Embedded atomic force microscope and control scanning system

Abstract

The invention discloses an embedded atomic force microscope and a control scanning system. The embedded atomic force microscope comprises an atomic force microscope system measuring head, an atomic force microscope system base, an embedded board card control system and a touch serial port screen facilitating interaction. The atomic force microscope measuring head is used for completing the extraction of sample morphology information from an optical signal to an electric signal; the atomic force microscope system base is used for completing approaching of a sample and a probe and displacement driving of the sample; the embedded board card control system is used for completing driving of a system measuring head, acquisition and uploading of an electric signal, control of a three-dimensional scanning method of a sample and storage and processing of a scanning data result; and the touch serial port screen is used for controlling to send an instruction and completing the display of the collected data. According to the invention, the embedded controller is adopted, so that unnecessary background processes are reduced; hardware configuration is optimized, and a low-delay hardware protocol SPI is used for communication; a scanning path can be planned, real-time adjustment can be performed in the scanning process, and experimental operation and data analysis are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of atomic force microscope scanning imaging technology, and particularly to an embedded atomic force microscope and a control scanning system. Background Art

[0002] By measuring the interaction force between the tip and the sample surface, the atomic force microscope can not only observe the microscopic morphology of polymer materials at the nanoscale, but also characterize their mechanical properties. At the same time, since only the force between the tip and the sample is measured, the atomic force microscope can be conveniently extended to test environments such as high and low temperatures, liquids, atmospheres or vacuums. Characterizing polymer materials not only has simple sample preparation and low requirements for the working environment, but also is convenient to be combined with various external fields for characterizing the morphological structure and evolution process. The atomic force microscope has become a very important general instrument in the field of nanotechnology, which can achieve atomic-level high-resolution imaging and the manipulation of single nanoparticles, and has been widely used in the fields of precision measurement, microelectromechanical systems, biomedicine, materials and energy, etc.

[0003] The research on the hardware facilities paired with atomic force microscopes at home and abroad is also very popular. There was once a scholar who developed a high-precision micro-motion scanning platform for an atomic force microscope. This platform has two components, namely a shear-type piezoelectric displacement platform composed of laminated piezoelectric ceramics and a piezoelectric ceramic tube scanner. Among them, the role of the shear-type piezoelectric displacement platform is to control the rapid approach between the sample and the probe for the rough positioning process, and the manual control mode is used in this process; when fine positioning is to be performed, it is completed by the cooperation of the shear-type piezoelectric displacement platform and the piezoelectric ceramic tube scanner, and the computer software is used for automatic control and approach positioning in this process.

[0004] Currently, traditional atomic force microscopes rely on discrete components and use a general computer to run control software. There are non-deterministic delays in task scheduling, and background processes, interruptions or resource competition may cause jitter or frame loss in the output of control signals. Moreover, the power supply noise, heat dissipation problems and component aging of general computers will directly affect the control accuracy. Summary of the Invention

[0005] Based on the technical problems existing in the background art, the present invention proposes an embedded atomic force microscope and a control scanning system.

[0006] An embedded atomic force microscope and a control scanning system, comprising an atomic force microscope system probe, an atomic force microscope system base, an embedded board control system, and a touch serial port screen for easy interaction. The atomic force microscope system probe and the atomic force microscope system base are both connected to the embedded board control system, and the embedded board control system is connected to the touch serial port screen through the port of the controller. The atomic force microscope probe is used to extract the sample topography information from the optical signal to the electrical signal. The atomic force microscope system base is used to complete the approximation of the sample and the probe and the displacement drive of the sample. The embedded board control system is used to complete the drive of the atomic force microscope system probe, the acquisition and upload of electrical signals, the method control of the three-dimensional scanning of the sample, and the storage and processing of the scanning data results. The touch serial port screen is used for interaction, sending instructions to the control of the embedded board control system, and completing the display of the acquired data.

[0007] Preferably, the atomic force microscope system probe includes a probe. The atomic force microscope system base includes a three-dimensional piezoelectric ceramic scanner, a sample stage, and a sample. The sample stage is arranged inside the three-dimensional piezoelectric ceramic scanner, and the sample is placed on the sample stage. The embedded board control system includes a direct digital frequency synthesizer, a high-precision analog-to-digital converter, a digital-to-analog converter, and a high-voltage amplifier circuit. Information is input through the touch serial port screen to drive the direct digital frequency synthesizer to output a sine wave signal to excite the probe, and at the same time drive the analog-to-digital converter to collect the amplitude signal of the probe. Drive the digital-to-analog converter to output a direct voltage, which is connected to the three-dimensional piezoelectric ceramic scanner through the high-voltage amplifier circuit to complete the Z-direction displacement drive, thereby completing the approximation of the probe and the sample on the sample stage. Information is input through the touch serial port screen, and the scanning method is selected to realize the topography measurement of the sample.

