CN107745197A - A kind of apparatus and method that electron microscopic sample in situ is prepared using convergence femtosecond laser - Google Patents

Abstract

The invention relates to the field of laser micro-area processing and the field of electron microscope in-situ sample preparation, in particular to a device and method for finely processing and forming electron microscope samples by using converged laser light. The device includes femtosecond laser and convergence scanning system, mechanical numerical control moving system of sample stage, coaxial microscopic observation and positioning system, computer centralized data monitoring and visualization system, shock absorption system and protection system. Using the above device, femtosecond laser can be used to quickly and conveniently perform fine processing such as CNC cutting and drilling on various electron microscope samples, such as metal sheets, alumina ceramic blocks, transparent quartz glass, etc. Therefore, through the present invention, in-situ electron microscope samples with specific shapes and notches can be prepared, and combined with electron microscope in-situ observation technology, in-situ observation and research on mechanics, electricity, and corrosion behavior of certain special tissues and structures can be carried out. It has the advantages of wide area, high precision, no heat affected zone and no pollution.

Description

A device and method for preparing samples for in-situ electron microscopy using converging femtosecond lasers

technical field

The invention relates to the field of laser micro-area processing of materials and the field of in-situ electron microscope sample preparation, in particular to a device and method for finely processing prepared samples using a micro-beam femtosecond laser, which can process various materials according to blueprint programming, and can target Different samples are processed in different ways, and there are a variety of sample stages to choose from.

Background technique

With the continuous development of laser technology, the performance of lasers has also been continuously improved. The research on the interaction between laser and matter has attracted people's attention, and laser processing technology has also made great progress.

In the early 1990s, with the emergence of broadband tunable laser crystal and self-locking mode technology, femtosecond laser technology has developed by leaps and bounds. The new generation of femtosecond lasers represented by titanium-doped sapphire can output light pulses with a duration as short as 5fs, and the laser center wavelength is in the near-infrared band (around 800nm). A nanojoule is amplified to hundreds of megajoules, or even joules. At this time, the peak power of the pulse can reach GW or TW, and the power density after focusing is 10 ¹⁵ ~ 10 ¹⁸ W/cm ² , or even higher. When a light pulse with such a high peak power and extremely short duration interacts with matter, it can inject all of its energy into a small area of action at an extremely fast speed, and the deposition of high energy density in an instant will make the absorption and movement of electrons The method changes to avoid the influence of laser linear absorption, energy transfer and diffusion, etc., thereby fundamentally changing the mechanism of interaction between laser and matter, making femtosecond pulse laser processing become ultra-high precision, ultra-high spatial resolution and ultra-high Extensive non-thermomelt "cold" treatment process creates a new field of laser processing.

At present, in the field of in-situ electron microscope sample preparation, there are four main technical methods: mechanical cutting, wire cutting, traditional laser and focused ion beam. The traditional mechanical processing/wire cutting method is still used for the in-situ electron microscopy sample preparation of bulk materials, which has high requirements for the plasticity and machinability of the sample. A series of problems such as pollution, edge effects, and low success rate of sample preparation seriously restrict the efficiency of in-situ electron microscopy research and the reliability of the results. However, ordinary continuous laser, nanosecond laser or even picosecond laser processing methods, due to their photothermal effect, cause large areas of remelting, recrystallization and oxidation reactions at the edge of material processing, and cannot be used as suitable in-situ electrode samples. Although the method of preparing in-situ electron microscope samples with focused ion beams can greatly eliminate the edge effect and achieve nanometer-level processing accuracy, the equipment cost is extremely high and the processing efficiency is extremely low, which cannot be widely promoted and applied.

Contents of the invention

The purpose of the present invention is to provide a device and method for preparing in-situ electron microscope samples by using converging femtosecond lasers, which can be programmed according to drawings, CNC cutting and processing samples of various shapes, and the processing accuracy can reach submicron level.

In order to achieve the above object, the technical scheme of the present invention is as follows:

A device for preparing an in-situ electron microscope sample by converging femtosecond laser, the device includes: femtosecond laser and converging scanning system, sample table mechanical numerical control moving system, coaxial microscopic observation and positioning system, computer centralized data monitoring and visualization system, Shock absorption system and protection system, after the femtosecond laser of the laser light source is emitted from the laser, after being converged by the multi-stage laser combination lens, it is connected to the common cold light of the ordinary light source in the form of coaxial light through different interfaces. Axial microscopic observation and positioning system; coaxial microscopic observation and positioning system and sample table mechanical numerical control moving system are connected with computer centralized data monitoring and visualization system through USB cable or network cable. The specific structure is as follows:

The laser light source and the ordinary light source are respectively connected to the laser convergence and microscopic observation system through an interface in the form of coaxial light through an optical cable, and the laser light source and the ordinary light source are switched by an electric switch; the laser convergence and microscopic observation system It is connected to the input end of the CCD camera, and the output end of the CCD camera and the input end of the motion controller are connected to the computer through a USB cable or network cable for microscopic observation positioning and numerical control programming; the laser convergence and microscopic observation system is equipped with long The focus objective lens is used for observation and selection according to different samples and processing requirements; the laser convergence and microscopic observation system is set on the mechanical movement system of the laser convergence module, and the output end of the motion controller is connected to the mechanical numerical control movement system of the sample stage, and the mechanical numerical control movement of the sample stage The system is set on the air flotation shock absorption platform, and the air intake end of the air flotation shock absorption platform is connected with the air pump.

