Atmospheric pressure electron microscope using multi-window thin film

Abstract

The present invention relates to an atmospheric pressure electron microscope. A multi-window thin film unit is made by covering, with an ultra-thin film, a support part (window frame) having a plurality of windows, an image is obtained by emitting electrons at a sample through the multi-window thin film unit, and an image of the sample can be obtained by synthesizing, through image stitching, a plurality of images captured while moving the sample by predetermined intervals.

Description

Atmospheric pressure electron microscope using multi-window thin films

[0001] The present invention relates to an atmospheric pressure electron microscope, and more specifically, to an atmospheric pressure electron microscope in which a multi-window thin film unit is formed by covering a support having a plurality of windows with an ultra-thin film, an image is obtained by irradiating electrons onto a sample through the multi-window thin film unit, and a plurality of images captured while moving the sample at a predetermined interval are combined by image stitching to obtain an image of the completed sample.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0182924 (Title: Atmospheric pressure electron microscope using multi-window thin film, Application date: December 15, 2023), and all contents of the application specification and drawings of the Korean Patent Application are incorporated herein by reference.

[0003] An atmospheric pressure electron microscope (Air-SEM) is an electron microscope that observes samples under atmospheric or low vacuum conditions, rather than under high vacuum. An APM offers higher resolution and a deeper depth of focus than an optical microscope, allowing for clearer observation of living biological samples.

[0004] An atmospheric pressure electron microscope includes a column having a high vacuum internal space, a membrane installed at the bottom of the column to separate the internal space from the outside, and a sample stage installed below the membrane.

[0005] The distance that electrons can freely move in the atmosphere without colliding with molecules (the mean-free path: MFP) is tens to hundreds of μm. The longer the MFP, the less electrons scatter, resulting in a stronger signal and less noise, resulting in a higher signal-to-noise ratio and higher image quality. Since the MFP is greatly affected by the number of molecules along the electron path, the higher the vacuum, the longer the MFP. Therefore, the interior of the tube, which accounts for most of the electron path, must be maintained at a high vacuum, while a low vacuum or atmospheric pressure must be created only near the sample to minimize electron scattering. Therefore, the high and low vacuums are separated by a thin film near the sample, which allows small electrons to pass through while blocking atoms much larger than the electrons. Electrons generated from the electron gun pass through the internal space without scattering and are irradiated while being scattered by the thin film (film transmittance: a ) and the air surrounding the sample. And, the electrons irradiated on the sample generate backscattered electrons (BSE) in the sample, and the generated BSE pass through the thin film again (transmittance: b. ) is detected by a backscatter electron detector.

[0006] The rate at which electrons pass through a thin film (electron transmittance) increases with thinner films, resulting in better image quality. Furthermore, a larger film surface area increases the field of view (FOV) of an electron microscope. However, the film must be manufactured to withstand deformation and damage caused by pressure differences between the two spaces, and a certain service life (durability) must be guaranteed. Therefore, the feasibility of manufacturing and applying a single window with a thin yet wide film to a system is highly uncertain.

[0007] 1) Conventional atmospheric pressure electron microscopes use thick Si3N4 thin films (typically 20 nm thick), or when using thin films (less than 1 nm), the area of ​​the thin film must be reduced to prevent damage to the film due to the pressure difference that occurs at the boundary between atmospheric pressure and high vacuum. When the film is thick, there is a significant loss in resolution and contrast, and when the film is thin, the FOV cannot be increased, which was a fatal weakness in the commercialization of atmospheric pressure electron microscopes. To solve this problem, a structure (two layers) is used that creates multiple small windows in a durable thick film (a structure in which small windows are arranged in one or two dimensions) and covers the entire film with a very thin, ultra-thin film (e.g., an ultra-thin film made of graphene or other 2D materials) that allows electrons to pass well (i.e., a multi-window-ultra-thin film two-layer structure). Since the force applied to the ultra-thin film due to the pressure difference (F=PA, P: pressure difference, A: area) is proportional to the area, dividing the window size into several parts can reduce the force applied to a single ultra-thin film window, thereby preventing deformation or damage to the individual ultra-thin films. Here, the window frame part serves to mechanically support the ultra-thin film and is an area where electrons cannot pass, and only electrons that pass through the ultra-thin film applied to the window are used for image acquisition.

