Sample manufacturing method

Abstract

To provide a sample manufacturing method with which it is possible to mitigate damage to a sample due to radiation of an electron ray, and technology associated therewith.SOLUTION: A sample manufacturing method according to one embodiment of the present invention pertains to a method for manufacturing a sample for electron microscope observation of a material. The sample manufacturing method includes: a first processing step for having a gaseous metal compound adhered to a surface of a small piece of the sample so as to form a layer of the metal compound; and a second processing step for reacting the metal compound with a gaseous oxidant and thereby forming a layer of metal oxide or a layer of metal from the layer of the metal compound. The material contains an organic compound.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing a sample and a method for observing a sample. [Background technology]

[0002] In order to observe the microstructure of soft materials, observation techniques using electron microscopes such as scanning electron microscopes (SEM) or transmission electron microscopes (TEM) are sometimes used.

[0003] As such an observation technique, for example, Non-Patent Document 1 describes a method for preparing a sample by subjecting a soft material to be observed to pretreatment such as a staining method, a replica method, and an etching method.

[0004] As an example of such an observation technique, Non-Patent Document 2 describes a method for cooling a sample and a method for adjusting the amount of electron beam in order to reduce damage to the sample caused by the electron beam irradiated by an electron microscope. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Hironari Sano, Tadashi Komoto, "TEM Observation Methods for Polymer Materials", Electron Microscopy, Japanese Society of Microscopy, 1997, Vol. 32, No. 2, p. 71-76 [Non-Patent Document 2] Yuji Otsuka and 5 others, "Application of TEM technology to organic and catalytic materials", Microscope, Japan Society of Microscopy, 2009, Vol. 44, No. 1, pp. 11-15 Summary of the Invention [Problem to be solved by the invention]

[0006] The observation technique described in Non-Patent Document 1 sometimes requires complex work such as optimizing pretreatment conditions depending on the thermal, mechanical, and chemical properties of the soft material to be observed. Also, the observation technique described in Non-Patent Document 2 requires additional sample cooling equipment to be installed in the electron microscope, and contrast may decrease due to a decrease in the amount of electron beam.

[0007] In order to solve the above problems, one aspect of the present invention aims to provide a sample manufacturing method and related techniques that can reduce damage to the sample caused by irradiation with an electron beam. [Means for solving the problem]

[0008] In order to solve the above problems, one embodiment of the present invention provides a method for producing a sample for observing a material under an electron microscope, the method for producing a sample including a first process step of forming a layer of the metal compound by adhering the gaseous metal compound to a surface of a small piece of the material, and a second process step of forming a layer of metal oxide or a layer of metal from the layer of the metal compound by reacting the metal compound with a gaseous oxidizing agent, wherein the material contains an organic compound. Effect of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a sample manufacturing method and related techniques that can reduce damage to a sample caused by irradiation with an electron beam. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an outline of an atomic layer deposition (ALD) apparatus for performing a method for producing a sample according to one embodiment of the present invention. [Diagram 2] 1 is a scanning transmission electron microscope (STEM) photograph of Sample 1 and Sample C1 according to an embodiment of the present invention. [Diagram 3]1 shows energy dispersive X-ray spectroscopy (EDX) mapping images of Sample 1 and Sample C1 according to an embodiment of the present invention. Each image shows, from left to right, a HAADF-STEM image (Grey), a C atom mapping (CK), and an O atom mapping (OK) of the corresponding region. [Figure 4] 1 shows energy dispersive X-ray spectroscopy (EDX) mapping images of Sample 1 and Sample C1 according to an embodiment of the present invention. From the left, each image shows F atom mapping (FK), Al atom mapping (AlK), and Pt atom mapping (PtL). [Diagram 5] FIG. 2 is a diagram showing energy dispersive X-ray spectroscopy (EDX) spectra of the catalyst layers of sample 1 and sample C1 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As used herein, the term "sample" means, unless otherwise specified, the entire object in which a metal oxide layer or a metal layer is formed on the surface of a small piece of material by the method for producing a sample according to one embodiment of the present invention. In addition, as used herein, the term "material" means, unless otherwise specified, the entire object to be observed. In addition, as used herein, the term "small piece of material" means, unless otherwise specified, the entire object having substantially the same composition distribution and state as the whole or part of the object to be observed and having the shape of a small piece. The small piece of material is contained in the sample. The small piece of material contained in the sample can be observed by an observation method using an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) through the metal oxide layer or metal layer formed on the sample.

[0012] <Method of manufacturing a sample according to one embodiment of the present invention> When a sample produced by a conventional method is subjected to an observation method using an electron microscope, the sample may be damaged by irradiation with an electron beam. Hereinafter, in this specification, "damage to a sample caused by irradiation with an electron beam" may be referred to as "sample damage". Examples of sample damage include ion migration caused by elastic scattering; thermal damage caused by inelastic scattering; and the like. The magnitude of sample damage varies depending on material properties such as the composition and shape of the material, and electron beam properties such as the accelerating voltage and irradiation area of ​​the electron beam. As an example, when the sample is produced using a material containing an organic compound as a raw material, the sample damage classified as thermal damage tends to be large, and changes in the shape of the sample such as dents, breaks, and bends may occur.