The device for preparing in-situ electron microscope samples using convergent femtosecond lasers, the femtosecond laser and the convergent scanning system include: a femtosecond laser, which consists of three parts: a femtosecond laser oscillator, a pump source and a femtosecond laser amplifier Matching composition, emitting ultrafast laser with pulse width <400fs and single pulse energy >50μJ; a set of combined lens installed at the laser output port, used to reduce the femtosecond laser spot in the first stage.

The device for preparing in-situ electron microscope samples by converging femtosecond lasers, the coaxial microscopic observation and positioning system includes a laser optical cable interface, an ordinary optical optical cable interface, an electric coaxial light source switching switch, a laser CCD camera, an ordinary The microscope eyepiece, objective lens and a set of ultra-long focal length objective lenses with different magnifications are matched, and the laser in the optical fiber is reconverged through the coaxial microscopic observation and positioning system.

The device for preparing in-situ electron microscope samples by converging femtosecond lasers, the mechanical numerical control moving system of the sample stage includes: a set of combined sliding stages that can move arbitrarily in the three-dimensional space of x, y, and z; A light-transmitting and airtight sample chamber; a detection device for real-time monitoring of the concentrated laser energy; a sample stage for clamping thin film samples, fiber samples and bulk samples; a liquid nitrogen cooling low-temperature processing table; among them,

A set of combined sliding tables that move freely in the three-dimensional space of x, y, z, each direction of the sliding table is controlled by a separate servo motor, and the three-dimensional combined sliding tables of x, y, z are connected to the same controller, and It is further connected to the computer, and the graphics program to be processed is input through the displacement control software window of the computer to realize the continuously adjustable movement with a repeat positioning accuracy of 0.5μm and a moving speed of 1mm/min～1000mm/min; The platform is controlled by a servo motor and uses computer software to rotate the sample;

A light-transmitting and sealed sample chamber with protective gas, which is equipped with a gas pumping port, a gas charging port, and an exhaust port, and a gas flowmeter is equipped at the front end of the gas charging port. Inert gas positive pressure anti-oxidation protection environment during processing, or purge the ash residue left when cutting the sample; at the same time, a mechanical dry pump is equipped at the front end of the suction port to obtain a <5Pa vacuum environment in the closed chamber; There is a laser lens-increasing sheet above the chamber, which is used to process the samples in the chamber through the femtosecond laser;

A liquid nitrogen cooling low-temperature processing table, which is provided with a liquid nitrogen cooling chamber and a heat insulation chamber; further, the liquid nitrogen cooling chamber includes: a liquid nitrogen injection port, and an exhaust port;

A detection device that monitors the concentrated laser energy in real time, aligns the power probe with the focused laser beam with the objective lens, and detects the actual laser power;

A sample stage for clamping film samples, fiber samples and bulk samples, the structure of which is fixed on one side and a horizontally moving slide table on the other side, extrusion type is used for bulk samples; for thin slices and fiber samples, There is a coaxial rotating motor on the upper side of the slider and the fixed block, and the sample is fixed in the center of the motor bearing by pressing the tablet, and the one-dimensional rotation of the sample is realized by computer control; fixed.

The device for preparing in-situ electron microscope samples by converging femtosecond lasers, the computer centralized data monitoring and visualization system includes: a set of software for numerical control and real-time monitoring of mechanical displacement, through inputting CAD vector graphics and editing programs to realize laser and Ordinary light switching, and image processing; a set of laser CCD camera images for imaging, convenient for observation, measurement and precise positioning, and also has the function of taking pictures, videos and adding rulers.

The device for preparing in-situ electron microscope samples by converging femtosecond lasers, the shock absorption system includes an air-floating optical platform and an air pump, which are used to install the mechanical numerical control moving system of the sample table and the coaxial microscopic observation and positioning system, The mechanical fixing method is adopted to prevent the sample from vibrating and the spot shifting during processing; the protection system includes: a protective cover that covers the mechanical numerical control moving system of the sample stage and the coaxial microscopic observation and positioning system to prevent the light leakage of the laser from affecting the operation Injury to personnel; a light filter glasses, used to protect the operator's eyes while working.

A method for preparing an in-situ electron microscope sample using a converging femtosecond laser using the device, the method comprising the steps of:

(1) micro-positioning step to determine the processing area;

(2) Processing graphics programming steps, editing processing parameters;

(3) Select the laser parameter step, select the laser parameter that meets the processing requirements;

(4) start step, start the mechanical movement system and the laser;

(5) Detection step, real-time monitoring of the processing process.

