Method for preparing transmission electron microscopy samples

Abstract

To enable more reliable preparation of a transmission electron microscopy sample from a sheet-like sample with pores.SOLUTION: A method for preparing a transmission electron microscopy sample is provided, the method comprising a preparation step of preparing a sheet-like sample having pores therein, a coating step of coating a surface of the sheet-like sample with an uncured liquid resin, an impregnation step of impregnating the sheet-like sample with the liquid resin by reducing the pressure of atmosphere surrounding the placed sheet-like sample, and a curing step of curing the liquid resin impregnated in the sheet-like sample to form a temporary molded body.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a specimen for a transmission electron microscope. [Background technology]

[0002] Samples for observation with a transmission electron microscope (TEM) must be thinned to a thickness that allows electron beams to pass through, for example, 100 nm or less. Thinning can be performed using, for example, a focused ion beam (FIB) or an Ar ion milling device.

[0003] Before processing the sample into thin sections, it is necessary to perform a specific pretreatment depending on the form it is in. For example, if the sample is in powder form, it has been proposed to mix the sample with a liquid resin, fill the holes in a single-hole mesh, and then harden the mixture (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-294594 Summary of the Invention [Problem to be solved by the invention]

[0005] Thin, void-filled sheet samples are also being considered for TEM observation. To process such sheet samples into TEM specimens, the following pretreatment process can be considered. For example, a liquid resin is first applied to the sheet sample and attached to a base substrate. The surface of the sheet sample is then polished to a smooth surface. A cover glass is then attached to the polished surface to create a laminate. TEM specimens can be prepared by cutting a specimen piece approximately 100 μm thick from the laminate using, for example, a diamond cutter, and then thinning the specimen piece.

[0006] However, according to the investigations of the present inventors, when a sample piece containing a sheet-like sample having voids is thinned, the periphery of the voids is easily milled, and depending on the location of the voids, the sheet-like sample may collapse before the thinning is completed. In other words, it was sometimes impossible to process the sheet-like sample into a form suitable for TEM observation.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a technique for more reliably preparing a transmission electron microscope specimen from a sheet-like specimen having voids. [Means for solving the problem]

[0008] A first aspect of the present invention is a preparation step of preparing a sheet-like sample having voids therein; a coating step of coating an uncured liquid resin on the surface of the sheet-like sample; an impregnation step of impregnating the sheet sample with the liquid resin by reducing the pressure of the atmosphere in which the sheet sample is placed; and a curing step of curing the liquid resin impregnated into the sheet-like sample to form a provisional molded body. A method for preparing a transmission electron microscope sample is provided.

[0009] A second aspect of the present invention is a method for producing a composition comprising the steps of: the liquid resin is a thermosetting resin, a placing step of placing the sheet-like sample coated with the thermosetting resin on a preheated metal member and heating the thermosetting resin to a low viscosity before the impregnation step; In the impregnation step, the pressure is reduced while the sheet sample is placed on the metal member, In the curing step, the thermosetting resin is heated and cured.

[0010] A third aspect of the present invention is a method for producing a composition comprising the steps of: The preheating temperature of the metal member is set to 50°C or higher and 70°C or lower.

[0011] A fourth aspect of the present invention is the second or third aspect, The thermosetting resin is an epoxy resin.

[0012] A fifth aspect of the present invention is a method for producing a composition comprising the steps of: The liquid resin is a room temperature curing resin, In the curing step, the room temperature curable resin is cured by irradiation with light or by contact with moisture.

[0013] A sixth aspect of the present invention is the method according to the fifth aspect, The room temperature curable resin is a photocurable acrylic resin or a cyanoacrylate resin.

[0014] A seventh aspect of the present invention is any one of the first to fifth aspects, The thickness of the sheet sample is 20 μm or more and 100 μm or less.

[0015] The eighth aspect of the present invention is any one of the first to seventh aspects, The size of the voids in the sheet sample is 1 μm or more and 10 μm or less.

