Pressure head and micro-column coaxial alignment method for micro-column compression experiment in SEM (scanning electron microscope) environment

Abstract

The invention discloses a pressure head and micro-column coaxial alignment method for a micro-column compression experiment in an SEM (scanning electron microscope) environment, which comprises the following steps: firstly, adjusting the position of a micro-column to enable a pressure head to be positioned above the micro-column and in the same visual field of a scanning electron microscope, then moving the micro-column until the central line of the micro-column and the central line of the pressure head are collinear up and down, then obtaining the depth of field, determining the depth of field boundary point of the micro-column, and finally aligning the depth of field. And moving the micro-column backwards for a distance of delta f / 2 + (R-r) from the depth-of-field boundary point to finish coaxial alignment of the pressure head and the micro-column. According to the method, the nanomechanical testing system and the scanning electron microscope are combined, specific operation steps are combined, accurate alignment of the pressure head and the micro-column can be achieved, the method is simple and convenient, operation is easy, and reduction of test errors of micro-column compression is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of microcolumn characterization, and in particular to a method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment. Background Art

[0002] Visualized in-situ micro-nanomechanical testing technology can realize real-time online observation of the indentation process, and then study the deformation and damage mechanism of the material surface under load. Microcolumn compression is a typical in-situ mechanical test. By slowly applying a compressive load to the indenter above the microcolumn and recording the load-displacement curve, the strength, hardness and elastic modulus of the microcolumn can be evaluated. During the microcolumn compression process, although the large indenter can easily cover the top surface of the microcolumn, the bottom of the indenter can easily block the microcolumn during the compression process, affecting observation. In addition, when the microcolumn is on the side of the indenter, the microcolumn may be subjected to uneven force, affecting the accuracy of the data.

[0003] The most suitable indenter is one that is slightly larger than or equal to the surface area of ​​the top of the microcolumn, but it is difficult to align the bottom of the indenter with the top of the microcolumn. The reason is that the camera image in the field of view of the scanning electron microscope is a flat image, but what we need to observe is the dynamic changes in three-dimensional space. There are visual errors during observation, which makes it difficult to align the bottom of the indenter with the top of the microcolumn. Therefore, how to make the indenter with a surface area slightly larger than or equal to the top of the microcolumn accurately align with the microcolumn during the test is a problem that needs to be solved urgently. Summary of the invention

[0004] The present invention aims to solve the problem that an indenter with a surface area slightly larger than or equal to that of the top of a microcolumn is difficult to accurately align with the microcolumn during the existing microcolumn compression test process, and provides an indenter-microcolumn coaxial alignment method for a microcolumn compression experiment in a SEM environment, which is simple and easy to operate and can achieve accurate alignment between the indenter and the microcolumn.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment, comprising the following steps: (1) The base of the microcolumn is mounted on the base of a scanning electron microscope, so that the pressure head in the nanomechanical testing system and the microcolumn are in the same field of view of the scanning electron microscope, and the radius r (μm) of the microcolumn is measured. The present invention combines the nanomechanical testing system with a scanning electron microscope, and uses the imaging capability of the SEM to observe the mechanical characterization process in real time, thereby realizing a visualized in-situ micro-nanomechanical test to study the deformation and damage mechanism of the material surface under load; the nanomechanical testing system is an instrument for realizing quantitative mechanical and tribological characterization of materials at the nanometer and micrometer scales, and is a well-known device in the art, so it is not described in detail; compression flat heads of different sizes can be selected according to the size of the microcolumn diameter; the microcolumn radius is measured by a scanning electron microscope.

[0006] (2) Raise the base of the microcolumn so that the bottom surface of the indenter and the projection of the indenter on the base of the microcolumn coincide with each other.

[0007] (3) Lower the base of the microcolumn and adjust the position of the microcolumn so that the indenter is located above the microcolumn and in the same field of view of the scanning electron microscope. The indenter is located above the microcolumn to ensure that the indenter will not collide with the microcolumn when it is moved later.

[0008] (4) Adjust the base position of the microcolumn so that the microcolumn moves to a position where the midline of the microcolumn and the midline of the indenter are aligned vertically.