[0008] 2) The problem that may arise in the above 1) is that electrons cannot penetrate the thin film window frame, resulting in a blind spot in the image. Therefore, the present invention aims to acquire multiple scan images by linking the movement of a sample (substance) according to the structure of a multi-window, and to eliminate the blind spot in the image through a stitching algorithm of the multiple images.

[0009] Therefore, it is expected that applying the above-described method will not only improve the resolution and clarity of atmospheric pressure electron microscopy, but also serve as an advantageous means for realizing atmospheric pressure electron microscopy technology with a wide FOV.

[0010] The image quality of a sample is directly proportional to the number of electrons reaching the BSD (Back Scattered Electron Detector).

[0011] The probability that the electron reaches BSD (P total ) can be calculated by Equation 1 below.

[0012] [Formula 1]

[0013] P total = a×b×P S And,

[0014] Therefore (if the energies of the BSE electron and the incident electron are almost the same),

[0015] P total = a 2 ×P S

[0016] In the above equation,

[0017] P total : The probability that BSE will reach BSD

[0018] a: The probability that an incident electron will penetrate the thin film (controlled by the film thickness)

[0019] P s : The probability that an electron that passes through the atmosphere and is incident on the sample will generate a BSE and then pass through the atmosphere again to reach the thin film (governed by atmospheric effects, i.e. pressure, atmospheric thickness (WD))

[0020] b: probability that BSE will penetrate backward through the thin film (dependent on the film thickness)

[0021] The number of electrons detected in BSD can be calculated by Equation 2 below.

[0022] [Formula 2]

[0023]

[0024] In the above equation,

[0025] N i : The total number of electrons irradiated on a thin film in an electron-optical system

[0026] N o : Total number of electrons detected in BSD

[0027] To increase a, the thickness of the film is reduced, and P s To increase the size, it is advantageous to reduce the WD (working distance, the gap between the atmosphere and the film).

[0028] Problem 1: As the film thickness decreases, its area must be reduced to prevent damage. However, this reduction in area also reduces the field of view.

[0029] Problem 2: P s In order to increase the FOV, the WD must be reduced. However, if the WD is very small, the window size (the width of the thin film) ≒ FOV, so in order to increase the FOV, the area of ​​the thin film must be increased.

[0030] Therefore, in order to solve the conflicting problems 1 and 2, the solution is to adopt a dual structure with a thin ultra-thin film and a film with a large area of ​​multi-windows.

[0031]

[0032] The present invention relates to an atmospheric pressure electron microscope that provides a wide FOV even if the WD is small (solving problem 2) by using a thin film with a large area (solving problem 1).

[0033] Specifically, an atmospheric pressure electron microscope (100) according to a preferred embodiment of the present invention is for observing a sample (S) placed in a space (1) that is at a lower vacuum or atmospheric pressure than the internal space of a tube (10), and may include a multi-window thin film unit (50) separating the internal space and the space (1); a sample stage (60) on which the sample (S) is placed and which is movable on a plane; a control unit that controls the movement of the sample stage (60), and an operation unit that performs image stitching of at least two captured images.

[0034] The multi-window thin film unit (50) is a penetrating window in which a plurality of windows (53) are formed in a thick thin film that does not allow electrons to pass through. The support member (52) serves as a window frame, becomes an adhesive surface to which the ultra-thin film (54) is adhered, and serves to support the ultra-thin film (54). The ultra-thin film (54) is applied to cover the entire window (53) and the support member (52, window frame). Electrons pass through the ultra-thin film (54) well, but air does not pass through the ultra-thin film (54), so the ultra-thin film (54) serves to separate a space (1) of atmospheric pressure or low vacuum from a space (11) of high vacuum.

