CN117030755A - Method for applying temperature gradient field in transmission electron microscope - Google Patents

Abstract

The invention relates to a method for applying an in-situ temperature gradient field in a transmission electron microscope, comprising the steps of: (1) Fixing a test chip loaded with a micro-nano sample to be tested with an in-situ sample rod, and enabling the micro-nano sample to be tested and the sample rod to form a passage; (2) Inserting an in-situ sample rod into a transmission electron microscope and connecting an external direct current source; (3) And (3) introducing a preset direct current into the test chip to form Joule heat and conducting the Joule heat to the micro-nano sample to be tested, so as to realize the application of an in-situ temperature gradient field to the micro-nano sample to be tested. Compared with the prior art, the invention realizes that the temperature gradient field is applied to the sample to be tested in the transmission electron microscope in-situ test platform, and has the advantages of simple processing, wide temperature rising range, real-time and real-space observation and the like.

Description

A method for applying temperature gradient fields in transmission electron microscopy

Technical field

The invention belongs to the technical field of micro-nano material temperature gradient field application, and in particular relates to a method for applying an in-situ temperature gradient field in a transmission electron microscope.

Background technique

As a micro-nano material analysis and characterization equipment with extremely high temporal and spatial resolution, transmission electron microscopy is widely used in the fields of materials science, biology, physics and chemistry. Among them, transmission electron microscopy in-situ characterization technology can realize real-time, real-space observation of the dynamic behavior of material evolution under complex conditions such as force, heat, light, electricity, etc., and can simultaneously obtain basic information corresponding to the material, including crystal structure. shape, crystal plane parameters, element types and distribution, etc., which provide an extremely important reference for revealing the evolution mechanism of materials under the action of external fields. Among them, applying a temperature gradient in an in-situ transmission electron microscope can effectively modulate the domain wall configuration and domain wall motion of magnetic materials. However, the current method of applying a temperature field relies on specially designed chips and sample rods, and can only apply a uniform and stable temperature field. In addition, this type of chip requires extremely complex processing of the sample, and the experimental failure rate is high, which limits the in situ A study of temperature gradient experiments was performed. Therefore, there is an urgent need for a method for in-situ application of a temperature gradient field that is simple to process and has a wide temperature rising range to facilitate subsequent research.

Patent Publication No. CN104815710B discloses a method and application for establishing a temperature gradient field in a microfluidic chip and its microchannel. By directly connecting the wires on both long sides of a rectangular piece of ITO-coated glass through conductive silver glue, a heating element with a heating area is formed. ITO coated glass has good light transmittance and thermal uniformity. It generates Joule heat when energized. It can process various heating devices and integrate them on the microfluidic chip. It does not affect the optical observation of the chip system and achieves a settable temperature gradient field. However, this invention only mentions the temperature gradient range of 23 to 45°C, which is a narrow range.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for in-situ application of a temperature gradient field that is simple to process and has a wide temperature rising range, so as to simultaneously apply an in-situ temperature gradient field to micro-nano scale materials. To realize the study of temperature-driven magnetic domain walls and observe the continuous changes of materials at different temperatures in real time.

The object of the present invention can be achieved through the following technical solutions:

A method for applying an in-situ temperature gradient field in a transmission electron microscope, including the following steps:

(1) Fix the test chip loaded with the micro-nano sample to be tested and the in-situ sample rod, and make the micro-nano sample to be tested and the sample rod form a path;

(2) Insert the in-situ sample rod into the transmission electron microscope and connect an external DC source;

(3) Pass a preset DC current to the U-shaped electrode connected to the sample on one side of the test chip. Joule heat is formed at the U-shaped electrode and the heat is conducted to the micro-nano sample to be measured, that is, the micro-nano sample to be measured is realized. The nanosample imposes an in-situ temperature gradient field.

Further, the loading process of the micro-nano sample to be tested on the test chip is specifically as follows:

(a) Select the test material, deposit a carbon protective layer on its surface, etching to obtain a cuboid sample, and transfer and fix it on the test chip;

(b) Use ion beam sprayed tungsten as wires to form four deposition circuits, namely tungsten electrodes, to connect the cuboid sample and the four chip electrodes of the test chip;

(c) Etch the surface of the cuboid sample to separate the four tungsten electrodes from each other;

(d) Thinning the cuboid sample to ensure that it can be observed in a transmission electron microscope, that is, completing the loading of the micro-nano sample to be tested on the test chip, and obtaining the sample/chip device.

Furthermore, in step (a), the carbon protective layer is an amorphous carbon layer with a thickness of 0.8-1.2 μm, preferably 1 μm.

Furthermore, in step (a), in order to ensure that there is enough space for depositing tungsten electrodes on the left and right sides of the sample, a width of 3 to 5 μm is left on the left and right sides of the cuboid sample, preferably 4 μm.

