Surface potential measuring method and device based on scanning probe microscope

Abstract

The invention provides a surface potential measurement method and device based on a scanning probe microscope, and the method comprises the steps: obtaining a time domain vibration signal of a probe on the scanning probe microscope when the probe vibrates on the surface of a sample to be measured, carrying out the frequency domain transformation processing of the time domain vibration signal, carrying out the first denoising processing of the frequency domain vibration signal, and carrying out the second denoising processing of the frequency domain vibration signal; carrying out filtering processing on the denoised frequency domain vibration signal through band-pass filtering; and calculating electrostatic force according to the filtered frequency domain vibration signal and a pre-tested frequency response function of the probe, and determining the surface potential of the to-be-tested sample based on the electrostatic force. According to the invention, after the frequency-domain vibration signal of the probe is denoised for the first time, the frequency-domain vibration signal after preliminary denoising is denoised again in a band-pass filtering mode, so that the signal-to-noise ratio of the vibration data of the probe can be improved, the denoising pertinence is enhanced, the denoising effect is improved, and the reliability of the probe is improved. Therefore, the problem of low time resolution of surface potential measurement in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of material testing, and in particular to a surface potential measurement method and device based on a scanning probe microscope. Background Art

[0002] Currently, Kelvin probe force microscopy (KPFM) can measure the distribution of surface potential of microscopic samples by measuring surface potential based on scanning probe microscopy. However, in the process of measuring surface potential, a phase-locked amplifier is required to measure the component with frequency ω, and a feedback system is required to measure the surface potential of the sample. However, the bandwidth of the phase-locked amplifier and the feedback system has limitations on the time resolution. Therefore, the time resolution of surface potential measured by KPFM is low, only on the order of milliseconds. In addition, the rapid free force reconstruction (F 3 R-KPFM (Fast Free Force Reconstruction-Kelvin Probe Force Microscopy) technology collects full-time domain data of probe vibration, directly calculates the electrostatic force acting on the probe from the vibration of the probe through a dynamic equation (constructed by a simple harmonic oscillator model), and then obtains the surface potential of the sample by fitting the calculated electrostatic force through a quadratic function. This method overcomes the problem of low time resolution of the surface potential and improves the time resolution because it no longer uses a phase-locked amplifier and feedback system. However, since the signal-to-noise ratio of the collected probe vibration data is usually low, the current method of removing noise is only through low-pass filtering, adding a threshold to the spectrum, and principal component analysis. This method has low specificity, unsatisfactory results, and may introduce some artifacts.

[0003] Therefore, the existing technology has defects and needs to be improved and developed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to resolve the problems in the prior art of low time resolution for measuring surface potential, low noise removal pertinence and unsatisfactory effect.

[0005] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0006] A method for measuring surface potential based on a scanning probe microscope, wherein the method comprises:

[0007] Acquire a time-domain vibration signal of a probe on a scanning probe microscope when it vibrates on the surface of a sample to be measured; wherein, after receiving a trigger signal from the scanning probe microscope, a signal generating device generates an excitation signal, transmits it to the scanning probe microscope, and applies it to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be measured;

[0008] Performing frequency domain transformation on the time domain vibration signal to obtain a frequency domain vibration signal representing vibration spectrum characteristics;

[0009] Performing a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, and filtering the denoised frequency domain vibration signal through a bandpass filter to obtain a filtered frequency domain vibration signal;

[0010] The electrostatic force on the probe is calculated according to the filtered frequency-domain vibration signal and a pre-tested frequency response function of the probe, and the surface potential of the sample to be tested is determined based on the electrostatic force.

[0011] In one implementation, obtaining a time-domain vibration signal of a probe on a scanning probe microscope when the probe vibrates on the surface of a sample to be measured includes:

[0012] A time domain vibration signal of a probe on a scanning probe microscope vibrating on the surface of a sample to be measured is acquired by a signal acquisition device.

[0013] In one implementation, the signal generating device is an arbitrary signal generator, the trigger signal is a pulse signal, and the excitation signal is a sinusoidal signal.