[0016] A ninth aspect of the present invention is the method according to any one of the first to eighth aspects, a filling step of placing a spacer on a base substrate, placing the temporary molded body on the bottom of a recess formed by the base substrate and the spacer, and then filling the recess with uncured liquid resin and curing it to form a filling body; a polishing step of polishing a surface of the filler opposite to the base substrate so that the provisional molded body is exposed; and a slicing step of laminating a glass member onto the polished surface of the polished packing body and then slicing the glass member.

[0017] A sixth aspect of the present invention is the method according to any one of the first to fifth aspects, The preheating temperature of the metal member is set to 50°C or higher and 70°C or lower. [Effects of the Invention]

[0018] According to the present invention, a transmission electron microscope sample can be more reliably prepared from a sheet-like sample having voids. [Brief explanation of the drawings]

[0019] [Figure 1A] FIG. 1A is a diagram showing a flow of a method for preparing a transmission electron microscope specimen according to one embodiment of the present invention. [Figure 1B] FIG. 1B is a diagram showing the flow of a method for preparing a transmission electron microscope specimen according to another embodiment of the present invention. [Figure 2] Figures 2(a) to (d) are schematic diagrams for explaining pretreatment of a sheet sample, where (a) shows the case where a liquid resin is applied to a sheet sample, (b) shows the case where a sheet sample is placed on a preheated metal member, (c) shows the case where a sheet sample is impregnated with resin, and (d) shows the case where the liquid resin impregnated into the sheet sample is heated and cured. [Figure 3] Figures 3(a) to (c) are diagrams for explaining the processing of a temporary molded body into a TEM sample, where (a) shows the case where the temporary molded body is filled with resin, (b) shows the case where the filled body is polished, and (c) shows the case where a glass member is bonded to the polished filled body. [Figure 4] FIG. 4 shows a modified example of resin impregnation into a sheet-like sample. DETAILED DESCRIPTION OF THE INVENTION

[0020] As mentioned above, when a sheet-like sample containing voids is thinned, the periphery of the voids collapses, making it impossible to maintain the shape suitable for TEM observation. In particular, the collapse of the sheet-like sample becomes more pronounced as the number of voids increases and their size increases.

[0021] The present inventors have investigated methods for preventing the outer periphery of voids from being easily milled by ion beam irradiation, and have focused on resin impregnation of sheet-like samples. Resin impregnation can fill the voids in a sheet-like sample with resin, thereby reducing the size of the voids. It can also completely fill the voids, reducing their number.

[0022] Therefore, the inventors applied uncured liquid resin to a sheet-like sample and then reduced the pressure of the sample's atmosphere to perform resin impregnation. As a result, they confirmed that this method could promote impregnation of the liquid resin into voids. However, they also confirmed that, depending on the type of liquid resin, for example, thermosetting resin, simply reducing the pressure of the atmosphere does not result in stable filling of the resin into voids. After investigating the cause of this, they found that the viscosity of liquid resins, such as thermosetting resins, at room temperature is not low enough to fill minute voids. The higher the viscosity of a thermosetting resin, the more difficult it is to impregnate a sheet-like sample. Therefore, for example, while the resin can fill voids on the surface of a sheet-like sample, it may not be possible to sufficiently fill voids in the interior.

[0023] For this reason, the inventors focused on a method of heating a thermosetting resin to reduce its viscosity. This is because the viscosity of a thermosetting resin gradually decreases as the temperature increases from room temperature and increases as the temperature approaches the curing temperature. After investigating this heating method, they discovered that placing a sheet-shaped sample coated with a thermosetting resin on a preheated metal member is effective because the sheet-shaped sample is contained in a sealable container (chamber) during resin impregnation. When placed on a preheated metal member, the temperature of the thermosetting resin can be maintained within a range that will not cause it to harden without excessive heating. Therefore, by reducing the pressure in the atmosphere while maintaining a low viscosity without curing the thermosetting resin, it is possible to impregnate the sheet-shaped sample with the thermosetting resin to its interior.

[0024] The present invention was made based on the above findings.

[0025] <One embodiment of the present invention> A method for preparing a transmission electron microscope specimen according to one embodiment of the present invention will be described below with reference to Fig. 1A, which is a diagram showing the flow of the method for preparing a transmission electron microscope specimen according to one embodiment of the present invention.