A method for preparing an in-situ electron microscope sample using a converging femtosecond laser using the device, the method comprising the steps of:

(1) Put the sample in the sample chamber, use a mechanical pump to pump a vacuum of <5Pa, then pass the protective gas to the atmospheric pressure, pump and pass again, and do this three times; finally open the exhaust valve to make the protective gas in The flow in the chamber keeps the chamber above an atmospheric pressure, so that the air pressure in the chamber reaches 0.105-0.11MPa;

(2) micro-positioning step to determine the processing area;

(3) Processing graphics programming steps, editing processing parameters;

(4) Select the laser parameter step, select the laser parameter that meets the processing requirements;

(5) start-up step, start the mechanical movement system and the laser;

(6) Detection step, real-time monitoring of the processing process.

A method for preparing an in-situ electron microscope sample using a converging femtosecond laser using the device, the method comprising the steps of:

(1) The sample is fixed on the upper surface of the cooling chamber with a pressing tablet, and liquid nitrogen is added to cool down the chamber;

(2) micro-positioning step to determine the processing area;

(3) Processing graphics programming steps, editing processing parameters;

(4) Select the laser parameter step, select the laser parameter that meets the processing requirements;

(5) start-up step, start the mechanical movement system and the laser;

(6) Detection step, real-time monitoring of the processing process.

The method for preparing an in-situ electron microscope sample using a converging femtosecond laser, the method further includes selecting an objective lens for microscopic observation and converging laser light; the method further includes a storage step, storing the edited processing drawings; the method further includes importing step, importing previously saved processing drawings or existing CAD vector drawings; the method further includes a laser spot adjustment step, adjusting the size of the laser spot to meet processing requirements.

Design idea of the present invention is as follows:

First of all, in view of the current field of in-situ electron microscope sample preparation, mechanical processing, wire cutting and long-pulse laser processing are generally used, and a series of problems such as secondary pollution, edge effects, and low success rate of sample preparation occur. The present invention uses The femtosecond laser light source with a pulse width of <400fs makes the width of a single pulse smaller than the relaxation time of material lattice heat conduction, effectively eliminating the problems of heat-affected zone and material spattering in the cut. Secondly, in the process of processing the material, the cooperation of the numerical control mechanical movement system is required, so the present invention designs the combined lens and the sample stage to be installed on the manual and electric combined sample stage capable of three-dimensional translation and rotation, and cooperates with the corresponding driver, Controller and computer to realize all-round movement of laser spot and sample. Again, because the processing size is very small, it needs to cooperate with the microscope for observation and positioning measurement. Therefore, the present invention designs the same group of microscope lenses to be connected to two coaxial optical cables of laser light and ordinary light at the same time, and can realize switching between the two. The equipped laser imaging CCD camera is imaged on the software operation window of the computer, which is convenient for real-time observation, positioning and measurement operations.

Based on the above three main design guiding ideologies, the present invention successfully realizes the CNC femtosecond laser cutting process of various materials with micron-level precision, and takes into account the unique processing methods of samples of different shapes. At the same time, by selecting a laser source with a suitable wavelength and power, the specific position inside the transparent material can be processed.

Advantage of the present invention and beneficial effect are as follows:

1. The device and laser method used in the present invention can process a variety of materials, and the processing basically has no heat-affected zone. A series of problems such as secondary pollution, edge effects, and low success rate of sample preparation caused by traditional in-situ electron microscope sample preparation methods can be well avoided. Mainly due to the high-power femtosecond laser used in the present invention, the pulse width is <400fs, the single pulse energy is >50μJ and can be adjusted, and the peak power can reach 100MW. Almost any material can be instantly transformed into a plasma state without affecting the side of the spot. s material.

2. The device and method used in the present invention have high processing precision. After the laser is converged in multiple stages, a light spot with sufficiently small size and highly concentrated energy is obtained on the sample, which causes local high temperature and vaporizes the local area of the sample. Because the laser spot is very small, it can realize the pattern processing of several microns.

3. The present invention is equipped with different sample stages for different materials. There are protective gas sample chambers designed for toxic and easily oxidized samples, squeeze-type clamping sample stages for block samples, and film and fiber samples. Hold the sample stage in the air. At the same time, the same sample stage takes into account the clamping of materials with different shape characteristics such as blocks, films, fibers, etc. The position of the lower slide table can be adjusted according to the length of films or fibers, and it also has a one-dimensional rotation function for fiber materials. It has the advantage of high integration.

4. The present invention adds internal liquid nitrogen to cool the sample table accessories for low-temperature processing. The use of liquid nitrogen for low-temperature cutting reduces the overall temperature of the sample, so that the sample that is not irradiated by the laser will not heat up due to the absorption of waste heat, and structural changes such as grain growth and defect reduction will occur, further reducing the heat-affected zone.