[0014] In one implementation, performing frequency domain transformation on the time domain vibration signal to obtain a frequency domain vibration signal representing vibration spectrum characteristics includes:

[0015] The time-domain vibration signal is subjected to frequency-domain transformation processing using a fast Fourier transform algorithm to obtain a frequency-domain vibration signal representing vibration spectrum characteristics.

[0016] In one implementation, performing a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal includes:

[0017] The frequency domain vibration signal is subjected to a first denoising process using a principal component analysis method to obtain a denoised frequency domain vibration signal.

[0018] In one implementation, the filtering of the denoised frequency domain vibration signal by bandpass filtering to obtain a filtered frequency domain vibration signal includes:

[0019] The denoised frequency domain vibration signal is filtered by bandpass filtering to obtain a filtered frequency domain vibration signal at a low frequency or one times the excitation frequency and a filtered frequency domain vibration signal at two times the excitation frequency.

[0020] In one implementation, determining the surface potential of the sample to be tested based on the electrostatic force includes:

[0021] A quadratic function fitting is performed on the electrostatic force to obtain the surface potential of the sample to be measured.

[0022] In one implementation, performing quadratic function fitting on the electrostatic force to obtain the surface potential of the sample to be tested includes:

[0023] The electrostatic force within a preset time period is selected, and a quadratic function fitting is performed on the electrostatic force within the preset time period based on a least squares method to obtain the surface potential of the sample to be measured.

[0024] In one implementation, the pre-tested frequency response function of the probe is a function tested by pre-calibrating the modal parameters of the probe.

[0025] The present invention also discloses a surface potential measurement device based on a scanning probe microscope, wherein the device comprises:

[0026] A vibration signal acquisition module is used to acquire a time-domain vibration signal of a probe on a scanning probe microscope when it vibrates on the surface of a sample to be measured; wherein, after receiving a trigger signal from the scanning probe microscope, the signal generating device generates an excitation signal, which is transmitted to the scanning probe microscope and applied to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be measured;

[0027] A frequency domain transformation module, configured to perform frequency domain transformation processing on the time domain vibration signal to obtain a frequency domain vibration signal representing the vibration spectrum characteristics;

[0028] a denoising module, configured to perform a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, and perform a filtering process on the denoised frequency domain vibration signal through a bandpass filter to obtain a filtered frequency domain vibration signal;

[0029] The surface potential measurement module is used to calculate the electrostatic force on the probe according to the filtered frequency domain vibration signal and the pre-tested frequency response function of the probe, and determine the surface potential of the sample to be tested based on the electrostatic force.

[0030] The present invention also discloses a terminal, which includes: a memory, a processor, and a surface potential measurement program based on a scanning probe microscope and bandpass filtering stored in the memory and runnable on the processor. When the surface potential measurement program based on a scanning probe microscope and bandpass filtering is executed by the processor, the steps of the surface potential measurement method based on a scanning probe microscope are implemented as described above.

[0031] The present invention also discloses a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program can be executed to implement the steps of the surface potential measurement method based on a scanning probe microscope as described above.

[0032] The present invention provides a surface potential measurement method and device based on a scanning probe microscope. The surface potential measurement method based on a scanning probe microscope includes: obtaining a time domain vibration signal of a probe on a scanning probe microscope when it vibrates on the surface of a sample to be measured; wherein, after receiving a trigger signal from the scanning probe microscope, an excitation signal generated by a signal generating device is transmitted to the scanning probe microscope and applied to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be measured; the time domain vibration signal is subjected to frequency domain transformation processing to obtain a frequency domain vibration signal characterizing the vibration spectrum characteristics; the frequency domain vibration signal is subjected to a first denoising processing to obtain a denoised frequency domain vibration signal, and the denoised frequency domain vibration signal is filtered by bandpass filtering to obtain a filtered frequency domain vibration signal; the electrostatic force applied to the probe is calculated according to the filtered frequency domain vibration signal and a frequency response function of the probe tested in advance, and the surface potential of the sample to be measured is determined based on the electrostatic force. It can be seen from this that after the present invention performs preliminary denoising on the frequency domain vibration signal of the probe, it further denoises the frequency domain vibration signal after preliminary denoising through bandpass filtering, thereby improving the signal-to-noise ratio of the probe vibration data, enhancing the denoising targeting, and improving the denoising effect, thereby solving the problems in the prior art of low time resolution of surface potential measurement, low noise removal targeting, and unsatisfactory effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of a preferred embodiment of the surface potential measurement method based on a scanning probe microscope in the present invention;

