mode, the sample is bombarded four times by the argon ion beam during one rotation. In comparison, the single-gun mode allows for a certain cooling time after one rotation, meaning that the argon ion beam causes less damage to the sample, thus improving the quality of the transmission electron microscopy image.

[0062] In dual-gun mode, the sample rotates at the same rate for one revolution. In single-gun mode, since the sample is bombarded by the ion beam in states ① and ②, but not in states ③ and ④, the rotation is slightly slower in states ① and ②, and slightly faster in states ③ and ④. This shortens the sample thinning time.

[0063] This invention utilizes a half-molybdenum ring design combined with a single-gun mode to thin the sample. The portion of the sample protruding parallel to the tangent of the molybdenum ring axis faces the direction of ion beam emission, allowing for direct thinning of the sample edge. This facilitates in-situ compression testing and avoids the drawbacks of traditional in-situ compressed sample fabrication using focused ion beam cutting (FIB), such as high cost, significant beam damage, limited thin area width, and difficulty in preservation. Furthermore, the single-gun mode causes less damage to the sample, resulting in a higher quality and larger area of ​​the thin sample.

[0064] (7) If used for in-situ compression experiments, remove the sample and place it in a carbon sprayer for double-sided carbon spraying to obtain a transmission electron microscope (TEM) sample suitable for in-situ compression experiments. If used only for TEM sample observation, remove the half-molybdenum ring attached to the sample and glue it to another complete molybdenum ring with AB glue. The outer diameter of the complete molybdenum ring is the same as that of the half-molybdenum ring in step (4), and its inner diameter is larger than that of the half-molybdenum ring in step (4). Therefore, the complete molybdenum ring will not obstruct the sample, which is convenient for subsequent TEM observation. Then, place the complete molybdenum ring on a pad paper, and wait for the glue to dry completely on a 40°C heating stage with the sample in a relatively suspended position. Place it in a carbon sprayer for double-sided carbon spraying to obtain the TEM sample. Alternatively, the sample can be carbon sprayed on both sides first and then glued to the complete molybdenum ring.

[0065] The half of the molybdenum ring attached to the sample is removed and glued to another complete molybdenum ring with AB glue. This is to prevent the half of the molybdenum ring from falling into the electron microscope chamber when it is placed into the sample holder of the transmission electron microscope.

[0066] Carbon spraying is performed on the sample because biomineralized materials are non-conductive. When observing the sample with a transmission electron microscope, it is necessary to allow the electron beam to pass through the sample. Therefore, carbon needs to be sprayed on both sides of the material to avoid the charging effect of the electron beam on the sample surface.

[0067] The thin region of the transmission electron microscope sample obtained by the single-gun mode thinning of this invention is located at the edge of the sample. When performing in-situ compression experiments, the probe of the PI95 rod can directly contact the edge of the thin region of the sample. It is also low in cost, easy to preserve, and convenient to manufacture. Figure 6 The diagram shows the sample being placed into the PI95 probe, which can directly contact the sample under computer control.

[0068] This invention improves the shape of the sample pre-thinning. For example... Figure 7 As shown, the sample after pre-thinning in this invention has arc-shaped protrusions with a crown-like structure, such as... Figure 7 As shown in (b), when the sample is attached to half of the molybdenum ring, the coronal arc-shaped protrusion extends beyond the axial tangent of the half-molybdenum ring. If the coronal arc-shaped protrusion is replaced with... Figure 7In the strip structure shown in (a), the sample edge plane is relatively thick, resulting in low thinning efficiency and poor quality of the thin area. If the coronal arc-shaped protrusion is replaced with the fan-shaped protrusion in (c), the protrusion is too sharp, and although a thin area can be formed, the area of ​​the thin area is very small. Therefore, this invention optimizes the design so that the sample forms the edge of the coronal arc-shaped protrusion structure through pre-thinning. When the sample is attached to half of the molybdenum ring, the corresponding coronal arc-shaped protrusion structure is located outside the axial tangent of half of the molybdenum ring. The distance from the highest point of the coronal arc-shaped protrusion structure to the lowest point of the inner wall of half of the molybdenum ring is less than two-thirds of the inner diameter of the molybdenum ring. The bottom angle between the coronal arc-shaped protrusion structure and the axial tangent of half of the molybdenum ring is preferably less than 30°. The outer edge of the coronal arc-shaped protrusion structure is arc-shaped, which is beneficial for subsequent thinning and obtaining a thin area with high quality and large area.

