Preparation method of three-dimensional atom probe sample for realizing component and structure coupling analysis

Abstract

The invention belongs to the field of micro-nano scale sample preparation, and particularly relates to a preparation method of a three-dimensional atom probe sample for realizing component and structure coupling analysis. The method is based on a transmission electron microscope double-spraying wafer-shaped sample, and comprises the following steps: step (1), preparing a double-spraying wafer-shaped sample; (2) pre-marking a region of interest through a transmission electron microscope; step (3), repositioning to the pre-marked region of interest in the step (2) in the FIB; step (4), extracting a target area; and step (5), girdling. According to the method, the three-dimensional atom probe tip sample is prepared through fixed-point sampling on the transmission electron microscope double-spraying sheet sample with known structure information, and the component information of a specified area in the sample is obtained at a fixed point, so that the structure information and the component information of the specified area are completely coupled, and more comprehensive sample information is obtained.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano scale sample preparation, and in particular relates to a three-dimensional atomic probe sample preparation method for realizing component and structure coupling analysis. Background Art

[0002] Three-dimensional atom probe technology is an analytical testing method with atomic-level spatial resolution. It is based on the principle of "field evaporation". By applying voltage pulses or laser pulses to the needle tip sample, the atoms on the needle tip surface evaporate, the surface atoms peel off layer by layer, and are collected by the detector. Finally, the three-dimensional structural characteristics of the material are reconstructed through software. The three-dimensional atom probe has obvious advantages in analyzing the segregation of elements in the material, the composition of the precipitated phase, the interface composition, and the dislocations with obvious segregation. Exploring the microscopic composition distribution inside the material through this technology is crucial to understanding the macroscopic properties of the material.

[0003] The preparation of three-dimensional atom probe tip samples can be performed by fixed-point preparation using a dual-beam focused ion beam system, or by electrolytic polishing of rod-shaped samples. After analyzing the tip sample, the composition distribution information of the elements inside the tip sample in three-dimensional space can be obtained. However, these two methods have limitations: they can only obtain accurate composition information, and cannot obtain structural information within the analysis area of ​​the tip sample. The microstructural information of the material is also crucial for understanding the macroscopic properties of the material. If the structural / composition information of the same area can be obtained at the same time, it will be more efficient to improve the characterization efficiency and understand the material properties. For example, Baik et al. reported a small transmission electron microscopy sample prepared by FIB in the journal Ultramicroscopy (Baik SI, Isheim D, Seidman D N. Systematic approaches for targeting an atom-probetomography sample fabricated in athin TEM specimen: Correlative structural, chemical and 3-D reconstruction analyses [J]. Ultramicroscopy, 2018, 184: 284-292.) and disclosed a method for preparing an APT tip from this small sample after TEM observation. However, this method has the following shortcomings: 1. It is necessary to repeatedly load the small samples cut by FIB, and the samples are easy to be lost; 2. Before preparing the APT tip sample, there is already a large amount of Ga ion damage, and further APT tip sample preparation will cause secondary damage; 3. It takes a long time from preparing TEM samples to making APT samples, and it is impossible to select multiple target areas, which is inefficient and time-consuming. Summary of the invention

[0004] The object of the present invention is to provide a three-dimensional atom probe sample preparation method for realizing component and structure coupling analysis based on a transmission electron microscope double-sprayed disc sample.

[0005] The technical solution to achieve the purpose of the present invention is: a three-dimensional atomic probe sample preparation method for component and structure coupling analysis, the method is based on a transmission electron microscope double-sprayed disc sample, and includes the following steps:

[0006] Step (1): preparing a double-sprayed disc sample;

[0007] Step (2): pre-marking the region of interest by transmission electron microscopy;

[0008] Step (3): relocate in the FIB to the region of interest pre-marked in step (2);

[0009] Step (4): extracting the target area;

[0010] Step (5): Circumcision.