[0008] Preferably, the touch serial port screen is provided with a probe sweep frequency control interface of the atomic force microscope system, an approximation control interface between the probe and the sample, and a three-dimensional scanning control interface. Through the probe sweep frequency control interface of the atomic force microscope system on the touch serial port screen, the sweep frequency parameters, namely the starting frequency and the step frequency, are input. Through the approximation control interface between the probe and the sample on the touch serial port screen, the approximation voltage parameter and the switch and rotation direction of the DC motor are input. Through the three-dimensional scanning control interface on the touch serial port screen, the scanning parameter ranges of X and Y and the step parameters of X and Y are input.

[0009] Preferably, the embedded board control system further includes an STM32 controller. The STM32 controller sets the working parameters of the embedded board control system according to the instructions issued by the touch serial port screen, converts them into digital quantity data through the high-precision analog-to-digital converter, stores the data in the SRAM externally expanded by the STM32 controller, and finally packs the processed data and sends it to the touch serial port screen for display through serial communication.

[0010] Preferably, the probe of the atomic force microscope system further includes a semiconductor laser and a quadrant photodetector. The probe, the semiconductor laser, and the quadrant photodetector are packaged and fixed together. When the probe approaches the sample surface, an interaction force will be generated between the two, causing the probe to deflect. The beam of the semiconductor laser is focused on the back of the probe through a lens and reflected onto the quadrant photodetector. The X-phase position information of the spot of the quadrant sensor, which is the amplitude information, is finally converted into a DC signal.

[0011] Preferably, the embedded board control system further includes a DC motor drive. The DC motor is connected to the probe of the atomic force microscope system through a guide rod, a coupling, and a micrometer head. The STM32 controller can drive the DC motor through the DC motor drive to complete the preliminary approach of the probe of the atomic force microscope system to the sample.

[0012] Preferably, the scanning mode includes a traditional raster scanning mode and a spiral path scanning mode.

[0013] The beneficial effects of the present invention are as follows:

[0014] An embedded atomic force microscope and scanning control system of the present invention uses an embedded controller to replace the software control of a computer, reducing unnecessary background processes, avoiding interference at the operating system and software levels, and dedicating resources to control tasks. At the same time, by optimizing the hardware configuration of the control system and using a low-latency hardware protocol for communication, signal delay is reduced.

[0015] The present invention provides a friendly interface and data processing function, facilitating experimental operation and data analysis. It can plan traditional raster scanning and spiral path scanning paths and make real-time adjustments during the scanning process, which is convenient for experimental operation and data analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 : Schematic diagram of the system structure of the present invention;

[0017] Figure 2 : Probe sweep frequency control interface diagram of the touch serial port screen of the present invention;

[0018] Figure 3 : Probe and sample approach control interface diagram of the touch serial port screen of the present invention;

[0019] Figure 4 : Three-dimensional scanning control interface diagram of the touch serial port screen of the present invention;

[0020] Figure 5 : Flowchart of the traditional raster scanning method of the present invention;

[0021] Figure 6 : Flowchart of the spiral path scanning method of the present invention. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0023] Embodiment 1:

[0024] Referring to Figures 1-6 , an embedded atomic force microscope and a control scanning system proposed by the present invention include an atomic force microscope system probe, an atomic force microscope system base, an embedded board control system, and a touch serial port screen for easy interaction. The atomic force microscope system probe and the atomic force microscope system base are both connected to the embedded board control system, and the embedded board control system is connected to the touch serial port screen through the port of the controller.

[0025] The atomic force microscope system probe is used to complete the extraction of sample topography information from optical signals to electrical signals, and includes a semiconductor laser, a quadrant photodetector, and a probe. The probe, the semiconductor laser, and the quadrant photodetector are packaged and fixed together. When the probe approaches the sample surface, an interaction force will be generated between the two, causing the probe to deflect; the beam of the semiconductor laser is focused on the back of the probe through a lens and reflected onto the quadrant photodetector. The X-phase position information of the spot of the quadrant sensor is the amplitude information, and finally it is converted into a DC signal.