[0069] In addition, the clamping method for half of the molybdenum ring in this invention is also different from existing technologies. Traditional clamping methods, such as... Figure 8 As shown in (b), the molybdenum ring is typically clamped at both ends. According to the principle of the ion thinning instrument, the direction of the sample exiting the thinned area is as indicated by the arrow in the figure. In this case, the ion gun fails to align with the coronal arc-shaped protrusion of the sample. In this invention, when clamping half of the molybdenum ring, the clamp is positioned so that it grips the center of the outer edge of the half-molybdenum ring, as shown... Figure 8 As shown in (a), this clamping method allows the ion beam to be aligned with the sample edge for thinning, achieving the desired effect.

[0070] The technical solution of the present invention will be described in detail below with specific examples.

[0071] Comparative Example 1

[0072] Biological aragonite calcium carbonate nacre was used as the sample. This sample belongs to biomineralized materials and was prepared according to the following steps:

[0073] (1) Take a suitable size bio-aragonite calcium carbonate nacre sample, glue it to the grinding table, and grind the sample on both sides in sequence on 1000#, 2000# and 3000# metallographic sandpaper. Place a smooth and flat glass plate under the sandpaper and grind it on the sandpaper in a figure-eight pattern to achieve uniform thinning. Mechanically thin it to a thickness of slightly less than 100μm, and then remove the sample.

[0074] (2) Wipe the residual glue on the sample surface with acetone, and clean it three times with anhydrous ethanol and deionized water in turn. Cut the mechanically thinned sample into a shape that can cover the inner diameter of the molybdenum ring after the sample is pasted onto the molybdenum ring with an outer diameter of 3 mm.

[0075] (3) Use a rubber to drag the sample on metallographic sandpaper to continue polishing. First, use 3000# sandpaper to polish. When the sample thickness drops below 90μm, switch to 5000# sandpaper. When the sample thickness drops below 70μm, switch to 7000# sandpaper until the sample thickness is about 20μm.

[0076] (4) Attach the sample to a molybdenum ring with an outer diameter of 3 mm using very thin AB glue, and place the sample on a heating table at 40°C to wait for the glue to dry completely.

[0077] (5) Place the sample on the loading stage wall of the sample holder that comes with the ion thinning instrument, open the clamp, and slide the arm forward so that the molybdenum ring is in the center of the clamp. Close the clamp, and the clamp will hold the two ends of the molybdenum ring.

[0078] (6) Align the ion beam in the ion thinner, place the sample in the ion thinner, adjust to dual-gun mode, voltage 5keV, ion gun angle 5°. After 1.5 hours of thinning, holes are observed on the sample. Adjust the ion gun angle to a low angle of 3°, dual-gun mode, voltage 4keV, and purge impurities from the sample surface for 3 minutes. Remove the sample and place it in a carbon sprayer for double-sided carbon spraying to obtain the transmission electron microscope sample.

[0079] The obtained transmission electron microscope (TEM) samples were observed using a JEOL-2100plus TEM, and the results are as follows: Figure 9 , Figure 11 , Figure 13 and Figure 14 As shown.

[0080] Example 1

[0081] Biological aragonite calcium carbonate nacre was used as the sample. This sample belongs to biomineralized materials and was prepared according to the following steps:

[0082] (1) Take a suitable size bio-aragonite calcium carbonate nacre sample, glue it to the grinding table, and grind the sample on both sides in sequence on 1000#, 2000# and 3000# metallographic sandpaper. Place a smooth and flat glass plate under the sandpaper and grind it on the sandpaper in a figure-eight pattern to achieve uniform thinning. Mechanically thin it to a thickness of slightly less than 100μm, and then remove the sample.

[0083] (2) Wipe the residual glue on the sample surface with acetone, and clean it three times with anhydrous ethanol and deionized water in turn. Cut the mechanically thinned sample. The cut sample edge has a crown-shaped arc-shaped protrusion structure.

[0084] (3) Use a rubber to drag the sample on metallographic sandpaper to continue polishing. First, use 3000# sandpaper to polish. When the sample thickness drops below 90μm, switch to 5000# sandpaper. When the sample thickness drops below 70μm, switch to 7000# sandpaper until the sample thickness is about 20μm.

[0085] (4) Cut the molybdenum ring with an outer diameter of 3 mm in half along the axis of symmetry. The cut line is the axial tangent. Use AB glue to attach a sample with a thickness of about 20 μm to half of the molybdenum ring. The coronal arc-shaped protrusion on the sample protrudes outside the axial tangent of the half of the molybdenum ring. Then let the glue dry on the heating stage.

[0086] (5) Place the sample on the loading stage wall of the sample rack that is matched with the ion thinner, open the clamp, and slide the arm forward so that one side of the clamp clamps half of the outer edge center of the molybdenum ring. The coronal arc-shaped protrusion on the sample is suspended in the air, and the coronal arc-shaped protrusion on the sample is located at the center of the clamp. Close the clamp.