5. The present invention can monitor the energy of the laser spot converged by the lens in real time, because the laser will attenuate during the process of being converged, and the energy of the actual processed sample is not displayed by the laser, so adding a laser power monitor is very useful necessary.

6. Most of the devices and methods used in the present invention can be controlled by computer software, and the multi-dimensional combination sliding table and light source conversion switch can be linked, and computer programming can realize automatic cutting of more complex image samples.

7. The present invention can process the inside of transparent materials such as quartz glass.

8. The device and method used in the present invention use a custom-made interface, which can be connected to two coaxial optical cables of laser and ordinary light at the same time, and can realize the electric switching between the two, so that it can ensure that the laser spot and the ordinary light spot are in the same position. The same position is convenient for positioning measurement and processing control.

9. The device and method used in the present invention can observe the processing process in real time by using a specially equipped laser microscopic combination lens and camera.

10. The device and method used in the present invention adopt an air-floating shock-absorbing platform, which has a better shock-absorbing effect than ordinary cast iron shock-absorbing platforms. The laser convergence system, microscopic observation system and mechanical movement system are placed on the air-floating shock-absorbing platform and isolated from the vibration unit, which can greatly reduce or eliminate the processing error caused by environmental vibration.

Description of drawings

Fig. 1 is the structural diagram of the experimental device made by the present invention. In the figure, 1 laser convergence and microscopic observation system; 2 laser light source; 3 ordinary light source; 4 air pump; System; 9 motion controller; 10 computer; 11 automatic switch of light source.

Fig. 2 is a structural diagram of a sample chamber in a protective atmosphere. In the figure, 12 mechanical vacuum pump; 13 exhaust valve; 14 protective gas cylinder; 15 gas mass flow controller; 16 intake valve; 17 laser anti-reflection window; 18 sample cavity.

Figure 3 is a structural diagram of the clamping sample stage for bulk, film and fiber samples. In the figure, 19 horizontal sliding table; 20 tablet press; 21 adjustable speed motor; 22 fiber chuck; 23 fixed table.

Fig. 4 is a structural diagram of a liquid nitrogen-cooled cryogenic processing platform. In the figure, 24 liquid nitrogen injection port; 25 exhaust port; 26 heat insulation material; 27 stainless steel cavity; 28 tablet pressing.

Detailed ways

In the specific implementation process, the core of the present invention is to provide a device that utilizes a highly focused femtosecond laser to finely process materials. The device utilizes a femtosecond laser whose pulse width is smaller than the relaxation time of lattice heat transfer. The energy can instantly transform the sample at the spot from solid state to plasma state, achieving the effect of removing material at a specific position. And because the pulse width is extremely small, basically a single pulse can only remove materials with a thickness of several nanometers, so that micro-scale three-dimensional configurations can be processed.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Referring to Fig. 1, a structural diagram of a device for finely processing and treating materials with a highly focused laser provided by an embodiment of the present invention is given. The device mainly includes the following systems: femtosecond laser and convergent scanning system, sample stage Mechanical numerical control mobile system 6. Coaxial microscopic observation and positioning system, computer centralized data monitoring and visualization system, shock absorption system and protection system. After the femtosecond laser of the laser light source is emitted from the laser, it is converged by the multi-stage laser combination lens. Ordinary cold light from ordinary light sources is connected to the coaxial microscopic observation and positioning system through different interfaces in the form of coaxial light; the coaxial microscopic observation and positioning system and the mechanical numerical control moving system of the sample stage are connected to the computer through a USB cable or a network cable. The centralized data monitoring and visualization system are connected, and the specific structure is as follows:

The laser light source 2 and the ordinary light source 3 are respectively connected to the laser convergence and microscopic observation system 1 through an optical cable in the form of coaxial light through a customized interface, and the laser light source 2 and the ordinary light source 3 can be switched by an electric switch 11 to switch. The laser convergence and microscopic observation system 1 is connected to the input end of the CCD camera 7, and the output end of the CCD camera 7 and the input end of the motion controller 9 are connected to the computer 10 through a USB cable or a network cable for microscopic observation positioning and numerical control programming. The laser convergence and microscopic observation system 1 is equipped with telephoto objective lenses of different magnifications, which is convenient for observation selection according to different samples and processing requirements. The laser convergence and microscopic observation system 1 is set on the mechanical movement system 8 of the laser convergence module, the output end of the motion controller 9 is connected to the mechanical numerical control movement system 6 of the sample stage, and the mechanical numerical control movement system 6 of the sample stage is set on the air bearing shock absorption platform 5, the air intake end of the air suspension damping platform 5 is connected with the air pump 4. The motion controller 9 of the device is used to store and convert the program commands of the computer to the motor driver; the motor driver of the device is used to send pulse electric signals to the stepping motor of the electric sample stage.