[0026] The atomic force microscope system base is used to complete the approach of the sample and the probe and the displacement drive of the sample, and includes a three-dimensional piezoelectric ceramic scanner, a sample stage, and a sample. The sample stage is arranged inside the three-dimensional piezoelectric ceramic scanner, and the sample is placed on the sample stage. During the scanning process, the STM32 controller drives the digital-to-analog converter to output a direct voltage, which is connected to the three-dimensional piezoelectric ceramic scanner through a high-voltage amplifier circuit to complete the displacement drive of the sample.

[0027] The embedded board control system is used to complete the drive of the atomic force microscope system probe, the acquisition and upload of electrical signals, the method control of the three-dimensional scanning of the sample, and the storage and processing of the scanning data results. Specifically, it includes a direct digital frequency synthesizer, a high-precision analog-to-digital converter, a digital-to-analog converter, a high-voltage amplifier circuit, an STM32 controller, and a DC motor drive.

[0028] The DC motor is connected to the atomic force microscope system probe through a guide rod, a coupling, and a micrometer head. The STM32 controller can drive the DC motor through the DC motor drive to complete the preliminary approach of the probe of the atomic force microscope system to the sample.

[0029] The touch serial screen is used for interaction, sending instructions to the control of the embedded board control system to complete the display of the collected data. It is provided with a probe sweep control interface of the atomic force microscope system, an approach control interface between the probe and the sample, and a three-dimensional scanning control interface.

[0030] In the present invention, the atomic force microscope system operates in the tapping mode, and its working principle is as follows: when the probe approaches the surface of the sample, an interaction force will be generated between the two, causing the probe to deflect; the beam of the semiconductor laser is focused on the back of the cantilever through a lens and reflected onto the quadrant photodetector. The X-phase position information of the spot of the quadrant sensor is the amplitude information, and finally it is converted into a DC signal.

[0031] Figure 1 It is a schematic diagram of the system structure of the present invention. As Figure 1 shown, an embedded atomic force microscope and a control scanning system of the present invention have the following specific operation and control principles:

[0032] (1) The STM32 controller sets the working parameters of the embedded board control system according to the instructions issued by the touch serial screen, and then converts them into digital quantity data through a high-precision analog-to-digital converter. The data is stored in the SRAM externally expanded by the STM32 controller, and finally, after data processing, it is packaged and sent to the touch serial screen for display through serial communication.

[0033] (2) Through the probe sweep control interface of the atomic force microscope system on the touch serial screen, input the sweep parameters, that is, the starting frequency and the step frequency; the diagram of the probe sweep control interface of the touch serial screen is as Figure 2 shown.

[0034] After receiving the instruction data, the embedded board control system parses it and drives the direct digital frequency synthesizer to output a sine wave signal to excite the probe. The communication method between the controller and the digital frequency synthesizer adopts the SPI communication protocol, and the sweep function is realized through software. Input the amplitude magnification factor of the sine wave waveform on the sweep control interface, and control the magnification factor through software programming. Depending on different probe tips, the obtained sweep results are different, so its working frequency will also change. The controller drives the analog-to-digital converter to collect the amplitude signal of the probe. The analog-to-digital converter has high precision and acquisition speed. The communication method between the controller and the analog-to-digital converter adopts the SPI communication protocol. Record the amplitude signal value corresponding to the excitation of the probe at the set frequency, draw the sweep curve, and obtain the working frequency of the probe.

[0035] (3) Obtain the working frequency of the probe through step (2). On the approach control interface between the probe and the sample on the touch serial screen, input the approach voltage parameter. The diagram of the approach control interface between the probe and the sample is as Figure 3 shown.

[0036] After receiving the command data, the embedded board control system parses it, drives the digital-to-analog converter to output a direct voltage, and connects it to the three-dimensional piezoelectric ceramic scanner via a high-voltage amplification circuit to complete the Z-direction displacement drive. Then, by inputting the DC motor switch command, the direction of adjustment and rotation is adjusted to drive the probe to approach the sample on the sample stage; at the same time, the embedded board control system controls the analog-to-digital converter to collect the probe amplitude signal and upload it to the touch serial port screen interface to determine whether the approach threshold is reached. If the threshold is reached, the control of the Z-direction of the three-dimensional piezoelectric ceramic scanner will be withdrawn, that is, it will return to the initial state; at the same time, the drive of the DC motor will be turned off. At this time, the digital-to-analog converter is controlled to gradually increase the output DC voltage, and the embedded board control system drives the analog-to-digital converter to collect the probe amplitude signal, records the probe amplitude signal value corresponding to the Z-direction displacement, and plots the approach curve.

