Method and apparatus for scanning probe imaging

Abstract

The present application is a kind of scanning probe imaging method and its device, belongs to the field of precision measurement.The device of the present application comprises: relatively movable carrier plane and sample table, feedback control system, data processing and storage system, power supply and motion control system and reference clock;probe array is fixed on the carrier plane, and the sample to be detected is fixed on the piezoelectric scanning table of the sample table.The method of the present application comprises: the distance sensing unit on each probe in the probe array generates a signal quantity related to the distance between the probe tip and the sample surface in a non-resonant manner, the feedback control system calculates the control signal driving the cantilever displacement according to the signal quantity, adjusts the signal quantity related to the distance to the set value, records the change quantity of the signal quantity in the scanning process, and realizes the imaging of the sample surface.The present application can realize high-throughput, nanometer to picometer level precision topography detection of large-scale high-density integrated probe array, avoid mechanical crosstalk, and realize high-speed imaging.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement technology, specifically relating to a method and apparatus for imaging using a scanning probe. Background Technology

[0002] Scanning probe microscopy (SPT) enables three-dimensional characterization and fabrication at the nanometer to sub-nanometer scales, making it an indispensable tool in cutting-edge scientific and technological fields such as advanced materials, chip manufacturing, and biomedical engineering. SPT encompasses all techniques that utilize micro / nanostructured probes and operate in a scanning manner, including but not limited to scanning tunneling microscopy, atomic force microscopy, and dip-pen lithography. Reference 1 provides a comprehensive overview of the types and principles of SPT.

[0003] Although scanning probe technology can achieve imaging with nanometer to picometer precision, it is limited by its principle of point-by-point measurement based on position scanning, making it difficult to achieve high-throughput detection with a single probe. Figure 1 This is a simplified schematic diagram of a single-probe scanning probe topography detection technology, mainly including a probe (tip, cantilever), feedback control, the surface to be detected, a position actuator, and a piezoelectric vibrator. The interaction between the probe tip and the surface to be detected generates a distance-dependent signal. For example, the vibration of the cantilever can be driven by the piezoelectric vibrator, and the resonant frequency of the cantilever is related to the distance between the probe tip and the surface to be detected. This vibration frequency can be read out by the piezoresistive effect, as described in Reference 2; or by the piezoelectric effect, as described in Reference 3; or by an optical method, as described in Reference 1. As the probe changes in spatial position, the change in the distance between the probe and the surface to be detected is reflected as a change in the signal. This signal is input into the feedback control system, which adjusts the position actuator to adjust the distance between the probe and the surface to be detected, thereby keeping the distance-dependent signal approximately at a set value. Throughout the probe scanning process, the change in the relative position of the probe and the sample actually reflects the change in the topography of the sample surface; therefore, the scanning probe can be used for imaging.

[0004] To achieve high-throughput detection, multiple probes can be used for parallel detection. In the case of multiple probes, the distance between each probe and the sample needs to be measured and controlled separately. Reference 4 introduces a method for parallel detection with multiple probes, which essentially replicates the aforementioned single-probe-based detection system, allowing multiple identical or similar systems to work synchronously. This method does not represent a breakthrough in principle, but mainly focuses on engineering optimization, and it is difficult to significantly increase the number of probes working in parallel. Reference 2 introduces a fully integrated technical solution in which a driving mechanism is integrated into the probe cantilever. Morphology measurement can be performed by simultaneously applying DC and AC signals. The principle is as follows: the DC signal controls the bending degree of the cantilever itself, thereby adjusting the distance between the probe and the sample; the AC signal excites the cantilever to resonate near its intrinsic frequency, which is related to the distance between the probe and the sample; by reading the vibration frequency of the probe and inputting the signal into the feedback system to adjust the DC signal, the vibration frequency can be maintained at a set value during the scanning process; the magnitude of the DC signal during the scanning process reflects the morphological changes of the sample.

[0005] Fully integrated schemes have the advantages of easy miniaturization and large-scale parallel integration. However, in the aforementioned fully integrated multi-probe parallel measurement technology, if the distance between two probes is close and they have the same or similar intrinsic frequencies, mechanical crosstalk will occur, affecting the accuracy of the measurement results. Reference 5 discloses a large-scale integrated scanning probe parallel measurement method. However, in this method, although the signal quantity related to distance is not obtained by monitoring the resonant frequency, the imaging mechanism does not involve the feedback control of each probe, so it cannot achieve accurate morphology measurement. At the same time, this scheme only needs to measure whether there is a depression on the sample, which can be regarded as a binary "present or absent" measurement, rather than an accurate analog quantity measurement of morphology.

