Transition metal chalcogenide layered material transmission electron microscope sample preparation method

Abstract

The invention relates to a transmission electron microscope sample preparation method of a transition metal chalcogenide layered material, which comprises the following steps: grinding a transition metal chalcogenide block, and selecting a slice in the transition metal chalcogenide block; placing the sheet on an adhesive tape, repeatedly folding and bonding for many times, tearing the adhesive tape for stripping, attaching the adhesive tape obtained after stripping to a transfer substrate, gently applying force to enable the surface of the adhesive tape to be tightly attached to the transfer substrate, and then tearing off the adhesive tape from the transfer substrate to obtain a substrate attached with a stripping thin layer; immersing the substrate in an infiltration solvent, carrying out ultrasonic treatment, and separating a transfer substrate and a stripping thin layer of the substrate; and taking out the transfer substrate in the infiltration solvent, immersing the electron microscope grid on the infiltration solvent liquid film on the surface of the transfer substrate, moving the electron microscope grid to enable the stripping thin layer to be carried on the electron microscope grid, drying, and waiting for observation of the transmission electron microscope. Compared with the prior art, the method is easy and convenient to operate, low in cost and free of additional instruments, and the large-area few-layer thin-area sample can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of material characterization and relates to a transmission electron microscope sample preparation method for a transition metal sulfide compound layered material. Background Art

[0002] Layered electrode materials achieve capacity storage and supply through the embedding / release of ions in the interlayer structure. They usually have stable cycle performance and excellent rate performance, and have been widely studied and used in both positive and negative electrodes of alkali metal ion batteries. Among them, transition metal chalcogenides (TMCs) have a large theoretical capacity and interlayer spacing. During the energy storage process, alkali metal ions are not only stored in their interlayers by the "embedding chemistry" mechanism, but also undergo alloying and conversion reactions with them. Therefore, they have a higher energy density and exhibit excellent rate performance. They are high-capacity battery negative electrode materials with great application potential. However, transition metal chalcogenides have large volume changes during the charge and discharge process and are prone to mechanical fracture, which leads to battery capacity decay and life decay, limiting their industrial application.

[0003] In order to explore effective structural regulation and targeted optimization strategies, it is particularly important to explore the reaction mechanism and capacity attenuation mechanism of transition metal chalcogenides during the charging and discharging process. High-resolution electron microscopy technology can study the phase structure at the atomic to nanoscale. Combined with energy spectrum or electron energy loss spectrum analysis, it can directly obtain the chemical composition, morphology and valence information of the sample. Using in-situ transmission electron microscopy technology, it can also obtain dynamic structural evolution information during the charging and discharging process of electrode materials. In order to better explore the reaction mechanism and capacity attenuation mechanism of transition metal chalcogenides during the charging and discharging process of batteries, the preparation of high-quality single-layer or few-layer transmission electron microscopy samples is a prerequisite.

[0004] Ion thinning and electrolytic double spraying are commonly used to thin samples for transmission electron microscopy. However, both methods are relatively complicated and are not suitable for the preparation and observation of transition metal chalcogenide layered materials. Especially for samples used for in-situ transmission electron microscopy, not only must the thickness be thin enough, but there are also certain requirements on the size.

[0005] Although transmission electron microscopy samples of transition metal sulfide compound layered materials can be obtained by solvent-assisted ultrasonic stripping and electrochemical stripping in the prior art, the transmission electron microscopy samples obtained by solvent-assisted ultrasonic stripping are severely damaged, have small thin areas, and are thick. The electrochemical stripping method destroys the crystallinity of the sample, and the transmission electron microscopy samples obtained are amorphous samples.