[0009] (5) After the edge of the indenter is clearly focused, the microcolumn is moved back and forth until the front surface of the microcolumn has a clear outline. At this time, the depth of field Δf (μm) of a clear image is obtained on the SEM imaging plane with the edge of the indenter as the center. For different brands of scanning electron microscopes, different methods can be used to obtain the depth of field under certain shooting conditions. For example, the depth of field of the Tesken scanning electron microscope can be directly read out on the software, while for electron microscopes produced by Zeiss, Hitachi and other companies, the depth of field under corresponding conditions can be calculated using the depth of field calculation formula. Obtaining the depth of field is a conventional technical means in this field, so it will not be repeated.

[0010] (6) Move the microcolumn forward to determine the boundary position between blur and clarity of the front side of the microcolumn, and use this position as the depth of field boundary point.

[0011] (7) Move the microcolumn backward from the depth of field boundary point by a distance Δf / 2+(Rr) to complete the coaxial alignment of the indenter and the microcolumn, where R is the indenter radius (μm).

[0012] Preferably, in step (1), the microcolumn is in a vertical state, and the bottom surface of the pressure head is parallel to the top surface of the microcolumn. The microcolumn is in a vertical state, and the force is concentrated and uniform; the higher the parallelism between the bottom surface of the pressure head and the top surface of the microcolumn, the smaller the test error. Therefore, in the present invention, the bottom surface of the pressure head and the top surface of the microcolumn are kept parallel to each other to reduce the test error of microcolumn compression.

[0013] Preferably, in step (1), the bottom surface area of ​​the pressure head is equal to or slightly larger than the top surface area of ​​the microcolumn. When the bottom surface area of ​​the pressure head is equal to or slightly larger than the top surface area of ​​the microcolumn, the bottom end of the pressure head is not easy to block the microcolumn during the compression process, which is convenient for observation, the microcolumn is more evenly stressed, and the data accuracy is good.

[0014] Preferably, in step (3), the distance between the indenter and the microcolumn is controlled to be less than 5 μm. The indenter and the microcolumn can be seen simultaneously in the SEM field of view with the lowest magnification, and subsequent needle insertion is relatively fast.

[0015] Preferably, the distance between the indenter and the microcolumn is controlled to be 2-3 μm.

[0016] Therefore, the present invention has the following beneficial effects: the indenter-microcolumn coaxial alignment method for a microcolumn compression experiment in a SEM environment of the present invention utilizes a nanomechanical testing system and a scanning electron microscope in combination with specific operating steps to achieve precise alignment of the indenter and the microcolumn, and the method is simple and easy to operate, which is beneficial to reducing the test error of microcolumn compression. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an electron microscope image of the state where the indenter and its projection on the base of the microcolumn overlap in step (2).

[0018] Figure 2 This is an electron microscope image of the state where the pressure head is located above the microcolumn in step (3).

[0019] Figure 3 This is an electron microscope image showing the midline of the microcolumn and the midline of the indenter in step (4) being collinear.

[0020] Figure 4 This is an electron microscope image of the microcolumn at the boundary point of the depth of field in step (6).

[0021] Figure 5 This is an electron microscope image of the coaxial alignment state of the pressure head and the microcolumn in step (7). DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] In the following examples, the scanning electron microscope is a Zeiss Sigma360 scanning electron microscope, with an acceleration voltage of 3kV, an aperture of 60μm, and a high beam mode to ensure sufficient electron quantity; the working distance is 14.4mm. The type of microcolumn is: a photosensitive material with 2-phenylethylthiol and pentaerythritol triacrylate as monomers and metal nanoclusters as photoinitiators, and a microcolumn printed by two-photon 3D printing technology; the microcolumn radius r is measured to be 4.16μm, and the height is 13.09μm; the indenter is: Bruker TI-0261 FlatPunch, the indenter diameter is 20μm, the cone angle is 60°, the Young's modulus is 1140GPa, and the Poisson's ratio is 0.07.