[0006] The references are as follows:

[0007] [1] K. Bian, C. Gerber, AJ Heinrich, et al. Scanning probemicroscopy. Nature Reviews Methods Primers, (2021) 1:36.

[0008] [2] Publication No. EP2926199B1, Publication Date 2020.9.23, Photolithography method and photolithography apparatus for components and circuits with micron-scale and nanon-scale structural dimensions.

[0009] [3]Mahdavi M,Coskun MB,Moheimani S.High Dynamic Range AFM CantileverWith aCollocated Piezoelectric Actuator-Sensor Pair[J].Journal ofMicroelectromechanical Systems,2020,PP(99):1-8.

[0010] [4] H. Sadeghian, R. Herfst, B. Dekker, et al. High-throughput atomic forcemicroscopes operating in parallel, Review of Scientific Instruments, 88, 033703 (2017).

[0011] [5]Pozidis H, Haberle W, Wiesmann DW, et al.Demonstration of Thermomechanical Recording at 641Gbit / in 2 [J].IEEE Transactions on Magnetics,2004,40(4):2531-2536. Summary of the Invention

[0012] Currently, when using integrated probe arrays to perform parallel detection of sample surface morphology, problems such as mechanical crosstalk and resonance occur due to the small probe spacing and the probes having the same or similar intrinsic frequencies, making it impossible to accurately measure the sample. Therefore, this invention addresses the problem of how to use integrated probe arrays of various sizes to perform accurate high-throughput detection of sample surface morphology by disclosing a scanning probe imaging method and apparatus.

[0013] The present invention discloses a scanning probe imaging device, comprising a carrier plane and a sample stage that can be moved relatively between them, wherein:

[0014] A probe array is fixed on the plane of the carrier; each probe array contains at least 3 probes, and a distance sensing unit and a cantilever driving unit are integrated on the cantilever of each probe; the distance sensing unit generates a signal in a non-resonant manner, and the signal quantity is related to the distance from the probe tip to the sample surface; the cantilever driving unit receives a control signal sent by the feedback control system, drives the cantilever to move, and adjusts the distance from the probe tip to the sample surface so that the signal quantity output by the distance sensing unit is maintained at a set value;

[0015] The sample stage includes a piezoelectric scanning stage and a displacement device; the sample to be tested is fixed on the piezoelectric scanning stage, and the displacement device is located below the piezoelectric scanning stage; the height and tilt angle of the sample are adjusted by the sample stage; the vertical distance, horizontal distance and included angle between the carrier plane and the sample stage can be adjusted by the displacement device.

[0016] The scanning probe imaging apparatus of the present invention further includes a feedback control system, a data processing and storage system, a power supply and motion control system, and a reference clock; wherein:

[0017] The feedback control system reads the distance-related signal output from each probe in real time and calculates the control signal to drive the cantilever movement based on the signal.

[0018] The data processing and storage system saves the control signals output by the feedback control system as they change over time, the signal quantities output by each probe, and calculates the change in the distance between the probe tip and the sample surface during the scanning process to achieve imaging of the sample surface.

[0019] The power and motion control system provides power to the distance sensing unit, piezoelectric scanning stage and displacement device, feedback control system, data processing and storage system, and reference clock; the power and motion control system also controls the movement of the piezoelectric scanning stage and displacement device, and adjusts the distance between the carrier plane and the sample, so that the maximum distance between each probe tip and the sample surface does not exceed the maximum movement distance achieved by the cantilever drive unit.

[0020] The reference clock provides a unified time scale reference for power and motion control systems, data processing and storage systems, and feedback control systems.

[0021] Accordingly, the present invention provides a scanning probe imaging method, comprising the following steps:

[0022] Step 1: Fix the probe array on the plane of the carrier. Set a distance sensing unit and a cantilever driving unit on the cantilever of each probe. The distance sensing unit generates a signal quantity related to the distance from the probe tip to the sample surface in a non-resonant manner.