[0006] Patent CN106289898A discloses a method for preparing a molybdenum disulfide transmission electron microscope sample with controllable number of layers, comprising: mechanical stripping, tearing off a molybdenum disulfide thin sheet from the surface of the molybdenum disulfide material, and bonding and separating it multiple times until the sample is relatively dense; transferring the sample, cutting out a silicon wafer, sticking the above-mentioned tape against the polished surface of the silicon wafer, and then tearing off the tape; observing with an optical microscope, accurately determining the number of layers of the molybdenum disulfide thin sheet by an atomic force microscope; after finding the thin area under the optical microscope, covering the thin area with a microgrid, and dripping isopropanol to fully combine the thin sheet with the carbon film; dripping potassium hydroxide solution onto the above-mentioned microgrid to etch the silicon wafer; placing the above-mentioned microgrid in deionized water to dissolve; transferring the above-mentioned microgrid to an isopropanol solution for immersion; and drying the above-mentioned microgrid to obtain the molybdenum disulfide transmission electron microscope sample with controllable number of layers. However, the method described in the patent requires the use of potassium hydroxide solution to etch silicon wafers. This process is very likely to cause sample preparation contamination, or chemical reactions in the sample due to long processing time. At the same time, the use of different solutions such as deionized water and isopropyl alcohol for dissolution and transfer is also very likely to introduce new contaminants. These will introduce new uncertainties to the subsequent observation of samples, such as severe amorphous layers, changes in sample structure, etc. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing samples of transition metal sulfide layered materials by transmission electron microscopy in order to overcome at least one defect of the above-mentioned prior art. The present invention is easy to operate, low-cost, does not require additional instruments, and can obtain large-area, small-layer, thin-area samples.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] One of the technical solutions of the present invention is to provide a method for preparing a sample of a transition metal chalcogenide layered material under a transmission electron microscope, the method comprising the following steps:

[0010] S1. Grinding a sample, grinding a transition metal chalcogenide block, and selecting a transition metal chalcogenide flake therein;

[0011] S2, mechanical stripping, placing the transition metal sulfide compound sheet on the tape, repeatedly folding and bonding, and tearing the tape to strip, and by adjusting the number of sticking and tearing, a single crystal micron sheet of desired thickness and size is stripped, and the tape obtained after stripping is attached to a clean transfer substrate, and force is gently applied to make the surface of the tape evenly and tightly adhere to the transfer substrate, and then the tape is torn off the transfer substrate, and the single crystal micron sheet is transferred to the transfer substrate to obtain a substrate with a transition metal sulfide compound stripping thin layer attached;

[0012] S3, ultrasonic treatment, immersing the substrate with the transition metal sulfide compound exfoliation layer attached thereto in an immersion solvent, and ultrasonically separating the transfer substrate of the substrate with the transition metal sulfide compound exfoliation layer attached thereto and the transition metal sulfide compound exfoliation layer;

[0013] S4. Sample transfer: take out the transfer substrate from the wetting solvent, immerse the electron microscope grid in the wetting solvent film on the surface of the transfer substrate, move the electron microscope grid, peel off the thin layer of transition metal sulfide compound and load it onto the electron microscope grid, dry it, and wait for transmission electron microscope observation to obtain the transmission electron microscope sample of transition metal sulfide compound layered material.

[0014] Furthermore, the grinding time in step S1 is 1-2 minutes, until the large blocks become small pieces, and the picked slices should be as thin and small as possible, with a thickness of 0.25-1 mm and a size of 3-5 mm, so as to facilitate repeated peeling.

[0015] As a preferred technical solution, in step S2, the tape is selected from 3M tape or blue film tape.

[0016] Furthermore, in step S2, the length of the tape is 15-25 cm, and the width is 15-25 mm.

[0017] Furthermore, the number of times of folding, gluing and tearing in step S2 is no less than 20 times, until the adhesive side of the tape presents a uniform black-gray color and has no obvious stickiness.

[0018] As a preferred technical solution, the number of folding, gluing and tearing in step S2 is no more than 100 times.

[0019] Furthermore, in step S2, the transfer substrate is selected from an oxide layer silicon substrate or a sapphire substrate, and the length of the transfer substrate is 1-2 cm, the width is 1-2 cm, and the thickness is 0.4-0.5 mm.