[0035] The control unit moves the sample stage (60) after capturing a sample (S) so that images captured before and after the movement overlap at least partly, and the operation unit stitches the overlapping captured images together to create a full image.

[0036] 1) When the window (53) is arranged in one dimension, the window (53) has a predetermined width (x o ) and a given length (y o ) are repeatedly formed along a first direction (e.g., x direction) with a first interval (x1), but the width (x o ) is longer than the first interval (x1) and has the length (y) o ) may be longer than the length of the part you want to film.

[0037] The control unit takes the first photograph of the sample (S), and then moves the sample stage (60) along the first direction to take the second photograph, such that the images taken before and after the movement overlap at least partially with each other. Furthermore, the operation unit can create an image of the sample by image stitching at least the first and second photographed images. Depending on the situation, the sample movement distance and number of movements can be varied, and in this case, three or more images can be acquired and used for image stitching to improve the accuracy of the image stitching.

[0038] 2) As an alternative to the above one-dimensional array, when the windows (53) are arranged in two dimensions, the windows (53) have a predetermined width (x o ) and a given length (y o ) can be repeatedly formed at a first interval (x1) along a first direction (e.g., x direction) and at a second interval (y1) along a second direction (e.g., y direction).

[0039] The above width (x) o ) is longer than the first interval (x1) and has the length (y) o ) is preferably longer than the second interval (y1).

[0040] The control unit may move the sample stage (60) along the first and second directions, respectively, after taking the first photograph of the sample (S), to take the second and third photographs, such that the images taken before and after the movement overlap at least partially with each other. The operation unit may create an image of the sample by image stitching at least the first, second, and third photographed images. Depending on the situation, the distance and number of times the sample is moved may be varied, and in this case, three or more images may be acquired and used for image stitching, thereby improving the accuracy of the image stitching.

[0041] The multi-window thin film unit (50) includes a frame (51), and a penetration portion (51a) may be formed in the frame (51). The frame (51) may be made of Si.

[0042] A support member (52, window frame) is installed on the lower surface of the frame (51), and multiple windows (53) are attached so that they all correspond to the penetration member (51a). Then, an ultra-thin film (54) is installed on the lower surface of the support member (52), and is installed so as to cover multiple windows (53) all. The side surface of the outermost penetration member (51a) is formed as an inclined surface, and accordingly, the upper part of the penetration member (51a) has a larger diameter than the lower part.

[0043] The support (52) is a thick film having a thickness of about 20 nm to 1 μm and can be made of Si3N4. Since the support (52) is intended to support the ultra-thin film (54), it is preferable that it be a film thicker than the ultra-thin film (54). The ultra-thin film (54) can be made of graphene or other 2D materials with high electron transmittance.

[0044] The atmospheric pressure electron microscope may include a lower chamber (80) installed at the lower portion of a tube (10) and having a low vacuum space (81) formed therein. A multi-window thin film unit (50) may be installed at the bottom of the lower chamber (80). Electrons generated from an electron gun sequentially pass through the internal space, the low vacuum space (81), and the multi-window thin film unit (50) to be irradiated onto a sample (S). The low vacuum space (81) serves as an intermediate vacuum section to minimize the pressure difference applied to the ultra-thin film (54), thereby alleviating damage to the ultra-thin film (54).

[0045] The atmospheric pressure electron microscope according to the present invention has the following effects.

[0046] First, the resolution and clarity of the image are improved by using a multi-window thin film unit with a thin and large area.

[0047] Second, it can provide a wide FOV even while using an extremely thin film.

[0048] Third, due to the improved signal-to-noise ratio (SNR) and increased FOV, it is possible to acquire high FPS (Frame Per Second) images over a large area compared to existing single-window films.

[0049] FIG. 1 is a drawing showing the main configuration of an atmospheric pressure electron microscope according to a preferred embodiment of the present invention.

[0050] Fig. 2 is a cross-sectional view showing the multi-window thin film unit of Fig. 1.