[0034] Figure 2 This is a schematic diagram of a specific surface potential measurement hardware connection disclosed in the present invention;

[0035] Figure 3 This is a schematic diagram of a periodic voltage signal disclosed in the present invention;

[0036] Figure 4It is a schematic diagram of an excitation signal and a time-domain vibration signal of a probe disclosed in the present invention;

[0037] Figure 5 Schematic diagram of vibration signal and electrostatic force through principal component analysis and bandpass filtering disclosed in the present invention;

[0038] Figure 6 Schematic diagram of the surface potential after applying a positive voltage and the surface potential after applying a negative voltage disclosed in the present invention;

[0039] Figure 7 Schematic diagram comparing surface potentials obtained by different methods disclosed in the present invention;

[0040] Figure 8 This is a schematic diagram of an image based on surface potential synthesis disclosed in the present invention;

[0041] Figure 9 This is a functional principle block diagram of a preferred embodiment of a surface potential measurement device based on a scanning probe microscope in the present invention;

[0042] Figure 10 It is a functional principle block diagram of a preferred embodiment of the terminal in the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clear and distinct, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] Currently, traditional Kelvin probe force microscopy measures the distribution of surface potential of microscopic samples and relies on the electrostatic force between the probe and the sample. The formula for the electrostatic force is as follows:

[0045]

[0046] Among them, F elec represents electrostatic force, C′ represents capacitance gradient, V tip Represents the voltage applied to the probe, V sample Represents the surface potential of the sample to be tested.

[0047] When a voltage V is applied to the probe tip =V0sinωt+V dc , then the component of the electrostatic force with frequency ω is:

[0048] F elec =-C′V0(V sample -V dc )sinωt;

[0049] Among them, Vdc represents the DC voltage, V0 represents the initial voltage, and the electrostatic force F elec Proportional to V dc With V sample The difference between the two, the frequency component of the probe vibration is proportional to V dc With V sample The difference between.

[0050] Then, by controlling this component to zero through the feedback system, the surface potential of the sample can be measured as:

[0051] V sample =V dc ;

[0052] Since a phase-locked amplifier is required to measure the component with a frequency of ω, and a feedback system is required to measure the surface potential of the sample, the bandwidth of both the phase-locked amplifier and the feedback system has limitations on the time resolution. Therefore, the time resolution of measuring the surface potential by KPFM is low, only on the order of milliseconds.

[0053] In addition, the existing rapid free force reconstruction technology collects the full time domain data of the probe vibration, and then directly constructs the dynamic equation by the simple harmonic oscillator model to calculate the electrostatic force acting on the probe from the full time domain data of the probe vibration.

[0054] When the voltage applied to the probe is V tip =V0sinωt, the calculated electrostatic force is passed through The surface potential of the sample can be obtained by fitting, that is, a quadratic function fitting is performed, and the symmetry axis is the surface potential.

[0055] This traditional method no longer uses a phase-locked amplifier and feedback system, and thus can improve the temporal resolution of the surface potential. However, since the signal-to-noise ratio of the collected probe vibration data is usually low, the rapid free force reconstruction technology only uses low-pass filtering, adding a threshold to the spectrum, and principal component analysis to remove noise. This method has low specificity, unsatisfactory effects, and may introduce some artifacts. To this end, the present application provides a surface potential measurement method based on a scanning probe microscope, which can improve the signal-to-noise ratio of the probe vibration data, enhance the specificity of denoising, and improve the denoising effect, thereby solving the problems of low temporal resolution of surface potential measurement, low specificity of noise removal, and unsatisfactory effects in the prior art.