[0013] The present inventors have found that a sample produced by forming a metal oxide layer or a metal layer on the surface of a small piece of material containing an organic compound can reduce sample damage. That is, a sample production method according to one aspect of the present invention is a sample production method for electron microscope observation of a material, which includes a first process step of forming a layer of the metal compound by attaching a gaseous metal compound to the surface of the small piece of the material, and a second process step of forming a metal oxide layer or a metal layer from the metal compound layer by reacting the metal compound with a gaseous oxidizing agent, the material containing an organic compound. By using the sample production method having such a configuration, a sample capable of reducing sample damage can be produced.

[0014] <Raw materials> The material and small pieces of material used as raw materials in the sample manufacturing method according to one embodiment of the present invention will be described below.

[0015] 〔material〕 In one embodiment of the present invention, the material contains an organic compound. Materials containing organic compounds are used in a wide range of industries. Therefore, a method for producing a sample for observing a material containing an organic compound with an electron microscope is useful.

[0016] In one embodiment of the present invention, the content of the organic compound in the material is preferably 80% by mass or more, more preferably 85% by mass or more, based on the entire material. In general, the greater the content of the organic compound in the material, the greater the tendency for sample damage to occur. However, by using the sample manufacturing method according to one aspect of the present invention, a sample capable of reducing sample damage can be manufactured even when a material with a large content of organic compounds is used as a raw material. In one embodiment of the present invention, there is no particular upper limit on the content of the organic compound in the material. The content of the organic compound in the material is, for example, 100% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less.

[0017] In one embodiment of the present invention, examples of the materials include electric and electronic materials, biomaterials, functional materials, research materials, polymer materials, and automotive materials. Examples of the electric and electronic materials include fuel cell materials, organic electroluminescence (organic EL) materials, organic semiconductor thin film materials, and organic thin film solar cell materials. Examples of the biomaterials include artificial skin. Examples of the functional materials include carbon fibers, cellulose nanofibers, and carbon nanotubes. Examples of the research materials include epoxy resins for embedding or supporting particles, electrophotographic toners, and carbon pastes. Examples of the polymer materials include polybutadiene, polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer (ABS) resins, and rubber components. Examples of the fuel cell materials include membrane electrode assemblies (MEAs). Examples of the organic semiconductor thin film materials include interlayer insulating films containing methylsilsesquioxane (MSQ), and poly-3-hexylthiophene (P3HT).

[0018] It should be noted that the above-listed electrical and electronic materials, biomaterials, functional materials, research materials, polymer materials, and automotive materials can be classified by either application or chemical structure. Therefore, it should be noted that these classified materials are not mutually exclusive and may overlap with each other. As an example, in one embodiment of the present invention, a material may be an electrical and electronic material and one or more of a biomaterial, a functional material, a research material, a polymer material, and an automotive material.

[0019] In one embodiment of the present invention, the organic compound contained in the material is selected from the group consisting of polymeric materials. Polymeric materials can be stable solids under mild conditions of room temperature and normal pressure, but when exposed to reduced pressure and electron beam irradiation under conditions of electron microscope observation, they are generally more susceptible to sample damage than materials other than polymeric materials. Polymeric materials can also take various shapes, such as thin films, particles, fibers, and blocks, with front and back surfaces and unevenness. Therefore, polymeric materials can be formed by chemical vapor deposition (CCVD) depending on their shapes. It may be difficult to perform surface treatment such as chemical vapor deposition (CVD) on polymeric materials. However, the method for producing a sample according to one embodiment of the present invention can reduce damage to the sample by forming a uniform metal oxide layer or metal layer on the front and back surfaces and unevenness of the polymeric material, and can produce a sample that allows detailed observation of the polymeric material. Therefore, the method for producing a sample according to one embodiment of the present invention can be suitably applied to polymeric materials of various shapes.

[0020] In one embodiment of the present invention, examples of the polymer material contained in the material include an ion-conductive polymer material, a conductive polymer material, a biodegradable polymer material, a thermoplastic resin, a thermosetting resin, etc. The polymer material contained in the material may be one type alone or a combination of two or more types.

[0021] In one embodiment of the present invention, the polymeric material contained in the material is preferably selected from the group consisting of ion-conducting polymeric materials, such as perfluorosulfonic acid polymers and other fluorine-based polymers containing sulfonic acid groups, polyolefin oxides such as polyethylene oxide and polypropylene oxide, polyacrylonitrile, polyvinyl chloride, and the like.

[0022] In one embodiment of the present invention, the material may contain other components besides organic compounds, such as precious metals having electrocatalytic properties, such as lead (Pb), platinum (Pt), ruthenium (Ru), iridium (Ir), and tantalum (Ta), as well as alloys containing these precious metals; metal oxides; ceramics; water; and the like.

[0023] [Small pieces of material] In one embodiment of the present invention, the material is subjected to the process described below in the form of small pieces. By using the material in the form of small pieces, the amount of material used to manufacture the sample can be reduced compared to the form of a bulk material. In addition, by using the material in the form of small pieces, the sample can have a shape that is easy for an electron beam to transmit through, and the resolution of the electron microscope observation can be improved. In general, a sample manufactured using a material in the form of small pieces as a raw material is more likely to suffer sample damage such as breakage and bending compared to a bulk material. However, in a sample manufactured by the method for manufacturing a sample according to one aspect of the present invention, a metal oxide layer or a metal layer is formed on the surface of the small piece of material, thereby reducing sample damage. Specific examples of small pieces include, but are not limited to, thin films, particles, and fibers.