[0087] (6) Align the ion beam in the ion thinner. Place the sample in the ion thinner and align the ion beam with the coronal arc-shaped protrusion on the sample. Adjust the ion thinner to single-gun mode, voltage 5keV, ion gun angle 5°, and thinning time 1.25h. Observe the change in shape of the coronal arc-shaped protrusion on the sample. Adjust the ion gun angle to a low angle of 3°, single-gun mode, voltage 4keV, and blow away impurities on the sample surface for 3min. Remove the sample.

[0088] The sample was removed and placed in a carbon sprayer for double-sided carbon spraying, thus obtaining the transmission electron microscope sample for in-situ compression testing. An in-situ compression test was performed on this sample, and the results are as follows... Figure 17 As shown, Figure 17 In the figure, (a) is the load-displacement curve of the in-situ compression test, and (b) is the image of the sample undergoing the in-situ compression test.

[0089] After the sample was carbon-coated on both sides, half of a molybdenum ring was attached to a complete molybdenum ring with an outer diameter of 3 mm but an inner diameter larger than half the inner diameter of the molybdenum ring. The sample was then observed in a JEOL-2100plus transmission electron microscope. The results are as follows. Figure 10 , Figure 12 , Figure 15 and Figure 16 As shown.

[0090] Figure 9 and Figure 10 These are TEM images of the samples from Comparative Example 1 and Example 1, respectively, under LOWMAG mode at 400x magnification. Measurements were performed using ImageJ software. Figure 9 and Figure 10 The thin region area is 74.031 μm.2 and 1064.4262μm 2 That is, the transmission electron microscope sample prepared by the method of the present invention has a larger thin edge area, while the sample thinned by the conventional sample preparation method in Comparative Example 1 has a serrated edge, and the sample thinned by the present invention has a smoother edge.

[0091] Figure 11 and Figure 12 These are TEM images of the samples from Comparative Example 1 and Example 1, respectively, under LOWMAG mode at 8000x magnification. Figure 11 and Figure 12 It can be seen that, at the same magnification, the sample thinned by the traditional sample preparation method has many holes. This is due to the damage to the sample by the argon ion beam during the thinning process. In contrast, the sample thinned by the present invention has a more uniform thin area and a larger thin area.

[0092] Figure 13 and Figure 14 All photos were taken in Montage Image Viewer mode for the samples in Comparative Example 1. Figure 15 and Figure 16 All photos were taken in Montage Image Viewer mode of the samples in Example 1. Figures 13-16 All images are nine images stitched together using the same multiple of detail. Figures 13-16 It allows for a more direct observation that samples thinned using traditional methods suffer from significant damage, small thin areas, and low quality. In contrast, samples thinned using the method of this invention exhibit the opposite characteristics: minimal damage, large thin areas, and high quality. Furthermore, samples thinned using traditional methods have thin areas located in the middle, making them unsuitable for in-situ compression experiments. The method of this invention, however, can be used for both in-situ compression experiments and observation using transmission electron microscopy, offering convenience and speed.

[0093] Based on Example 1, the present invention adjusts the relevant parameters during the ion thinning process, as follows:

[0094] Example 2

[0095] Compared with Example 1, in this example, the ion thinning instrument is adjusted to single-gun mode, the voltage is 3keV, the ion gun angle is 5°, and the thinning time is 2.5h. The remaining steps are the same as in Example 1.

[0096] Example 3

[0097] Compared with Example 1, in this example, the ion thinning instrument is adjusted to single-gun mode, the voltage is 7keV, the ion gun angle is 5°, and the thinning time is 40min. The remaining steps are the same as in Example 1.

[0098] Example 4

[0099] Compared with Example 1, in this example, the ion thinning instrument is adjusted to single-gun mode, the voltage is 5keV, the ion gun angle is 3°, and the thinning time is 4.5h. The remaining steps are the same as in Example 1.

[0100] Example 5

[0101] Compared with Example 1, in this example, the ion thinning instrument is adjusted to single-gun mode, the voltage is 5keV, the ion gun angle is 7°, and the thinning time is 1h. The remaining steps are the same as in Example 1.

[0102] Example 6

[0103] Compared with Example 1, in this example, the ion thinning instrument is adjusted to dual-gun mode, the voltage is 5keV, the ion gun angle is 5°, and the thinning time is 1.5h. The remaining steps are the same as in Example 1.

[0104] The transmission electron microscope (TEM) samples prepared in Examples 1-6 were observed in a JEOL-2100plus TEM, and the results are as follows: Figure 15 , Figure 18 , Figure 19 , Figure 20 , Figure 21 and Figure 22 The detailed comparison table is shown in Table 1 below.

[0105] Table 1. Comparison of relevant thinning parameters and thinning effects of samples prepared in Examples 1-6.