[0020] Furthermore, the time for applying force in step S2 is 3-5 minutes.

[0021] Furthermore, when the tape is torn off in step S2, the peeling angle between the tape and the transfer substrate is 140-160°, so that the peeled thin layer of the transition metal sulfide compound is more completely retained on the substrate.

[0022] Furthermore, in step S3, the infiltration solvent is selected from ethanol, isopropanol or acetone, the volume of the infiltration solvent is 3-5 mL, the frequency of ultrasound is 20-40 kHz, and the time is 3-5 min.

[0023] As a preferred technical solution, in step S4, the electron microscope grid is selected from ordinary carbon film copper grid, ultra-thin carbon film copper grid, micro-grid copper grid or micro-grid molybdenum grid.

[0024] Furthermore, in step S4, the drying temperature is 40-60° C. and the drying time is 10-20 min.

[0025] As a preferred technical solution, the area of ​​the thin area of ​​the TEM sample of the transition metal sulfide compound layered material prepared by the method is less than 20nm and is greater than 200μm 2 .

[0026] As a more preferred technical solution, the area of ​​the thin area of ​​the transition metal sulfide compound layered material transmission electron microscope sample with a thickness of less than 10nm is greater than 20μm 2 .

[0027] Furthermore, the sum of the absolute values ​​of the α and β tilt angles does not exceed 15° when observed under transmission electron microscopy at the edge of a thin region of a transmission electron microscopy sample of a transition metal chalcogenide layered material.

[0028] One of the technical solutions of the present invention is to provide a transmission electron microscope sample of a transition metal sulfide compound layered material, wherein the sample is prepared by the method described.

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

[0030] (1) The present invention provides a method for preparing samples for transmission electron microscopy of transition metal sulfide layered materials. The transmission electron microscopy samples obtained by the method have a large thin area, a thickness of less than 10 nm, and a good crystal structure. The main reason why this method can be achieved is that since the layered materials have weak interlayer interactions, a single layer or a few atomic layers can be non-destructively peeled off from the block by applying external force by sticking and tearing with tape. The prepared samples can find the required band axis under a transmission electron microscope and obtain a high-resolution atomic image.

[0031] (2) The present invention uses ultrasound to separate the substrate transfer substrate from the peeled sample thin layer and clean the residual glue on the sample. No additional organic solvents, polymer films or other equipment are required during the sample transfer process, and the sample can be effectively transferred to the electron microscope grid under simple operation;

[0032] (3) The transmission electron microscopy sample preparation method proposed in the present invention is simple and low-cost, and is not only applicable to various transition metal chalcogenide layered materials such as tellurium (Te)-based, selenium (Se)-based and sulfur (S)-based, but also applicable to the exfoliation of other layered materials bound together by weak van der Waals forces;

[0033] (4) The present invention avoids problems such as sample contamination or structural changes caused by multiple immersions in solvents, and is simple and flexible to operate, and can efficiently obtain high-quality thin-layer transmission electron microscopy samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 1 of the present invention 2 Scanning electron microscope (SEM) images of the samples;

[0035] Figure 2 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 1 of the present invention 2 Samples in Transmission electron microscopy (TEM) high-resolution atomic image and selected area electron diffraction (SAED) pattern under the belt axis;

[0036] Figure 3 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 1 of the present invention 2 Samples in TEM high-resolution atomic image and SAED pattern under the belt axis;

[0037] Figure 4 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 1 of the present invention 2 Samples in Scanning transmission electron microscope high angle annular dark field image (HAADF-STEM) image under the belt axis;

[0038] Figure 5 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 1 of the present invention 2 SEM and corresponding energy dispersive X-ray spectroscopy (EDS) images of the samples;

[0039] Figure 6 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 2 of the present invention 2 SEM images of the samples;

[0040] Figure 7 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 2 of the present invention 2 Samples in TEM high-resolution atomic image and SAED pattern under the belt axis;

[0041] Figure 8 The NiTe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 2 of the present invention 2 Samples in HAADF-STEM image with axis below;