[0024] It should be noted that the "thin film" included in the terms such as the organic semiconductor thin film material and the organic thin film solar cell material described above as specific examples of materials is distinguished from the "thin film" described above as a specific example of the shape of a small piece of material. As an example, an organic semiconductor thin film and an organic thin film solar cell are in the category of a small piece of material that is a thin film. As another example, an object having a thin film shape obtained by cutting an organic semiconductor thin film or an organic thin film solar cell in any direction is also in the category of a small piece of material that is a thin film.

[0025] The small pieces of material are typically at least one of: (1) the material itself; (2) an object obtained by cutting a part of the material into the shape of a small piece; (3) an object having the shape of a small piece manufactured by using the raw material and manufacturing method substantially the same as those used to manufacture the material; but are not limited thereto. The form of the small pieces of material can be appropriately selected within a range that does not impair the effects of the present invention. As an example, when the shape of the material itself is a small piece, the small pieces of material may be (1) the material itself. As an example, when the shape of the material is a bulk such as a lump, the small pieces of material may be (2) an object obtained by cutting a part of the material into the shape of a small piece. As an example, when the shape of the material is a particle or liquid, the small pieces of material may be (3) an object having the shape of a small piece manufactured by using the raw material and manufacturing method substantially the same as those used to manufacture the material.

[0026] In one embodiment of the present invention, the small pieces of material may have a uniform composition distribution or a non-uniform composition distribution. When the small pieces of material have a non-uniform composition distribution, the small pieces of material may contain a material containing an organic compound in the composition constituting the matrix. The shape of the material contained in the matrix may be particles, fibers, or other irregular shapes.

[0027] In one embodiment of the present invention, the small piece of material is preferably a thin film. By the small piece of material being a thin film, the amount of material used to manufacture the sample can be further reduced. In addition, by the small piece of material being a thin film, the sample can have a shape that allows the electron beam to pass through, so that the resolution of the electron microscope observation can be further improved. The thickness of the thin film is preferably 1000 nm or less, more preferably 100 nm or less, even more preferably 70 nm or less, and even more preferably 50 nm or less, from the viewpoint of further reducing the amount of material used and further improving the resolution. In addition, the lower limit of the thickness of the thin film is not particularly limited from the viewpoint of further reducing the amount of material used and further improving the resolution. The thickness of the thin film is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 10 nm or more, and even more preferably 20 nm or more, from the viewpoint of further reducing the amount of material used and further improving the resolution. In addition, in one embodiment of the present invention, the thickness of the thin film can be determined by a measurement method conventionally known in the art. Examples of the measurement methods conventionally known in the art include EELS (electron energy loss spectroscopy), etc. The thickness of the thin film is preferably determined as the average thickness of the entire thin film.

[0028] In another embodiment of the present invention, the small pieces of material are preferably particles contained in a powder. As used herein, a particle means a single granular object, and a powder means a group of particles. That is, in another embodiment of the present invention, the material can be subjected to the process described below in the form of a powder, which is a group of particles. By the small pieces of material being particles contained in a powder, the amount of material used to manufacture the sample can be further reduced. In addition, by the small pieces of material being particles contained in a powder, the sample can have a shape that allows the particle size distribution of the powder and the composition distribution inside one particle to be observed by electron microscopy. The weight average particle diameter of the primary particles of the powder is preferably 100 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less, from the viewpoint of STEM observation. In addition, the weight average particle diameter of the primary particles of the powder is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more, from the viewpoint of STEM observation. In addition, in one embodiment of the present invention, the weight average particle diameter of the primary particles of the powder can be determined by a measurement method conventionally known in the art. An example of a measurement method conventionally known in the art is EELS (electron energy loss spectroscopy).

[0029] <Sample manufacturing method> Hereinafter, the materials used as raw materials and each step in which small pieces of the materials are provided in the method for producing a sample according to one embodiment of the present invention will be described.

[0030] [Cutting process] In one embodiment of the present invention, the method for producing a sample may include a cutting step of cutting a material to obtain small pieces of the material before the first processing step. Whether or not the method for producing a sample includes a cutting step can be appropriately determined depending on the shape of the material. As an example, when the shape of the material is a bulk such as a lump, it is preferable that the method for producing a sample according to one embodiment of the present invention includes a cutting step. By including a cutting step, the method for producing a sample according to one embodiment of the present invention can produce samples with reduced sample damage from materials having various shapes.

[0031] The method of cutting out the material can be appropriately selected from methods conventionally known in the art according to the components and shape of the material, within the scope of not impairing the effects of the present invention. Examples of the method of cutting out the material include, but are not limited to, a focused ion beam (FIB), a microtome method, an electrolytic polishing method, a chemical polishing method, an Ar ion milling method, and pulverization. The method of cutting out the material is preferably a microtome method from the viewpoint of reducing chemical and thermal interference with the organic compounds contained in the material.

[0032] The dimensions of the small pieces of material cut out in the cutting step can be appropriately selected. For example, the material may be cut out so that the small pieces of material have a long width of 30 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and a short width of 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less.

[0033] [Pretreatment process] In one embodiment of the present invention, the method for producing a sample may include a pretreatment step of pretreating the material or a small piece of material before the first treatment step. The method for pretreating the material or the small piece of material may be appropriately selected from methods conventionally known in the art, as long as the effect of the present invention is not impaired. Examples of the method for pretreating the material or the small piece of material include, but are not limited to, a staining method and an etching method.

