Patent Application
20250022678
This application claims priority to Japanese Patent Application No. 2023-114800 filed on Jul. 13, 2023, the entire contents of which are incorporated by reference herein.
The present invention relates to an environmental cell that holds a sample to be observed with an electron microscope in a gas or liquid, and the electron microscope on which the environmental cell can be mounted.
As one of the electron microscope observation needs for an environmental field, for example, there is catalyst observation in a liquid environment or a gas environment using an environmental cell. A environmental cell as shown in
A sample 71 is sealed in a space sandwich between the membrane 3 and the membrane 7, and an environment of the space in which the sample 71 is controlled from a sample holder (not shown). In this state, an electron beam 53 is emitted, and the sample 71 is observed. A problem of this observation method is that electron beam scattering occurs when the electron beam 53 passes through the membranes 3 and 7, and therefore, an image quality deteriorates in an observation image of the sample 71.
In PTL 1, a region required to have a minimum limit for observation of a sample, minute holes through which an electron beam can pass are provided in a membrane, and a sample supporting film for supporting the sample is provided at a position between upper and lower membranes to support the sample. By using a thin carbon film or a mesh microgrid having opening holes as the sample supporting film, an observation result of an optical quality of the sample can be obtained in a state in which a pattern of the supporting film is hardly superimposed on the sample or is not superimposed on the sample at all.
A environmental cell according to an embodiment of the invention is an environmental cell for holding a sample to be observed by an electron microscope. The environmental cell includes: a first chip including a first membrane and a frame supporting the first membrane and having a first opening portion; a second chip including a second membrane and a frame supporting the second membrane and having a second opening portion; and a sample holding member. The first chip and the second chip are disposed such that the first membrane and the second membrane face each other and the first opening portion and the second opening portion overlap each other in a top view. The sample holding member is disposed on the second membrane in a manner of straddling a contour of the second opening portion in the top view. The sample is attached to a region located in the second opening portion in the top view of the sample holding member.
In liquid environment observation or gas environment observation using the environmental cell, highly accurate measurement is possible without being affected by deflection of the membranes. Other problems and novel features will become apparent from description of this description and the accompanying drawings.
Hereinafter, embodiments according to the invention will be described with reference to the drawings. However, the invention is not to be construed as being limited to the description of the following embodiments. It will be easily understood by those skilled in the art that the specific configuration can be changed without departing from the spirit or scope of the invention. In a configuration of the invention described below, the same parts or parts having the same functions are denoted by the same reference numerals in different drawings, and redundant description thereof may be omitted.
First, a configuration of the transmission electron microscope 51 will be described. The transmission electron microscope 51 includes an electron source 54, a condenser lens 55, deflectors 56, an objective lens 57, an electron biprism 58, a projection lens system 59, a fluorescent plate 60, a camera (imaging unit) 61, a goniometer 62, and a control PC 65.
The electron source 54 includes a cathode for emitting the electron beam 53 and an accelerating tube for accelerating the electron beam 53. The condenser lens 55 focuses the electron beam 53 emitted and accelerated by the electron source 54. The deflectors 56 deflect the electron beam 53 focused by the condenser lens 55 and adjusts an incident angle to an environmental cell 64. The objective lens 57 is a lens for adjusting a spot diameter of the electron beam 53 emitted to the sample 71, and includes an upper magnetic pole piece disposed upstream of the electron beam 53 and a lower magnetic pole piece disposed downstream of the electron beam 53. The electron biprism 58 forms an electron beam interference fringe (hologram) by superimposing an electron wave passing through the sample 71 to be observed and a reference electron wave path through a vacuum. The projection lens system 59 includes a plurality of lenses for enlarging the hologram and projecting an image. The fluorescent plate 60 is a plate that emits fluorescence by the electron beam 53 imaged by the projection lens system 59. The camera 61 acquires a hologram image obtained by the projection lens system 59 when the fluorescent plate 60 is opened.
The goniometer 62 adjusts a position of a sample holder 63 to be mounted. When the sample holder 63 is attached to the goniometer 62, the environmental cell 64 provided at a tip end of the sample holder 63 is located between the upper magnetic pole piece and the lower magnetic pole piece of the objective lens 57. A structure of the environmental cell 64 will be described later.
The control PC 65 controls the electron source 54, the condenser lens 55, the deflectors 56, the objective lens 57, the electron biprism 58, the projection lens system 59, the camera 61, and the goniometer 62, and stores the hologram image acquired by the camera 61 in a storage unit (not shown). A display device (not shown) is connected to the control PC 65, and can display control contents of the control PC 65, the hologram image acquired by the camera 61, or the like.
