Scanning tunneling microscope control system based on STM32

Abstract

The invention discloses a scanning tunneling microscope control system based on STM32, and belongs to the technical field of scanning probe microscopes. The control system comprises a main control chip STM32, a stepping motor module, a scanning module, a signal acquisition module, a communication module, a voltage reference module and a power supply module. Wherein the power supply module converts input + / -15V voltage into 5V and 3.3 V voltage and supplies power to the main control chip STM32 and all the modules, the voltage reference module provides stable reference voltage for the circuit of the whole system, the stepping motor module serves as a coarse feeding mechanism, the scanning module is moved to the position above a sample, and the scanning module is moved to the position above the sample. The scanning module drives a scanning head and a probe on the scanning module to perform three-dimensional scanning on the surface of a sample, and the signal acquisition module is used for collecting tunnel current between a needle tip and the sample and sending current information to the control software through the communication module; an STM32 is adopted as a main control chip, two 12-bit DACs are arranged, compared with an ESP32, the high resolution is achieved, and finer signal control can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of scanning probe microscopes, and in particular relates to a scanning tunneling microscope control system based on STM32. Background Art

[0002] A scanning tunneling microscope is a microscope that uses a scanning probe to scan a sample line by line to obtain information about the sample surface. Its working principle is to describe the electronic properties of the sample surface by controlling the tunneling current between the probe and the sample. The scanning tunneling microscope is mainly composed of a drive motor, a scanning head, and a sample. In actual work, the function of the drive motor is to move the scanning head with a scanning probe to the vicinity of the sample; then a voltage is applied to form a tunneling current between the probe and the sample; finally, the scanning head drives the probe tip to scan the two-dimensional plane of the sample. During this process, the size of the tunneling current is also synchronously collected and stored for real-time imaging of the host computer. The control system of the scanning tunneling microscope is divided into two parts: the host computer and the slave computer.

[0003] The functions of the lower computer mainly include: 1) Generate the control signal of the drive motor. The drive motor is generally made of piezoelectric materials, which are of various types and have different drive signals. Usually, the signal is required to be programmable. 2) Generate the control signal of the scanning head. The control signal of the scanning head is generally a dual-channel triangle wave, which is used to drive the movement in the x-axis and y-axis directions. 3) Collect the tunnel current and transmit it to the upper computer. The transmission method generally uses high-speed USB communication.

[0004] The functions of the host computer mainly include: 1) Adjust the parameters of the motor control signal, such as frequency, peak voltage, etc., to change the step speed and step length of the motor. 2) Adjust the parameters of the scanning head drive signal, such as frequency, amplitude, etc., to change the scanning speed and scanning range. 3) Collect tunnel current signals, realize real-time imaging and store current data.

[0005] At present, the control systems of scanning tunneling microscopes available in the commercial market are complex, and their main components include industrial control boards, data acquisition cards, and drive circuits. The industrial control board is equipped with a real-time operating system and is connected to the host PC via Ethernet. The corresponding software is installed on the PC to manage the slave computer and the data acquisition card to output the necessary drive signals and collect the required signals. Although such systems have excellent performance and mature technology, they also have some shortcomings: the scanning speed of scanning tunneling microscopes is usually slow, and the demand for high-speed data acquisition is not high, which leads to a large waste of hardware resources of industrial control boards and high-performance data acquisition cards.

[0006] At the same time, the invention patent with publication number CN116754795A discloses a scanning tunneling microscope control system based on ESP32, in which two 8-bit DAC channels are used as the control signal of the scanning head, and only 256×256 pixel images can be obtained, which is obviously too small; if a large-scale scan is performed, the resolution will be seriously insufficient. In addition, the two DACs only support triangle wave scanning, and some distortion-free scanning methods (such as spiral scanning) are not supported. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a scanning tunneling microscope control system based on STM32, which solves the problems in the prior art.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] A scanning tunneling microscope control system based on STM32 includes: a main control chip STM32, a stepper motor module, a scanning module, a signal acquisition module, a communication module, a voltage reference module and a power supply module;

[0010] Among them, the power module converts the input ±15V voltage into 5V and 3.3V to power the main control chip STM32 and each module. The voltage reference module provides a stable reference voltage for the circuit of the entire system. The stepper motor module is a coarse feed mechanism, which is controlled by the DAC1 channel of the main control chip STM32. The scanning module is moved above the sample, and the 4-way DAC channels of two MCP4922s and the DAC2 channel of the main control chip STM32 are used to drive the scanning head and probe on the scanning module to perform three-dimensional scanning on the sample surface. The signal acquisition module collects the tunnel current between the needle tip and the sample through the ADC1 channel of the main control chip STM32, and the communication module sends the current information to the control software through the high-speed USB communication of the main control chip STM32.