[0034] When both the cutting step and the pretreatment step are performed, the order in which they are performed can be appropriately determined depending on the components and shape of the material.

[0035] [ALD equipment] A method for manufacturing a sample according to one aspect of the present invention is a method for manufacturing a sample by using atomic layer deposition (ALD).

[0036] An apparatus for suitably carrying out ALD will be described with reference to Fig. 1. Fig. 1 is a diagram illustrating an outline of an ALD apparatus 10 for carrying out a method for producing a sample according to one embodiment of the present invention. As shown in Fig. 1, the ALD apparatus 10 includes a reaction chamber 11, a pressure reduction section 12, a precursor gas supply section 13, an oxidant gas supply section 14, and a purge gas supply section 15. In addition, the ALD apparatus 10 may optionally include a control section (not shown).

[0037] The reaction chamber 11 is a space where the first process step and the second process step are mainly performed. The reaction chamber 11 is separately connected to each of the pressure reducing section 12, the precursor gas supply section 13, the oxidizing gas supply section 14, and the purge gas supply section 15. The reaction chamber 11 also includes a heating section (not shown) such as an infrared heater. The reaction chamber 11 can adjust the temperature inside the reaction chamber 11 by the heat generated by the heating section.

[0038] The pressure reducing unit 12 includes a pump (not shown), such as a turbo molecular pump or a rotary pump. By operating the pump, the pressure reducing unit 12 can adjust the air pressure inside the reaction chamber 11 and also discharge gases, such as unreacted gaseous metal compound, unreacted gaseous oxidant, and purge gas, remaining inside the reaction chamber 11 to the outside of the reaction chamber 11.

[0039] The precursor gas supply unit 13 supplies a gaseous metal compound, i.e., a precursor gas, into the reaction chamber 11. The precursor gas supply unit 13 includes a mass flow controller (MFC) (not shown). The precursor gas supply unit 13 can control the flow rate and temperature of the precursor gas by operating the MFC, and can thereby control the flow rate of the precursor gas supplied into the reaction chamber 11.

[0040] The oxidizing gas supply unit 14 supplies a gaseous oxidizing agent, i.e., an oxidizing gas, into the reaction chamber 11. The oxidizing gas supply unit 14 includes a mass flow controller (MFC) (not shown). The oxidizing gas supply unit 14 can control the flow rate and temperature of the oxidizing gas by operating the MFC, and can thereby control the flow rate of the oxidizing gas supplied into the reaction chamber 11.

[0041] The purge gas supply unit 15 can supply a purge gas into the reaction chamber 11 and can also control the flow rate of the purge gas.

[0042] The control unit controls each of the reaction chamber 11, the pressure reduction unit 12, the precursor gas supply unit 13, the oxidant gas supply unit 14, and the purge gas supply unit 15. For example, when the first processing step and the second processing step are repeated multiple times as a series of steps, it is preferable that the control unit controls each of the reaction chamber 11, the pressure reduction unit 12, the precursor gas supply unit 13, the oxidant gas supply unit 14, and the purge gas supply unit 15 in a linked manner.

[0043] The first and second processing steps, which are processing steps for subjecting the small pieces of material to ALD, will be described below. As shown in FIG. 1, the small pieces of material S may be subjected to the first and second processing steps while being supported by a support 20. There is no particular limitation on the support 20 as long as it can support the small pieces of material S. Examples of the support 20 include a glass, metal or resin plate, a petri dish, or a mesh. The support 20 is preferably a mesh. The support 20 is preferably a mesh generally used in electron microscope observation, and more preferably a metal mesh such as gold, copper, nickel, molybdenum, or stainless steel (SUS). The support 20 may have a coating formed on its surface.

[0044] [First processing step] In one embodiment of the present invention, the method for producing a sample includes a first process step of forming a layer of a metal compound by attaching a gaseous metal compound to the surface of the material piece. The first process step is a process of depositing a metal compound on the surface of the material piece S. This forms a layer of the metal compound on the surface of the material piece S. The first process step is performed by the precursor gas supply unit 13 supplying a gaseous metal compound, i.e., a precursor gas, into the reaction chamber 11 in which the material piece S is placed.

[0045] Before carrying out the first processing step, the air inside the reaction chamber 11 may be purged by placing the small piece of material S inside the reaction chamber 11 and then supplying a purge gas into the reaction chamber 11. In the first processing step, the gaseous metal compound may be supplied into the reaction chamber 11 together with an inert gas such as nitrogen.

[0046] The metal compound used in the first treatment step is a precursor of a metal oxide or metal constituting a metal oxide layer or metal layer formed on the surface of the material piece S in the second treatment step. The metal compound is supplied in a gaseous state from the precursor gas supply unit 13 into the reaction chamber 11. The metal compound may be any metal compound that can be gasified under a heating environment or a heating and reduced pressure environment and can generate a metal oxide or metal by reacting with an oxidizing agent.