[0056] See Figure 1 , Figure 1 FIG. 1 is a flow chart of the surface potential measurement method based on scanning probe microscopy in the present invention. Figure 1 As shown, the surface potential measurement method based on a scanning probe microscope according to an embodiment of the present invention includes:

[0057] Step S11, obtaining a time domain vibration signal of the probe on the scanning probe microscope when it vibrates on the surface of the sample to be measured; wherein, after receiving the trigger signal emitted by the scanning probe microscope, the signal generating device generates an excitation signal, which is transmitted to the scanning probe microscope and applied to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be measured.

[0058] In this embodiment, a scanning probe microscope transmits a trigger signal to a signal generating device. Upon receiving the trigger signal, the signal generating device generates an excitation signal and a periodic voltage signal. The excitation signal is transmitted to the scanning probe microscope and applied to the probe to generate vibration. The periodic voltage signal is then applied to the sample to be measured. A time-domain vibration signal of the scanning probe vibrating on the surface of the sample to be measured is then acquired. Specifically, the time-domain vibration signal of the scanning probe microscope vibrating on the surface of the sample to be measured is acquired by the signal acquisition device. It will be understood that a scanning probe microscope characterizes surface morphology or properties through physical or chemical interactions between the probe tip and the sample surface, such as electrostatic forces and van der Waals forces. In a dynamic mode, the probe typically vibrates at a fixed frequency, such as near its resonant frequency. When the probe approaches or contacts the surface of the sample to be measured, the vibration characteristics, such as amplitude, phase, and frequency, change due to the interaction. Therefore, the time-domain vibration signal of the scanning probe is acquired so that the surface potential can be subsequently measured based on the time-domain vibration signal.

[0059] It should be pointed out that the probe does not vibrate all the time. It will only vibrate after applying an excitation signal to the probe, such as applying an AC voltage. That is, when applying an AC voltage to the probe, the probe will be subjected to periodically changing electrostatic force, causing vibration. In addition, the probe needs to maintain a certain distance from the surface of the sample to be tested, otherwise the vibration of the probe will be significantly interfered with by the sample to be tested.

[0060] In this embodiment, the signal generating device can be an arbitrary signal generator, that is, the arbitrary signal generator generates an excitation signal and a periodic voltage signal after receiving a trigger signal emitted by the scanning probe microscope, and the excitation signal is transmitted to the scanning probe microscope and applied to the probe, and the periodic voltage signal is applied to the sample to be tested. At the same time, the excitation signal and the periodic voltage signal are collected by the signal acquisition device, as well as the time domain vibration signal of the probe on the scanning probe microscope on the surface of the sample to be tested. The three collected signals are transmitted to a computer capable of data processing for data processing, and the computer performs subsequent data processing operations on the time domain vibration signal.

[0061] The trigger signal sent at the beginning of each line scanned by the scanning probe microscope may be a pulse signal, and the excitation signal generated by the arbitrary signal generator after receiving the trigger signal sent by the scanning probe microscope may be a sinusoidal signal.

[0062] For example, see Figure 2 As shown, the working parameters of the SPM (Scanning Probe Microscope) are set by a computer, and the SPM starts scanning. A pulse is sent as a trigger signal at the beginning of each line scanned by the SPM. After the AWG (Arbitrary Waveform Generator) receives the trigger signal, the AWG generates a sinusoidal signal and a periodic stimulation signal (periodic voltage signal), respectively. The sinusoidal signal is connected to the SPM and finally applied to the probe. The periodic voltage signal, such as the square wave signal, is applied to the sample to be tested, and the AWG also simultaneously collects these two signals and the vibration signal of the SPM probe. Then, after each line of scanning is completed, the AWG transmits the collected sinusoidal signal, square wave signal and vibration signal of the probe to the computer for subsequent data processing, that is, the computer obtains the vibration signal of the probe collected by the AWG for data processing.