[0011] Furthermore, the stepper motor module includes: an inertial motor, a DAC1 channel, two MCP4922 external DAC chips and an amplifier circuit;

[0012] The DAC1 channel is used to output the inertial motor drive signal to control the inertial motor to move forward or backward; the two MCP4922 external DAC chips have a total of four DAC outputs for driving other types of stepper motors; the amplifier circuit proportionally amplifies the DAC1 channel and the DAC output signal to between -10 and +10V.

[0013] Furthermore, the scanning module includes: a scanning head, a DAC2 channel, two MCP4922 external DAC chips and an amplifying circuit;

[0014] The DAC2 channel output voltage controls the movement of the scanning head in the Z-axis direction; two MCP4922 external DAC chips have a total of 4 DAC output scanning control signals, which are used to control the movement of the scanning head in a direction parallel to the sample, and the amplifier circuit proportionally amplifies the scanning control signal to between -10 and +10V.

[0015] Further, the signal acquisition module includes: an ADC1 channel, an ADC2 channel and a reduction circuit;

[0016] The ADC1 channel is used to collect tunnel current; the ADC2 channel is used as a reserved collection interface to collect temperature and bias voltage signals; the reduction circuit reduces the external signal to between 0 and 3.3V.

[0017] Further, the communication module includes: USB and Uart1 communication interfaces;

[0018] The USB is used for communication between the main control chip and the host computer control software; the Uart1 communication interface is used for debugging the program.

[0019] Further, the voltage reference module includes: a REF2033 chip;

[0020] The REF2033 chip outputs a 1.65V and a 3.3V as reference voltages for the entire circuit. The 3.3V voltage provides a reference level signal for the main control chip STM32, and the 1.65V voltage is transmitted to each amplifier circuit as a reference voltage.

[0021] Further, the power module includes: MP4462 chip and ME6211 chip;

[0022] The MP4462 chip converts the input 15V voltage into a stable 5V output, which is provided to an external DAC chip, etc.; the ME6211 chip converts the input 5V voltage into a stable 3.3V output, which is provided to the main control chip STM32.

[0023] Furthermore, in the stepper motor module, the amplifier chip of the amplifier circuit is OPA602;

[0024] In the scanning module, the amplifier chip of the amplifier circuit is OPA202.

[0025] Furthermore, the reduction circuit reduces the signal to between 0 and 3V through two OP07 chips.

[0026] The control method of a scanning tunneling microscope control system based on STM32 according to claim 7 comprises the following steps:

[0027] S1, connect the upper and lower computers. After opening the upper computer software, turn on the power of the lower computer and connect the USB data cable to the USB port of the upper computer.

[0028] S2, set the motor step parameters, the scanning mode options are: constant height scanning, constant current scanning; SetPoint sets the amplified tunnel current threshold. When the tunnel current is amplified and is greater than this voltage, it is considered that the motor step has been in place;

[0029] S3, after the setting is completed, the stepper motor is controlled to step forward, and the DAC2 channel first outputs voltage to allow the scanning head to extend to probe. At the same time, the ADC1 channel collects the tunnel current and transmits it to the control software via USB. If the scanning head is extended to the end and still cannot detect, or the threshold voltage is still not reached, then DAC2 outputs 0 voltage to allow the scanning head to shrink back to the origin, and DAC1 starts to output a cycle of control signals to drive the motor to step down one step, and then DAC2 continues to output voltage to allow the scanning head to probe, and this process is repeated until the voltage converted by the tunnel current reaches the set threshold;

[0030] S4, when the voltage converted by the tunnel current reaches the set threshold, the distance between the scanning head and the sample is sufficient to normally collect the tunnel current, and the sample begins to be scanned;

[0031] S5, after the setting is completed, the scanning starts. The DACs of the two MCP4922 chips output the control waveforms in the X and Y directions of the scanning head respectively. The waveforms are triangular waves. At this time, the scanning head will scan the sample line by line, and use ADC1 to collect the tunnel current and transmit it to the control software via USB.