In the transmission electron microscope 51, the electron beam 53 emitted from the electron source 54 passes through the condenser lens 55 and the upper magnetic pole piece of the objective lens 57, and is emitted to the environmental cell 64. The electron beam 53 transmitted through the environmental cell 64 passes through the lower magnetic pole piece of the objective lens 57 and the projection lens system 59 including a plurality of lenses. When the fluorescent plate 60 is opened, electron wave information acquired by the camera 61 is displayed on the display device of the control PC 65. Since the electron biprism 58 is provided between the environmental cell 64 and the projection lens system 59 in the transmission electron microscope 51, it is possible to perform electron holography observation capable of acquiring phase information of the electron wave.
The number of electron biprisms 58 is not particularly limited, and may be two. Further, as long as the phase information of the electron wave can be acquired, a method other than the electron holography, or another charged particle device such as a scanning transmission electron microscope or a scanning electron microscope may be used.
The control device 52 changes a focal position of a plurality of pieces of electron wave information (for example, hologram images) stored in the storage unit of the control PC 65 to the lower membrane 7, and calculates an amplitude and a phase of the electron wave derived from the upper membrane 3, the sample 71, and the lower membrane 7 based on an amplitude and a phase included in electron wave information after the change of the focal position. Exchange of data between the control PC 65 and the control device 52 of the transmission electron microscope 51 may be performed via a dedicated communication line or network, or may be performed via a recording medium.
A environmental cell provided with a sample holding member will be described in Embodiment 1 with reference to
The sample holding member 11 has a surface (referred to as a “side surface”) perpendicular to a surface (referred to as a “bottom surface”) in contact with the membrane. The sample 71 is dispersed and attached to the side surface. Here, as the sample 71, an example of a μm-sized spherical carrier, on which fine particles (nanoparticles) having catalytic activity such as a noble metal and ceramics are supported, is shown, but fine particles themselves may be used. A material of the sample holding member 11 is, for example, Si, and the sample 71 is attached to the side surface of the sample holding member 11 due to an electrostatic force. The bottom surface of the sample holding member 11 is disposed in a manner of straddling a contour of the opening portion 8 of the frame 6 in a top view, and the side surface of the sample holding member 11 is located in the opening portion 8 of the frame 6 in the top view. The sample holding member 11 is fixed on the membrane 7 by a fixture 12. The fixture 12 can be formed by vapor deposition of tungsten, carbon, or the like.
An overall shape of the sample holding member 11 is not particularly limited. For example, a depth of the sample holding member 11 (a length of a side where the bottom surface and the side surface intersect) may be shorter (the example of
The structure shown in
Here, as shown in a coordinate axis of
By placing the upper Si chip 1 on the lower Si chip 5 shown in
In contrast to the environmental cell according to Embodiment 1, an environmental cell provided with a sample holding member, in which a degree of freedom of an irradiation direction of the electron beam to the sample 71 is further increased, will be described in Embodiment 2. In the following description, differences from Embodiment 1 will be mainly described, and redundant description will be omitted.
The sample 71 needs to be attached to a region located in the opening portion 8 in a top view of the sample holding member. However, in the sample holding member 11 according to Embodiment 1, when the electron beam is inclined in a direction intersecting the YZ plane, the sample holding member 11 is included in the path of the electron beam transmitted through the sample 71, which causes a decrease in the image quality. In a sample holding member 13 according to Embodiment 2, a thickness of a surface to which the sample 71 is attached is reduced. Specifically, the sample holding member 13 shown in
A method of manufacturing the sample holding member 13 will be described. The sample holding member 13 is formed by cutting out a Si substrate 15 having a comb-shaped structure shown in
An overall shape of the sample holding member 11 is not particularly limited. For example, in the example of
When the sample 71 is used as a catalyst, activity of the catalyst becomes high if an electric field is applied to the catalyst. A environmental cell capable of applying an electric field to the sample (catalyst) 71 will be described in Embodiment 3. Although
On the lower Si chip 5 shown in
By putting the environmental cell and the electron microscope described above into practical use for observation with the electron microscope in a gas environment or a liquid environment, it is possible to measure an electromagnetic field during reaction in a catalyst or an electrode with high accuracy. From an observation function newly implemented by a new system using the invention, for example, a mechanism of the catalyst is clarified, and it is expected to contribute to development of a fuel cell and a CO2 fuel conversion catalyst having high performance and high durability, which are required for implementing a carbon neutral society which is required in the world in the future.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-114800 | Jul 2023 | JP | national |
