JP6710269B2 - Observation method - Google Patents

Description

The present invention relates to an observation method for observing a sample using a charged particle beam.

In addition to observing the sample at room temperature with an electron microscope, there is a method of observing the sample in situ by heating or cooling to high temperature, applying voltage, and applying tensile stress. Alternatively, there is a method of in-situ observation in various gas atmospheres.

As an electron microscope apparatus for applying a voltage to a desired portion of a sample and observing its reaction in real time under high temperature and a specific atmosphere, as described in Patent Document 1, a MEMS (Micro Electro Mechanical System) provided with electrodes is used. There is a device in which a micro sample is mounted on a chip by FIB (Focused Ion Beam), sandwiched and sealed by different MEMS chips having a thin film that transmits an electron beam, and a liquid and a gas are introduced into the space.

The in-situ observation technique is used for observing various reaction processes, and its application is attempted as a means for clarifying catalyst deterioration processes in fuel cells and the like. For example, as described in Non-Patent Document 1, a minute simulated cell of a fuel cell is produced by MEMS, and instead of introducing hydrogen and air into each electrode to generate a voltage, a voltage similar to that during power generation is applied. There is a method of observing the change of the catalyst particles applied to the electrode in the electrolytic solution.

Patent No. 5699207

S. Nagashima et al., In situ Liquid TEM Study for Degradation Mechanisms of Fuel Cell Catalysts during Potential Cycling Test, Microsc. Microanal. 21 (Suppl 3), 2015, p.1295-1296, DOI: 10.1017/S1431927615007266

In the above-mentioned prior art, it was difficult to separately introduce different gases into different desired locations of a single sample, and it was difficult to observe the chemical reaction caused thereby and measure the voltage and current of the sample. Moreover, the observation target was limited to the nanoparticles in the electrolytic solution applied to the electrodes.

Therefore, for example, when observing the catalyst deterioration process of a fuel cell, the same voltage can be applied to the electrode coated with the catalyst, and a structure simulating a chemical reaction is produced by the MEMS technique. This is a structure different from an actual fuel cell, and is different from the actual environment in which the fuel cell operates, and no consideration was given to the reaction generated by gas introduction.

Therefore, it is an object of the present invention to provide an observation method capable of observing phenomena on the surface of a sample and inside that occur in different gas spaces.

In order to solve the above-mentioned subject, the composition described in a claim is adopted, for example.

The present application includes a plurality of means for solving the above problems, and one example thereof is an observation method for observing a sample using a charged particle beam, which comprises a first portion having a first thickness, A sample having a second portion having a second thickness that is thicker than the first thickness is prepared, and a first gas and a second gas are jetted to the sample to perform electrical measurement of the sample. The sample is irradiated with a charged particle beam.

According to the present invention, it is possible to provide an observation method capable of observing phenomena on the surface of a sample and inside that occur in different gas spaces.

Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The partially expanded top view of the sample holder 1 (Example 1). The partial cross section figure of the sample holder 1 (Example 1). 1 is an overall view of a sample holder 1 (Example 1). The enlarged top view of the front-end|tip part of the sample holder 1 (Example 1). The block diagram of the grip 9 part of the sample holder 1 (Example 1). Explanatory drawing of a sample preparation method. Explanatory drawing of a sample preparation method. Explanatory drawing of a sample preparation method. Explanatory drawing of a sample preparation method. Explanatory drawing of a sample preparation method. The basic block diagram of the electron microscope 22. FIG. 4 is an operation explanatory view of the fuel cell. The partially expanded top view of the sample holder 1 (Example 2). The partially expanded top view of the sample holder 1 (Example 3). An enlarged top view of the tip of the sample holder 1 (Example 4). Partially enlarged top view of the tip part of the sample holder 1 (Example 5). The longitudinal cross-sectional view of the sample holder 1 (Example 5). The cross-sectional view of the sample holder 1 (Example 5). The figure which shows the shape of the sample 5 (Example 6). The partial expanded top view of the sample holder 1 (Example 6). The partial expanded sectional view of the sample holder 1 (Example 6). The top view of the sample holder 1 (Example 7). The figure in the state where the center shaft 36 of the sample holder 1 of FIG. The partial expanded top view of the front-end|tip part of the sample holder 1 (Example 8). The partial expanded top view of the sample holder 1 (Example 9). The partial cross section figure of the sample holder 1 (Example 9).