[0032] Beneficial effects of the present invention:

[0033] 1. The present invention adopts STM32 as the main control chip and is equipped with two 12-bit DACs. Compared with ESP32, it has higher resolution and can achieve more precise signal control.

[0034] 2. The present invention has low cost, and the adopted STM32 main control board, benchmark and amplifier circuit have low cost.

[0035] 3. The control system of the present invention is compact and integrates the main control board, filter circuit and amplifier circuit together, which greatly reduces the size of the entire controller.

[0036] 4. The hardware resources of the STM32 of the present invention are fully utilized, and compared with imported controllers, there is very little waste.

[0037] 5. Based on the control and imaging characteristics of the scanning tunneling microscope, simple hardware facilities are used to achieve atomic resolution imaging of the scanning tunneling microscope.

[0038] 6. The scanning part of the present invention uses 4 independent DACs to support a distortion-free scanning method. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 It is a basic architecture diagram of the control system of the present invention;

[0041] Figure 2 It is a schematic diagram of the control interface of the control system of the present invention;

[0042] Figure 3 is a control flow chart of the control system of the present invention;

[0043] Figure 4 It is the circuit connection principle diagram of the main control chip STM32 of the present invention;

[0044] Figure 5 It is a circuit schematic diagram of the voltage reference of the present invention;

[0045] Figure 6 It is a schematic diagram of the circuit principle diagram of the DAC of the present invention after passing through the amplification circuit;

[0046] Figure 7 It is a schematic diagram of the circuit principle diagram of the external DAC of the present invention after passing through the amplification circuit;

[0047] Figure 8 It is a schematic diagram of the structure of the MCP4922 connection circuit principle diagram of the present invention;

[0048] Fig. 9 It is a schematic diagram of the structure of the ADC reduction circuit principle diagram of the present invention;

[0049] Fig.10 It is a power supply diagram of the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] like Figure 1As shown, a scanning tunneling microscope control system based on STM32 includes: a main control chip STM32, a stepper motor module, a scanning module, a signal acquisition module, a communication module, a voltage reference module and a power supply module;

[0052] Among them, the power module converts the input ±15V voltage into 5V and 3.3V to power the main control chip STM32 and each module. The voltage reference module provides a stable reference voltage for the circuit of the entire system. The stepper motor module is a coarse feed mechanism, which is controlled by the DAC1 channel of the STM32. Its function is to move the scanning module above the sample. The 4-channel DAC channels of two MCP4922s and the DAC2 channel of the STM32 are used to drive the scanning head and probe on the scanning module to perform three-dimensional scanning on the sample surface. The signal acquisition module collects the tunnel current between the needle tip and the sample through the ADC1 channel of the STM32. The communication module sends the current information to the control software through the high-speed USB communication of the STM32.

[0053] The stepper motor module includes: inertial motor, DAC1 channel (built-in STM32), two MCP4922 external DAC chips, and amplifier circuit;

[0054] Among them, the DAC1 channel is used to output the inertial motor drive signal to control the inertial motor to move forward or backward; since the reference level of STM32 is 3.3V, the DAC1 channel can only output 0~3.3V signals, so an amplifier circuit is needed to amplify it proportionally to between -10~+10V. The two MCP4922 external DAC chips have a total of four DAC outputs, which are used to drive other types of stepper motors. Of course, an amplifier circuit is also needed to amplify the output signal proportionally to between -10~+10V.

[0055] The scanning module includes: scanning head, DAC2 channel (built-in STM32), two MCP4922 external DAC chips, and amplifier circuit;

[0056] Among them, the DAC2 channel output voltage controls the movement of the scanning head in the Z-axis direction; the two MCP4922 external DAC chips have a total of 4 DAC output scanning control signals, which are used to control the movement of the scanning head in the direction parallel to the sample. The amplifier circuit proportionally amplifies the scanning control signal to between -10 and +10V.