Furthermore, in step (b), the connection ends of the cuboid sample and the test chip are kept parallel.

Furthermore, in step (b), the thickness of the tungsten electrode is 0.6-1.0 μm, preferably 0.8 μm.

Furthermore, in step (b), each laid tungsten electrode is connected to a corresponding chip electrode.

Furthermore, in step (c), the etching process is:

After depositing the tungsten electrodes, the ion beam is used to conduct through-etching on the two ends of the cuboid sample to separate the tungsten electrodes, thereby forming U-shaped electrodes on the left and right sides of the sample.

Furthermore, the preferred distance between two tungsten electrodes is 0.8 μm or more.

Furthermore, in step (d), the thinning process is: etching and thinning the area of the cuboid sample where no electrodes are laid, so that the thickness is 80-120 nm, preferably no more than 100 nm.

Furthermore, after applying an in-situ temperature gradient field, the effect of the temperature gradient field on the in-situ test sample can be simultaneously observed in a transmission electron microscope.

Compared with the prior art, the present invention has the following advantages:

(1) Compared with traditional complex heating chips, they have extremely high requirements for sample preparation and can only provide a stable temperature field. The present invention proposes a micro-nano sample processing method with simple technology and rich functions, which can accurately process the sample and realize flexible application of the temperature gradient field of the sample.

(2) In the present invention, current is injected into the U-shaped electrode on one side of the sample, Joule heat is generated at the U-shaped electrode, and the heat energy is transferred to the sample side through thermal conduction, causing an increase in temperature and ultimately forming a temperature gradient. After preparation, the U-shaped electrode is directly connected to the sample and has extremely high heat transfer efficiency.

(3) The present invention can provide real-time, real-space high-resolution observation of the magnetic domain/magnetic structure of the material accompanied by changes in the temperature field under the condition of applying a temperature gradient field;

(4) The tungsten electrode used in the present invention can realize the application of extremely high upper limit temperature gradient field, covering the operating temperature of most ferromagnetic materials;

(5) The present invention can adjust the size and direction of the applied temperature gradient field by changing the size and direction of the current injected into the U-shaped electrode on one side of the sample according to user needs to meet various experimental scenarios.

Description of the drawings

Figure 1 is a schematic diagram of the carbon protective layer processing in Example 1;

Figure 2 is a schematic diagram of the cuboid sample in Example 1 being transferred and fixed to the in-situ test chip port;

Figure 3 is a schematic diagram of the connection between the cuboid sample and the in-situ test chip through tungsten electrodes in Example 1;

Figure 4 is a schematic diagram of applying a thermal gradient field on one side in Embodiment 1;

Figure 5 is a schematic diagram of the temperature gradient of the micro-nano scale test sample in Example 1.

Description of markings in the picture:

1-carbon protective layer, 2-cuboid sample, 3-tungsten electrode one, 4-tungsten electrode two, 5-tungsten electrode three, 6-tungsten electrode four, 7-chip electrode one, 8-chip electrode two, 9-chip Electrode three, 10-chip electrode four, 11-etching area one, 12-etching area two, 13-etching area three, 14-separation area one, 15-separation area two, 16-separation area three, 17- Separation area four.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention and provides detailed implementation modes and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

In the following implementation modes or examples, the in-situ test chip is prepared with reference to patent CN209495986U, and the in-situ sample rod is a four-electrode low-temperature sample rod of Gatan Company, model number is Gatan Model 613. If there are no specially stated raw materials or processing technologies for the rest, it means that they are all conventional raw materials or conventional processing technologies in this field.

In order to simultaneously apply an in-situ temperature gradient field to micro- and nano-scale materials, so as to realize the study of temperature-driven magnetic domain walls, and to observe the continuous changes of materials at different temperatures in real time, the present invention provides a transmission electron microscope. The method of applying an in-situ temperature gradient field includes the following steps:

(1) Fix the test chip loaded with the micro-nano sample to be tested and the in-situ sample rod, and make the micro-nano sample to be tested and the sample rod form a path;

(2) Insert the in-situ sample rod into the transmission electron microscope and connect an external DC source;

(3) Pass a preset DC current to the U-shaped tungsten electrode connected to the sample on one side of the test chip. Joule heat is formed at the U-shaped electrode and the heat is conducted to the micro-nano sample to be tested, that is, the test is completed. Micro-nano samples are subjected to an in-situ temperature gradient field.