[0042] Fig. 9The Fe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 3 of the present invention 1.02 Se 0.3 Te 0.7 TEM high-resolution atomic image and SAED pattern of the sample under the

[001] band axis;

[0043] Fig.10 The Fe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 3 of the present invention 1.02 Se 0.3 Te 0.7 Samples in HAADF-STEM image with axis below;

[0044] Fig.11 The Fe prepared by the transmission electron microscope sample preparation method of the transition metal sulfide layered material in Example 3 of the present invention 1.02 Se 0.3 Te 0.7 SEM and corresponding EDS images of the samples;

[0045] Fig.12 NiTe prepared by the transmission electron microscope sample preparation method of the transition metal chalcogenide layered material in the comparative example of the present invention 2 SEM images of the samples;

[0046] Fig.13 NiTe prepared by the transmission electron microscope sample preparation method of the transition metal chalcogenide layered material in the comparative example of the present invention 2 Samples in TEM high-resolution atomic image and HAADF-STEM image under the belt axis;

[0047] Fig.14 NiTe prepared by the transmission electron microscope sample preparation method of the transition metal chalcogenide layered material in the comparative example of the present invention 2 Samples in SAED pattern with axes below. DETAILED DESCRIPTION

[0048] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0049] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0050] In the following examples, the transition metal chalcogenide layered single crystal sample NiTe 2 and Fe 1.02 Se 0.3 Te 0.7 All samples were prepared in the laboratory by the self-fluxing method according to the proportion, ground in the glove box, and sintered in the tube furnace. The 3M tape used was the Sko invisible tape; the oxide layer silicon substrate was purchased from Nanjing Muke Nanotechnology Co., Ltd., single-sided polishing, double-sided oxidation, and the crystal orientation was 100; the electron microscope carrier was purchased from Zhongjing Keyi Technology Co., Ltd.

[0051] Embodiment 1:

[0052] A method for preparing a sample of a transition metal sulfide layered material under transmission electron microscope, and preparing a transition metal sulfide layered material NiTe 2 To obtain high-quality TEM samples, the specific steps are as follows:

[0053] S1. Grind the sample and grind NiTe in a quartz mortar. 2 Block samples for 1 minute, until the large blocks become small pieces, and select the sample slices. The sample slices should be as thin and small as possible, with a thickness of 0.5 mm and a size of 4 mm;

[0054] S2, mechanical stripping, cut a small piece of 3M tape with a length of 20cm and a width of 20mm, place the sample slice in the center of the 3M tape, repeatedly fold it in half and peel it off, repeat 40 times, the adhesive side of the tape is uniformly black-gray and has no obvious stickiness, and the 3M tape obtained after the stripping is attached to a clean oxide layer silicon substrate. The size of the oxide layer silicon substrate is a square with a side length of 1.5cm and a thickness of 0.5mm. Use fingers to press and apply force gently to make the surface of the 3M tape evenly fit the oxide layer silicon substrate tightly. After 5min, tear off the 3M tape from the oxide layer silicon substrate, use tweezers to clamp the 3M tape and the oxide layer silicon substrate at a peeling angle of 150°, transfer the peeled sample thin layer to the oxide layer silicon substrate, and obtain a silicon dioxide substrate with attached peeled sample thin layer;

[0055] S3, ultrasonic treatment, immersing the silicon dioxide substrate with the attached and peeled sample thin layer in 4 mL of ethanol, and ultrasonicating at 30 kHz for 5 min to separate the oxide layer silicon substrate of the silicon dioxide substrate with the attached and peeled sample thin layer and the peeled sample thin layer;

[0056] S4. Sample transfer: take out the oxide layer silicon substrate from ethanol, use tweezers to hold the ordinary carbon film copper mesh and immerse it in the ethanol liquid film on the surface of the oxide layer silicon substrate, move the carbon film copper mesh, so that the peeled sample thin layer is carried on the carbon film of the copper mesh, and use an infrared heating lamp to dry it at 50℃ for 15 minutes. 2 sample.