The femtosecond laser and converging scanning system of the device includes a femtosecond laser, which is composed of femtosecond laser oscillator, pump source and femtosecond laser amplifier. It can emit pulse width <400fs, single pulse energy> 50μJ ultrafast laser; a set of combined lenses installed at the laser outlet, used to reduce the femtosecond laser spot in the first stage.

The laser convergence and microscopic observation system 1 of the device is provided with a coaxial microscopic observation and positioning system, which includes a laser optical cable interface, an ordinary optical optical cable interface, an electric coaxial light source switching switch (automatic switching of the light source) Switch 11), a laser CCD camera 7, ordinary microscope eyepieces, objective lenses and a group of ultra-long focal length objective lenses with different magnifications perform secondary convergence on the laser in the optical fiber to meet the requirements of processing and processing accuracy.

The mechanical movement system 8 of the laser convergence module drives the laser convergence and microscopic observation system 1 to move arbitrarily in the three-dimensional space of x, y, and z, which is used for the focus of the microscope and the movement of the light spot. The mechanical numerical control moving system 6 of the sample stage drives the sample stage to move arbitrarily in the three-dimensional space of x, y, and z, and its repeated positioning accuracy can reach 0.1 μm. CNC and real-time status monitoring of samples. Laser convergence and microscopic observation system 1 is equipped with a microscopic imaging system with adjustable magnification and a coaxial light source, which is used for laser spot positioning and sample observation, processing and processing, etc. The observation resolution can reach 0.5 μm, and the cutting resolution Up to 4μm, laser spot up to 4μm. Moreover, the numerical control and real-time monitoring of the mechanical displacement are realized through the computer control software, the repeat positioning accuracy is 0.5μm, and the moving speed is continuously adjustable from 1mm/min to 1000mm/min.

The mechanical numerical control moving system 6 of the sample stage includes: a set of combined sliding stages that can move arbitrarily in the three-dimensional space of x, y, and z; sample cavity); a detection device that can monitor the concentrated laser energy in real time; a sample stage that can hold film samples, fiber samples, and block samples in different shapes (that is, a clamping sample stage); a liquid Nitrogen cooled cryogenic processing bench. in:

A set of combined sliding table that can move freely in the three-dimensional space of x, y, z, each direction of the sliding table is controlled by a separate servo motor, and the three-dimensional combined sliding table of x, y, z is connected to the same motion controller 9. It is further connected to the computer, and the graphic program to be processed is input through the displacement control software window of the computer, which can realize the continuously adjustable movement with repeat positioning accuracy of 0.5μm and moving speed of 1mm/min～1000mm/min. At the same time, it is also equipped with an in-plane rotating slide table, which is controlled by a servo motor and uses computer software to rotate the sample.

A light-transmitting and sealed sample chamber that can pass protective gases such as Ar gas. It is equipped with a gas pumping port, a gas charging port, and an exhaust port, and a gas flowmeter is equipped at the front end of the gas charging port. , can realize the protection environment of inert gas positive pressure anti-oxidation during laser processing, or purge the ash residue left when cutting samples. At the same time, a mechanical dry pump is equipped at the front end of the suction port to obtain a <5Pa vacuum environment in the closed chamber. Above the chamber, there is a lens-increasing sheet for a laser with a specific wavelength, which is used to process the samples in the chamber through the femtosecond laser.

As shown in Figure 2, the protective atmosphere sample chamber includes: mechanical vacuum pump 12, exhaust valve 13, protective gas cylinder 14, gas mass flow controller 15, inlet valve 16, laser anti-reflection window 17, sample chamber 18, The specific structure is as follows: the upper part of the sample chamber 18 is provided with an exhaust valve 13, and the lower part of the sample chamber 18 is communicated with the mechanical vacuum pump 12 through a pipeline; the other side of the sample chamber 18 is connected with a protective gas cylinder 14 through a pipeline, A gas mass flow controller 15 and an intake valve 16 are arranged on the pipeline. The beam of laser light source 2 or ordinary light source 3 enters the sample cavity 18 through the laser anti-reflection window 17 from the laser convergence and microscopic observation system 1, and the sample in the sample cavity 18 is finely processed by micro-beam femtosecond laser.

A detection device that can monitor the concentrated laser energy in real time, align the power probe with the focused laser beam with the objective lens, and detect the actual laser power.

A sample stage that can hold different shapes such as film samples, fiber samples and block samples. For the fiber sample, there is a coaxial rotating motor on the upper side of the slider and the fixed block, and the sample is fixed in the center of the motor bearing by means of a chuck, and the one-dimensional rotation of the sample is realized by computer control; for the thin film sample, the top end is used Press to fix.

As shown in Figure 3, the clamping sample stage includes: a horizontal slide table 19, a tablet press 20, an adjustable speed motor 21, a fiber chuck 22, and a fixed table 23. The specific structure is as follows: the horizontal slide table 19 is arranged opposite to the fixed table 23 , The horizontal sliding table 19 and the fixed table 23 are respectively provided with a pressing sheet 20, an adjustable speed motor 21, and a fiber chuck 22, and the horizontal sliding table 19 is corresponding to the fiber chuck 22 on the fixed table 23.