Embodiments of the present invention will be described below with reference to the drawings. In the following description, an embodiment of an observation method for observing a sample using a charged particle beam will be described using an electron microscope as an example for a charged particle beam device.

1A and 1B are a partially enlarged top view (FIG. 1A) and a cross-sectional view (FIG. 1B) of a sample holder 1 for a charged particle beam apparatus for observing a sample using a charged particle beam. The sample supporting film frame 2 is a Si chip made of a circular MEMS, has a square frame window 3 which is a portion through which an electron beam penetrates, and has a thickness through which the electron beam can penetrate on one side of the Si chip. The sample support film 4 is attached. The sample support film 4 is an insulator such as SiN. A sample 5 cut into small pieces is mounted on the sample support film 4 located in the frame window 3 portion. Two gas injection nozzles 6 each having a gas introduction port toward the sample 5 are arranged at both ends of the sample 5. At the center of the sample 5 located between the gas injection nozzles 6, there is a partition wall 7 for blocking the gas atmosphere injected from each gas injection nozzle 6. The distance between the gas ejection port of the gas ejection nozzle 6 and the sample 5 is preferably 1 mm or less. The voltage measuring terminals 8 (electrodes) are in contact with both ends of the sample 5.

2A shows an overall view of the sample holder 1, FIG. 2B shows an enlarged top view of the tip of the sample holder 1, and FIG. 2C shows a configuration diagram of the grip 9 of the sample holder 1. The gas introduction tube 10 connected to the gas injection nozzle 6 passes through the shaft of the sample holder 1 and is connected from the inside of the vacuum to the outside of the vacuum. The tip of the O-ring 11 mounted on the shaft of the sample holder 1 is inserted into the vacuum portion of the microscope body of the electron microscope. The gas injection nozzle 6 is connected to a gas supply device 32 as shown in FIG. 4 via a gas introduction pipe 10 that passes through the axis of the sample holder 1. The voltage measuring terminal 8 is connected to the lead wire/measuring terminal connecting portion 13. The lead wire/measurement terminal connection portion 13 is fixed to an insulating lead wire/measurement terminal connection base 14, and the lead wire/measurement terminal connection base 14 is fixed to the sample holder 1. The lead wire 15 is connected to the voltage/current measuring unit 34 in the voltage control unit 33 outside the electron microscope body as shown in FIG. The voltage control unit 33 includes a voltage power supply for applying a voltage to the sample 5 via the voltage measuring terminal 8. The sample support film frame 2 is fixed to the sample holder 1 by adhesion or the like. The partition wall 7 that shuts off the gas atmosphere is a removable plate-shaped member and is sandwiched by the partition wall holding portion 16 of the sample holder 1.

A sample preparation method is shown in FIGS. 3A to 3E. FIG. 3A is an exploded three-dimensional view of the sample in the state of FIG. 3B. In order to ensure the contact between the voltage generating section or voltage applying section 18 of the sample 5 and the voltage measuring terminal 8, as shown in FIG. 3B, the voltage generating section or voltage applying section 18 of the sample 5 is required for electrical measurement. The conductive film 19 (Au foil or similar conductive material) that will serve as a terminal is bonded. As shown in FIG. 3C, the sample 5 to which the conductive film 19 is bonded is embedded with the resin 20. As shown in FIG. 3D, a thin film is formed and shaped by a microtome or the like so that each cross section has a thickness that allows electron beam transmission. As shown in FIG. 3E, the shaped thin film portion is arranged on the sample support film 4 so that it can be connected to the voltage measurement terminal 8. This makes it possible to reliably measure the voltage generated in the thin film portion.