[0051] Figure 3 is a plan view showing that windows are repeatedly formed at a first interval in a first direction (x-axis direction) on a support member (thick film) of a multi-window film unit and that an ultra-thin film is installed on the windows.

[0052] Figure 4 is a plan view showing that windows are repeatedly formed at a first interval in a first direction (x-axis direction) and at a second interval in a second direction (y-axis direction) on a support member (thick film) of a multi-window film unit, and an ultra-thin film is installed on the windows.

[0053] Figure 5 shows an image (left) captured using a multi-window thin film unit having a two-dimensional 3x3 array graphene window, and a graph (right) showing the signal intensity of points connecting points A and B in the left image.

[0054] Figure 6 is a cross-sectional view showing a modified example of an atmospheric pressure electron microscope, in which the lower chamber is installed at the bottom of the tube and the BSD is installed at the bottom of the lower chamber.

[0055] Figure 7 is a cross-sectional view showing another variation of an atmospheric pressure electron microscope, in which the lower chamber is installed at the bottom of the tube and the BSD is installed at the bottom of the tube.

[0056] Hereinafter, the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be interpreted as limited to their conventional or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations depicted in the drawings are merely embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist that can replace them at the time of this application.

[0057] In the drawings below, identical reference numerals represent identical or substantially identical components. In addition, the x, y, and z axes in the drawings are three axes of the Cartesian coordinate system described for the convenience of understanding and explaining the drawings, and the x, y, and z axes are perpendicular to each other.

[0058]

[0059] Fig. 1 is a drawing showing the main configuration of an atmospheric pressure electron microscope according to a preferred embodiment of the present invention, and Fig. 2 is a cross-sectional view showing the multi-window thin film unit of Fig. 1. In Fig. 1, the blue line represents the path through which various electrical control signals, data, images, etc. are transmitted, and the red line represents the path through which electrons generated from the electron gun move to the sample.

[0060] As shown in the drawing, the atmospheric pressure electron microscope (100) may include a tube (10), a multi-window thin film unit (50), a sample stage (60), and a central processing unit.

[0061] The tube (10) has a high vacuum space (11) inside it. Inside the tube (10), an electron gun (20) that generates electrons, an electron optical system (30) including a focusing lens, an objective lens, a deflector, etc., and a BSD (Back Scattered Electron Detector, 40) etc. can be installed. Since the configuration of the electron gun (20) is well known, its description will be omitted here.

[0062] The electron optical system (30) can change the movement path of electrons according to a control signal transmitted from the control unit of the central processing unit (CPU), and preferably, this control signal can be linked to the movement of the sample stage (60). For example, a deflector (deflector or scanner) inside the electron optical system (30) can adjust the movement path of the electron beam to allow electrons to pass through a specific window (53) among several windows (53) or to pass through all windows (53).

[0063] The BSD (40) may be installed under the electro-optical system (30). As an alternative, the BSD (40) may be installed on the lower surface of the frame (51) of the multi-window thin film unit (50).

[0064] BSD (40) detects backscattered electrons and transmits the signal to the central processing unit, and the operation unit of the central processing unit processes the transmitted signal, for example, by image stitching, to create an entire image and output it to the display unit.

[0065] A multi-window thin film unit (50) can be installed at the bottom of the barrel (10). The multi-window thin film unit (50) can include a frame (51), a support member (52, window frame) installed (attached) to the lower surface of the frame (51), and an ultra-thin film (54) installed to cover the lower surface of the support member (52).

[0066] The frame (51) can be installed at the bottom of the barrel (10). In addition, a penetration portion (51a) is formed in the center of the frame (51). The penetration portion (51a) is a hole formed to penetrate the frame (51) upward and downward, and its side surface is an inclined surface. Accordingly, the upper part of the penetration portion (51a) has a larger diameter than the lower part. The frame (51) can be made of Si. The shape of the penetration portion (51a) can be manufactured in various shapes that are modified from a square.