[0047] Examples of the metal compound used in the first treatment step include metal compounds containing: (1) a metal selected from the group consisting of hafnium (Hf), zirconium (Zr), aluminum (Al), silicon (Si), and titanium (Ti); and (2) a functional group selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 11 carbon atoms, and a halogen such as chlorine and bromine, and hydrogen. By using these metal compounds, it is possible to manufacture a sample with reduced sample damage. Specific examples of such metal compounds include: (1) hafnium compounds such as tetrakis hafnium; (2) aluminum compounds such as diethylaluminum ethoxide, tris(ethylmethylamido)aluminum, aluminum sec-butoxide, aluminum tribromide, aluminum trichloride, triethylaluminum, triisobutylaluminum, trimethylaluminum (TMA), and tris(diethylamido)aluminum; (3) silicon compounds such as tetramethoxysilane and monosilane (SiH4), and (4) titanium compounds such as tetraethoxytitanium. Among them, trimethylaluminum can be suitably gasified and can be rapidly reacted with the oxidizing agent inside the reaction chamber 11. Therefore, the metal compound is preferably trimethylaluminum.

[0048] The metal compound used in the first treatment step may react with an oxidizing agent in the subsequent second treatment step to form a metal or a complex of a metal oxide and a metal, rather than a metal oxide, depending on the type and ALD conditions. Therefore, the terms "metal oxide" and "metal oxide layer" described below can be interpreted as being replaced with "metal" and "metal layer", respectively. However, for convenience, the present invention will be described herein using only the terms "metal oxide" and "metal oxide layer" unless otherwise specified.

[0049] In the first process, when the precursor gas is supplied into the reaction chamber 11, the OH group present on the surface of the material piece S reacts with the metal compound. This reaction generates a by-product in which the hydrogen atom of the OH group is bonded to one functional group of the metal compound, while the oxygen atom of the OH group is bonded to the metal atom of the metal compound. At this time, the functional group of the metal compound is not completely removed from the metal compound, and the metal compound is chemically bonded to the surface of the material piece S in a partially oxidized state. The type of by-product varies depending on the type of metal compound. The by-product may be, for example, an alkane such as methane and ethane, an alcohol such as ethanol, a halogen, or hydrogen gas.

[0050] In one first processing step, the supply amount of the precursor gas may be adjusted appropriately depending on the type and amount of the material pieces S to be subjected to the processing step. The supply amount of the precursor gas is preferably a flow rate within the range of 0.5 to 1 SCCM. This allows a metal compound to be supplied into the reaction chamber 11 in an amount sufficient to react with the OH groups present on the surfaces of the material pieces S. Also, it is preferable that one first processing step is performed for 1 to 5 seconds. This allows a sufficient amount of metal compound to be supplied to the surfaces of the material pieces S.

[0051] [Second processing step] In one embodiment of the present invention, the method for producing a sample includes a second process step of forming a metal oxide layer or a metal layer from the metal compound layer by reacting the metal compound with a gaseous oxidizing agent. The second process step is a step of oxidizing the metal compound bonded to the surface of the material piece S. This forms a metal oxide layer on the surface of the material piece S. The second process step is performed by supplying a gaseous oxidizing agent, i.e., an oxidizing gas, from the oxidizing gas supply unit 14 into the reaction chamber 11 in which the material piece S is placed.

[0052] The oxidizing gas used in the second treatment step may be, for example, a gaseous oxidizing agent selected from the group consisting of water vapor, ozone, and oxygen plasma. This allows the metal compound and the oxidizing gas to react favorably. In the second treatment step, the oxidizing gas may be supplied into the reaction chamber 11 together with an inert gas such as nitrogen.

[0053] In the second process, when an oxidant gas is supplied into the reaction chamber 11, the oxidant gas reacts with the metal compound deposited on the surface of the material piece S. As a result, the functional group of the metal compound is replaced by an OH group, and a metal oxide layer is formed. At this time, by-products similar to those produced in the first process are generated.

[0054] In one second processing step, the supply amount of the oxidant gas may be adjusted as appropriate depending on the type of the material pieces S to be subjected to the processing step and the amount of the material. The supply amount of the oxidant gas is preferably a flow rate within the range of 0.5 to 1 SCCM. This allows the oxidant gas to be supplied into the reaction chamber 11 in an amount that allows the functional groups of the metal compound to react sufficiently. In addition, one second processing step is preferably performed for 1 to 5 seconds. This allows the oxidant gas to be supplied sufficiently to the surface of the material pieces S.

[0055] In the second processing step, it is preferable to react the metal compound with the gaseous oxidant at a temperature of 20° C. or more and 200° C. or less. This allows the metal compound and the oxidant gas to react favorably. The reaction temperature can be adjusted, for example, by maintaining the temperature inside the reaction chamber 11 at the above temperature. Also, in the second processing step, it is preferable to react the metal compound with the gaseous oxidant at a pressure of 200 mPa or more and 300 mPa or less. This allows the metal compound and the oxidant gas to react favorably. The reaction pressure can be adjusted, for example, by adjusting the supply amount of the oxidant gas or by operating a pump provided in the pressure reducing section.

[0056] [Series of processes] In the method for producing a sample according to one embodiment of the present invention, it is preferable to repeat the first and second processing steps as a series of steps multiple times. That is, the method for producing a sample preferably includes a series of steps, each of which includes the first and second processing steps. According to this configuration, the first and second processing steps are alternately performed multiple times each. This allows the thickness of the metal oxide layer formed on the surface of the small piece S of material to be suitably adjusted.

[0057] In one embodiment of the present invention, the series of steps preferably further includes a purge step of purging unreacted gaseous metal compounds and unreacted gaseous oxidizing agents with an inert gas between the first and second process steps and between the second and first process steps, respectively, which can reduce or prevent the deposition of unreacted materials on the surface of the material pieces S, and can form a more homogeneous metal oxide layer on the surface of the material pieces S.