[0024] Example 1 (1) The base of the microcolumn is mounted on the base of a scanning electron microscope so that the indenter and the microcolumn in the nanomechanical testing system are in the same field of view of the scanning electron microscope, and the radius r (4.16 μm) of the microcolumn is measured. The microcolumn is in a vertical state, the bottom surface of the indenter is parallel to the top surface of the microcolumn, and the bottom surface area of ​​the indenter is slightly larger than the top surface area of ​​the microcolumn; (2) Raise the base of the microcolumn so that the bottom surface of the indenter and the projection of the indenter on the base of the microcolumn coincide with each other (e.g. Figure 1(3) Lower the base of the microcolumn and adjust the position of the microcolumn so that the indenter is located above the microcolumn. Under the conditions of a magnification of 500 times and a working distance of 14.4 mm, it can be seen that the indenter and the microcolumn are in the same field of view of the scanning electron microscope (as shown in FIG. Figure 2 As shown), the distance between the indenter and the micropillar is controlled at 5 μm; (4) Adjust the magnification to 2000x and adjust the base position of the microcolumn so that the midline of the microcolumn is aligned with the midline of the indenter (e.g. Figure 3 shown); (5) The magnification is magnified to 3000x, the bottom of the indenter and the microcolumn are in the same field of view, the edge of the indenter is clearly focused, and the microcolumn is moved back and forth until the front surface of the microcolumn is clearly outlined. Under the current shooting conditions, M is 3000, D is 14.4 mm, d is 0.03 μm (the maximum spot of the thermal field emission electron gun is calculated to be d = 0.03), a is 60 μm, and the depth of field Δf is calculated to be 2.2 μm; (6) With the edge of the indenter as the center, move the microcolumn forward to determine the boundary position between blur and clarity on the front side of the microcolumn, and use this position as the depth of field boundary point (e.g. Figure 4 shown); (7) Move the microcolumn backward from the depth of field boundary point by a distance of Δf / 2+(Rr) (i.e., 6.94 μm) to complete the coaxial alignment between the indenter and the microcolumn (e.g., Figure 5 As shown in the figure, the micro-column compression experiment can be carried out after lowering the pressure head to the micro-column surface.

[0025] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment, characterized in that: The following steps are involved: (1) The base of the microcolumn is mounted on the base of a scanning electron microscope so that the indenter and the microcolumn in the nanomechanical testing system are in the same field of view of the scanning electron microscope, and the radius r (μm) of the microcolumn is measured; (2) raising the base of the microcolumn so that the bottom surface of the indenter and the projection of the indenter on the base of the microcolumn coincide with each other; (3) lowering the base of the microcolumn and adjusting the position of the microcolumn so that the indenter is located above the microcolumn and in the same field of view of the scanning electron microscope; (4) adjusting the base position of the microcolumn so that the microcolumn is moved to a position where the midline of the microcolumn and the midline of the indenter are collinear; (5) After the edge of the indenter is clearly focused, the microcolumn is moved back and forth until the front surface of the microcolumn has a clear outline. At this time, the depth of field Δf (μm) of a clear image is obtained on the SEM imaging plane with the edge of the indenter as the center; (6) Move the microcolumn forward to determine the boundary position between blur and clarity on the front side of the microcolumn, and use this position as the depth of field boundary point; (7) Move the microcolumn backward from the depth of field boundary point by a distance Δf / 2+(Rr) to complete the coaxial alignment of the indenter and the microcolumn, where R is the indenter radius (μm).

2. The method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment according to claim 1, characterized in that: In step (1), the microcolumn is in a vertical state, and the bottom surface of the pressure head and the top surface of the microcolumn are parallel to each other.

3. The method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment according to claim 1, characterized in that: In step (1), the bottom surface area of ​​the pressure head is equal to or slightly larger than the top surface area of ​​the microcolumn.

4. The method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment according to claim 1, characterized in that: In step (3), the distance between the indenter and the microcolumn is controlled to be less than 5 μm.

5. The method for coaxially aligning an indenter microcolumn in a microcolumn compression experiment in a SEM environment according to claim 4, characterized in that: The distance between the pressure head and the micro-column is controlled at 2-3 μm.

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