[0057] The signal acquisition module includes: ADC1 channel (built-in STM32), ADC2 channel (built-in STM32), and reduction circuit;

[0058] Among them, ADC1 channel is used to collect tunnel current; ADC2 channel is a reserved acquisition interface, which can collect signals such as temperature and bias voltage. Since the reference level of STM32 is 3.3V, the ADC channel can only collect 0~3.3V signals, so it is necessary to reduce the circuit to reduce the external signal to between 0~3.3V. Both built-in ADCs are 12 bits, which is sufficient for collecting tunnel current signals and other voltage signals.

[0059] The communication module includes: USB (built-in STM32), Uart1 communication interface;

[0060] Among them, USB is used for communication between the main control chip and the host computer control software; Uart1 communication interface is used for debugging programs. The communication rate of full-speed USB is 12Mbps, and the communication rate of high-speed USB is 480Mbps. The STM32F4 series chip internally supports full-speed / high-speed USB communication, which is sufficient for data transmission between the host computer and the main control chip.

[0061] The voltage reference module includes: REF2033 chip;

[0062] Among them, the REF2033 chip can output a 1.65V and a 3.3V as the reference voltage of the entire circuit. On the one hand, the 3.3V voltage provides a high-precision reference level signal for the main control chip STM32. On the other hand, the 1.65V voltage is transmitted to each amplifier circuit as a reference voltage, and the DAC output of 0~3.3V can be accurately amplified to -10~+10V by precisely controlling it.

[0063] The power module includes: MP4462 chip and ME6211 chip.

[0064] Among them, the MP4462 chip converts the input 15V voltage into a stable 5V output, which is provided to the external DAC chip, etc. The ME6211 chip converts the input 5V voltage into a stable 3.3V output, which is provided to the main control chip STM32.

[0065] The control interface of the control system is as follows Figure 2 As shown, the control flow is as follows Figure 3 As shown, the following steps are included:

[0066] S1, connect the upper and lower computers. After opening the upper computer software, turn on the power of the lower computer and connect the USB data cable to the USB port of the upper computer. At this time, the upper computer will automatically scan the serial port number and display the available serial port number in the "Port" column. The user selects the correct port number and clicks Connect, and the upper and lower computers are connected.

[0067] S2, set the motor stepping parameters. The scanning mode options include "constant height scanning" and "constant current scanning";

[0068] SetPoint sets the amplified tunnel current threshold, that is, when the tunnel current is amplified and is greater than this voltage, the motor is considered to have stepped into position. The "Motor Voltage" slider can set the motor step voltage; the forward / backward checkbox selects the direction of motor movement. Clicking "Storage Path" will allow the user to select the image storage location.

[0069] S3. After the settings are completed, click the "Start Stepping" button. The DAC2 channel will output voltage first, allowing the scanning head to extend to "probe". At the same time, the ADC1 channel will collect the tunnel current and transmit it to the control software via USB. If the scanning head is extended to the end and still cannot "probe", or the threshold voltage is still not reached, DAC2 will output 0 voltage, allowing the scanning head to shrink back to the origin, and DAC1 will start to output a cycle of control signals to drive the motor to step down one step. Then DAC2 will continue to output voltage to allow the scanning head to "probe". This process is repeated until the voltage converted by the tunnel current reaches the set threshold.

[0070] S4, when the voltage converted by the tunnel current reaches the set threshold, the distance between the scanning head and the sample is sufficient to normally collect the tunnel current, and the sample can be scanned. The scanning range, resolution, scanning speed and other settings can be selected by yourself. Click the green box on the right side of the "Start Scanning" button to change the scanning area.

[0071] S5, after the settings are completed, click the "Start Scan" button. The DACs of the two MCP4922 chips output the control waveforms in the X and Y directions of the scanning head respectively. The waveforms are triangular waves. At this time, the scanning head will scan the sample line by line, and use ADC1 to collect the tunnel current and transmit it to the control software via USB. The scanning mode can be selected through step S2: "Constant High Scan" and "Constant Current Scan". After the scan is completed, if "Store Data" is checked, a txt file will be automatically generated to save the scanned data.

[0072] Example

[0073] In this embodiment, a specific control system example is proposed to specifically explain its control principle.

[0074] The control system in this embodiment uses STM32F405RGT6 as the main control chip. The pin definitions of STM32 are shown in Table 1, where the basic configurations such as power supply and crystal oscillator are not given. The pin allocation scheme is not unique and can be adjusted as needed. The circuit diagram of the main control chip STM32 is shown in Figure 4 There are also multiple schemes for the STM scanning process shown. This embodiment integrates two schemes: constant height scanning and constant current scanning.