[0067] The support member (52, window frame) is a membrane having a predetermined thickness and is installed (or attached) to the lower surface of the frame (51) to cover the penetration portion (51a). A plurality of windows (53) are formed in the support member (52) to penetrate the support member (52), and all of the windows (53) can be attached to the frame (51) so as to correspond to the penetration portion (51a).

[0068] The window (53) is a hole through which electrons pass, and the support (52) excluding the window (53) does not allow electrons to pass. Windows (53) of the same shape can be repeatedly formed and patterned. For example, as shown in FIG. 3, a rectangular window (53) having a long length can be repeatedly formed along the x-direction (first direction), or as shown in FIG. 4, a square window (53) can be repeatedly formed along the x-direction (first direction) and the y-direction (second direction).

[0069] Preferably, the support (52) has a thickness of 20 nm or more and is made of SiN x As a thick film made of (e.g., Si3N4), it has a thickness thicker than an ultra-thin film (54).

[0070] The above thick film may have an area of ​​3 mm wide × 3 mm long and may be attached to a predetermined frame (a wafer piece on which the BSD is manufactured, for attaching the BSD in the air) using wax or epoxy. The window (53) may be patterned using photolithography and reactive ion etching.

[0071] The ultra-thin film (54) is attached to the lower surface of the support (52, window frame) so as to cover the entire multiple windows (53). The ultra-thin film (54) allows electrons to pass through but does not allow air to pass through. The ultra-thin film (54) can be made of graphene or a two-dimensional material (2D material) with high electron transmittance. Typically, a thickness of 1 to 10 nm is preferable, taking into account resolution and strength, as a multiple of a single layer of graphene or other 2D material.

[0072] If the thickness of the above-mentioned support Si3N4 thin film (52, window frame) is less than 20 nm and the width of one side is more than 200 μm, it is difficult to withstand the pressure difference between the spaces on both sides and the service life is shortened, so it is not preferable. If the thickness exceeds 1 μm, electrons may be scattered from the side of the window pierced in the thin film, so the clarity of the image is reduced, so it is not preferable.

[0073] In the existing atmospheric pressure electron microscope technology, a thin film (52) without a window was used as it was, and it was difficult to make the Si3N4 thin film thin and uniformly to a few nm. As a result, the existing atmospheric pressure electron microscope technology had no choice but to use a thick film of more than 20 nm for strength, which limited the resolution and clarity of the image. Graphene can be made uniformly to a few nm in thickness by stacking multiple layers, with a single layer of 0.2 nm. Graphene has been used to wrap samples for observing samples in a vacuum, and recent studies have shown that a thin film made of graphene provides an electron transparent window with a contrast reduction of only 2%. Therefore, when a graphene thin film (54, ultra-thin film) is applied to a support (52) with a window (53) and used as an electron transmission window of an atmospheric pressure electron microscope, the signal / noise ratio is improved five times compared to using a Si3N4 thin film, thereby enabling high contrast in backscattering, transmission, and surface imaging modes. In addition, a thin graphene thin film (ultra-thin film, 54) has good electron transparency, so that deterioration and contamination by electron beams are much reduced compared to Si3N4, and mechanical durability is also excellent.

[0074] Figure 3 shows that a window (53) is formed one-dimensionally and repeatedly on a support (52, thick film). That is, the window (53) has a width (x o ) compared to the length (y) o) is formed repeatedly at a first interval (x1) along the first direction (x-axis direction) as a very long rectangular hole. Width (x o ) is longer than the first interval (x1), and the length (y o ) is preferably longer than the length of the part you want to shoot. Length (y) o ) is longer than the length of the part to be photographed, the entire image can be acquired with only one x-axis movement (offset) of the sample stage (60), so the shooting time can be reduced.

[0075] width(x o ) is preferably at least 1 μm or more and at most 10 μm or less, but can be adjusted depending on the thickness of the ultra-thin film (54), and the length (y o ) is the width (x o ) may vary depending on the size, but can be determined by considering the maximum FOV, and it is generally desirable to have a minimum of 100 μm and a maximum of 1 mm.