[0058] That is, in one embodiment of the present invention, the method for producing a sample preferably includes a series of steps, each of which includes: (1) a first processing step; (2) a first purge step for purging unreacted gaseous metal compounds with an inert gas between the first processing step and the second processing step; (3) a second processing step; and (4) a second purge step for purging unreacted gaseous oxidizing agent with an inert gas between the second processing step and the first processing step. This allows the thickness of the metal oxide layer formed on the surface of the material piece S to be suitably adjusted, and the metal oxide layer to be more uniform.

[0059] When a series of steps are carried out inside the reaction chamber 11, the temperature inside the reaction chamber 11 is preferably maintained at 20° C. or more and 200° C. or less in order to favorably react the metal compound with the oxidizing agent. Also, when a series of steps are carried out inside the reaction chamber 11, the pressure inside the reaction chamber 11 is preferably maintained at 200 mPa or more and 300 mPa or less.

[0060] Moreover, the series of steps is preferably repeated 10 to 30 times in order to form a metal oxide layer of sufficient thickness.

[0061] [First purge step] In one embodiment of the present invention, the method for producing a sample preferably includes a first purge step of purging unreacted gaseous metal compounds with an inert gas after the first process step and before the second process step. The first purge step can be performed by supplying a purge gas from the purge gas supply unit 15 into the reaction chamber 11 and purging the purge gas from the pressure reduction unit 12. This makes it possible to purge the unreacted gaseous metal compounds supplied into the reaction chamber 11 in the first process step and by-products generated by the reaction to the outside of the reaction chamber 11. This makes it possible to preferably prevent the oxidant gas supplied in the subsequent second process step from reacting with the unreacted gaseous metal compounds remaining in the reaction chamber 11 and depositing on the surface of the small piece S of material.

[0062] In one embodiment of the present invention, the purge gas is preferably an inert gas, such as nitrogen and rare gases such as argon and helium.

[0063] The supply amount of the purge gas in one first purge step is preferably within a flow rate range of 90 to 100 SCCM, and one first purge step is preferably performed for 5 to 50 seconds.

[0064] [Second purge step] In one embodiment of the present invention, the method for producing a sample preferably includes a second purge step in which unreacted gaseous oxidant is purged with an inert gas after the second process step and before the first process step. The second purge step can be performed in the same manner as the first purge step. This allows the unreacted gaseous oxidant supplied to the reaction chamber 11 in the second process step and by-products generated by the reaction to be purged to the outside of the reaction chamber 11. In addition, the precursor gas supplied in the subsequent first process step can be preferably prevented from reacting with the unreacted gaseous oxidant remaining in the reaction chamber 11 and depositing on the surface of the small piece S of material.

[0065] The conditions for supplying the purge gas into the reaction chamber 11 in the second purge step are similar to the conditions for supplying the purge gas in the first purge step, and therefore a description thereof will be omitted.

[0066] In one embodiment of the present invention, the sequence of steps is preferably terminated with a second purge step as the final step.

[0067] <Sample> A sample produced by a method for producing a sample according to one embodiment of the present invention will be described below.

[0068] The sample produced by the production method according to one embodiment of the present invention is a sample in which a metal oxide layer or a metal layer is formed on the surface of a small piece of material.

[0069] The metal oxide contained in the metal oxide layer is typically selected from the group consisting of HfO2, Al2O3, SiO2, ZrO2, and TiO2, and the metal contained in the metal layer may typically be selected from the group consisting of Ti and Si.

[0070] In one embodiment of the present invention, the thickness of the metal oxide layer or metal layer formed on the sample is preferably 0.5 nm or more, more preferably 1.0 nm or more. This can further reduce damage to the sample. Also, in one embodiment of the present invention, the thickness of the metal oxide layer or metal layer formed on the sample is preferably 5.0 nm or less, more preferably 3.0 nm or less. This can reduce the amount of metal compound required to manufacture the sample.

[0071] The sample produced by the above-mentioned production method can be suitably used as a sample for observation with an electron microscope, for example.

[0072] <Sample observation method> A method for observing a sample according to an embodiment of the present invention includes a manufacturing step of manufacturing a sample by carrying out a manufacturing method for a sample according to an embodiment of the present invention, and an observation step of observing the sample using an electron microscope. The sample manufactured by the manufacturing method according to an embodiment of the present invention can be observed in detail using an electron microscope because damage to the sample can be reduced.

[0073] In one embodiment of the present invention, examples of the electron microscope used in the observation step include a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a scanning transmission electron microscope (STEM). The electron microscope is preferably a TEM or a STEM, and more preferably a STEM. This allows the sample to be observed in detail. The electron microscope may be a high angle dark field scanning transmission electron microscope (HAADF-STEM). When the electron microscope is a HAADF-STEM, the composition distribution of the sample can be measured based on the spectrum of the electron beam.

[0074] In a TEM, a sample is irradiated with a parallel electron beam, and the electron beam that passes through the sample is imaged on a fluorescent screen using a magnetic lens. Image contrasts include diffraction contrast or absorption contrast, which utilizes the difference in the scattering angle of the electron beam depending on the density and crystal orientation of the material that composes the sample, and phase contrast, which is obtained by interfering with the electron beam whose phase has been changed by the internal potential of the sample.

