Method for adjusting crystal orientation in transmission electron microscope

Abstract

The invention relates to the technical field of transmission electron microscope using methods, in particular to a method for adjusting crystal orientation in a transmission electron microscope, which comprises the following steps: S1, determining a current crystal zone axis; s2, determining that a current crystal zone axis X and a target crystal zone axis Y need to tilt along a Z Kikuchi line, and calculating an included angle theta between the two crystal zone axes; measuring the included angle gamma between the Z Kikuchi line and the horizontal direction; delta alpha and delta beta are calculated, delta alpha is equal to theta cos gamma, and delta beta is equal to theta sin gamma; adjusting a crystal zone axis in an electron microscope according to the numerical values of the alpha 2 and the beta 2; s6, if the target ribbon axis Y is not reached after adjustment, a small amount of deviation exists; a target crystal belt axis Y is achieved after fine adjustment; according to the method, a Kikuchi line length-angle quantitative conversion model is established, and the Kikuchi line length is quickly converted into the angle, so that the required rotation angle can be quickly estimated, and the time of manual operation and trial and error is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of the use method of a transmission electron microscope, and specifically to a method for adjusting the crystal orientation in a transmission electron microscope. Background Art

[0002] In a transmission electron microscope, the adjustment of crystal orientation is a key step for high-resolution imaging and diffraction analysis; traditional crystal orientation adjustment methods rely on manual operation and repeated trial and error, especially when tilting at large angles, the efficiency is low and the time consumption is long; Kikuchi lines, as characteristic lines of crystal diffraction, can provide important information on crystal orientation; however, there is a lack of a method in the prior art for quickly and accurately converting Kikuchi line information into crystal orientation adjustment parameters. Summary of the Invention

[0003] The main purpose of the present invention is to provide a method for adjusting the crystal orientation in a transmission electron microscope, so as to solve the problem in the above-mentioned prior art that there is a lack of a method for quickly and accurately converting Kikuchi line information into crystal orientation adjustment parameters.

[0004] To achieve the above purpose, the present invention provides a method for adjusting the crystal orientation in a transmission electron microscope, including the following steps:

[0005] S1. Determine the current zone axis: Load the sample in the transmission electron microscope, and find the target grain or area to be detected in the sample; Tilt the sample slightly along the α and β axes, and the rotation angles are α1 and β1 respectively, and find the low-index zone axis X with the closest distance as the current zone axis X, and take a Kikuchi pattern.

[0006] S2. Determine that the current zone axis X and the target zone axis Y need to be tilted along the Z Kikuchi line by referring to the standard Kikuchi diagram, and calculate the angle between the two zone axes as θ through the crystal plane angle formula; Measure the angle between the Z Kikuchi line and the horizontal direction as γ.

[0007] S3. Calculate the angular deviations Δα and Δβ of the current zone axis X and the target zone axis Y along the α and β axes in the electron microscope: Δα = θcosγ, Δβ = θsinγ.

[0008] S4. Calculate the angles α2 and β2 that the sample needs to rotate along the α and β axes in the electron microscope.

[0009] S5. Adjust the zone axis in the electron microscope according to the values of α2 and β2.

[0010] S6. After adjustment, the target zone axis Y has not been reached and there is a small deviation; After fine adjustment, the target zone axis Y is reached.

[0011] Further, in step S4, according to the position of the target zone axis relative to the current zone axis, there are four different tilting situations; when the target zone axis is located in the upper right corner of the current zone axis, the calculation formulas are: α2 = α1 + |Δα|, β2 = β1 + |Δβ|; when the target zone axis is located in the lower right corner of the current zone axis, the calculation formulas are: α2 = α1 + |Δα|, β2 = β1 - |Δβ|; when the target zone axis is located in the upper left corner of the current zone axis, the calculation formulas are: α2 = α1 - |Δα|, β2 = β1 + |Δβ|; when the target zone axis is located in the lower left corner of the current zone axis, the calculation formulas are: α2 = α1 - |Δα|, β2 = β1 - |Δβ|.

[0012] The beneficial effects of the present invention are:

[0013] Limited by the mechanical angle range of the Double-Tilt Holder (usually ±30° to ±35°), the phenomenon of freedom saturation is likely to occur in continuous large-angle tilting operations, resulting in the interruption of zone axis adjustment; based on the linear mapping relationship between the zone axis angle and the projection length of Kikuchi lines in Kikuchi diffraction geometry, by establishing a quantitative conversion model of Kikuchi line length - angle, the required rotation angle can be quickly estimated by quickly converting the Kikuchi line length into an angle, thereby reducing the time of manual operation and trial and error; avoiding the phenomenon of freedom saturation; this method has universality and can be compatible with typical crystal structure materials such as face-centered cubic (FCC) and body-centered cubic (BCC), and is especially suitable for the repetitive zone axis positioning requirements in in-situ characterization of multiple regions of homogeneous materials (such as long-period observation of age precipitation phases in aluminum alloys). BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0015] Figure 1 It is the diffraction pattern of multiple Kikuchi poles of aluminum alloy in the embodiment;