[0026] (Preparation process S1) First, a sheet-like sample 10 is prepared as the sample to be observed. The sheet-like sample 10 is porous and has voids therein. The voids are, for example, spherical, and the void size is preferably 5 μm or more and 10 μm or less in maximum diameter. The thickness of the sheet-like sample 10 is not particularly limited, but is preferably, for example, 20 μm or more and 100 μm or less. The sheet-like sample 10 is formed from, for example, an inorganic material or an organic material. An example of such a sheet-like sample 10 is a porous sintered body obtained by sintering powder.

[0027] As described above, the sheet sample 10 is easily damaged during the thinning process if left as is, so in this embodiment, the sheet sample 10 is subjected to the pretreatment shown in Figures 2(a) to 2(d). Figures 2(a) to 2(d) are schematic diagrams for explaining the pretreatment of the sheet sample 10.

[0028] (Coating process S2) Next, an uncured liquid resin to be applied to the sheet-like sample 10 is prepared. A liquid resin is a resin that is liquid at room temperature and that is cured, for example, by heat, light, or moisture. Examples of such liquid resins include thermosetting resins and room-temperature curing resins. Here, room-temperature curing resins refer to resins that are cured at room temperature without the use of heat. Room-temperature curing resins refer to resins that do not require heating for curing and that are cured in a room-temperature environment. The curing temperature is not particularly limited, but is preferably, for example, between 10°C and 40°C. Examples of room-temperature curing resins include photocuring resins that are cured by irradiation with light, and moisture-curing resins that are cured by reacting with moisture in the air.

[0029] As the thermosetting resin, for example, a heat-curable epoxy resin can be used. The curing temperature of the thermosetting resin is preferably, for example, 80°C or higher and 120°C or lower, and more preferably 115°C or higher and 125°C or lower, from the viewpoint of suppressing deterioration of the sheet-shaped sample 10 during heat curing. Compared to photocurable resins and the like, thermosetting resins are less likely to shrink during curing, and therefore deformation of the sheet-shaped sample 10 can be suppressed.

[0030] As the room temperature curing resin, a photocurable resin or a moisture curable resin can be used. As the photocurable resin, for example, a photocurable acrylic resin such as epoxy acrylate or urethane acrylate can be used. As the moisture curable resin, for example, a cyanoacrylate resin can be used. Cyanoacrylate resin has a carbonyl group and can be cured by reacting and polymerizing when it comes into contact with moisture. Since the room temperature curable resin can be cured without heating, a material that is sensitive to heat can be selected for the sheet-like sample 10.

[0031] Hereinafter, a case where a thermosetting resin is used as the liquid resin will be described.

[0032] Next, as shown in FIG. 2(a), a liquid thermosetting resin is applied to the surface of the sheet sample 10 as the liquid resin 20. The surface of the sheet sample 10 is covered with the liquid resin 20. The amount of the applied resin should be adjusted appropriately so that the voids in the sheet sample 10 are filled. Any conventionally known method can be used as the application method.

[0033] (Placement process S3) 2(b), the sheet-like sample 10 coated with a thermoplastic resin as the liquid resin 20 is placed on a preheated metal member 30. As described above, among the liquid resins 20, it is difficult for a thermosetting resin to be impregnated into voids in a reduced pressure atmosphere alone, so the sheet-like sample 10 is placed on the preheated metal member 30. Here, it is preferable to place the sheet-like sample 10 on the metal member 30 so that the surface coated with the liquid resin 20 faces upward.

[0034] The preheated metal member 30 can heat the applied liquid resin 20 together with the sheet-like sample 10 by heat transfer. Furthermore, heat transfer allows the liquid resin 20 to be heated appropriately without excessively heating the liquid resin 20, without hardening the liquid resin 20. This allows the viscosity of the liquid resin 20 to be maintained low without hardening it.

[0035] The preheating temperature of the metal member 30 is preferably higher than room temperature but lower than the curing temperature of the liquid resin 20. More preferably, the preheating temperature is (T-60)°C or higher and (T-20)°C or lower, where T is the curing temperature of the liquid resin 20. For example, if the liquid resin 20 is a heat-curing epoxy resin, the preheating temperature should be 50°C or higher and 70°C or lower. By setting the preheating temperature at this level, the viscosity of the liquid resin 20 can be maintained low without raising the temperature of the liquid resin 20 above the curing temperature. Note that the metal member 30 can be a metal plate such as a stainless steel plate.