In some specific implementations, as shown in Figures 1 to 3, the loading process of the micro-nano sample to be tested on the test chip is specifically as follows:

(a) Select the test material, deposit a carbon protective layer on its surface, etching to obtain a cuboid sample, and transfer and fix it on the test chip;

(b) Use ion beam sprayed tungsten as wires to form four deposition circuits, namely tungsten electrodes (respectively), to connect the cuboid sample and the four chip electrodes of the test chip;

(c) Etch the surface of the cuboid sample to separate the four tungsten electrodes from each other;

(d) Thinning the cuboid sample to ensure that it can be observed in a transmission electron microscope, that is, completing the loading of the micro-nano sample to be tested on the test chip, and obtaining the sample/chip device.

In a more specific embodiment, in step (a), the carbon protective layer is an amorphous carbon layer with a thickness of 0.8-1.2 μm.

In a more specific embodiment, in step (a), in order to ensure sufficient space for depositing tungsten electrodes on the left and right sides of the sample, a width of 3 to 5 μm, preferably 4 μm, is left on the left and right sides of the cuboid sample along the long axis.

In a more specific embodiment, in step (b), the connection ends of the cuboid sample and the test chip are kept parallel.

In a more specific embodiment, in step (b), the thickness of the tungsten electrode is 0.6-1.0 μm.

In a more specific implementation, in step (b), each laid tungsten electrode is connected to a corresponding chip electrode.

In a more specific implementation, in step (c), the etching process is:

After depositing the tungsten electrodes, the ion beam is used to conduct through-etching on the two ends of the cuboid sample to separate the tungsten electrodes, thereby forming U-shaped electrodes on the left and right sides of the sample.

More preferably, the preferred distance between two tungsten electrodes is 0.8 μm or more.

In a more specific embodiment, in step (d), the thinning process is: etching and thinning the area of the cuboid sample where electrodes are not laid, so that the thickness is 80-120 nm.

In some specific embodiments, after applying an in-situ temperature gradient field, the effect of the temperature gradient field on the in-situ test sample can be simultaneously observed in a transmission electron microscope.

Each of the above embodiments can be implemented individually or in any combination of two or more.

The above embodiments will be described in more detail below with reference to specific examples.

Example 1

In the first step, as shown in Figure 1, the amorphous carbon protective layer 1 is deposited on the surface of the test material using electron beam and ion beam induced deposition to prevent the ion beam from damaging the test material during the subsequent etching process. , the carbon protective layer 1 is an amorphous carbon layer with a thickness of about 1 μm. Make the test material face the ion beam, and use an ion beam with an acceleration voltage of 30kV and a beam intensity of 9.3nA to etch both sides of the test material to obtain a cuboid sample 2. After the etching is completed, tilt the sample stage ±1° from the viewing angle facing the ion beam, switch the ion beam intensity to 0.79nA, and expose both sides of the sample for rough trimming. After the rough trimming operation is completed, the cuboid sample 2 is facing the electron beam by rotating the sample stage, and U-cutting is performed on the cuboid sample 2 in the ion beam window (that is, all the left, bottom, and right parts connecting the sample to the matrix are cut off). The U-cut depth is 4 μm. At this time, insert the manipulator and the platinum needle, move the manipulator to align it with the cuboid sample 2, and connect the cuboid sample 2 and the manipulator through ion beam induced platinum deposition. Then, rotate and move the sample stage so that the in-situ test chip is parallel to the horizontal plane, then transfer the cuboid sample 2 on the manipulator to the in-situ test chip, and then etch the right part of the cuboid sample 2, which makes the cuboid sample The horizontal plane of 2 is parallel to the plane of the in-situ test chip.

In the second step, the sample stage is rotated, and the manipulator is appropriately moved to bring the cuboid sample 2 close to and touch the end face of the in-situ test chip, and the cuboid sample 2 and the in-situ test chip are facing the ion beam window, and tungsten is induced to be deposited through the ion beam. Cuboid sample 2 is connected to the in-situ test chip, as shown in Figure 2. On this basis, two deposition circuits were deposited on both sides of the sample, namely tungsten electrodes (tungsten electrode one 3, tungsten electrode two 4, tungsten electrode three 5, tungsten electrode four 6). Specifically, ion beam sprayed tungsten was used as The width and thickness of the wire and sputtered tungsten electrode are both 0.8μm. The end of the tungsten electrode is connected to the corresponding preset electrode of the chip (i.e. chip electrode one 7, chip electrode two 8, chip electrode three 9, chip electrode four 10), as shown in Figure 3. Adjust the ion beam acceleration voltage to 30kV and the intensity to 0.23nA. Modify the lower end of rectangle 2 close to the chip and remove the etching areas between the tungsten electrodes (respectively, etching area one 11, etching area two 12, etching area two). Etched area three 13), as shown in Figure 3, thereby separating all four tungsten electrodes to avoid the existence of thin areas of tungsten on the surface, which may form short circuits and affect the test.