[0023] Step 2: The sample to be tested is fixed on the piezoelectric scanning stage. A displacement device is set under the piezoelectric scanning stage. The distance between the carrier plane and the sample stage is adjusted by the displacement device so that the maximum distance between each probe tip in the probe array and the sample surface does not exceed the maximum movement distance that the cantilever drive unit can achieve.

[0024] Step 3: Move the sample in the xy plane using a piezoelectric scanning stage. The distance sensing unit of each probe outputs the detected signal in real time and transmits it to the feedback control system. The feedback control system calculates and outputs the control signal to drive the cantilever displacement based on the signal and sends it to the cantilever drive unit. By driving the probe cantilever displacement, the distance between the probe tip and the sample surface is adjusted so that the signal output by the probe distance sensing unit is kept at the set value.

[0025] Step 4: Record the control signal output by the feedback control system that changes over time, as well as the signal output by each probe. Combine this with the change in the spatial position of the sample during the scanning motion, calculate the change in the distance from the probe tip to the sample surface during the scanning motion, and thus achieve image imaging of the sample surface.

[0026] Compared with the prior art, the advantages and positive effects of the present invention are as follows: (1) The device of the present invention uses an integrated probe array for multi-probe synchronous detection, which can realize ultra-large-scale probe integration and high-throughput, high-precision morphology detection, and can realize morphology detection with nanometer to picometer level precision. The device and method of the present invention can be applied to large-scale, high-density integrated probe arrays, such as probe spacing less than 200 micrometers and tens of thousands of probes. The imaging efficiency of each probe is similar to that of a single probe imaging system. Since each probe works in parallel at different spatial positions, the imaging speed of the overall system is roughly proportional to the scale of probe integration. (2) The distance adjustment mechanism based on cantilever drive of the present invention can be realized by mature semiconductor microelectromechanical integration technology, and the working efficiency of scanning probe imaging technology can be improved by several orders of magnitude. (3) In the probe array of the present invention, the distance sensing unit integrated on each probe outputs a signal related to the distance between the probe and the sample without the need for cantilever vibration, avoiding the mechanical crosstalk problem caused by the vibration of adjacent cantilever in the case of high-density (near distance) probe integration. Therefore, the present invention can not only achieve high-speed imaging, but also ensure imaging quality with nanometer to picometer precision. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a single-probe scanning probe imaging system;

[0028] Figure 2 This is a structural framework diagram of the scanning probe imaging device of the present invention;

[0029] Figure 3 These are the driving circuits and signal processing circuits of the scanning probe array and motion control component of the present invention.

[0030] In the picture:

[0031] 1-Probe tip; 2-Cantilever; 3-Distance sensing unit; 4-Cantilever drive unit; 5-Carrier plane; 6-Sample;

[0032] 7-Piezoelectric scanning stage; 8-Displacement device; 9-Feedback control system; 10-Power supply and motion control system;

[0033] 11-Data processing and storage system; 12-Reference clock. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0035] This invention provides a measurement and control method and apparatus for a large-scale integrated probe array, achieving high-throughput morphology detection with nanometer to picometer-level precision. High-throughput targets can be detected by multiple probes in parallel, using arrays of tens or even tens of thousands of probes. High-precision targets require measurement and control accuracy at the nanometer to picometer level. Depending on the integrated scale of the probes, the method of this invention can achieve a morphology detection speed several orders of magnitude faster than existing scanning probe detection methods.

[0036] like Figure 2 As shown, the scanning probe imaging device of the present invention includes: a probe array fixed to a carrier plane 5, wherein each probe consists of a probe tip 1, a cantilever 2, and a distance sensing unit 3 and a cantilever driving unit 4 integrated on the cantilever; a sample stage capable of moving in at least four spatial degrees of freedom for fixing a sample 6, the sample stage including a piezoelectric scanning stage 7 in the xy plane and a displacement device 8 in the z direction for adjusting the height and tilt angle of the sample. The sample 6 is fixed on the piezoelectric scanning stage 7, and the displacement device 8 is disposed below the piezoelectric scanning stage 7. The system coordinates of the scanning probe imaging device of this embodiment are as follows: Figure 2 As shown, the xy plane is parallel to the plane of the piezoelectric scanning stage 7, and the positive z-axis is perpendicular to the xy plane and pointing upwards.