[0057] The above samples are subjected to the following tests or experiments, and then the test or experiment results are analyzed.

[0058] Test Example 1:

[0059] For NiTe in Example 1 2 The samples were tested by scanning electron microscopy (SEM) and corresponding energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) high-resolution atomic imaging and selected area electron diffraction (SAED), and scanning transmission electron microscopy high-angle annular dark field imaging (HAADF-STEM).

[0060] like Figure 1 As shown, it can be seen that NiTe in Example 1 2 The sample surface is flat, and the area of ​​the thin area with a thickness less than 20nm is greater than 200μm 2 .

[0061] like Figure 5 As shown, it can be seen that NiTe in Example 1 2 The clear and uniform distribution of Ni and Te elements in the sample indicates that the thin layer sample was successfully peeled off.

[0062] The NiTe in Example 1 was observed using a spherical aberration scanning transmission electron microscope. 2 The sample has an α tilt angle of 4.82° and a β tilt angle of -0.04°, observed at the edge of the thin area. The inset in the upper left corner is the selected area electron diffraction result of the corresponding area.

[0063] like Figure 2 and Figure 3 As shown, it can be seen that and NiTe in Example 1 with shaft 2 The sample has good crystallinity, and clear high-resolution transmission electron microscope images can be observed. The single crystal electron diffraction spot can also match NiTe 2 of and The strip axis indicates that a high-quality single crystal TEM sample with no surface damage and well-maintained crystal structure has been successfully obtained.

[0064] like Figure 4 As shown, it can be seen that NiTe in Example 1 with shaft 2The scanning transmission electron microscope image of the sample clearly shows the Ni and Te atomic arrays. Each layer of the crystal under the band axis is composed of hexagonally arranged Te atoms and 1T-structured Ni atoms sandwiched between Te atoms, which is consistent with the results in the literature.

[0065] Embodiment 2:

[0066] A method for preparing a sample for a transition metal chalcogenide layered material under transmission electron microscopy is basically the same as that in Example 1, except that the number of times of folding, gluing and tearing in step S2 is increased from 40 times to 80 times. The specific steps are as follows:

[0067] S1. Grind the sample and grind NiTe in a quartz mortar. 2 Block samples for 1 minute, until the large blocks become small pieces, and select the sample slices. The sample slices should be as thin and small as possible, with a thickness of 0.5 mm and a size of 4 mm;

[0068] S2, mechanical stripping, cut a small piece of 3M tape with a length of 20cm and a width of 20mm, place the sample slice in the center of the 3M tape, repeatedly fold it in half and peel it off, repeat 80 times, the adhesive side of the tape is uniformly black-gray and has no obvious stickiness, and the 3M tape obtained after the stripping is attached to a clean oxide layer silicon substrate. The size of the oxide layer silicon substrate is a square with a side length of 1.5cm and a thickness of 0.5mm. Use fingers to press and apply force gently to make the surface of the 3M tape evenly fit the oxide layer silicon substrate tightly. After 5 minutes, tear off the 3M tape from the oxide layer silicon substrate, use tweezers to clamp the 3M tape and the oxide layer silicon substrate at a peeling angle of 150°, transfer the peeled sample thin layer to the oxide layer silicon substrate, and obtain a silicon dioxide substrate with attached peeled sample thin layer;

[0069] S3, ultrasonic treatment, immersing the silicon dioxide substrate with the attached and peeled sample thin layer in 4 mL of ethanol, and ultrasonicating at 30 kHz for 5 min to separate the oxide layer silicon substrate of the silicon dioxide substrate with the attached and peeled sample thin layer and the peeled sample thin layer;

[0070] S4. Sample transfer: take out the oxide layer silicon substrate from ethanol, use tweezers to hold the ordinary carbon film copper mesh and immerse it in the ethanol liquid film on the surface of the oxide layer silicon substrate, move the carbon film copper mesh, so that the peeled sample thin layer is carried on the carbon film of the copper mesh, and use an infrared heating lamp to dry it at 50℃ for 15 minutes. 2 sample.