[0106] Example Thinning parameters thinning time Thinning effect Example 1 5°, 5keV, single-gun mode 1.25h See Figure 13 Example 2 5°, 3keV, single-gun mode 2.5h See Figure 18 Example 3 5°, 7keV, single-gun mode 40min See Figure 19 Example 4 3°, 5keV, single-gun mode 4.5h See Figure 20 Example 5 7°, 5keV, single-gun mode 1h See Figure 21 Example 6 5°, 5keV, dual-gun mode 1.5h See Figure 22

[0107] This invention improves the parameter settings during ion thinning. By thinning the same sample under different parameters, the rationality of the selected parameters is verified based on the thinning effect and the thinning time. As shown in Table 1, the samples after thinning in Examples 1 and 2 both exhibit large-area, high-quality thin regions. However, Example 1 requires less time and is more efficient. Comparing Examples 1 and 3, it is clearly observed that Example 1 has a better thinning effect and less beam damage. Although the thinning time in Example 3 is very short, the quality of the thin region of the sample is significantly lower than that in Example 1. Similarly, comparing Examples 1, 4, and 5, Examples 1 and 4 have good thinning quality, but Example 4 has a long thinning time, and the thin region area in Example 5 is very small. Comparing Examples 1 and 6, it can be seen that the sample in the dual-gun mode in Example 6 suffers greater beam damage.

[0108] As can be seen from the above, the higher the voltage, the greater the beam damage to the sample; the larger the ion gun angle, the smaller the area of ​​the thin region of the sample; while too small a voltage and ion gun angle will greatly increase the thinning time; and dual-gun mode will also cause beam damage. Therefore, the most suitable thinning parameters obtained by this invention are: ion gun angle 5°, voltage 5keV, and single-gun mode.

Claims

1. A method for preparing transmission electron microscopy samples suitable for in-situ compression experiments, characterized in that, Includes the following steps: (1) The sample was mechanically polished with sandpaper to reduce its thickness to slightly less than 100 μm; (2) The sample in step (1) is pre-cut, and one side edge of the pre-cut sample has a crown-shaped arc protrusion structure; (3) Continue to mechanically polish the sample in step (2) with sandpaper until the sample thickness is 20±1μm; (4) Cut the molybdenum ring in half along the axial tangent, and attach the sample from step (3) to half of the molybdenum ring, with the coronal arc protrusion of the sample protruding outside the axial tangent of the half molybdenum ring. (5) Place the sample on the sample holder of the ion thinning instrument, so that one side of the clamp on the sample holder holds half of the molybdenum ring, and the coronal arc-shaped protrusion of the sample is located at the center of the clamp. (6) Place the sample into the ion thinner and align the ion beam in the ion thinner so that the ion beam is just aligned with the coronal arc-shaped protrusion on the sample. (7) Set the ion thinner to single gun mode, adjust the voltage and ion gun angle, set the thinning time, and make the ion gun spray argon ion beam to bombard the coronal arc-shaped protrusion structure on the sample. (8) After the thinning time is over, observe whether there is any change in the shape of the coronal arc-shaped protrusion. If there is no change, increase the thinning time until the shape of the coronal arc-shaped protrusion is observed to change. (9) Adjust the ion gun angle to 3°, single gun mode, voltage 4keV, purge impurities on the sample surface for 3 minutes, and then remove the sample.

2. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, The sample is a biomineralized material.

3. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, In step (7), the voltage is adjusted to 5keV and the ion gun angle is 5°.

4. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, The maximum length of the coronal arc-shaped protrusion structure protruding beyond the tangent of half of the molybdenum ring does not exceed 1 / 6 of the inner diameter of the molybdenum ring.

5. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 4, characterized in that, The angle between the line connecting the highest and lowest points of the coronal arc-shaped protrusion and the tangent of the molybdenum ring axis does not exceed 30°.

6. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, In step (5), one side of the clamp on the sample holder clamps the center of the outer edge of half of the molybdenum ring.

7. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, In step (1), 1000#, 2000# and 3000# metallographic sandpaper were used to mechanically polish both sides of the sample in sequence.

8. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, In step (3), 3000#, 5000# and 7000# metallographic sandpaper are used to mechanically polish both sides of the sample in sequence.

9. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 8, characterized in that, When the sample thickness is 90-100 μm, use 3000# metallographic sandpaper for polishing; when the sample thickness is reduced to 70-90 μm, use 5000# metallographic sandpaper for polishing; when the sample thickness is reduced to less than 70 μm, use 7000# metallographic sandpaper for polishing.

10. The method for preparing transmission electron microscopy samples suitable for in-situ compression experiments according to claim 1, characterized in that, In step (4), the sample is attached to half of the molybdenum ring with the sample AB glue and allowed to dry completely on a heating stage at 40°C.

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