[0076] The above offset distance can be expressed by the following equation.

[0077] [Formula 3]

[0078]

[0079] In the above equation,

[0080] Δx: The length of the part that overlaps in the x-axis direction before and after the x-axis offset.

[0081] 'width(x o ) > the first interval (x1)', and to acquire the image with the square area size (x1).

[0082]

[0083] Adjust so that the overlap (Δx) is equal to the width (x o ) is desirable to make image stitching easier.

[0084] The control unit takes the first image without moving the sample (S), and then moves the sample stage (60) along the first direction (x-axis direction) to take the second image, such that the images taken before and after the movement overlap at least partially with each other. Then, the control unit transmits the signal of the taken image to the operation unit, and the operation unit stitches the first and second images to create a full image.

[0085] The maximum scan area of ​​the entire image above can be calculated using the following equation.

[0086] [Formula 4]

[0087]

[0088] In the above equation,

[0089] Lx: Maximum scan area (or width of maximum scan area)

[0090] N: Number of windows (53)

[0091] P x : The interval at which the window (53) repeats

[0092] The above explanation was given using a rectangular window (53) as an example, but various window shapes are possible, and the above explanation can also be applied to a case where a peanut-shaped window (not shown in the drawing) is repeatedly arranged in one dimension.

[0093] In the case where rectangular windows (53) or peanut-shaped windows are repeatedly formed in one dimension (1D array scanning), it is advantageous over a two-dimensional array (2D array scanning) because only two shots are required to obtain one image. Of course, the scope of the present invention does not exclude shooting three or more times (i.e., additional offset and shooting in the x-axis direction after the second shooting) to increase the accuracy of image stitching when the windows (53) are repeatedly arranged in one dimension.

[0094] Fig. 4 is a plan view showing that windows (53) are repeatedly formed at a first interval in the x-axis direction and a second interval in the y-axis direction on a support (thick film, 52) and that an ultra-thin film (54) is installed on the windows (53).

[0095] That is, a given width (x o ) and a given length (y o ) are repeatedly formed at a first interval (x1) along the first direction (x-axis direction) and at a second interval (y1) along the second direction (y-axis direction). And, the width (x o ) is longer than the first interval (x1) and has the length (y) o ) is longer than the second interval (y1).

[0096] The control unit takes the first shot without moving the sample (S), and then moves (offsets) the sample stage (60) along the first and second directions to take the second and third shots, which are described in detail below.

[0097] (i) First shot

[0098] Taken without moving the sample stage (60). That is, x-axis offset = 0, y-axis offset = 0

[0099] (ii) Second shooting

[0100] The sample stage (60) is positioned in the x-axis direction ' was taken while moving (offset) by that amount and not moving (offset) in the y-axis direction.

[0101] (iii) The sample stage (60) is not offset in the x-axis direction but in the y-axis direction. ' was taken with the offset set to that amount.

[0102] (iv) Image stitching

[0103] The three images captured in (i) to (iii) above are stitched and synthesized in two dimensions in the calculation unit.

[0104] From above, This is done so that the size of the rectangular area is proportional to the length of x1 and the length of y1.

[0105] To optimize image acquisition in a rectangular area, in the same context as in the one-dimensional case,

[0106] and,

[0107]

[0108] It is desirable to adjust it so that it becomes .

[0109] In the case where a window (53) like this is formed in two dimensions repeatedly (2D array), more than three times of shooting are required to obtain one image, but since the thickness of the ultra-thin film (54) can be made thinner than in the case of a conventional single window (single hole), the SNR is greater than that of a conventional thick film, so the scanning speed can be increased, and therefore an image can be obtained with sufficient FPS even with multiple scans.

[0110] Meanwhile, the sample stage (60) can be moved on a plane (along the x-axis and y-axis) while the sample (S) is loaded on its upper surface. In an atmospheric pressure electron microscope, the sample stage (60) is placed in an atmospheric pressure space or a low vacuum space.