FIG. 4 shows a basic configuration diagram of an electron microscope 22 including the sample holder 1 of this embodiment. The mirror body of the electron microscope 22 includes an electron gun 23, a condenser lens 24, an objective lens 25, and a projection lens 26. The sample holder 1 is inserted between the condenser lens 24 and the objective lens 25. A fluorescent plate 27 is mounted below the projection lens 26, and a camera 28 is mounted below the fluorescent plate 27. The camera 28 is connected to the image display unit 29. The gas introduction pipe 10 of the sample holder 1 is connected to the gas supply device 32 via the flowmeters 30a and 30b and the gas pressure control valves 31a and 31b. The lead wire 15 of the sample holder 1 is connected to the voltage/current measuring unit 34 in the voltage control unit 33 outside the microscope body of the electron microscope 22.

The electron beam 35 generated from the electron gun 23 is converged by the condenser lens 24 and irradiated on the sample 5. The electron beam 35 transmitted through the sample 5 is imaged by the objective lens 25, enlarged by the projection lens 26, and projected on the fluorescent plate 27. Alternatively, the fluorescent plate 27 may be removed from the path of the electron beam 35, the electron beam 35 transmitted through the sample 5 may be projected on the camera 28, and a transmission image may be displayed on the image display unit 29. A gas injection nozzle 6 is attached near the sample 5 so that gas can be blown.

The voltage generated by the reaction between the sample 5 and the gas may be measured while observing the reaction of the sample 5 while blowing a small amount of gas on the fluorescent plate 27 or the transmission electron image projected on the camera 28. It is possible. Alternatively, it is possible to observe the change of the sample 5 to which the voltage is applied under the introduction of gas. At this time, the sample 5 is placed on the plane of the sample support film 4, and the adhesion between the sample 5 and the sample support film 4 is increased. Therefore, the gas is supplied from a side different from the sample support film 4 side of the sample 5. be introduced. Therefore, it is possible to introduce the gas only from the front surface of the sample 5 and to capture the internal change caused by the locally introduced gas without exposing the back surface of the sample 5 to the mixed gas at a position away from the sample 5. It is possible.

The present invention can be implemented not only by the transmission electron microscope using the transmission electron image described above but also by the scanning electron microscope using the secondary electron image. In the case of a scanning electron microscope, the projection lens 26 is not required, and a finely focused electron beam having an electron beam incident energy of tens of keV or less is scanned on the surface of the sample 5 to detect secondary electrons generated from the surface of the sample 5. This makes it possible to observe the reaction state on the surface of the sample 5.

FIG. 5 shows an explanatory diagram of the operation of the fuel cell. Fuel cells are an example of a technical field in which observations according to the present invention would be beneficial. A fuel cell has a basic structure called a membrane/electrode assembly (Membrane Electrode Assembly. MEA) in which electrodes are provided on both sides of a central electrolyte membrane. Currently, a carbon-based carrier (carbon black, graphitized carbon, Ketjen black, etc.) and a noble metal fine particle catalyst of platinum (Pt) or Pt alloy fine particles are used for both electrodes. Fuel such as hydrogen (H _{2 in} FIG. 5) is supplied to the fuel electrode 51 of the membrane/electrode assembly 50, and decomposes into protons (H ^{+ in} FIG. 5) and electrons (e ^{− in} FIG. 5). Protons move in the electrolyte membrane 52 and electrons move in the conducting wire 53 to the air electrode 54. At the air electrode 54, the protons from the electrolyte membrane 52 and the electrons from the lead wire react with oxygen in the air (O _{2 in} FIG. 5) to generate water (H ₂ O in FIG. 5). For example, a sample 5 imitating this fuel cell MEA is prepared, set in the sample holder 1 of this embodiment, and different gases are blown to the respective electrodes, so that observation simulating the operating state of the fuel cell can be performed in real time. It will be possible.

FIG. 6A shows a partially enlarged top view of another embodiment of the sample holder 1. Since the gas injection nozzle 6 has conductivity, as shown in FIG. 6A, the voltage measurement terminal 8 is brought into contact with the gas injection nozzle 6 instead of being brought into contact with the sample 5, and the gas injection nozzle 6 is brought into contact with both ends of the sample 5. May be. Although it is difficult to bring the voltage measuring terminal 8 of Example 1 into contact with the small sample 5, the voltage of the sample 5 can be measured only by sandwiching the sample 5 between the gas injection nozzles 6 in the embodiment.