[0016] Figure 2 It is the schematic diagram of the mathematical model in the embodiment;

[0017] Figure 3 It is the pattern at the

[011] zone axis of aluminum alloy in the embodiment;

[0018] Figure 4 It is the pattern at the

[001] zone axis of aluminum alloy in the embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0019] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0020] Embodiment 1

[0021] As Figure 3 and 4 shown, a method for adjusting the crystal orientation in a transmission electron microscope, the detection material is 6xxx aluminum alloy, ground with water sandpaper until the thickness reaches 50 μm, and a sample is intercepted for double spraying and ion thinning instrument to prepare a thin area; the adjustment method includes the following steps:

[0022] S1. Determine the current zone axis: Load the sample in the transmission electron microscope, find the target grain or area to be detected in the sample; Tilt the sample slightly along the α and β axes, and the rotation angles are α1 and β1 respectively, α1 and β1 are -14.23° and -1.43° respectively, find the low-index zone axis

[011] with the closest distance, which is the current zone axis

[011] , and take a Kikuchi pattern.

[0023] S2. Determine that the current zone axis

[011] and the target zone axis

[001] need to be tilted along the (200) Kikuchi line by referring to the standard Kikuchi diagram, and calculate the angle θ between the two zone axes as 45° through the crystal plane angle formula; the crystal plane angle formula is Save the Kikuchi pattern as a digital image, and use the image processing software Photoshop to measure the angle γ between the (200) Kikuchi line and the horizontal direction as 6.8°.

[0024] S3. Calculate the angular deviations Δα and Δβ of the current zone axis X and the target zone axis Y along the α and β axes of the electron microscope: Δα = θcosγ, Δβ = θsinγ; that is, Δα = 44.68°; Δβ = 5.33°.

[0025] S4. Calculate the angles α2 and β2 that the sample needs to rotate along the α and β axes in the electron microscope: According to the position of the target zone axis relative to the current zone axis, there are four different tilting situations; when the target zone axis is located in the upper right corner of the current zone axis, the calculation formula is: α2 = α1 - |Δα|, β2 = β1 - |Δβ|; when the target zone axis is located in the lower right corner of the current zone axis, the calculation formula is: α2 = α1 - |Δα|, β2 = β1 + |Δβ|; when the target zone axis is located in the upper left corner of the current zone axis, the calculation formula is: α2 = α1 + |Δα|, β2 = β1 - |Δβ|; when the target zone axis is located in the lower left corner of the current zone axis, the calculation formula is: α2 = α1 + |Δα|, β2 = β1 + |Δβ|;

[0026] The target zone axis

[001] is located at the lower left corner of the current zone axis

[011] ; the calculation formula is: α2 = α1 + |Δα|, β2 = β1 + |Δβ|; α2 and β2 are obtained as 30.45° and 3.90° respectively;

[0027] S5. Adjust the zone axis in the electron microscope according to the values of α2 and β2;

[0028] S6. After adjustment, the target zone axis

[001] has not been reached and there are small deviations; after fine adjustment, the target zone axis

[001] is reached; finally, the angles of rotation of the sample along the α and β axes in the electron microscope are α'2 and β'2, which are 28.38° and 3.46° respectively.

[0029] Example 2

[0030] A method for adjusting the crystal orientation in a transmission electron microscope, the detected material is 6xxx aluminum alloy, ground with water sandpaper to a thickness of 50 μm, and a sample is intercepted and prepared into a thin area by double spraying and an ion thinning instrument; the adjustment method includes the following steps:

[0031] S1. Determine the current zone axis: Load the sample in the transmission electron microscope, find the target grain or area to be detected in the sample; Tilt the sample slightly along the α and β axes, and the rotation angles are α1 and β1 respectively. α1 and β1 are -17.81° and -14.63° respectively, and find the low-index zone axis

[011] closest to it, which is the current zone axis

[011] , and take a Kikuchi pattern.

[0032] S2. Determine that the current zone axis

[011] and the target zone axis

[001] need to be tilted along the (200) Kikuchi line by referring to the standard Kikuchi diagram, and calculate the included angle θ between the two zone axes as 45° through the crystal plane included angle formula; the crystal plane included angle formula is Save the Kikuchi pattern as a digital image, and use the image processing software Photoshop to measure the included angle γ between the (200) Kikuchi line and the horizontal direction as 34°;

[0033] S3. Calculate the angular deviations Δα and Δβ of the current zone axis X and the target zone axis Y along the α and β axes in the electron microscope: Δα = θcosγ, Δβ = θsinγ; that is, Δα = 37.31°; Δβ = 25.16°.