[0111] The above movement (offset) of the sample stage (60) is intended to capture a portion (square area) covered by the support (52, window frame). To precisely perform this movement and scan at a high speed, it is preferable to use a piezo stage, but the present invention is not limited thereto. The piezo stage is a stage that combines a piezoelectric element and a displacement measuring sensor to enable ultra-precise position control of 1 nm. Since its configuration is well known, its description will be omitted here.

[0112] The applicant implemented 6 FPS (TV mode) using the above-described method, and confirmed that the frame rate was implemented at a level similar to the normal image acquisition speed.

[0113] The central processing unit (CPU) includes a control unit and a calculation unit. As described above, the control unit controls the operation of the electron gun (20), the electro-optical system (30), the BSD (40), and the sample stage (60). When the user inputs an offset in the x-axis direction and the y-axis direction, the control unit transmits a corresponding control signal to the sample stage (60), and the sample stage (60) moves its position according to the control signal.

[0114] And, the control unit controls the scanner within the electron optical system (30) to control the position and degree of bending of the electron beam, and this control can be linked to the offset of the sample stage (60).

[0115] In addition, multiple image signals transmitted from BSD (40) are image stitched and synthesized by the operation unit, and this synthesized image is finally displayed on the display unit.

[0116] The scanner within the electro-optical system (30) can change the movement path of electrons according to a control signal transmitted from the control unit, and preferably, this control signal can be linked to the movement of the sample stage (60). For example, the electro-optical system (30) can control the movement path of electrons so that electrons pass through the entire window, select some of a plurality of windows (53), or select one specific window (53) to acquire an image. When scanning so as to pass through one specific window (53), a high-magnification image can be acquired without image stitching, and thus the image update speed can be faster than when using multiple multi-windows.

[0117] Meanwhile, Fig. 5 is an image (left) captured using a multi-window thin film unit (50) having a two-dimensional 3x3 array graphene window (53), and a graph (right) showing the signal intensity of points connecting points A and B in the left image.

[0118] 50 nm thick support (52, made of Si3N4) A 3x3 (total of 9) square hole (window, 53) was created in a thick film) and 4 to 5 layers of graphene were applied to the entire surface. In Fig. 5, the left image is an atmospheric pressure electron microscope image measured with this multi-window thin film unit (50), and the graph on the right shows the signal intensity of the points connecting points A and B in the left image. In the graph, the light green part represents the support (Si3N4, thickness: 50 nm) area, and the red part represents the graphene (1 nm or less in thickness, composed of 4 to 5 stacked graphene monolayers) window (53) area. The signal generated by electrons passing through the graphene window (53) area is much stronger and has less noise than the signal generated by electrons passing through the support (52, Si3N4).

[0119]

[0120] [A modified example of an atmospheric pressure electron microscope]

[0121] Fig. 6 is a cross-sectional view showing a modified example of an atmospheric pressure electron microscope. This atmospheric pressure electron microscope has a lower chamber (80) installed at the bottom of a tube (10), and the interior of the lower chamber (80) is a low vacuum space (81). In addition, a multi-window thin film unit (50) is installed at the bottom of the lower chamber (80). Electrons generated from an electron gun (20) sequentially pass through the interior space (11) of the tube (10), an objective lens, the low vacuum space (81), and the multi-window thin film unit (50) to be irradiated onto a sample (S). The multi-window thin film unit (50) can be bonded to the lower surface of the BSD (70) using UV epoxy.

[0122] A low vacuum space (81) can be added inside the lower chamber (80), which reduces the stress applied to the multi-window thin film unit (50) by reducing the pressure difference between the upper and lower portions of the multi-window thin film unit (50).