[0037] For clarity of illustration, the embodiments of the present invention are presented in this way. Figure 2 The probe array consists of three probes arranged collinearly. In the implementation of this invention, each probe array contains at least three probes. Multiple probes can be non-collinearly arranged, but should be arranged coplanarly as much as possible to reduce systematic errors. In this embodiment, multiple probes being coplanar means that multiple probes are located on the same plane, such as a plane parallel to the sample, or a plane parallel to the xy-plane. Ideally, all probes are on the same plane.

[0038] Figure 2Only three probes are shown in the diagram to represent a multi-probe array. In the implementation of this invention, the probe array can be a single array or multiple arrays. The number of probes in each array must include at least three probes that can be measured and controlled independently. The specific number depends on the area of ​​the vehicle platform and the size of a single probe. There is no fixed total number limit.

[0039] When the probe array is not collinear, the relative position of the sample stage and the carrier plane 5 needs to be adjusted in at least five spatial degrees of freedom. This can be achieved by a piezoelectric scanning stage 7 in the xy plane plus three displacement devices 8 on the z-axis, or by a scanning stage 7 in the xy plane plus one z-axis displacement device 8 and two tilting stages. Similarly, Figure 2 The two z-axis displacement devices 8 in the diagram can also be replaced by one z-axis displacement device 8 and a tilting stage. For example... Figure 2 As shown, the piezoelectric scanning stage 7 allows adjustment of the sample's movement in the xy-plane, while the displacement device 8 allows adjustment of the sample's spatial position along the z-axis. Simultaneously, the displacement device 8 also enables adjustment of the sample in at least one rotational degree of freedom, which can be rotation around the x-axis, rotation around the y-axis, or rotation around both the x and y axes. The position of the carrier plane 5 can also be adjusted using an additional displacement device, but it is not shown in the figure.

[0040] Figure 2 The positions of the mid-range sensing unit 3 and the cantilever driving unit 4 relative to the cantilever 2 are for reference only. In the implementation of this invention, there is no strict limitation on the specific positions of the two. The distance sensing unit 3 and the probe tip 1 can be the same entity. For example, when the signal quantity related to distance is current, electrons are emitted from the probe tip 1 to the sample surface 6, and the probe tip 1 plays the role of the distance sensing unit 3, providing a signal quantity related to distance. Figure 2 The cantilever drive unit 4 shown may be, but is not limited to, a piezoelectric actuator, an electrothermal actuator, or an electrostatic actuator integrated on the cantilever 2. The cantilever drive unit 4 controls the displacement of the cantilever 2, thereby controlling the distance between the probe tip 1 and the surface of the sample 6.

[0041] like Figure 3 As shown, the scanning probe array driving circuit and signal processing circuit of the scanning probe imaging device of the present invention mainly include a distance sensing unit 3, a cantilever driving unit 4, a piezoelectric scanning stage 7 and a displacement device 8 of the sample stage, a feedback control system 9, a power supply and motion control system 10, a data processing and storage system 11, and a reference clock 12.

[0042] In measuring the distance between the probe and the sample, existing technologies, such as Reference 2, use an alternating current signal to excite cantilever resonance. The vibration frequency is related to the distance between the probe and the sample, and the distance value is obtained by reading the probe vibration frequency. This invention, however, eliminates the need for cantilever vibration. It detects the distance from the probe tip 1 to the sample surface 6 using a distance sensing unit, employing a non-resonant method. This can be based on, but is not limited to, thermal or electrical methods. For example, when there is a temperature difference between the probe and the surface being tested, as described in Reference 6, a temperature-sensitive resistor can be integrated on the probe to react to distance changes. The distance sensing unit 3 is a temperature-sensitive resistor, and the temperature difference is determined by measuring the resistance, thereby determining the distance between the probe tip 1 and the sample surface 6. When there is a potential difference between the probe and the surface being tested, the probe tip can emit electrons towards the surface, and the current magnitude is related to the distance. As described in Reference 7, the distance sensing unit 3 is integrated with the probe tip 1, and the distance is detected by the electron emission from the probe tip 1. The method of this invention avoids the mechanical crosstalk problem caused by the vibration of adjacent cantilever in the case of high-density (close-range) probe integration, thereby enabling not only high-speed imaging, but also ensuring imaging quality with nanometer to picometer precision.

[0043] References: 6: Williams CC, Wickramasinghe H K. Scanning thermal profiler[J]. Applied Physics Letters, 1986; 7: Behzadirad M, Mecholdt S, Randall JN, et al. Advanced Scanning Probe Nanolithography Using GaN Nanowires[J]. Nano letters, 2021(13):21.