A liquid nitrogen cooling cryogenic processing table is provided with a liquid nitrogen cooling chamber and a heat insulation chamber. Further, the liquid nitrogen cooling chamber includes: a liquid nitrogen injection port and an exhaust port.

As shown in Figure 4, the liquid nitrogen cooling low-temperature processing table includes: liquid nitrogen injection port 24, exhaust port 25, heat insulation material 26, stainless steel chamber 27, and pressing sheet 28. The specific structure is as follows: the stainless steel chamber 27 is arranged on the heat insulation material In 26, the lower part of one side of the stainless steel chamber 27 is connected to the liquid nitrogen injection port 24 through a pipeline, and the top of the stainless steel chamber 27 is provided with an exhaust port 25 and a pressing piece 28, and the sample is placed on the top of the stainless steel chamber 27 through the pressing piece 20.

The computer centralized data monitoring and visualization system includes: a set of software for numerical control and real-time monitoring of mechanical displacement, which can input CAD and other vector graphics, editable programs to realize switching between laser and ordinary light, and realize some complex image processing. A certain degree of automation features; one set can image the image of the laser CCD camera for convenient implementation of observation, measurement and precise positioning, and also has the functions of taking pictures, recording videos and adding scales.

The shock absorption system includes an air-floating optical platform and an air pump, which are mainly used to install the mechanical numerical control moving system of the sample stage and the coaxial microscopic observation and positioning system. After a firm mechanical fixation, it can prevent the The sample shakes and the light spot shifts to improve the precision and stability of processing and handling.

The protective system includes: a protective cover, which covers the mechanical numerical control moving system of the sample stage and the coaxial microscopic observation and positioning system, so as to prevent the light leakage of the laser from causing harm to the operator; a filter glasses, which are mainly used for the operator when working Protect your eyes from laser damage.

Using the above device, femtosecond laser can be used to quickly and conveniently perform fine processing such as CNC cutting and drilling on various electron microscope samples, such as metal sheets, alumina ceramic blocks, transparent quartz glass, etc. Therefore, through the present invention, in-situ electron microscope samples with specific shapes and notches can be prepared, and combined with electron microscope in-situ observation technology, in-situ observation and research on mechanics, electricity, and corrosion behavior of certain special tissues and structures can be carried out. It has the advantages of wide area, high precision, no heat affected zone and no pollution. Especially for in-situ observation of the sample, it is required to minimize or avoid the influence on the structure of the sample itself during the processing, and the femtosecond laser processing device and method adopted in the present invention can reduce or even eliminate the heat-affected zone excellently, and meet the requirements of the preparation electron microscope. In situ sample requirements.

As shown in Fig. 1, the present invention provides a kind of material processing method, and this method utilizes above-mentioned experimental device, through micropositioning, steps such as selection laser parameter, laser focusing, numerical control programming carry out laser processing to material, specifically comprise the following steps:

(S1) Analyze the material to be processed, select a suitable laser, consult the information to find the ablation threshold of the material, use this as a reference, use a power detector to detect the energy of the actual processing spot, select the appropriate laser power, and use The multiples of the microscope objective lens, the sample stage movement speed of the sample stage mechanical numerical control moving system 6 during processing and other parameters, connect the selected laser optical cable to the laser convergence and microscopic observation system 1.

The laser wavelength, laser power, repetition frequency and laser generator type of the laser used can be selected according to actual processing requirements and material types.

(S2) Select a suitable sample stage, and fix the sample on the sample stage. Turn on the ordinary light source 3, adjust the laser convergence and the height of the microscope in the microscopic observation system 1, adjust the focus, and perform positioning by observing the imaging of the CCD camera 7 in the microscope imaging software window of the computer 10, and select the position that needs to be processed. It is coaxial with ordinary light, so the laser spot is located at the very center of the imaging of the CCD camera 7 .

For materials that are toxic and easily react with gases in the air, a protective atmosphere chamber can be selected. Extrusion-type clamping method is used for bulk materials, and sheet-pressing clamping method is used for film and fiber type.

(S3) Open the displacement control software window of the computer 10, input the graphics and processing parameters to be processed therein or import the saved graphics processing files, at this time, a trial run can be performed to ensure that the laser processing process will not be caused by the sample stage exceeding the range interrupted due to other reasons.

(S4) Close the laser shield to prevent the laser leakage from causing harm to the operator or others.

(S5) Turn off the ordinary light source 3, and set the parameters of the laser. Start the programmed processing program and perform processing operations. At this point, the processing process can be monitored in real time through the microscope imaging software window and displacement control software window on the computer.

(S6) After the processing program is finished, turn off the laser, open the protective cover, and then take out the processed sample.

The content of the present invention is further explained or illustrated by the following examples.