[0071] The above samples are subjected to the following tests or experiments, and then the test or experiment results are analyzed.

[0072] Test Example 2:

[0073] For NiTe in Example 2 2 The samples were tested by scanning electron microscopy, transmission electron microscopy high-resolution atomic imaging, selected area electron diffraction, and scanning transmission electron microscopy high-angle annular dark field imaging.

[0074] like Figure 6 As shown, it can be seen that NiTe in Example 2 2 The sample surface is flat, and the thin area is less than 10nm in thickness and is larger than 20μm 2 The thickness and size of the sample sheet can be adjusted by adjusting the number of peeling times. Compared with the sample peeled 40 times in Example 1, the sample peeled 80 times in Example 2 is thinner, has fewer layers, and is smaller in size.

[0075] Spherical aberration scanning transmission electron microscope was used to observe the NiTe in Example 2 2 The sample has an α tilt angle of 13.6° and a β tilt angle of 0°, and is observed at the edge of the thin area. The inset in the lower right corner is the selected area electron diffraction result of the corresponding area.

[0076] like Figure 7 As shown, it can be seen that NiTe in Example 2 with shaft 2 The sample has good crystallinity, and clear high-resolution transmission electron microscope images can be observed. The single crystal electron diffraction spot can also match NiTe 2 of The strip axis indicates that a high-quality single crystal TEM sample with no surface damage and well-maintained crystal structure has been successfully obtained.

[0077] like Figure 8 As shown, it can be seen that NiTe in Example 2 with shaft 2 The scanning transmission electron microscope image of the sample can clearly observe the Ni and Te atomic columns, which is consistent with the results in the literature. The clear atomic image indicates that the prepared transmission electron microscope sample is of excellent quality.

[0078] Embodiment 3:

[0079] A method for preparing a sample of a transition metal sulfide layered material under transmission electron microscope, and preparing a transition metal sulfide layered material Fe 1.02 Se 0.3 Te 0.7 The high-quality transmission electron microscope sample is basically the same as that in Example 2, except that in step S1, the Fe 1.02 Se 0.3 Te 0.7 Block sample, Fe 1.02 Se 0.3 Te 0.7Sample, the specific steps are as follows:

[0080] S1. Grind the sample and grind Fe 1.02 Se 0.3 Te 0.7 Block samples for 1 minute, until the large blocks become small pieces, and select the sample slices. The sample slices should be as thin and small as possible, with a thickness of 0.5 mm and a size of 4 mm;

[0081] S2, mechanical stripping, cut a small piece of 3M tape with a length of 20cm and a width of 20mm, place the sample slice in the center of the 3M tape, repeatedly fold it in half and peel it off, repeat 40 times, the adhesive side of the tape is uniformly black-gray and has no obvious stickiness, and the 3M tape obtained after the stripping is attached to a clean oxide layer silicon substrate. The size of the oxide layer silicon substrate is a square with a side length of 1.5cm and a thickness of 0.5mm. Use fingers to press and apply force gently to make the surface of the 3M tape evenly fit the oxide layer silicon substrate tightly. After 5min, tear off the 3M tape from the oxide layer silicon substrate, use tweezers to clamp the 3M tape and the oxide layer silicon substrate at a peeling angle of 150°, transfer the peeled sample thin layer to the oxide layer silicon substrate, and obtain a silicon dioxide substrate with attached peeled sample thin layer;

[0082] S3, ultrasonic treatment, immersing the silicon dioxide substrate with the attached and peeled sample thin layer in 4 mL of ethanol, and ultrasonicating at 30 kHz for 5 min to separate the oxide layer silicon substrate of the silicon dioxide substrate with the attached and peeled sample thin layer and the peeled sample thin layer;

[0083] S4. Sample transfer: Take out the oxide layer silicon substrate from ethanol, use tweezers to hold the ordinary carbon film copper mesh and immerse it in the ethanol liquid film on the surface of the oxide layer silicon substrate, move the carbon film copper mesh, so that the peeled sample thin layer is carried on the carbon film of the copper mesh, and use an infrared heating lamp to dry it at 50℃ for 15 minutes. 1.02 Se 0.3 Te 0.7 sample.