[0011] Furthermore, the double-sprayed disc-shaped sample prepared in step (1) has a thin region with a thickness of less than 120 nanometers.

[0012] Furthermore, the region of interest pre-marked in step (2) is a grain boundary, a precipitated phase, or a region of a specific shape that needs to be observed.

[0013] Furthermore, step (2) is specifically as follows: using TEM to record the position characteristics of the region and obtain the structural information in the region of interest.

[0014] Furthermore, step (3) is specifically as follows: placing the sheet sample on the FIB sample stage, and repositioning it to a designated region of interest in a dual-beam focused ion beam system based on shape features of the region of interest whose structural information has been observed and obtained.

[0015] Furthermore, step (4) is specifically as follows:

[0016] Step (41): Plating a Pt protective layer: using an electron beam to deposit a Pt layer on the region of interest, and making the Pt layer completely cover the region of interest;

[0017] Step (42): Extract the target area: Tilt the sample stage to 24°, cut one side of the area of ​​interest after the Pt layer is plated, and keep the bottom and the other side still connected to the sample;

[0018] Step (43): insert the nanohand, bring the nanohand close to a corner of the cut side of the region of interest, and then use Pt to connect the nanohand to the sample; after confirming the adhesion, use an ion beam to cut the bottom and the other side of the region of interest to separate the region of interest from the sheet sample, and withdraw the nanohand;

[0019] Step (44): placing the prefabricated silicon-based micro-pillar array into the dual-beam focused ion beam system, selecting available silicon-based micro-pillars, and tilting the sample stage to 24°;

[0020] Step (45): Place the target area: insert the nanohand, rotate the nanohand 90° around the axis, so that the extracted region of interest is nearly 90° with a silicon-based microcolumn surface platform, insert the air needle, place the extracted region of interest on the silicon-based microcolumn, and deposit Pt at the junction of the extracted region of interest and the silicon-based microcolumn to make them adhere; then cut and separate the nanohand from the region of interest, withdraw the nanohand and the air needle, and complete the placement of the region of interest.

[0021] Furthermore, the sample stage was tilted to 54° to face the ion beam, and circular cutting was performed under the ion beam using a beam current of 30 kV and 20 pA-50 pA to prepare the APT needle tip sample.

[0022] Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) The method of the present invention is based on a double-sprayed sheet transmission sample prepared by conventional means, which is convenient for observing and selecting multiple regions of interest using a transmission electron microscope, and all structural information of the regions of interest can be obtained simultaneously.

[0024] (2) The method of the present invention utilizes double spraying to prepare transmission samples instead of using FIB to prepare transmission electron microscope samples, which greatly reduces Ga ion damage in the sample before preparing the APT needle tip and improves the sample quality of the needle tip.

[0025] (3) The present invention utilizes the thin area in the double-sprayed sheet-like transmission sample to directly prepare the APT needle tip sample, saving the time cost and processing cost of FIB sample preparation.

[0026] (4) In the method of the present invention, all processes directly use a small beam current of 30kV 20-50pA to process and prepare APT needle tip samples, avoiding the large Ga ion damage caused by large beam current processing during FIB sample preparation.

[0027] (5) The method of the present invention can realize the coupling of structural and compositional information in the same region and comprehensively obtain the information contained in the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1Figure 2 is a diagram of a sheet sample and the structural information of the area of ​​interest obtained using a transmission electron microscope; a is the morphology of the electrolytic double-spray sample; b is the thin area with a thickness of less than 100 nm at the edge of the sample recorded by a transmission electron microscope, where the red box is the area of ​​interest selected for APT sample preparation; c is the bright field image of the area of ​​interest recorded by a transmission electron microscope; d is the structural information of the area of ​​interest recorded by a transmission electron microscope.