Example 1 Processing of SEM single crystal Ni stretched V-notch sample in situ.

As shown in Figure 1, the equipment used for processing is as described above.

Processing method: Clamp the single crystal Ni sheet on the sample stage, select an infrared femtosecond laser with a wavelength of 1040nm, and set the power of the laser. By performing the detailed steps of the above-mentioned material processing method, the required strip-shaped scanning in-situ stretching sample with a V-shaped notch can be obtained.

The results of the examples show that the device of the present invention can quickly and conveniently use the femtosecond laser to finely process various materials, such as metal nickel sheet, transparent quartz glass, etc., with a sample size of less than 10cm×10cm. At the same time, by adjusting the single pulse energy of the femtosecond laser, the spot size, the moving speed of the mechanical platform, etc., an in-situ electron microscope sample with almost no heat-affected zone can be obtained. Therefore, through the present invention, large-scale, high-precision and low-loss numerical control processing can be performed on the material, and the original microstructure of the sample after cutting can not be affected as much as possible. It has the advantages of high positioning accuracy, high energy concentration, low processing loss, high degree of visualization, high degree of automation, no noise, no pollution, no heat-affected zone, etc. Moreover, combined with microscope digital imaging, it is possible to realize micro-nano-scale processing of materials, which has great application prospects in the field of in-situ electron microscope sample preparation, and is of great help in the scientific research of these materials.

The device and method for preparing an in-situ electron microscope sample by using converging femtosecond laser provided by the present invention are described above in detail. In this paper, specific examples are used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. The utility model provides an adopt and assemble femto second laser preparation normal position electron microscope sample's device which characterized in that, the device includes: the system comprises a femtosecond laser, a convergence scanning system, a sample stage mechanical numerical control moving system, a coaxial microscopic observation positioning system, a computer centralized data monitoring and visualization system, a damping system and a protection system, wherein the femtosecond laser of a laser light source is emitted from the laser, converged by a multi-stage laser combined lens, and connected to the coaxial microscopic observation positioning system in a coaxial light form through different interfaces with the common cold light of a common light source; the coaxial microscopic observation positioning system and the sample stage mechanical numerical control moving system are connected with a computer centralized data monitoring and visualization system through a USB (universal serial bus) line or a network cable, and the structure is as follows:

the laser light source and the ordinary light source are respectively connected to the laser convergence and microscopic observation system in a coaxial light mode through an interface through an optical cable, and are switched through the electric switch; the laser convergence and microscopic observation system is connected with the input end of the CCD camera, and the output end of the CCD camera and the input end of the motion controller are connected with a computer through a USB (universal serial bus) line or a network cable to carry out microscopic observation positioning and numerical control programming; the laser convergence and microscopic observation system is provided with the long-focus objective lenses with different multiples, and observation selection is carried out according to different samples and processing requirements; the laser gathering and microscopic observation system is arranged on the laser gathering module mechanical moving system, the output end of the motion controller is connected with the sample table mechanical numerical control moving system, the sample table mechanical numerical control moving system is arranged on the air floatation damping platform, and the air inlet end of the air floatation damping platform is connected with the air pump.

2. The apparatus for preparing in-situ electron microscope samples by using condensed femtosecond lasers according to claim 1, wherein the femtosecond laser and the condensed scanning system comprise: the femtosecond laser device is formed by matching a femtosecond laser oscillator, a pumping source and a femtosecond laser amplifier and emits ultrafast laser with the pulse width of less than 400fs and the single pulse energy of more than 50 mu J; and the combined lens is arranged at a light outlet of the laser and is used for carrying out first-stage reduction on the femtosecond laser facula.

3. The apparatus of claim 1, wherein the coaxial micro-observation positioning system comprises a laser cable interface, a common optical cable interface, an electric coaxial light source switch, a laser CCD camera, a common microscope eyepiece, an objective lens, and a set of ultra-long focal length objective lenses with different magnifications, and the coaxial micro-observation positioning system is used for performing secondary convergence on the laser in the optical fiber.

4. The apparatus for preparing in-situ electron microscope samples by using condensed femtosecond lasers according to claim 1, wherein the sample stage mechanical numerical control moving system comprises: a set of combined sliding tables which can move freely in x, y and z three-dimensional space; a light-transmitting and sealing sample cavity communicated with protective gas; a detecting device for monitoring the converged laser energy in real time; a sample stage for holding a film sample, a fiber sample and a bulk sample; a liquid nitrogen cooling low temperature processing table; wherein,

the combined sliding tables move randomly in x, y and z three-dimensional spaces, each direction sliding table is controlled by a separate servo motor, the three-dimensional combined sliding tables of x, y and z are connected into the same controller and further connected into a computer, and a graphic program needing to be processed is input through a displacement control software window of the computer, so that the continuously adjustable movement with the repeated positioning precision of 0.5 mu m and the movement speed of 1-1000 mm/min is realized; meanwhile, a sliding table rotating in the plane is also arranged, and the sample is rotated by computer software under the control of a servo motor;