[0084] The above samples are subjected to the following tests or experiments, and then the test or experiment results are analyzed.

[0085] Test Example 3:

[0086] For NiTe in Example 3 2 The samples were tested by scanning electron microscopy and corresponding energy dispersive X-ray spectroscopy, transmission electron microscopy high-resolution atomic imaging and selected area electron diffraction, and scanning transmission electron microscopy high-angle annular dark field imaging.

[0087] like Fig.11As shown, it can be seen that Fe in Example 3 1.02 Se 0.3 Te 0.7 The clear and uniform distribution of Fe, Se and Te elements in the sample indicates that the thin layer of sample was successfully peeled off.

[0088] The Fe in Example 3 was observed using a spherical aberration scanning transmission electron microscope. 1.02 Se 0.3 Te 0.7 The sample has an α tilt angle of 7.32° and a β tilt angle of 1.66°, and is observed at the edge of the thin area. The inset in the lower right corner is the selected area electron diffraction result of the corresponding area.

[0089] like Fig. 9 As shown, it can be seen that under the

[001] band axis, Fe 1.02 Se 0.3 Te 0.7 The sample has good crystallinity, and clear high-resolution transmission electron microscope images can be observed. The single crystal electron diffraction spot can also match the Fe 1.02 Se 0.3 Te 0.7 The

[001] zone axis indicates that a high-quality single crystal TEM sample with no surface damage and well-maintained crystal structure was successfully obtained.

[0090] like Fig.10 As shown, it can be seen that Fe in Example 3 under the belt axis 1.02 Se 0.3 Te 0.7 The scanning transmission electron microscope image of the sample clearly shows the Fe and Se / Te atomic arrays. 1.02 Se 0.3 Te 0.7 It has a tetragonal crystal structure, consisting of FeSe 4- The tetrahedrons are stacked layer by layer, which is consistent with the results in the literature.

[0091] In this embodiment, iron telluride selenide, other sulfur-based and tellurium-based transition metal chalcogenide layered materials with different element ratios can also be stripped in a similar manner.

[0092] Comparative Example:

[0093] A method for preparing a sample of a transition metal sulfide layered material under transmission electron microscope, and preparing a transition metal sulfide layered material NiTe 2 To obtain high-quality TEM samples, the specific steps are as follows:

[0094] S1. Grind the sample. Simply grind 10 mg NiTe using a quartz mortar. 2 Block samples for 20 min, until the large blocks become sample powder;

[0095] S2, ultrasonic treatment, immerse the sample powder in 30 mL of ethanol, ultrasonicate at 30 kHz for 20 min, let it stand for 30 min and take the supernatant;

[0096] S3, sample transfer, the supernatant was added to the electron microscope copper grid covered with a common carbon film support film, and dried at 50°C for 15 minutes using an infrared heating lamp. 2 sample.

[0097] The above samples are subjected to the following tests or experiments, and then the test or experiment results are analyzed.

[0098] Test example 4:

[0099] NiTe 2 The samples were tested by scanning electron microscopy, transmission electron microscopy high-resolution atomic imaging, scanning transmission electron microscopy high-angle annular dark field imaging, and selected area electron diffraction.

[0100] like Fig.12 As shown, it can be seen that the NiTe prepared by the tape stripping and substrate transfer in step S2 is not used in the comparative example. 2 The sample sizes vary greatly, with most of the bulk sizes in the 1-10 μm range, and the sample layers are still relatively thick, with thicknesses in the 200-500 nm range.