[0075] Table 1 Definition of each pin of STM32

[0076]

[0077]

[0078] like Figure 4 As shown in the figure, in the main control chip STM32, the PA4 and PA5 pins are used as 12-bit DAC outputs. Among them, PA4 corresponds to DAC1, which is responsible for outputting peak signals to drive the inertial motor, and PA5 corresponds to DAC2, which is responsible for voltage control of the electrodes in the scanning tube. In this embodiment, the VDDA pin is connected to a 3.3V reference voltage, so the DAC output is an accurate 0 to 3.3V. The schematic diagram of the amplification circuit of DAC1 and DAC2 in the stepper motor module and the scanning module is shown in Figure 6 As shown, the amplifier chip of DAC1 in the stepper motor module uses OPA602, and the amplifier chip of DAC2 in the scanning module uses OPA202. Both chips have good capacitive driving performance and can drive piezoelectric materials well. OPA602 has a higher slew rate and can pass higher frequency signals, which is suitable for amplifying inertial motor signals. By accessing a high-precision 1.65V reference voltage, the output signal is accurately amplified from 0 to 3.3V to between -10 and +10V, and the output is consistent with the traditional controller output. The circuit schematic of the voltage reference module is shown below. Figure 5 As shown, high-precision 3.3V and 1.65V reference voltage signals can be output.

[0079] The rest of the scanning module is as follows Figure 8 As shown in the figure, two DAC chips MCP4922 communicate through SPI1. The chip has two DAC outputs, so the SPI1 bus can drive four DAC outputs. At the same time, the chip can be connected to an external reference voltage, which also uses the 3.3V reference source provided by the voltage reference module, so that the output amplitude of the DAC is consistent with the output of the main control chip. The amplification circuit of this part of the scanning module is shown in Figure 7 As shown, the amplifier chip used is OPA4202, and the amplification reference voltage is also connected to the 1.65V output of the voltage reference module, which accurately amplifies the output signal from 0 to 3.3V to between -10 and +10V.

[0080] Figure 2 The "reserved output" displayed by the external DAC also uses two MCP4922 chips, which are controlled by the SPI2 of the main control chip. Its connection circuit and amplification circuit are the same as Figure 8 , Figure 7 The same is used for other types of stepper motor signal control. Not drawn here.

[0081] Since the VDDA pin of the main control chip is connected to a 3.3V voltage reference, the ADC of the main control chip can only collect voltages from 0 to 3.3V. The amplified tunnel current signal is higher than this voltage, so it needs to be reduced. Fig. 9 As shown in the figure, the reduction circuit reduces the collected signal to between 0 and 3 V through two OP07 chips. The resistance values ​​of the voltage divider resistors R3, R4, R8 and R9 are determined according to the specific demand scenario.

[0082] The power module of the whole circuit is powered by a DC power supply of about ±15V. Fig.10 As shown in the figure, the power supply is responsible for powering the amplifier chips OP07, OPA2202, OPA4202 and OPA602, and on the other hand, it is converted into 5V voltage through the ME3116 chip to power the DAC chip MCP4922 and the reference voltage chip. The 5V power supply is then converted into 3.3V through the MP4462 to power the STM32 main control chip.

[0083] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0084] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A scanning tunneling microscope control system based on STM32, characterized in that: include: Main control chip STM32, stepper motor module, scanning module, signal acquisition module, communication module, voltage reference module and power module; Among them, the power module converts the input ±15V voltage into 5V and 3.3V to power the main control chip STM32 and each module. The voltage reference module provides a stable reference voltage for the circuit of the entire system. The stepper motor module is a coarse feed mechanism, which is controlled by the DAC1 channel of the main control chip STM32. The scanning module is moved above the sample, and the 4-way DAC channels of two MCP4922s and the DAC2 channel of the main control chip STM32 are used to drive the scanning head and probe on the scanning module to perform three-dimensional scanning on the sample surface. The signal acquisition module collects the tunnel current between the needle tip and the sample through the ADC1 channel of the main control chip STM32, and the communication module sends the current information to the control software through the USB communication of the main control chip STM32.