[0036] (Impregnation step S4) Next, the atmosphere is reduced in pressure while the sheet sample 10 is placed on the metal member 30. Specifically, as shown in Fig. 2(c), the sheet sample 10 is placed on the metal member 30 and stored in a sealed container 41, and the gas inside the sealed container 41 is evacuated by a pump 42 to create a reduced pressure environment.

[0037] By reducing the pressure of the atmosphere around the sheet sample 10, the liquid resin 20 applied to the surface of the sheet sample 10 can be impregnated into the interior of the sheet sample 10. In this embodiment, by placing the sheet sample 10 on a preheated metal member 30, the temperature of the liquid resin 20 during the impregnation process can be maintained at a temperature that reduces the viscosity but does not cause hardening. This allows the liquid resin 20 to more reliably impregnate into the interior of the sheet sample 10.

[0038] The impregnation process may be terminated by placing the sheet sample 10 in a reduced pressure environment for a predetermined period of time, or by confirming that the liquid resin 20 has been impregnated into the sheet sample 10. This can be confirmed, for example, by checking for the occurrence of air bubbles. During the process of impregnating the sheet sample 10 with the liquid resin 20, air contained in the voids escapes from the liquid resin 20 as air bubbles. Therefore, it can be determined that the filling of the voids with the liquid resin 20 has been completed when the occurrence of air bubbles has ceased.

[0039] The pressure inside the closed vessel 41 is not particularly limited as long as it is lower than atmospheric pressure, and the lower the pressure the better from the viewpoint of more reliably impregnating the liquid resin 20 into the sheet-like sample 10. Preferably, the vessel is evacuated.

[0040] (Curing process S5) Next, as shown in FIG. 2(d), the sheet-like sample 10 impregnated with the liquid resin 20 is removed from the sealed container 41 and cured. This curing method may be changed as appropriate depending on the type of liquid resin 20. In this embodiment, since the liquid resin 20 is a thermosetting resin, the sheet-like sample 10 is heated to a temperature equal to or higher than its curing temperature. This hardens the liquid resin 20 to form a provisionally formed body 11. The provisionally formed body 11 is formed by filling the voids in the sheet-like sample 10 with a cured resin.

[0041] The heating method is not particularly limited, but for example, heating can be performed using a non-contact heating unit 51 such as a heating furnace, or a contact heating unit 51 such as a hot plate.

[0042] As shown in FIG. 2(d), when heating is performed using a contact-type heating unit 51, it is preferable to place the sheet sample 10 on the heating unit 51 via a release member 52. This makes it possible to prevent the sheet sample 10 from adhering to the heating unit 51. It is also preferable to place the sheet sample 10 so that the surface on which the liquid resin 20 is applied faces the heating unit 51. This makes it possible to more reliably heat and harden the liquid resin 20 impregnated in the sheet sample 10. The release member 52 can be, for example, a silicon substrate.

[0043] The provisionally formed body 11 may be sliced ​​as is, but from the viewpoint of providing for TEM observation, it is preferable to carry out the filling step S6, polishing step S7, and slice-forming step S8 described below. A specific explanation will be given below with reference to Figures 3(a) to 3(c). Figures 3(a) to 3(c) are diagrams for explaining the processing of the provisionally formed body 11 into a TEM sample.

[0044] (Filling process S6) First, as shown in Fig. 3(a), spacers 62 are placed on the main surface of a base substrate 61. For example, two spacers 62 may be placed on the main surface of the base substrate 61 so as to face two sides of the main surface. A recess 63 is formed by the base substrate 61 and the spacers 62. This recess 63 becomes a region for accommodating the temporary molded body 11.

[0045] Next, the temporary molded body 11 is placed on the main surface of the base substrate 61, at the bottom of the recess 63. For example, the temporary molded body 11 may be adhered to the base substrate 61 using an adhesive. Thereafter, the recess 63 is filled with a liquid resin 20'. The liquid resin 20' to be filled may be the same as or different from the liquid resin 20 used to form the temporary molded body 11. Preferably, it is the same resin, and the liquid resin 20' may be, for example, a thermosetting epoxy resin. The filled liquid resin 20' is then heated and hardened to form a hardened resin 21'. In this way, the filling body 12 is obtained.