[0034] S4. Calculate the angles α2 and β2 that the sample needs to rotate along the α and β axes in the electron microscope: According to the position of the target zone axis relative to the current zone axis, there are four different tilting situations; when the target zone axis is located in the upper right corner of the current zone axis, the calculation formula is: α2 = α1 - |Δα|, β2 = β1 - |Δβ|; when the target zone axis is located in the lower right corner of the current zone axis, the calculation formula is: α2 = α1 - |Δα|, β2 = β1 + |Δβ|; when the target zone axis is located in the upper left corner of the current zone axis, the calculation formula is: α2 = α1 + |Δα|, β2 = β1 - |Δβ|; when the target zone axis is located in the lower left corner of the current zone axis, the calculation formula is: α2 = α1 + |Δα|, β2 = β1 + |Δβ|;

[0035] The target zone axis

[001] is located in the lower left corner of the current zone axis

[011] ; the calculation formula is: α2 = α1 + |Δα|, β2 = β1 + |Δβ|; α2 and β2 are obtained as 19.50° and 10.53° respectively;

[0036] S5. Adjust the zone axis in the electron microscope according to the values of α2 and β2;

[0037] S6. After adjustment, the target zone axis

[001] has not been reached and there is a small deviation; after fine adjustment, the target zone axis

[001] is reached; finally, the angles α'2 and β'2 that the sample rotates along the α and β axes in the electron microscope are 21.62° and 10.78° respectively.

[0038] The derivation process of the formulas Δα = θcosγ and Δβ = θsinγ is as follows:

[0039] S1. Calibrate the Kikuchi pattern:

[0040] S1.1. Load the aluminum alloy sample using the double-tilt sample holder of the Talos F200X transmission electron microscope and find the target particles to be detected in the sample;

[0041] S1.2. In the STEM mode, exit the HAADF probe and enter the diffraction mode;

[0042] S1.3. Find the diffraction pattern of multiple Kikuchi poles, as Figure 1 shown, and take a record;

[0043] S2. Calculate the scale factor P:

[0044] S2.1. Calibrate the multiple diffraction patterns. There are Kikuchi poles A, B, and C in the figure; use the crystal plane angle formula to calculate the angles between each zone axis,

[0045] The crystal plane angle formula is The angles between each Kikuchi pole are

[0046] S2.2. Using the Camera of the transmission electron microscope stage as the negative film, measure the distances between Kikuchi poles A, B, and C, which are AB, BC, and AC respectively;

[0047] S2.3. The scale factor formula is

[0048] S3. Calculate the angle θ between the current zone axis X and the target zone axis Y through the crystal plane angle formula; through Calculate the length L from the current Kikuchi pole to the target Kikuchi pole:

[0049] S4. As Figure 2 shown, the current zone axis X and the target zone axis Y need to be tilted along the Z Kikuchi line, and the angle between the Z Kikuchi line and the horizontal direction is γ; calculate the angular deviations Δα and Δβ of the current zone axis X and the target zone axis Y along the α and β axes:

[0050] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for adjusting crystal orientation in a transmission electron microscope, characterized in that, Including the following steps: S1. Determine the current zone axis: Load the sample in the transmission electron microscope, and find the target grain or area to be detected in the sample; Tilt the sample slightly along the α and β axes, with the rotation angles being α1 and β1 respectively, find the low-index zone axis X with the closest distance, which is the current zone axis X, and take a Kikuchi pattern; S2. Determine that the current zone axis X and the target zone axis Y need to be tilted along the Z Kikuchi line by referring to the standard Kikuchi diagram, and calculate the angle between the two zone axes as θ using the crystal plane angle formula; Measure the angle between the Z Kikuchi line and the horizontal direction as γ; S3. Calculate the angular deviations Δα and Δβ of the current zone axis X and the target zone axis Y along the α and β axes in the electron microscope: Δα = θcosγ, Δβ = θsinγ; S4. Calculate the angles α2 and β2 that the sample needs to rotate along the α and β axes in the electron microscope; S5. Adjust the zone axis in the electron microscope according to the values of α2 and β2; S6. After adjustment, the target zone axis Y has not been reached and there is a small deviation; After fine adjustment, the target zone axis Y is reached.

2. The method for adjusting the crystal orientation in a transmission electron microscope according to claim 1, characterized in that In step S4, according to the position of the target zone axis relative to the current zone axis, there are four different tilting situations; When the target zone axis is located in the upper right corner of the current zone axis, the calculation formula is: α2 = α1 + |Δα|, β2 = β1 + |Δβ|; When the target zone axis is located in the lower right corner of the current zone axis, the calculation formula is: α2 = α1 + |Δα|, β2 = β1 - |Δβ|; When the target zone axis is located in the upper left corner of the current zone axis, the calculation formula is: α2 = α1 - |Δα|, β2 = β1 + |Δβ|; When the target zone axis is located in the lower left corner of the current zone axis, the calculation formula is: α2 = α1 - |Δα|, β2 = β1 - |Δβ|.

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