[0101] NiTe in the comparative example 2 The sample is still thick even in smaller areas. It is very difficult to find thin areas using spherical aberration scanning transmission electron microscopy, and it is difficult to obtain transmission electron microscope images under low index axes by rotating the α and β tilt angles. Only when the α and β tilt angles are both 0°, a clearer transmission electron microscope image is observed at the edge of the thin area. The illustration in the upper right corner is the result of the high-angle annular dark field image of the corresponding area by the scanning transmission electron microscope.

[0102] like Fig.13 and Fig.14 As shown, it can be seen that the NiTe 2 The thin area of ​​the sample is very small and the thickness is uneven, so it is impossible to obtain low-index single crystal electron diffraction spots. It is difficult to obtain high-quality single crystal transmission electron microscope samples with no surface damage and well-maintained crystal structure.

[0103] In summary, the present invention uses tape mechanical stripping to thin the sample, and uses ultrasound to separate the substrate from the stripped sample layer, and no additional organic solvents, polymer films, or other equipment are required during the sample transfer process. Large thin-layer transition metal sulfide compound layered material samples can be effectively transferred to the electron microscope grid through simple operations, thereby conveniently obtaining high-quality transmission electron microscope samples. The transmission electron microscope sample prepared by the present invention has a smooth and undamaged surface, maintains a good crystal structure, can be well applied to technical fields such as energy materials, and is of great significance for material performance research.

[0104] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing samples of transition metal chalcogenide layered materials under transmission electron microscopy, characterized in that: The method comprises the following steps: S1, grinding the transition metal chalcogenide block and selecting the transition metal chalcogenide flakes therein; S2, placing a transition metal sulfide compound sheet on a tape, repeatedly folding and bonding the tape and tearing the tape to peel it off, attaching the tape obtained after the peeling to a transfer substrate, gently applying force to make the surface of the tape and the transfer substrate fit tightly, and then tearing the tape off from the transfer substrate to obtain a substrate with a transition metal sulfide compound peeling thin layer attached; S3, immersing the substrate with the transition metal sulfide compound exfoliation layer attached thereto in an immersion solvent, and performing ultrasound to separate the transfer substrate of the substrate with the transition metal sulfide compound exfoliation layer attached thereto and the transition metal sulfide compound exfoliation layer; S4. Take out the transfer substrate from the immersion solvent, immerse the electron microscope grid in the immersion solvent film on the surface of the transfer substrate, move the electron microscope grid, and allow the transition metal sulfide compound to be peeled off and loaded onto the electron microscope grid, dry it, and wait for transmission electron microscopy observation.

2. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: The grinding time in step S1 is 1-2 minutes, the thickness of the slice is selected to be 0.25-1 mm, and the size is 3-5 mm.

3. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: In step S2, the length of the adhesive tape is 15-25 cm, and the width is 15-25 mm.

4. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: In step S2, the number of folding, gluing and tearing the tape is no less than 20 times, until the adhesive side of the tape appears dark grey and non-sticky.

5. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: In step S2, the transfer substrate is selected from an oxide layer silicon substrate or a sapphire substrate, and the transfer substrate has a length of 1-2 cm, a width of 1-2 cm, and a thickness of 0.4-0.5 mm.

6. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: The time for applying force in step S2 is 3-5 minutes.

7. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: When the adhesive tape is removed in step S2, the peeling angle between the adhesive tape and the transfer substrate is 140-160°.

8. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: In step S3, the infiltration solvent is selected from ethanol, isopropanol or acetone, the volume of the infiltration solvent is 3-5 mL, the frequency of ultrasound is 20-40 kHz, and the time is 3-5 min.

9. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: The drying temperature in step S4 is 40-60° C. and the drying time is 10-20 min.

10. The method for preparing samples for transmission electron microscopy of transition metal chalcogenide layered materials according to claim 1, characterized in that: The sum of the absolute values ​​of the α and β tilt angles does not exceed 15° when observed under transmission electron microscopy at the edge of a thin area of ​​a transmission electron microscopy sample of a transition metal chalcogenide layered material.

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