[0046] The base substrate 61 is a member that supports the provisionally formed body 11. The base substrate 61 is preferably made of a component that does not cause contamination, unlike the components contained in the sheet-like sample 10. For example, a silicon substrate can be used as the base substrate 61. The thickness of the base substrate 61 is not particularly limited, and is preferably, for example, 350 μm to 500 μm.

[0047] The spacer 62 is a member having a thickness that allows the formation of a recess 63 deep enough to accommodate the sheet sample 10. As the spacer 62, for example, a glass member such as a cover glass can be used.

[0048] (Polishing process S7) Next, as shown in FIG. 3(b), the surface of the filler 12 opposite the base substrate 61 is polished so that the provisionally formed body 11 is exposed. As shown in FIG. 3(a), when a sample with one raised surface and uneven thickness is directly thinned, the grinding balance between the raised and non-raised sides may be lost. This may result in errors in the TEM observation results. Therefore, in the polishing step S7, the raised side is polished and flattened so that the filler 12 is exposed. This results in a polished body 13.

[0049] In the polishing step S7, it is preferable to polish the filler 12 so as to remove a portion of the provisionally formed body 11 in the thickness direction. This makes it possible to more reliably expose the provisionally formed body 11 on the surface of the polishing body 13. Note that, as a polishing method, a conventionally known method such as mechanical polishing can be used. For mechanical polishing, for example, a precision surface grinder (HLA-2, manufactured by JEOL Ltd.) can be used.

[0050] 3(c), a glass member 71 is attached to the polishing surface 13a of the polishing body 13 so as to cover the entire surface, thereby forming a laminate 14. A so-called cover glass can be used as the glass member 71, and its thickness may be, for example, 100 μm or more and 150 μm or less.

[0051] (Thinning process S8) Next, a sample piece is cut from the laminate 14 to a thickness of about 100 μm using, for example, a diamond cutter, etc. This sample piece is introduced into a thin section processing device and thinned to prepare a TEM sample. At this time, it is preferable to perform thin section processing so that the thickness of the thin section is, for example, 10 nm to 100 nm.

[0052] As a thinning device, for example, a focused ion beam device (FIB) or an Ar ion milling device can be used. Among them, a cryo-ion slicer (CIS), which is a type of Ar ion milling device, is preferred. Compared to an FIB, a CIS can thin a wider area. This allows a wider observation field to be secured, and a field suitable for observation can be more reliably obtained.

[0053] In this way, a sample for TEM observation is obtained.

[0054] <Effects of this embodiment> According to this embodiment, one or more of the following effects are achieved.

[0055] (a) In this embodiment, before processing a sheet-like sample 10 having internal voids into a TEM sample, the sheet-like sample 10 is impregnated with a thermosetting resin as a liquid resin 20, and the liquid resin 20 is then cured. Specifically, during the impregnation, the sheet-like sample 10, whose surface is coated with the liquid resin 20, is placed on a preheated metal member 30, and the atmosphere therein is reduced pressure. The reduced pressure atmosphere can promote the impregnation of the liquid resin 20 into the sheet-like sample 10. Furthermore, during the reduced pressure impregnation, the sheet-like sample 10 is placed on the preheated metal member 30 and heated to maintain a low viscosity without curing the liquid resin 20, thereby more reliably impregnating the voids with the resin. For example, the resin can be more reliably impregnated not only into the voids present in the surface layer of the sheet-like sample 10, but also into the voids present inside the sheet-like sample 10. As a result, the provisional compact 11 obtained by curing the resin-impregnated sheet-like sample 10 is configured so that the number and size of voids are reduced by filling the voids with the cured resin. Such provisional compact 11 reduces damage to the TEM sample caused by collapse at the periphery of the voids when thinning is performed in the process of processing it into a TEM sample, thereby making it possible to more reliably prepare a TEM sample.