[0044] In terms of control, microelectromechanical actuators based on piezoelectricity, thermal stress, electrostatic force and other methods can achieve stable and repeatable motion control of probes at the nanometer or even picometer level.

[0045] like Figure 3As shown, the feedback control system 9 reads the distance-related signal output by each probe in real time and calculates the control signal to drive the displacement of the cantilever 2 based on the signal. The data processing and storage system 11 saves the control signal output by the feedback control system as it changes over time, the signal output by each probe, and calculates the change in distance from the probe tip to the sample surface during the scanning process, thus achieving image imaging of the sample surface. The power and motion control system 10 supplies power to the distance sensing unit 3, the piezoelectric scanning stage 7 and the displacement device 8, the feedback control system 9, the data processing and storage system 11, and the reference clock 12. The power and motion control system 10 also controls the movement of the piezoelectric scanning stage 7 and the displacement device 8, adjusting the distance between the carrier plane 5 and the sample 6 so that the maximum distance between each probe tip 1 and the sample surface does not exceed the maximum movement distance achieved by the cantilever drive unit 4. The reference clock 12 provides a unified time scale reference for the power and motion control system 10, the data processing and storage system 12, and the feedback control system 9.

[0046] based on Figure 2 and Figure 3 The device shown, and the probe array measurement, control, and imaging method implemented by the present invention, can be as follows: Under the control of the power supply and motion control system 10, the piezoelectric scanning stage 7 and the displacement device 8 adjust the distance between the carrier plane 5 and the sample 6, ensuring that the maximum distance between each probe tip 1 in the probe array and the surface of the sample 6 does not exceed the maximum movement distance H achievable by the probe cantilever drive unit 4; the distance sensing unit 3 integrated on each probe, powered by the power supply and motion control system 10, measures the signal quantity S related to the distance from the probe tip 1 to the surface of the sample 6, and this signal quantity is provided to the feedback control system 9; as the relative position between the sample 6 and the carrier plane 5 changes, scanning motion is performed along the x-axis or y-axis direction. Due to the non-uniformity of the sample 6 surface morphology, the aforementioned signal quantity S may change; during the scanning process, the signal quantity S of each probe is transmitted to the feedback control system 9 in real time, and the signal quantity of the i-th probe can be marked as S. i Where i is a positive integer, the feedback control system 9 pairs each signal quantity S i The process involves sending a control signal C to the cantilever drive unit integrated on each probe arm. The control signal sent to the i-th probe can be labeled as C. i The control signal can drive the cantilever to move through the cantilever drive unit 4, adjusting the distance between the probe tip 1 and the sample 6, thereby increasing the signal quantity S output by each of the aforementioned distance sensing units 3. i Maintain the signal quantity S output by the distance sensing unit 3 at a set value, such as a preset constant value X. i Within the range [Xt, X+t], where t is the allowable floating range value; the control signal C for each cantilever 2. iThe changes over time are also transmitted to the data processing and storage system 11. Combined with the changes in spatial position information over time during the scanning motion, the overall measurement result can be obtained by stitching together the local morphology of the samples measured by each probe through data processing. The system clock 12 provides a unified time reference for the power supply and control unit 10, the feedback control system 9, and the data processing and storage system 11. After receiving the signal from the probe, the feedback control system 9 determines whether the signal exceeds the normal range. If it does, it indicates that there may be a problem with the current system, and the scanning needs to be stopped.

[0047] Except for the technical features described in the specification, all other technologies are known to those skilled in the art. Descriptions of well-known components and technologies are omitted in this invention to avoid redundancy and unnecessary limitation. The embodiments described above do not represent all embodiments consistent with this application. Various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this invention are still within the protection scope of this invention.