[0029] Figure 2 The flowchart of preparing the needle tip sample from the selected area of ​​interest under the dual-beam system; wherein a is the morphology of the area of ​​interest under the focused ion beam in the transmission electron microscope; b is a picture of a Pt protective layer deposited on the selected area of ​​interest by electron beam deposition, and after Pt is plated, one side is cut by ion beam; c is a picture of the nanohand connected to a corner of the cut side; d is a picture of the bottom being cut by ion beam; e is a picture of the other side being cut by ion beam and separated from the sheet sample; f is a picture of the nanohand after axial rotation 90° after extracting the area of ​​interest; g is a front view of the area of ​​interest after the area of ​​interest is adhered to the silicon-based microcolumn; h is a side view of the area of ​​interest after the area of ​​interest is adhered to the silicon-based microcolumn; i is a schematic diagram of the ring cutting of the area of ​​interest; k is a needle tip sample suitable for three-dimensional atomic probe analysis obtained by ring cutting. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0031] The method of the present invention is used to prepare a three-dimensional atomic probe tip, and a transmission electron microscope sheet-shaped sample prepared by double spraying is selected to observe the thin area, and multiple areas of interest are selected and recorded; according to the transmission observation results, the target area is selected to prepare the three-dimensional atomic probe tip. The traditional tip sample preparation method cannot achieve the purpose of obtaining complete structural information of multiple areas of interest using a transmission electron microscope before preparing the tip sample, and lacks structural information of the area where the tip sample is prepared. This method improves the traditional method and proposes to use samples that have been observed through transmission to select multiple areas of interest for the preparation of three-dimensional atomic probe tip samples, which can not only obtain more comprehensive structural information, but also obtain high-precision composition information; in addition, this method takes a short time to prepare the tip sample, avoids secondary damage to the sample caused by long-term ion beam processing, and can meet the requirements of preparing tip samples for multiple areas of interest, thereby improving sample preparation efficiency and reducing costs.

[0032] Example

[0033] The following is a specific example of the double-spray transmission sample processing needle tip sample of Ni-B alloy:

[0034] The TEM samples of Ni-B alloy were prepared by conventional electrolytic double spraying and characterized by TEM. Multiple areas of interest can be selected. Figure 1 Figure 2 is a diagram of a sheet sample and the structural information of the area of ​​interest obtained using a transmission electron microscope. a is the morphology of the electrolytic double-spray sample; b is the thin area with a thickness of less than 100 nm at the edge of the sample recorded by a transmission electron microscope, where the red box is the area of ​​interest selected for APT sample preparation; c is the bright field image of the area of ​​interest recorded by a transmission electron microscope; d is the structural information of the area of ​​interest recorded by a transmission electron microscope.

[0035] The transmission double-sprayed sheet sample with the area of ​​interest selected after transmission observation is fixed on the sample stage, placed in the dual-beam focused ion beam system, and vacuum is drawn.