[0056] For example, a sheet-like sample 10 with void sizes ranging from 2 μm to 10 μm was prepared, and a TEM sample was fabricated through the resin impregnation described above. It was confirmed that, after 10 thin-sectioning operations, breakage occurred two times, but TEM samples were obtained without breakage eight times. This is because the voids in the sheet-like sample 10 were filled with cured resin, preventing collapse around the periphery of the voids. In fact, when the cross section of the polished filler 12 was observed, it was confirmed that the voids had been filled with cured resin, reducing the number of voids. Furthermore, it was confirmed that the size of the remaining voids that were not completely filled with cured resin was in the range of 2 μm to 5 μm, which was smaller than the original size.

[0057] On the other hand, as a comparative example, a sheet-like sample 10 having internal voids was subjected to the above-mentioned filling step S6 to thinning step S8 without undergoing the pre-treatment from the above-mentioned coating step S2 to the curing step S5, and it was confirmed that the TEM samples were frequently damaged during thinning.

[0058] For example, when a sheet-like sample 10 with void sizes in the range of 2 μm to 10 μm was processed into a TEM sample without pretreatment, breakage occurred 8 times out of 10 times of thin section processing. This is thought to be because, in the comparative example, although the sheet-like sample 10 is filled with liquid resin 20 in filling step S6, the liquid resin 20 is not able to penetrate into the voids. In fact, when the TEM sample was inspected, it was confirmed that the filling of the cured resin into the voids did not progress, and there were many voids. Furthermore, even when the cured resin was filled, the filling was insufficient, and it was confirmed that the void size was in the range of 2 μm to 10 μm.

[0059] (b) In this embodiment, by carrying out the above-described pretreatment, even a sheet-like sample 10 having a thickness of 20 μm or more and 100 μm or less can be impregnated with resin to the inside and the voids can be filled with cured resin. As a result, breakage during thinning can be suppressed.

[0060] (c) In this embodiment, the effect of (a) can be obtained even if the size of the voids in the sheet-like sample 10 is 1 μm or more and 10 μm or less. The larger the void size, the more likely it is that the periphery of the voids will collapse. However, by filling the voids with a cured resin, damage to the TEM sample can be suppressed.

[0061] (d) As the thermosetting resin, it is preferable to use a thermosetting epoxy resin that is liquid at room temperature. Epoxy resins can promote resin impregnation into the sheet-like sample 10 when heated to a temperature below the thermosetting temperature. Furthermore, epoxy resins have minimal shrinkage upon curing and are not easily deteriorated by electron beam irradiation, allowing for more accurate TEM observation.

[0062] (e) The preheating temperature of the metal member 30 is preferably 50°C or higher and 70°C or lower. By using such a preheating temperature, the temperature of the liquid resin 20 can be maintained within a temperature range where the liquid resin 20 has a low viscosity without hardening. For example, when an epoxy resin is used as the liquid resin 20, the viscosity of the epoxy resin can be maintained low, and the resin can be more reliably impregnated into voids. As a result, the effect of (a) above can be more reliably obtained.

[0063] (f) It is preferable that the temporary compact 11 is processed into the filler 12 in the above-mentioned filling step S6, and then the filler 12 is processed into the polished body 13 in the polishing step S7. The polished body 13 is easier to handle than when the temporary compact 11 is directly sliced, and the thinning process can be performed more accurately. This makes it possible to more reliably obtain the above-mentioned effect (a).

[0064] <Other Embodiments of the Present Invention> Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention.

[0065] In the above embodiment, a case where a thermosetting resin is used as the liquid resin 20 when forming the temporary molded body 11 and the filling body 12 has been described, but a room-temperature curing resin may also be used. Room-temperature curing resins tend to have lower viscosity than thermosetting resins, so the above-mentioned mounting step S3 may be omitted. Specifically, a transmission electron microscope sample can be prepared according to the flow shown in FIG. 1B. Below, the differences between the cases where a photocurable resin and a moisture-curable resin are used as room-temperature curing resins and the case where a thermosetting resin is used will be described.