2. A scanning tunneling microscope control system based on STM32 according to claim 1, characterized in that: The stepper motor module includes: an inertial motor, a DAC1 channel, two MCP4922 external DAC chips and an amplifier circuit; The DAC1 channel is used to output the inertial motor drive signal to control the inertial motor to move forward or backward; the two MCP4922 external DAC chips have a total of four DAC outputs for driving other types of stepper motors; the amplifier circuit proportionally amplifies the DAC1 channel and the DAC output signal to between -10 and +10V.

3. A scanning tunneling microscope control system based on STM32 according to claim 2, characterized in that: The scanning module includes: a scanning head, a DAC2 channel, two MCP4922 external DAC chips and an amplifier circuit; The DAC2 channel output voltage controls the movement of the scanning head in the Z-axis direction; two MCP4922 external DAC chips have a total of 4 DAC output scanning control signals, which are used to control the movement of the scanning head in a direction parallel to the sample, and the amplifier circuit proportionally amplifies the scanning control signal to between -10 and +10V.

4. A scanning tunneling microscope control system based on STM32 according to claim 3, characterized in that: The signal acquisition module includes: an ADC1 channel, an ADC2 channel and a reduction circuit; The ADC1 channel is used to collect tunnel current; the ADC2 channel is used as a reserved collection interface to collect temperature and bias voltage signals; the reduction circuit reduces the external signal to between 0 and 3.3V.

5. A scanning tunneling microscope control system based on STM32 according to claim 4, characterized in that: The communication module includes: USB and Uart1 communication interfaces; The USB is used for communication between the main control chip and the host computer control software; the Uart1 communication interface is used for debugging the program.

6. A scanning tunneling microscope control system based on STM32 according to claim 5, characterized in that: The voltage reference module includes: a REF2033 chip; The REF2033 chip outputs a 1.65V and a 3.3V as reference voltages for the entire circuit. The 3.3V voltage provides a reference level signal for the main control chip STM32, and the 1.65V voltage is transmitted to each amplifier circuit as a reference voltage.

7. A scanning tunneling microscope control system based on STM32 according to claim 6, characterized in that: The power module includes: MP4462 chip and ME6211 chip; The MP4462 chip converts the input 15V voltage into a stable 5V output, which is provided to an external DAC chip, etc.; the ME6211 chip converts the input 5V voltage into a stable 3.3V output, which is provided to the main control chip STM32.

8. A scanning tunneling microscope control system based on STM32 according to claim 3, characterized in that: In the stepper motor module, the amplifier chip of the amplifier circuit is OPA602; In the scanning module, the amplifier chip of the amplifier circuit is OPA202.

9. A scanning tunneling microscope control system based on STM32 according to claim 4, characterized in that: The reduction circuit reduces the signal to between 0 and 3V through two OP07 chips.

10. The control method of a scanning tunneling microscope control system based on STM32 according to claim 7, characterized in that: The following steps are involved: S1, connect the upper and lower computers. After opening the upper computer software, turn on the power of the lower computer and connect the USB data cable to the USB port of the upper computer. S2, set the motor step parameters, the scanning mode options are: constant height scanning, constant current scanning; SetPoint sets the amplified tunnel current threshold. When the tunnel current is amplified and is greater than this voltage, it is considered that the motor step has been in place; S3, after the setting is completed, the stepper motor is controlled to step forward, and the DAC2 channel first outputs voltage to allow the scanning head to extend to probe. At the same time, the ADC1 channel collects the tunnel current and transmits it to the control software via USB. If the scanning head is extended to the end and still cannot detect, or the threshold voltage is still not reached, then DAC2 outputs 0 voltage to allow the scanning head to shrink back to the origin, and DAC1 starts to output a cycle of control signals to drive the motor to step down one step, and then DAC2 continues to output voltage to allow the scanning head to probe, and this process is repeated until the voltage converted by the tunnel current reaches the set threshold; S4, when the voltage converted by the tunnel current reaches the set threshold, the distance between the scanning head and the sample is sufficient to normally collect the tunnel current, and the sample begins to be scanned; S5, after the setting is completed, the scanning starts. The DACs of the two MCP4922 chips output the control waveforms in the X and Y directions of the scanning head respectively. The waveforms are triangular waves. At this time, the scanning head will scan the sample line by line, and use ADC1 to collect the tunnel current and transmit it to the control software via USB.

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