[0036] Move the sample stage under the electron beam field of view, and reposition it to the region of interest according to the existing transmission electron microscopy results; use electron beam to deposit Pt to protect the region, tilt the sample stage 24°, cut one side of the region of interest, and keep the bottom and the other side still connected to the disc-shaped sample; insert the nanohand, bring the nanohand close to a corner of the cut side of the region of interest, and then use Pt to connect the nanohand to the region of interest; after confirming the adhesion, use ion beam cutting to separate the bottom and the other side of the region of interest from the sheet sample; take the sample stage out of the focused ion beam system, and remove the prefabricated silicon-based microcolumns. The array is placed in a dual-beam focused ion beam system. After selecting an available silicon-based microcolumn, the sample stage is tilted to 24°, and a nanohand with an area of ​​interest is inserted. The nanohand is rotated 90° around the axis to make the extracted area of ​​interest vertical to a silicon-based microcolumn surface platform. Then, an air needle is inserted, and the area of ​​interest is placed on the silicon-based microcolumn surface platform. Pt is then deposited to make the area of ​​interest adhere to the silicon-based microcolumn surface platform. The nanohand is then cut and separated from the area of ​​interest, and the nanohand and air needle are withdrawn to complete the placement of the target area. The sample stage is then tilted to 54° to face the ion beam, and a small beam current of 30kv 20-50pA is selected under the ion beam for conventional ring cutting operations to prepare a needle tip suitable for three-dimensional atomic probe analysis. For the specific process, please refer to Figure 2 , Figure 2Figure 2 is a flow chart for preparing a needle tip sample from a selected region of interest under a dual-beam system; a is a morphology image of the region of interest under a focused ion beam in a transmission electron microscope; b is a Pt protective layer of less than 50 nm deposited on the selected region of interest using electron beam deposition; after Pt plating, a picture of one side being cut open by an ion beam; c is a picture of the nanohand connected to a corner of the cut side; d and e are pictures of the bottom and the other side being cut open by an ion beam to separate them from the sheet sample; f is a picture of the nanohand extracting the region of interest and rotating 90° axially; g and h are side and front views of the region of interest after it is bonded to a silicon-based microcolumn; i is a schematic diagram of ring cutting of the region of interest; k is a needle tip sample suitable for three-dimensional atomic probe analysis obtained by ring cutting.

Claims

1. A three-dimensional atomic probe sample preparation method for realizing coupled composition and structure analysis, characterized in that: The method is based on a transmission electron microscope double-sprayed disc sample and includes the following steps: Step (1): preparing a double-sprayed disc sample; Step (2): pre-marking the region of interest by transmission electron microscopy; Step (3): relocate in the FIB to the region of interest pre-marked in step (2); Step (4): extracting the target area; Step (5): Circumcision.

2. The method according to claim 1, characterized in that: The double-sprayed disc-shaped sample prepared in step (1) has a thin region with a thickness of less than 120 nanometers.

3. The method according to claim 2, characterized in that The region of interest pre-marked in step (2) is a grain boundary, a precipitated phase, or a region of a specific shape that needs to be observed.

4. The method according to claim 3, characterized in that Step (2) specifically includes: using TEM to record the positional features of the region and obtain structural information in the region of interest.

5. The method according to claim 4, characterized in that Step (3) is specifically as follows: placing the sheet sample on the FIB sample stage, and repositioning it to a designated region of interest in a dual-beam focused ion beam system based on the shape features of the region of interest whose structural information has been observed and obtained.

6. The method according to claim 5, characterized in that Step (4) is specifically as follows: Step (41): Plating a Pt protective layer: using an electron beam to deposit a Pt layer on the region of interest, and making the Pt layer completely cover the region of interest; Step (42): Extract the target area: Tilt the sample stage to 24°, cut one side of the area of ​​interest after the Pt layer is plated, and keep the bottom and the other side still connected to the sample; Step (43): insert the nanohand, bring the nanohand close to a corner of the cut side of the region of interest, and then use Pt to connect the nanohand to the sample; after confirming the adhesion, use an ion beam to cut the bottom and the other side of the region of interest to separate the region of interest from the sheet sample, and withdraw the nanohand; Step (44): placing the prefabricated silicon-based micro-pillar array into the dual-beam focused ion beam system, selecting available silicon-based micro-pillars, and tilting the sample stage to 24°; Step (45): Place the target area: insert the nanohand, rotate the nanohand 90° around the axis, so that the extracted region of interest is nearly 90° with a silicon-based microcolumn surface platform, insert the air needle, place the extracted region of interest on the silicon-based microcolumn, and deposit Pt at the junction of the extracted region of interest and the silicon-based microcolumn to make them adhere; then cut and separate the nanohand from the region of interest, withdraw the nanohand and the air needle, and complete the placement of the region of interest.

7. The method according to claim 6, characterized in that The sample stage was tilted to 54° to face the ion beam, and circular cutting was performed under the ion beam using a beam current of 30kV 20pA-50pA to prepare the APT tip sample.

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