[0066] When using a room-temperature curable resin, the sheet-shaped sample 10 is coated with the room-temperature curable resin, and then the sheet-shaped sample 10 coated with the room-temperature curable resin is placed in a sealed container 41 as shown in FIG. 4 . The gas inside the sealed container 41 is then evacuated using a pump 42 to create a reduced-pressure environment. This allows the resin to be impregnated into the voids in the sheet-shaped sample 10. The sheet-shaped sample 10 is then removed, and the room-temperature curable resin is cured. This curing method can be appropriately changed depending on the type of room-temperature curable resin. In the case of a photocurable resin, the resin-impregnated sheet-shaped sample 10 is irradiated with light (ultraviolet light). This hardens the photocurable resin, forming the provisional molded body 11. On the other hand, in the case of a moisture-curable resin, the resin-impregnated sheet-shaped sample 10 is left in the air. At this time, the moisture-curable resin hardens by reacting with moisture in the air. As a result, the moisture-curable resin hardens, forming the provisional molded body 11.

[0067] Room-temperature curable resins do not require heating for hardening, so a heat-sensitive material can be selected for the sheet sample 10. Furthermore, the hardening time can be shortened compared to thermosetting resins. This improves the efficiency of preparing samples for transmission electron microscopes. Room-temperature curable resins tend to shrink significantly when hardened, but in this embodiment, the sheet sample 10 is thin, so the effects of shrinkage due to hardening can be suppressed.

[0068] In the above embodiment, the same thermosetting resin is used as the liquid resin 20 when forming the temporary molded body 11 and when forming the filler 12, but the present invention is not limited to this. Different types of liquid resin 20 may be used when forming the temporary molded body 11 and the filler 12. For example, different types of liquid resin 20 may be used, such as using a thermosetting resin when forming the temporary molded body 11 and using a photocurable resin when forming the filler 12. [Explanation of symbols]

[0069] 10 Sheet sample 11 Temporary molded body 12 Filler 13 Polishing body 13a Polished surface 14 Laminate 20 Liquid Resin 30 Metallic parts 41 Airtight containers 42 Pump 51 Heating section 52 Release material 61 Base substrate 62 Spacer 63 Recess 71 Glass components

Claims

1. a preparation step of preparing a sheet-like sample having voids therein; a coating step of coating an uncured liquid resin on the surface of the sheet-like sample; an impregnation step of impregnating the sheet sample with the liquid resin by reducing the pressure of the atmosphere in which the sheet sample is placed; and a curing step of curing the liquid resin impregnated into the sheet-like sample to form a provisional molded body. Methods for preparing specimens for transmission electron microscopy.

2. the liquid resin is a thermosetting resin, a placing step of placing the sheet-like sample coated with the thermosetting resin on a preheated metal member and heating the thermosetting resin to a low viscosity before the impregnation step; In the impregnation step, the pressure is reduced while the sheet sample is placed on the metal member, In the curing step, the thermosetting resin is heated to be cured.

2. A method for preparing a transmission electron microscope sample according to claim 1.

3. The preheating temperature of the metal member is 50°C or higher and 70°C or lower.

3. The method for preparing a transmission electron microscope sample according to claim 2.

4. The thermosetting resin is an epoxy resin.

3. The method for preparing a transmission electron microscope sample according to claim 2.

5. The liquid resin is a room temperature curing resin, In the curing step, the room temperature curable resin is cured by irradiation with light or contact with moisture.

2. A method for preparing a transmission electron microscope sample according to claim 1.

6. The room temperature curable resin is a photocurable acrylic resin or a cyanoacrylate resin.

6. The method for preparing a transmission electron microscope sample according to claim 5.

7. The thickness of the sheet sample is 20 μm or more and 100 μm or less.

2. A method for preparing a transmission electron microscope sample according to claim 1.

8. the size of the voids in the sheet sample is 1 μm or more and 10 μm or less; 2. A method for preparing a transmission electron microscope sample according to claim 1.

9. a filling step of placing a spacer on a base substrate, placing the temporary molded body on the bottom of a recess formed by the base substrate and the spacer, and then filling the recess with uncured liquid resin and curing it to form a filling body; a polishing step of polishing a surface of the filler opposite to the base substrate so that the provisional molded body is exposed; A thinning process is performed by laminating a glass member to the polished surface of the polished filler and then thinning the glass member.

2. A method for preparing a transmission electron microscope sample according to claim 1.

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