[0037] (4) When measuring the three-dimensional topography, the atomic force microscope system operates in the constant height mode, that is, during the scanning of the sample, the height between the probe and the sample remains the same.

[0038] Through the approach curve drawn in step (3), the sensitivity and resolution of the probe are obtained, and the working voltage of the PI feedback control circuit is set in the three-dimensional scanning control interface of the touch serial port screen, where the three-dimensional scanning control interface is as Figure 4 shown.

[0039] The embedded board control system controls the analog-to-digital converter to collect the probe amplitude signal, where the probe amplitude signal is connected to the PI feedback control circuit. Taking the working voltage of the PI feedback control circuit as the target value, the feedback voltage output by the PI feedback control circuit is connected to the Z-direction piezoelectric ceramic tube of the three-dimensional piezoelectric ceramic via a high-voltage amplification circuit. Therefore, when scanning the sample, the probe will bend and undulate with the surface topography of the sample under feedback adjustment, and the reflected light beam received by the quadrant photodetector will also shift accordingly, indicating that the probe amplitude signal will change. In order to maintain this signal always, the atomic force microscope system will enter the PI feedback control state to scan the surface topography of the sample to be measured. The probe amplitude signal is compared with the working point set by the PI feedback control circuit to determine the entry into the PID closed-loop working state.

[0040] Input the scanning range parameters of X and Y and the step parameters of X and Y in the three-dimensional scanning control interface of the touch serial port screen, and the number of rows and columns to be scanned in the X and Y directions is calculated in the program. Selecting the three-dimensional scanning button control means selecting the traditional raster scanning method, and the flow chart of this method is as Figure 5As shown in the figure, the STM32 controller drives the digital-to-analog converter to output a DC voltage, which is transmitted to the three-dimensional piezoelectric ceramic scanner via a high-voltage amplifier, driving the piezoelectric ceramic tube in the Y direction to displace the set step displacement, driving the piezoelectric ceramic tube in the X direction to displace the set step displacement, driving the DC voltage output by the digital-to-analog converter to increase point by point. The STM32 controller drives the analog-to-digital converter to collect the feedback voltage output by the PI feedback control circuit. When the set number of scan columns is completed, the DC voltage output by the digital-to-analog converter is driven to decrease point by point. The STM32 controller drives the analog-to-digital converter to collect the feedback voltage output by the PI feedback control circuit, driving the piezoelectric ceramic tube in the Y direction to displace the set step displacement until the set number of scan rows is completed, and the scanning ends.

[0041] Enter the scan range parameters of X and Y and the step parameters of X and Y in the three-dimensional scan control interface of the touch serial screen. The number of rows and columns to be scanned in the X and Y directions is calculated in the program. Set the number of scan micro-blocks to perform segmented scanning on a large scanning area. The flowchart of the spiral path scanning method is as Figure 6 shown. Selecting the spiral scan button control means selecting the spiral path scanning method to measure the topography of the sample. The first micro-block scanned is regarded as an ideal image not affected by drift. Among them, the single micro-block scan adopts the traditional raster scanning method, as Figure 5 shown. The micro-block consists of voltage values one by one. The drift amount of the current micro-block is obtained by performing correlation calculation on the saved voltage scan data and the scan data of adjacent micro-blocks. The correlation calculation is to select a region in the micro-block as a template to search and match with adjacent micro-blocks to obtain the relative offset amount of the two micro-blocks, that is, the drift amount. Since the micro-block is very small and may contain fewer feature points, the drift amount calculated by the correlation calculation may be incorrect. Therefore, it is necessary to judge the calculated drift. If it is judged that the calculated drift is correct, drift compensation is performed. If it is judged that the calculated drift is incorrect, this compensation is discarded and the scanning of the next micro-block is directly performed. If the number of scanned micro-blocks is greater than num, the spiral scan ends.

[0042] The embedded board control system controls the analog-to-digital converter to collect the feedback voltage, records the feedback voltage output by the PI feedback, and draws the surface topography characteristic curve to realize the topography measurement of the sample.

[0043] An embedded atomic force microscope and scanning control system of the present invention uses an embedded controller to replace the software control of a computer, reducing unnecessary background processes, avoiding interference at the operating system and software levels, and dedicating resources to control tasks; at the same time, by optimizing the hardware configuration of the control system and using a low-latency hardware protocol for communication, signal delay is reduced.