[0063] In a test, the collected periodic voltage signal, that is, the square wave voltage signal is as follows Figure 3 As shown, the collected excitation signal and the probe's time domain vibration signal are as follows Figure 4 As shown, in this test, the SPM scans a row of periodic voltage signals applied to the sample to be tested for a total of 125 cycles, and the figure shows the signals in two of the cycles.

[0064] Step S12: performing frequency domain transformation processing on the time domain vibration signal to obtain a frequency domain vibration signal representing vibration spectrum characteristics.

[0065] In this embodiment, after obtaining the time domain vibration signal of the probe on the scanning probe microscope when it vibrates on the surface of the sample to be measured, the time domain vibration signal is subjected to frequency domain transformation processing to obtain a frequency domain vibration signal that characterizes the vibration spectrum characteristics. Specifically, the time domain vibration signal is subjected to frequency domain transformation processing using a fast Fourier transform algorithm to obtain a frequency domain vibration signal that characterizes the vibration spectrum characteristics. It can be understood that by transforming the probe's time domain vibration data into the frequency domain through fast Fourier transform, frequency domain analysis can remove noise through filtering, improve measurement accuracy, thereby improving the signal-to-noise ratio and separating different frequency components.

[0066] Step S13: performing a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, and filtering the denoised frequency domain vibration signal through bandpass filtering to obtain a filtered frequency domain vibration signal.

[0067] In this embodiment, after the vibration data of the probe is transformed from the time domain to the frequency domain, the frequency domain vibration signal is subjected to a first denoising process. Specifically, the frequency domain vibration signal is subjected to a first denoising process using the principal component analysis method to obtain a denoised frequency domain vibration signal, and then the denoised frequency domain vibration signal is filtered by bandpass filtering to obtain a filtered frequency domain vibration signal, and the filtered frequency domain vibration signal is mainly distributed at the low frequency or the one-time frequency and the two-time frequency of the excitation frequency, that is, the denoised frequency domain vibration signal is filtered by bandpass filtering to obtain a filtered frequency domain vibration signal at the low frequency or the one-time frequency of the excitation frequency and a filtered frequency domain vibration signal at the two-time frequency. It is understandable that the frequency domain signal of the probe may contain thermal noise and circuit noise, etc. The principal component of the interaction between the probe resonance peak and the sample is separated by principal component analysis to remove high-frequency random noise, but retaining too many principal components will result in incomplete denoising, so further filtering and denoising can be performed by bandpass filtering, thereby effectively improving the signal quality and laying the foundation for subsequent surface potential test analysis.

[0068] It should be pointed out that principal component analysis is a statistical method that projects high-dimensional data into a low-dimensional space through linear transformation, retaining the direction with the largest variance in the data, namely the principal component, thereby extracting the main features and removing redundancy or noise. In other words, it finds the main direction of change of the data (principal component) and ignores the secondary direction (usually corresponding to noise). The principal component analysis method retains the main features, thereby avoiding the signal distortion that may be caused by traditional filtering methods, such as low-pass filtering.

[0069] For example, see Figure 5 As shown in FIG, according to the spectrum analysis of the electrostatic force, it can be known that the frequency domain data of the electrostatic force are distributed at low frequencies or the one and two times of the excitation frequency, so the denoised frequency domain vibration signal obtained by the PCA (Principal Component Analysis) method can be filtered by digital bandpass filtering, and the rest can be filtered out, leaving the frequency domain vibration signal distributed at low frequencies or the one and two times of the excitation frequency.

[0070] Step S14: calculating the electrostatic force on the probe according to the filtered frequency-domain vibration signal and the pre-tested frequency response function of the probe, and determining the surface potential of the sample to be tested based on the electrostatic force.