In the third step, the tungsten electrodes on both sides of the rectangular sample 2 are etched by ion beam (acceleration voltage 30kV, beam intensity 80pA) and tilted to thin the rectangular sample 2, and the sample is thinned to a thickness of 100nm and separated. Obtain the separation area (that is, form separation area one 14, separation area two 15, separation area three 16, and separation area four 17 as shown in Figure 2 and Figure 3), make the two tungsten electrodes on both sides independent of each other, and complete the overall processing. , get the sample/chip device.

The fourth step is to install the sample/chip device on the corresponding in-situ test sample rod, and connect the in-situ test and the sample/chip device through an enameled wire, so that the entire device is in a path state.

The fifth step is to connect the in-situ test sample rod to the external DC source, and set the current with preset intensity and action time (the current action time is preferably no more than 80ns. The current intensity can be set by the user according to the temperature zone that the specific sample can withstand. ) is injected through tungsten electrode one 3 and chip electrode one 7, and output through tungsten electrode two 4 and chip electrode two 8, so that heat is generated on one side of the sample to induce a temperature gradient field, and then the electron beam is turned on to observe the position of the chip device, and a single Side-applied thermal gradient field and micro-nano scale test sample temperature gradient related data.

Figure 4 is a simulation diagram illustrating the generation of the temperature gradient field of the sample due to the temperature rise caused by Joule heat and heat conduction after current is injected into the U-shaped tungsten electrode on the left side of the sample. The electrodes on both sides of the sample in the picture are tungsten and the sample is pure iron. The left side is the high-temperature area, with the highest temperature being 135K. The right side is the low-temperature area, where the temperature gradient shows a downward trend from the hot end. The lowest temperature is the ambient temperature set in the transmission electron microscope, which is about 100K.

Figure 5 shows the effects of different current application time, voltage (current) intensity, tungsten electrode thickness and sample thickness on the applied temperature gradient field based on Example 1. The results show that the current action time and voltage are the main influencing factors of the temperature gradient field. The longer the current action time, the larger the voltage field and the larger the temperature gradient field. However, the overall impact on the thickness of the tungsten electrode and the sample thickness is small. , and as the sample thickness increases, the temperature gradient gradually decreases.

The above description of the embodiments is to facilitate those of ordinary skill in the technical field to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without inventive efforts. Therefore, the present invention is not limited to the above embodiments. Based on the disclosure of the present invention, improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims (10)

1. A method for applying an in-situ temperature gradient field in a transmission electron microscope, characterized in that it includes the following steps: (1) Fix the test chip loaded with the micro-nano sample to be tested and the in-situ sample rod, and make the micro-nano sample to be tested and the sample rod form a path; (2) Insert the in-situ sample rod into the transmission electron microscope and connect an external DC source; (3) Pass a preset DC current into the test chip to form Joule heat and conduct heat to the micro-nano sample to be measured, thereby applying an in-situ temperature gradient field to the micro-nano sample to be measured. 2. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 1, characterized in that the loading process of the micro-nano sample to be measured on the test chip is specifically: (a) Select the test material, deposit a carbon protective layer on its surface, etching to obtain a cuboid sample, and transfer and fix it on the test chip; (b) Use ion beam sprayed tungsten as wires to form four deposition circuits, namely tungsten electrodes, to connect the cuboid sample and the four chip electrodes of the test chip; (c) Etch the surface of the cuboid sample to separate the four tungsten electrodes from each other; (d) Thinning the cuboid sample to ensure that it can be observed in a transmission electron microscope, that is, completing the loading of the micro-nano sample to be tested on the test chip, and obtaining the sample/chip device. 3. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that in step (a), the carbon protective layer is an amorphous carbon layer with a thickness of 0.8 -1.2μm. 4. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that in step (a), the cuboid sample leaves 3~ 5μm width. 5. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that in step (b), the connection ends of the cuboid sample and the test chip are kept parallel. 6. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that in step (b), the thickness of the tungsten electrode is 0.6-1.0 μm. 7. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that in step (b), each laid tungsten electrode is connected to a corresponding chip electrode. 8. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that in step (c), the etching process is: After depositing the tungsten electrodes, the ion beam is used to conduct penetration etching on the two ends of the cuboid sample to separate the tungsten electrodes, thereby forming U-shaped electrodes on the left and right sides of the micro-nano sample to be tested. 9. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 8, characterized in that the distance between two tungsten electrodes is 0.8 μm or more. 10. A method for applying an in-situ temperature gradient field in a transmission electron microscope according to claim 2, characterized in that, in step (d), the thinning process is: performing the thinning process on the area of the cuboid sample where no electrodes are laid. Etching and thinning to a thickness of 80-120nm.