FIG. 6B shows a partially enlarged top view of another embodiment of the sample holder 1. Since the gas injection nozzle 6 has conductivity, the gas injection nozzle 6b is brought into contact with the sample 5 and the lead wire 15 is contacted so that the gas injection nozzle 6 itself functions as the voltage measurement terminal 8 as shown in FIG. 6B. It may be configured to be connected to the voltage/current measuring unit, etc. Similar to the second embodiment, the voltage of the sample 5 can be measured only by sandwiching the sample 5 between the gas injection nozzles 6 in this embodiment.

FIG. 7 shows an enlarged top view of the tip of another embodiment of the sample holder 1. The gas injection nozzle 6 may be fixed by the leaf springs 17 so as to contact both ends of the sample 5. As a result, both the gas injection nozzle 6 and the sample 5 are fixed. The tip of the leaf spring 17 has a ring shape, and the tip of tweezers or the like is inserted into the ring portion and pinched, so that the spring can be loosened to release the fixation.

8A to 8C show an enlarged top view (FIG. 8A), a vertical cross-sectional view (FIG. 8B), and a horizontal cross-sectional view (FIG. 8C) of the tip portion of the sample holder 1. The sample 5 and the voltage measurement terminal 8 are set, and the gas injection nozzle 6 is also arranged at a predetermined position. Then, the polymer film 21 is covered so as to include each voltage measurement terminal 8, the gas injection nozzle 6 and the sample 5. To do. As a result, the polymer film 21 is brought into close contact with the sample 5 portion to form the partition wall 7 as shown in FIG. 8C, and the gas injection nozzles 6 are separated from each other. It becomes possible to form a space.

9A shows a shape of another embodiment of the sample 5, FIG. 9B shows a partially enlarged top view of the sample holder 1 in which the sample 5 of FIG. 9A is arranged, and FIG. 9C shows a partially enlarged cross-sectional view of the sample holder 1 of FIG. 9A. .. With the shape of the sample 5 as shown in Example 1, the entire surface can be observed, but the volume of the sample 5 is small, so that the amount of current is small and it is difficult to measure the voltage/current change. Therefore, instead of cutting the sample 5 from the state of FIG. 3C into a thin film shape, the sample 5 is cut into a shape including a thick portion and a thin portion, for example, a wedge shape. The reaction amount can be increased in the thick portion, and the transmission image can be easily obtained in the thin portion. Therefore, by making a thick portion of the sample 5 a contact portion with the voltage measuring terminal 8 and a thin portion a transmission image observation portion, it is possible to measure a voltage/current change generated inside the sample 5 and observe the transmission image. It becomes compatible. Further, the shape of the sample 5 also has an effect that the operation is easy.

FIG. 10A shows a top view when the sample holder 1 is configured as a side entry type sample holder for an electron microscope, and FIG. 10B shows a state in which the center shaft 36 of the sample holder 1 of FIG. 10A is rotated by 90 degrees. The sample holder 1 has an outer shell 38 that rotates coaxially with the sample holder 37, and the outer shell 38 can be inclined at least ±90 degrees. As a result, for example, when the electron beam 35 is incident in the direction of arrow A in FIG. 10B, by observing the state in FIG. 10B and the state rotated 180 degrees from the state in FIG. It becomes possible to observe the secondary electron image and the backscattered electron image.

FIG. 11 shows a partially enlarged top view of the tip portion of another embodiment of the sample holder 1. A heater 39 is provided on the sample support film 4, and the heater 39 is connected to a heating power source installed outside the mirror body. By heating the heater 39, the sample support film 4 is heated and the sample 5 can be heated. This makes it possible to observe the reaction between the sample 5 and the gas supplied from the gas injection nozzle 6 when the sample 5 is heated.

12A and 12B show a partially enlarged top view (FIG. 12A) and a sectional view (FIG. 12B) of another embodiment of the sample holder 1. The partition wall 7 for partitioning the gas space was formed of a plate-shaped member in Example 1-3 and the polymer film 21 in Example 5. However, the partition wall 7 may be formed by the sample 5 itself. For example, as shown in FIG. 12A and FIG. 12B, the part of the sample 5 located between the two gas injection nozzles 6 can be blocked to the extent that the gas atmosphere injected from each gas injection nozzle 6 can be blocked. The shape may be such that it is formed thick and the other portions are formed thin.