the sample cavity is provided with an air exhaust port, an inflation port and an exhaust port, a gas flowmeter is arranged at the front end of the inflation port, and the gas flowmeter is used for adjusting the reading of the flowmeter to realize the protective environment of positive pressure anti-oxidation of inert gas during laser processing or blow the ash residue left during cutting of the sample; meanwhile, a mechanical dry pump is arranged at the front end of the air extraction opening, and a vacuum environment of less than 5Pa is obtained in the closed cavity; a laser anti-reflection lens is arranged above the cavity and used for processing a sample in the cavity through femtosecond laser;

the liquid nitrogen cooling low-temperature processing table is provided with a liquid nitrogen cooling chamber and a heat insulation cavity; further, the liquid nitrogen cooling chamber comprises: a liquid nitrogen inlet, an exhaust port;

a detection device for monitoring the converged laser energy in real time, wherein a power probe is used for focusing the laser beam on the positive objective lens and detecting the laser power actually acting;

the structure of the sample stage is that one side of the sample stage is fixed, and the other side of the sample stage is a sliding table which moves horizontally and adopts extrusion type to the block sample; for thin slice and fiber samples, a coaxial rotating motor is respectively arranged at the upper sides of a sliding block and a fixed block, the samples are fixed in the center of a motor bearing in a tabletting mode and are controlled by a computer, and the samples rotate in one dimension; for the film samples, the fixation was performed using a top pressed sheet.

5. The apparatus for preparing in situ electron microscope samples using condensed femtosecond lasers according to claim 1, wherein the computer centralized data monitoring and visualization system comprises: a set of software for carrying out numerical control and real-time monitoring on mechanical displacement realizes the switching between laser and common light and the processing of images by inputting a CAD vector diagram and editing a program; one set of laser CCD camera image of imaging, conveniently carry out and implement observation, measurement and accurate positioning, also possess simultaneously and shoot, record a video and add the scale function.

6. The apparatus for preparing in-situ electron microscope samples by using condensed femtosecond lasers according to claim 1, wherein the shock absorption system comprises an air-floating optical platform and an air pump, is used for installing a sample stage mechanical numerical control moving system and a coaxial microscopic observation positioning system, and adopts a mechanical fixing mode to prevent the samples from vibrating and light spots from deviating during the processing process; the protection system includes: the protective cover covers the mechanical numerical control moving system and the coaxial microscopic observation positioning system of the sample stage, so that the damage of laser light leakage to operators is prevented; a filter glasses for protecting the eyes of the operator while working.

7. A method for preparing in situ electron microscope samples using a focused femtosecond laser using the device according to any one of claims 1 to 6, wherein the method comprises the following steps:

(1) a microscopic positioning step, namely determining a processing area;

(2) programming a processing graph, and editing processing parameters;

(3) selecting laser parameters, namely selecting the laser parameters meeting the processing requirements;

(4) starting a mechanical moving system and a laser;

(5) and a detection step, namely monitoring the processing process in real time.

8. A method for preparing in situ electron microscope samples using a focused femtosecond laser using the device according to any one of claims 1 to 6, wherein the method comprises the following steps:

(1) putting a sample in a sample cavity, pumping a vacuum with a pressure less than 5Pa by using a mechanical pump, introducing protective gas to atmospheric pressure, pumping again, and then pumping again for three times; finally, opening an exhaust valve to enable protective gas to flow in the cavity, and keeping the pressure of the cavity higher than one atmosphere to enable the pressure in the cavity to reach 0.105-0.11 MPa;

(2) a microscopic positioning step, namely determining a processing area;

(3) programming a processing graph, and editing processing parameters;

(4) selecting laser parameters, namely selecting the laser parameters meeting the processing requirements;

(5) starting a mechanical moving system and a laser;

(6) and a detection step, namely monitoring the processing process in real time.

9. A method for preparing in situ electron microscope samples using a focused femtosecond laser using the device according to any one of claims 1 to 6, wherein the method comprises the following steps:

(1) fixing the sample on the upper surface of the cooling cavity by using a pressing sheet, and adding liquid nitrogen to cool the cavity;

(2) a microscopic positioning step, namely determining a processing area;

(3) programming a processing graph, and editing processing parameters;

(4) selecting laser parameters, namely selecting the laser parameters meeting the processing requirements;

(5) starting a mechanical moving system and a laser;

(6) and a detection step, namely monitoring the processing process in real time.

10. The method for preparing in-situ electron microscope samples by using the condensed femtosecond laser according to claim 7, 8 or 9, wherein the method further comprises selecting an objective lens for microscopic observation and condensing the laser; the method further includes a storing step of storing the edited processing drawing; the method further comprises a step of importing, namely importing a processing drawing stored before or an existing CAD vector drawing; the method further comprises a laser spot adjusting step, wherein the size of the laser spot is adjusted to meet the processing requirement.