Claims

1. A scanning probe imaging device, characterized in that, The device includes: The system comprises a carrier plane and a probe array fixed to the carrier plane; each probe array contains at least three probes, and each probe's cantilever integrates a distance sensing unit and a cantilever driving unit; the distance sensing unit generates a signal in a non-resonant manner, the signal quantity of which is related to the distance from the probe tip to the sample surface; the cantilever driving unit receives a control signal sent by a feedback control system, drives the cantilever to move, and adjusts the distance from the probe tip to the sample surface, so that the signal quantity output by the distance sensing unit is maintained at a set value; The sample stage includes a piezoelectric scanning stage and a displacement device; the sample to be tested is fixed on the piezoelectric scanning stage, and the displacement device is located below the piezoelectric scanning stage; the height and tilt angle of the sample are adjusted by the sample stage. The feedback control system reads the distance-related signal output from each probe in real time and calculates and outputs the control signal to drive the cantilever movement based on the signal. The data processing and storage system saves the control signals output by the feedback control system as they change over time, as well as the signal quantities output by each probe. Based on the control signals, it calculates the change in the distance between the probe tip and the sample surface during the scanning process and images the sample surface. The power and motion control system provides power to the distance sensing unit, piezoelectric scanning stage and displacement device, feedback control system, data processing and storage system, and reference clock. The power and motion control system also controls the movement of the piezoelectric scanning stage and displacement device, and adjusts the distance between the carrier plane and the sample, so that the maximum distance between each probe tip and the sample surface does not exceed the maximum movement distance achieved by the cantilever drive unit. The reference clock provides a unified time scale reference for power and motion control systems, data processing and storage systems, and feedback control systems.

2. The apparatus according to claim 1, characterized in that, In the device described, the probes in each probe array are arranged collinearly or coplanarly.

3. The apparatus according to claim 1, characterized in that, The distance sensing unit uses thermal or electrical methods to acquire signal quantities related to the distance from the probe tip to the sample surface.

4. The apparatus according to claim 1 or 3, characterized in that, The distance sensing unit and the probe tip are the same entity. The probe tip emits electrons to the sample surface and obtains a current signal by utilizing the potential difference between the probe tip and the sample surface. This current signal changes with the distance between the probe tip and the sample surface.

5. The apparatus according to claim 1, characterized in that, The cantilever drive unit is a piezoelectric actuator, an electrothermal actuator, or an electrostatic actuator.

6. The apparatus according to claim 1, characterized in that, In the sample stage, the piezoelectric scanning stage adjusts the movement of the sample in the xy plane, and the displacement device realizes the spatial position adjustment of the sample in the z-axis direction and the adjustment of at least one rotational degree of freedom, the rotational degree of freedom including rotation about the x-axis and rotation about the y-axis; the xy plane is parallel to the piezoelectric scanning stage plane.

7. A scanning probe imaging method, characterized in that, Includes the following steps: Step 1: Fix a probe array on the carrier plane. Each probe array contains at least 3 probes. A distance sensing unit and a cantilever driving unit are set on the cantilever of each probe. The distance sensing unit generates a signal quantity related to the distance from the probe tip to the sample surface in a non-resonant manner. Step 2: The sample to be tested is fixed on the piezoelectric scanning stage. A displacement device is set under the piezoelectric scanning stage. The distance between the carrier plane and the sample stage is adjusted by the displacement device so that the maximum distance between each probe tip in the probe array and the sample surface does not exceed the maximum movement distance of the cantilever drive unit. Step 3: Move the sample in the xy plane using a piezoelectric scanning stage. The distance sensing unit of each probe outputs the detected signal in real time and transmits it to the feedback control system. The feedback control system calculates and outputs the control signal to drive the cantilever displacement based on the signal and sends it to the cantilever drive unit. The distance between the probe tip and the sample surface is adjusted by the probe cantilever displacement so that the signal output by the probe distance sensing unit is kept at the set value. Step 4: Record the control signal output by the feedback control system that changes over time, as well as the signal quantity output by each probe. Combine the change of the sample's spatial position over time during the scanning motion to calculate the change in the distance from the probe tip to the sample surface during the scanning process, thereby achieving image imaging of the sample surface.

8. The method according to claim 7, characterized in that, In step 1, the distance sensing unit of the probe and the probe tip are set to be the same entity. Electrons are emitted from the probe tip to the sample surface, and a current signal is obtained by utilizing the potential difference between the probe tip and the sample surface. The current signal changes with the distance between the probe tip and the sample surface.

9. The method according to claim 7, characterized in that, In step 3, during the scanning process, the movement of the sample in the xy plane is adjusted by the piezoelectric scanning stage, and the spatial position of the sample in the z-axis direction and at least one rotational degree of freedom are adjusted by the displacement device. The rotational degree of freedom includes rotation about the x-axis and rotation about the y-axis. The xy plane is parallel to the plane of the piezoelectric scanning stage.

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