[0044] The present invention provides a friendly interface and data processing functions, which facilitate experimental operations and data analysis, can plan traditional raster scanning and spiral path scanning paths, and make real-time adjustments during the scanning process, facilitating experimental operations and data analysis.

[0045] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. An embedded atomic force microscope and control scanning system, including an atomic force microscope system probe, an atomic force microscope system base, an embedded board control system and a touch serial port screen for easy interaction, characterized in that: The atomic force microscope system probe and the atomic force microscope system base are both connected to the embedded board control system, and the embedded board control system is connected to the touch serial port screen through the port of the controller; the atomic force microscope probe is used to complete the extraction of sample morphology information from optical signals to electrical signals; The base of the atomic force microscope system is used to complete the approach of the sample and the probe and the displacement drive of the sample; the embedded board control system is used to complete the drive of the atomic force microscope system probe, the collection and upload of electrical signals, the control of the method of three-dimensional scanning of the sample, and the storage and processing of the scanning data results; The touch serial port screen is used for interaction, sending instructions to the control of the embedded board control system to complete the display of collected data.

2. The embedded atomic force microscope and control scanning system according to claim 1, characterized in that: The probe of the atomic force microscope system includes a probe; the base of the atomic force microscope system includes a three-dimensional piezoelectric ceramic scanner, a sample stage and a sample, the sample stage is arranged in the three-dimensional piezoelectric ceramic scanner, and the sample is placed on the sample stage; the embedded board control system includes a direct digital frequency synthesizer, a high-precision analog-to-digital converter, a digital-to-analog converter and a high-voltage amplifier circuit; information is input through a touch serial port screen, the direct digital frequency synthesizer is driven to output a sinusoidal wave signal to excite the probe, and the analog-to-digital converter is driven to collect the amplitude signal of the probe; the digital-to-analog converter is driven to output a direct voltage, which is connected to the three-dimensional piezoelectric ceramic scanner via a high-voltage amplifier circuit to complete the Z-direction displacement drive, thereby completing the approach of the probe to the sample on the sample stage; information is input through the touch serial port screen, and a scanning mode is selected to achieve morphology measurement of the sample.

3. The embedded atomic force microscope and control scanning system according to claim 1, characterized in that: The touch serial port screen is provided with a probe frequency sweep control interface of the atomic force microscope system, an approach control interface of the probe and the sample, and a three-dimensional scanning control interface; the frequency sweep parameters, namely, the starting frequency and the step frequency, are input through the probe frequency sweep control interface of the atomic force microscope system on the touch serial port screen; the approach voltage parameters and the switch and the rotation direction of the DC motor are input through the approach control interface of the probe and the sample on the touch serial port screen; and the scanning parameter range of X and Y and the step parameters of X and Y are input through the three-dimensional scanning control interface on the touch serial port screen.

4. The embedded atomic force microscope and control scanning system according to claim 2, characterized in that: The embedded board control system also includes an STM32 controller, which sets the working parameters of the embedded board control system according to the instructions issued by the touch serial port screen, and then converts the data into digital data through a high-precision analog-to-digital converter. The data is stored in the SRAM expanded by the STM32 controller, and finally the data is packaged after processing and sent to the touch serial port screen for display through serial communication.

5. The embedded atomic force microscope and control scanning system according to claim 1, characterized in that: The probe of the atomic force microscope system also includes a semiconductor laser and a four-quadrant photodetector. The probe, the semiconductor laser and the four-quadrant photodetector are packaged and fixed together. When the probe is close to the sample surface, an interaction force is generated between the two, causing the probe to deflect. The light beam of the semiconductor laser is focused to the back of the probe through a lens, and is reflected to the four-quadrant photodetector. The four-quadrant sensor light spot X-phase position information, that is, amplitude information, is finally converted into a DC signal.

6. The embedded atomic force microscope and control scanning system according to claim 4, characterized in that: The embedded board control system also includes a DC motor drive, which is connected to the atomic force microscope system probe through a guide rod, a coupling and a micrometer head. The STM32 controller can drive the DC motor through the DC motor drive to complete the initial approach between the probe of the atomic force microscope system probe and the sample.

7. The embedded atomic force microscope and control scanning system according to claim 1, characterized in that: The scanning method includes a traditional raster scanning method and a spiral path scanning method.

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