[0071] In this embodiment, the denoised frequency-domain vibration signal is filtered using bandpass filtering to obtain a filtered frequency-domain vibration signal. The electrostatic force acting on the probe can then be calculated based on the filtered frequency-domain vibration signal and a pre-tested frequency response function of the probe. The pre-tested frequency response function of the probe is a function obtained by pre-calibrating the modal parameters of the probe, and the modal parameters of the probe may include, but are not limited to, mode shapes and natural frequencies.

[0072] It should be pointed out that the frequency response function is an inherent characteristic of the system, related to the system itself, and has nothing to do with external factors such as excitation and response. For the probe, its frequency response function reflects the dynamic characteristics of the probe itself. At the same time, the frequency response function is reciprocal, which means that the frequency response function matrix is symmetrical. This means that when applying excitation and measuring responses at different positions, the resulting frequency response functions are equivalent under certain conditions. To obtain the frequency response function of the probe, it is first necessary to excite the probe and measure its response. A suitable excitation method can be used to apply force to the probe. At the same time, a sensor is used to measure the response of the probe at different positions. The measured time domain data is converted to the frequency domain to obtain complex frequency response data. The multiple measured frequency response functions are usually represented in matrix form. By analyzing and processing these data, combined with the theoretical expression of the frequency response function, appropriate mathematical methods such as the least squares method are used to fit and calculate the various parameters of the frequency response function, thereby determining the frequency response function of the probe.

[0073] In this embodiment, after the electrostatic force is calculated based on the filtered frequency-domain vibration signal and the frequency response function, the surface potential of the sample to be tested is determined based on the electrostatic force. Specifically, a quadratic function is fitted to the electrostatic force to obtain the surface potential of the sample to be tested. For example, the electrostatic force within a preset time period is selected, and a quadratic function is fitted to the electrostatic force within the preset time period based on the least squares method to obtain the surface potential of the sample to be tested.

[0074] For example, the collected data is (x i ,y i ),i=1,2,…,n, where x i is the magnitude of the AC voltage applied to the probe, y i To calculate the electrostatic force on the probe, the quadratic function to be fitted is: y = ax 2 +bx+c, the fitted value of the coefficient should be Minimum, so the surface potential is: That is, by changing the AC voltage applied to the probe, measuring the electrostatic force, fitting a quadratic function, and using the coefficient relationship to calculate the surface potential.

[0075] It should be noted that after determining the surface potential of the sample to be tested, images with temporal and spatial resolution can be synthesized. For example, by processing the probe's vibration data 100 μs after the falling edge of the square wave at each pixel, images of the surface potential distribution at different locations during this time can be obtained. By synthesizing these images at different moments, a video of the sample's surface potential evolution can be obtained. To ensure that the selected vibration data contains at least one complete parabola, the time range of the selected vibration data should be at least greater than or equal to one cycle of the excitation signal.

[0076] Furthermore, in one test, a periodic voltage signal (square wave voltage signal) is applied to the sample to be tested, and the surface potential corresponding to the positive half-cycle voltage signal and the negative half-cycle voltage signal of the square wave voltage signal applied to the sample to be tested is obtained according to the surface potential test scheme of the present application. Figure 6 shown.

[0077] See also Figure 7 As shown in FIG, the surface potential of the sample to be tested obtained by bandpass filtering is compared with the surface potential of the sample to be tested obtained by lowpass filtering combined with threshold filtering. It can be seen that bandpass filtering has a better noise removal effect, and, see Figure 8 As shown in the figure, the image synthesized by bandpass filtering to obtain the surface potential of the sample to be tested is compared with the image synthesized by low-pass filtering combined with threshold filtering to obtain the surface potential of the sample to be tested. It can be seen that bandpass filtering greatly increases the clarity of the test results and significantly improves the spatial resolution capability of the test method.