[0075] In one embodiment of the present invention, the accelerating voltage can be appropriately selected in the observation of the sample by the electron microscope in the observation step. In general, when a sample manufactured by a conventional method is irradiated with an electron beam using a high accelerating voltage, the sample is likely to be damaged, and in that case, the original composition and shape of the material contained in the sample may not be observed. However, in the observation method of the sample according to one embodiment of the present invention, since a metal oxide layer or a metal layer is formed on the surface of the sample, the damage to the sample is reduced even when a high accelerating voltage is used. In one embodiment of the present invention, the accelerating voltage is preferably within a range of, for example, 30 to 300 kV. This makes it possible to further reduce the damage to the sample and to observe the sample with good contrast using the electron microscope.

[0076] In one embodiment of the present invention, in the observation step, the sample may be observed by combining the electron microscope observation with another observation method. The other observation method may be appropriately selected from conventionally known methods that can be combined with the electron microscope observation. Examples of the other observation method include elemental analysis using energy dispersive X-ray spectroscopy (EDX) or electron energy loss spectroscopy (EELS).

[0077] <Summary> A method for producing a sample according to one aspect of the present invention is a method for producing a sample for electron microscope observation of a material, the method comprising a first process step of forming a layer of the metal compound by attaching a gaseous metal compound to a surface of a small piece of the material, and a second process step of forming a layer of a metal oxide or a metal layer from the layer of the metal compound by reacting the metal compound with a gaseous oxidizing agent, the material containing an organic compound, thereby making it possible to produce a sample that can reduce damage to the sample caused by irradiation with an electron beam.

[0078] In the sample manufacturing method according to one aspect of the present invention, the small pieces of material are preferably (1) thin films having a thickness of 1 nm to 1000 nm, or (2) particles contained in powder having a weight average particle size of primary particles of 1 nm to 100 nm, thereby making it possible to further reduce the amount of material used to manufacture the sample.

[0079] In the method for producing a sample according to one aspect of the present invention, the organic compound is preferably selected from the group consisting of polymeric materials, which allows the polymeric material to be observed in detail.

[0080] The method for producing a sample according to one aspect of the present invention preferably includes a cutting step of cutting the material to obtain small pieces of the material before the first processing step, which makes it possible to produce samples from materials having various shapes with reduced sample damage.

[0081] In the method for producing a sample according to one aspect of the present invention, the metal contained in the metal compound is preferably selected from the group consisting of hafnium, zirconium, aluminum, silicon, and titanium, thereby making it possible to produce a sample with reduced sample damage.

[0082] In the method for producing a sample according to one aspect of the present invention, the metal compound is preferably trimethylaluminum, which is preferable because it can be suitably gasified and can be rapidly reacted with an oxidizing agent.

[0083] In the method for producing a sample according to one aspect of the present invention, the gaseous oxidizing agent is preferably selected from the group consisting of water vapor, ozone, and oxygen plasma, thereby allowing the metal compound to react favorably with the oxidizing agent gas.

[0084] In the sample manufacturing method according to one aspect of the present invention, in the second treatment step, it is preferable to react the metal compound with the gaseous oxidizing agent at a temperature of 20° C. or more and 200° C. or less. This allows the metal compound to react favorably with the oxidizing agent gas.

[0085] In the sample manufacturing method according to one aspect of the present invention, the first treatment step and the second treatment step are preferably repeated multiple times as a series of steps, which allows the thickness of the metal oxide layer formed on the surface of the small piece of material to be suitably adjusted.

[0086] In the method for producing a sample according to one aspect of the present invention, the series of steps preferably further includes a purge step of purging unreacted substances of the gaseous metal compound and unreacted substances of the gaseous oxidizing agent with an inert gas between after the first treatment step and before the second treatment step, and between after the second treatment step and before the first treatment step, respectively. This can reduce or prevent the deposition of unreacted substances on the surface of the material piece, and can form a more homogeneous metal oxide layer on the surface of the material piece.

[0087] A method for observing a sample according to an aspect of the present invention includes a manufacturing step of manufacturing a sample by carrying out the manufacturing method for a sample according to an aspect of the present invention, and an observation step of observing the sample using an electron microscope. The sample manufactured by the manufacturing method according to an aspect of the present invention can be observed in detail using an electron microscope because damage to the sample can be reduced.

[0088] In the sample observation method according to one aspect of the present invention, the electron microscope is preferably a transmission electron microscope or a scanning transmission electron microscope, which allows the sample to be observed in detail.

[0089] In the method for observing a sample according to one aspect of the present invention, the sample is preferably observed with the electron microscope at an accelerating voltage in the range of 30 to 300 kV, which can further reduce damage to the sample and enable observation of the sample with the electron microscope with good contrast.

[0090] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. EXAMPLES

[0091] An embodiment of the present invention will now be described.

[0092] In this example, a sample was prepared using a material made of a resin with a membrane electrode assembly (MEA) embedded in it as a raw material, and then the sample was observed using a scanning transmission electron microscope (STEM).

[0093] <Sample preparation> Example 1 (Material preparation) MEA with electrolyte membrane and catalyst layer (purchased from Fuel Cell Specialty Store Dot JP, product name "3 The MEA (25 cm2 Catalyst Coated Membrane) was embedded in an embedding epoxy resin (Buehler, product name "Epoxi Cure 2"). The embedded MEA was then left to stand at room temperature for 24 hours to harden the embedding epoxy resin, and material 1 was obtained.