In any of the embodiments, it is possible to appropriately adopt the plate-shaped member, the polymer film 21, or the shape of the sample 5 itself for forming the partition wall 7, and to use them in combination. Is also possible.

The effects of the present invention are summarized below.

By adopting the present invention, it is possible to observe phenomena on the sample surface and inside that occur in different gas spaces.

Further, it is possible to observe changes in the sample due to voltage and changes in polarity in real time in different gas spaces, and to measure the voltage and current.

Further, it becomes possible to observe the reaction between the sample and the gas supplied from the gas supply means when the sample is heated.

Also, using a charged particle beam device, different minute gas atmospheres containing the sample are formed without affecting the vacuum state of the charged particle beam device with a small amount of gas, and the change of the sample structure in the atmosphere is observed. Also, the voltage and current generated in the sample can be measured at the same time.

Moreover, it becomes possible to perform atomic level dynamic observation and voltage/current measurement in a sample while heating in a micro gas atmosphere and applying a voltage.

It should be noted that the present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, it is possible to add or replace a part of the configuration of each embodiment with another configuration.

1... Sample holder, 2... Sample support film frame, 3... Frame window, 4... Sample support film, 5... Sample, 6,6b... Gas injection nozzle, 7... Partition wall, 8... Voltage measurement terminal, 9... Grip, 10 ... Gas introduction pipe, 11... O-ring, 13... Lead wire/measurement terminal connection part, 14... Lead wire/measurement terminal connection block, 15... Lead wire, 16... Partition holding part, 17... Leaf spring, 18... Voltage generation Section or voltage applying section, 19... Conductive film, 20... Resin, 21... Polymer film, 22... Electron microscope, 23... Electron gun, 24... Condenser lens, 25... Objective lens, 26... Projection lens, 27... Fluorescent plate , 28... Camera, 29... Image display section, 30a, 30b... Flowmeter, 31a, 31b... Gas pressure control valve, 32... Gas supply device, 33... Voltage control section, 34... Voltage/current measuring section, 35... Electron beam , 36... Central shaft, 37... Sample holding part, 38... Outer shell, 39... Heater, 50... Membrane/electrode assembly, 51... Fuel electrode, 52... Electrolyte membrane, 53... Conductive wire, 54... Air electrode

Claims (6)

Providing a sample having a first portion of a first thickness and a second portion of a second thickness greater than said first thickness,
Injecting a first gas and a second gas into the sample by making the gas ejection directions different from each other in the thickness direction of the sample,
The second portion is used as a contact portion with a measurement terminal to perform electrical measurement of the sample,
An observation method comprising irradiating the charged particle beam to the first portion as an observation part of the sample such that the optical axis direction of the charged particle beam device is in the thickness direction of the sample. The observation method according to claim 1, wherein
An observation method, characterized in that the sample is prepared by cutting out in a wedge shape having the first portion and the second portion. The observation method according to claim 2 , wherein
An observing method comprising injecting the first gas from one side surface side of the opposed side surfaces of the wedge-shaped sample and injecting the second gas from the other side surface side. Providing a sample having a first portion of a first thickness and a second portion of a second thickness greater than said first thickness,
A voltage is applied to the sample by using the second portion as a contact portion with the measurement terminal ,
Injecting a first gas and a second gas into the sample by making the gas ejection directions different from each other in the thickness direction of the sample,
An observation method comprising irradiating the charged particle beam to the first portion as an observation part of the sample such that the optical axis direction of the charged particle beam device is in the thickness direction of the sample. The observation method according to claim 4 ,
An observation method, characterized in that the sample is prepared by cutting out in a wedge shape having the first portion and the second portion. The observation method according to claim 5 , wherein
An observing method comprising injecting the first gas from one side surface side of the opposed side surfaces of the wedge-shaped sample and injecting the second gas from the other side surface side.

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