[0078] It can be seen that in the embodiment of the present invention, the time domain vibration signal of the probe on the scanning probe microscope is obtained when it vibrates on the surface of the sample to be measured, the time domain vibration signal is subjected to frequency domain transformation processing, the frequency domain vibration signal is subjected to the first denoising processing, and the denoised frequency domain vibration signal is filtered by bandpass filtering; the electrostatic force is calculated based on the filtered frequency domain vibration signal and the frequency response function of the probe tested in advance, and the surface potential of the sample to be measured is determined based on the electrostatic force. It can be seen that after the frequency domain vibration signal of the probe is denoised for the first time, the present invention further denoises the frequency domain vibration signal after the initial denoising by bandpass filtering, thereby improving the signal-to-noise ratio of the probe vibration data, enhancing the targeted denoising, and improving the denoising effect, thereby solving the problems in the prior art of low time resolution for measuring surface potential, low targeted noise removal, and unsatisfactory effect.

[0079] In one embodiment, if Figure 9 As shown, based on the above-mentioned surface potential measurement method based on a scanning probe microscope, the present invention also provides a surface potential measurement device based on a scanning probe microscope, comprising:

[0080] The vibration signal acquisition module 11 is used to obtain the time domain vibration signal of the probe on the scanning probe microscope when it vibrates on the surface of the sample to be tested. After receiving the trigger signal from the scanning probe microscope, the signal generating device transmits the excitation signal generated by the signal generating device to the scanning probe microscope and applies the excitation signal to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be tested.

[0081] A frequency domain transformation module 12 is used to perform frequency domain transformation processing on the time domain vibration signal to obtain a frequency domain vibration signal representing the vibration spectrum characteristics;

[0082] a denoising module 13 configured to perform a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, and to filter the denoised frequency domain vibration signal through a bandpass filter to obtain a filtered frequency domain vibration signal;

[0083] The surface potential measurement module 14 is configured to calculate the electrostatic force exerted on the probe according to the filtered frequency-domain vibration signal and the pre-tested frequency response function of the probe, and determine the surface potential of the sample to be measured based on the electrostatic force.

[0084] In some specific embodiments, the vibration signal acquisition module 11 may specifically include:

[0085] The signal acquisition unit is used to acquire the time domain vibration signal of the probe on the scanning probe microscope collected by the signal acquisition device when the probe vibrates on the surface of the sample to be measured.

[0086] In some specific embodiments, the frequency domain transformation module 12 may specifically include:

[0087] The frequency domain transform unit is used to perform frequency domain transform processing on the time domain vibration signal using a fast Fourier transform algorithm to obtain a frequency domain vibration signal representing the vibration spectrum characteristics.

[0088] In some specific embodiments, the denoising module 13 may specifically include:

[0089] The first denoising unit is used to perform a first denoising process on the frequency domain vibration signal by using a principal component analysis method to obtain a denoised frequency domain vibration signal.

[0090] In some specific embodiments, the denoising module 13 may specifically include:

[0091] The second denoising unit is used to filter the denoised frequency domain vibration signal through bandpass filtering to obtain a filtered frequency domain vibration signal at a low frequency or one times the excitation frequency and a filtered frequency domain vibration signal at two times the excitation frequency.

[0092] In some specific embodiments, the surface potential measurement module 14 may specifically include:

[0093] The fitting unit is used to perform quadratic function fitting on the electrostatic force to obtain the surface potential of the sample to be measured.

[0094] In some specific embodiments, the fitting unit is specifically used to:

[0095] The electrostatic force within a preset time period is selected, and a quadratic function fitting is performed on the electrostatic force within the preset time period based on a least squares method to obtain the surface potential of the sample to be measured.

[0096] Figure 10 This is a schematic diagram of the structure of a terminal provided in an embodiment of the present application. The terminal may include:

[0097] Memory 501 , processor 502 , and computer programs stored in the memory 501 and executable on the processor 502 .

[0098] When the processor 502 executes the program, the surface potential measurement method based on the scanning probe microscope provided in the above embodiment is implemented.

[0099] Furthermore, the terminal further includes:

[0100] The communication interface 503 is used for communication between the memory 501 and the processor 502 .

[0101] The memory 501 is used to store computer programs that can be run on the processor 502 .