[0094] (Cutting process) Using an ultramicrotome (manufactured by Leica, product name "ULTRACUT S"), material 1 was cut out at room temperature to obtain a small piece of material 1, which was a thin film having a thickness of 100 nm. The cutting was performed by cutting material 1 in the direction along the lamination direction of the electrolyte membrane and catalyst layer of the MEA. As a result, the cross section of the MEA was exposed on the surface of small piece of material 1.

[0095] (ALD processing) A microgrid (Nisshin EM Co., Ltd., microgrid film attached mesh, mesh size: 200 mesh) on which a small piece of material 1 was placed was fixed inside the reaction chamber of an ALD device AT-400 (Anric Technologies), and an ALD process was performed. The ALD process was performed by performing 20 cycles, each of which is a series of steps consisting of: (1) a first process step of supplying a precursor gas; (2) a first purge process step of supplying a first purge gas and purging the precursor gas; (3) a second process step of supplying an oxidizer gas; and (4) a second purge process step of supplying a second purge gas and purging the oxidizer gas. The total process time was 30 minutes.

[0096] The ALD treatment conditions are as follows: Precursor gas: Trimethylaluminum (TMA) Oxidant gas: Water vapor (H2O) Purge gas: Nitrogen (N2) Reaction chamber internal temperature: 150℃ Pressure inside the reaction chamber: 225Pa Precursor gas supply: 0.5 seconds, flow rate 0.75 SCCM First purge gas supply: 8 seconds, flow rate 96 SCCM Oxidant gas supply: 0.5 seconds, 0.75 SCCM Second purge gas supply: 10 seconds, flow rate 96 SCCM

[0097] A sample 1 was obtained in which a metal layer having a thickness of 2.0 nm was formed on the surface of a small piece of material 1 by the ALD process.

[0098] Comparative Example 1 A piece of material 1 itself, obtained in a manner similar to that described in Example 1, without ALD treatment, was obtained as sample C1.

[0099] <Sample Observation> (STEM observation) Sample 1 and sample C1 were observed using a scanning transmission electron microscope JEM-ARM200F (manufactured by JEOL Ltd.). In the STEM observation, the acceleration voltage was set to 200 kV. Each sample was photographed at a magnification of 200,000 times. Bright-field STEM and HAADF-STEM photographs of sample 1 treated with ALD and sample C1 not treated with ALD are shown in Figure 2.

[0100] (EDX mapping) In parallel with the STEM observation, energy dispersive X-ray spectroscopy (EDX) mapping of sample 1 and sample C1 was performed. EDX mapping photographs of sample 1 treated with ALD and sample C1 not treated with ALD are shown in FIG. 3 and FIG. 4. In FIG. 3, each photograph shows, from left to right, a HAADF-STEM image (Grey), a C atom mapping (CK), and an O atom mapping (OK) of the corresponding area. In FIG. 4, each photograph shows, from left to right, an F atom mapping (FK), an Al atom mapping (AlK), and a Pt atom mapping (PtL). Note that the Al atom spectrum of sample C1 was weak, so an Al atom mapping could not be created. In addition, FIG. 5 shows EDX spectra of the catalysts of sample 1 treated with ALD and sample C1 not treated with ALD.

[0101] <Result> As shown in Figure 2, when sample C1 that had not been subjected to ALD treatment was irradiated with an electron beam for STEM observation, the interface between the electrolyte membrane and catalyst layer in the piece of material 1 contained in sample C1 was easily peeled off. Furthermore, when sample C1 was irradiated with an electron beam, fracture occurred in sample C1, so that the piece of material 1 contained in sample C1 could not be observed sufficiently. In contrast, sample 1 that had been subjected to ALD treatment did not suffer from sample damage such as fracture or peeling even when observed with STEM.

[0102] In addition, as shown in Figures 3 and 4, the intensity of the F atom spectrum of the catalyst layer of the ALD-treated sample 1 was significantly enhanced compared to that of the non-ALD-treated sample C1. Furthermore, as shown in Figure 5, the integrated intensity ratio (F atom / C atom) between the F atom spectrum and the C atom spectrum in the catalyst layer was about 5:1 when compared between the samples 1 and C1. That is, the contrast of the F atom spectrum of the ALD-treated sample 1 tended to be enhanced compared to the non-ALD-treated sample C1. From this, it can be said that the distribution state of the ionomer having F atoms in the catalyst layer could be clearly visualized by subjecting the small piece of material 1 to the ALD treatment. [Explanation of symbols]

[0103] 10 ALD equipment 11 Reaction chamber 12 Pressure reducing section 13 Precursor gas supply unit 14 Oxidant gas supply unit 15 Purge gas supply section 20 Support S Small piece of material

Claims

[Claim 1] A method for producing a sample for observing a material with an electron microscope, comprising the steps of: The method for producing the sample includes the steps of: a cutting step, prior to the first processing step, of cutting the material to obtain small pieces of the material; a first process step of depositing a gaseous metal compound on a surface of the piece of material to form a layer of the metal compound; a second treatment step of forming a metal oxide layer or a metal layer from the metal compound layer by reacting the metal compound with a gaseous oxidizing agent, The method for producing a sample, wherein the material contains an organic compound.

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