[0123] In the atmospheric pressure electron microscope (100) of Fig. 1, since the BSD (40) is installed inside the tube (10), the backscattered electrons must pass through the multi-window thin film unit (50). However, in this atmospheric pressure electron microscope, since the BSD (70) is installed at the bottom of the lower chamber (80), the BSE can be detected without passing through the multi-window thin film unit (50) again, and by using this, the BSE scattered at a large angle can be detected, which is advantageous for side observation of a sample with a large inclination.

[0124] Meanwhile, FIG. 7 shows that the BSD (70) is installed inside the lower chamber (80) but is installed at the bottom of the tube (10), and since the distance between the sample (S) and the BSD (70) is far, it mainly detects signals scattered at a low angle.

Claims

1. In an atmospheric pressure electron microscope for observing a sample (S) placed in a space (1) that is at a lower vacuum or atmospheric pressure than the internal space of a tube (10), A multi-window thin film unit (50) separating the interior space and the space (1); A sample stage (60) on which the above sample (S) is placed and which can move on a plane; A control unit for controlling the movement of the sample stage (60); and, A computational unit for image stitching at least two captured images; The multi-window thin film unit (50) is A support member (52) having a plurality of windows (53) formed through a membrane through which electrons cannot pass; and It is installed on a support (52) to cover the window (53) and includes an ultra-thin film (54) that does not allow air to pass through but allows electrons to pass through; The control unit moves the sample stage (60) to capture the sample (S) after capturing it, so that the images captured before and after the movement overlap at least partly with each other. An atmospheric pressure electron microscope using a multi-window thin film, characterized in that the operation unit synthesizes the overlapping captured images by image stitching.

2. In paragraph 1, The window (53) has a predetermined width (x o ) and a given length (y o ) is repeatedly formed along the first direction at a first interval (x1), but with the width (x) o ) is longer than the first interval (x1) and the length (y) o ) is longer than the length of the part you want to shoot, The control unit moves the sample stage (60) along the first direction after taking the first photograph of the sample (S) to take the second photograph, such that the images taken before and after the movement overlap at least partly with each other. An atmospheric pressure electron microscope using a multi-window thin film, characterized in that the operation unit creates an image of the sample by image stitching at least the first and second captured images.

3. In paragraph 1, The window (53) has a predetermined width (x o ) and a given length (y o ) are repeatedly formed at a first interval (x1) along the first direction and at a second interval (y1) along the second direction. The above width(x) o ) is longer than the first interval (x1) and the length (y) o ) is longer than the second interval (y1), The control unit moves the sample stage (60) along the first and second directions respectively after taking the first photograph of the sample (S) to take the second and third photographs, so that the images taken before and after the movement overlap at least partly with each other. An atmospheric pressure electron microscope using a multi-window thin film, characterized in that the operation unit creates an image of the sample by image stitching at least the first, second and third captured images.

4. In any one of paragraphs 1 to 3, The multi-window thin film unit (50) includes a frame (51), and a penetration portion (51a) is formed in the frame (51). A support member (52) is installed on the lower surface of the frame (51), and the entire window (53) is attached to correspond to the penetration member (51a). An ultra-thin film (54) is installed on the lower surface of the support (52) so as to cover the entire window (53). An atmospheric pressure electron microscope using a multi-window thin film, characterized in that the side of the penetration portion (51a) is formed as an inclined surface and the upper part of the penetration portion (51a) has a larger diameter than the lower part.

5. In paragraph 4, The support (52) is a thin film having a thickness of 20 nm to 1 μm and is thicker than the ultra-thin film (54). An atmospheric pressure electron microscope using a multi-window thin film, characterized in that the ultra-thin film (54) is made of graphene or a two-dimensional material (2D material) with high electron transmittance.

6. In any one of paragraphs 1 to 3, It includes a lower chamber (80) installed at the lower part of the tube (10) and having a low vacuum space (81) formed inside, The multi-window thin film unit (50) is installed at the bottom of the lower chamber (80). An atmospheric pressure electron microscope using a multi-window thin film, characterized in that electrons generated from an electron gun sequentially pass through an internal space, a low vacuum space (81), and a multi-window thin film unit (50) to be irradiated onto a sample.

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