[0102] The memory 501 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0103] If the memory 501, processor 502, and communication interface 503 are implemented independently, the communication interface 503, memory 501, and processor 502 can be interconnected via a bus to enable communication between them. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. Buses can be classified as address buses, data buses, control buses, etc. For ease of illustration, the figure shows only one line, but this does not mean that there is only one bus or only one type of bus.

[0104] Optionally, in a specific implementation, if the memory 501, the processor 502 and the communication interface 503 are integrated on a chip, the memory 501, the processor 502 and the communication interface 503 can communicate with each other through an internal interface.

[0105] The processor 502 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0106] This embodiment further provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the surface potential measurement method based on a scanning probe microscope is implemented as described above.

[0107] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the claims.

[0108] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" 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 application. In this specification, the schematic expressions of the above terms do 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 N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein may be considered, for example, as a sequenced list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can read and execute instructions from an instruction execution system, apparatus, or device).

[0110] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiment, the N steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field-programmable gate array (FPGA), etc.

[0111] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A surface potential measurement method based on a scanning probe microscope, characterized in that: The method comprises: Acquire a time-domain vibration signal of a probe on a scanning probe microscope when it vibrates on the surface of a sample to be measured; wherein, after receiving a trigger signal from the scanning probe microscope, a signal generating device generates an excitation signal, transmits it to the scanning probe microscope, and applies it to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be measured; Performing frequency domain transformation on the time domain vibration signal to obtain a frequency domain vibration signal representing vibration spectrum characteristics; Performing a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, and filtering the denoised frequency domain vibration signal through a bandpass filter to obtain a filtered frequency domain vibration signal; The electrostatic force on the probe is calculated according to the filtered frequency-domain vibration signal and a pre-tested frequency response function of the probe, and the surface potential of the sample to be tested is determined based on the electrostatic force.

2. The surface potential measurement method based on a scanning probe microscope according to claim 1, characterized in that: The step of obtaining a time domain vibration signal of a probe on a scanning probe microscope when the probe vibrates on the surface of a sample to be measured comprises: A time domain vibration signal of a probe on a scanning probe microscope vibrating on the surface of a sample to be measured is acquired by a signal acquisition device.

3. The surface potential measurement method based on scanning probe microscopy according to claim 2, characterized in that: The signal generating device is an arbitrary signal generator, the trigger signal is a pulse signal, and the excitation signal is a sinusoidal signal.

4. The surface potential measurement method based on a scanning probe microscope according to claim 1, characterized in that: The step of performing frequency domain transformation processing on the time domain vibration signal to obtain a frequency domain vibration signal representing vibration spectrum characteristics includes: The time-domain vibration signal is subjected to frequency-domain transformation processing using a fast Fourier transform algorithm to obtain a frequency-domain vibration signal representing vibration spectrum characteristics.

5. The surface potential measurement method based on scanning probe microscopy according to claim 1, characterized in that: The first denoising process is performed on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, comprising: The frequency domain vibration signal is subjected to a first denoising process using a principal component analysis method to obtain a denoised frequency domain vibration signal.

6. The surface potential measurement method based on scanning probe microscopy according to claim 1, characterized in that: The filtering process of the denoised frequency domain vibration signal by bandpass filtering to obtain a filtered frequency domain vibration signal includes: The denoised frequency domain vibration signal is filtered by bandpass filtering to obtain a filtered frequency domain vibration signal at a low frequency or one times the excitation frequency and a filtered frequency domain vibration signal at two times the excitation frequency.

7. The surface potential measurement method based on a scanning probe microscope according to claim 1, characterized in that: Determining the surface potential of the sample to be tested based on the electrostatic force includes: A quadratic function fitting is performed on the electrostatic force to obtain the surface potential of the sample to be measured.

8. The surface potential measurement method based on scanning probe microscopy according to claim 7, characterized in that: The performing quadratic function fitting on the electrostatic force to obtain the surface potential of the sample to be measured includes: The electrostatic force within a preset time period is selected, and a quadratic function fitting is performed on the electrostatic force within the preset time period based on a least squares method to obtain the surface potential of the sample to be measured.

9. The surface potential measurement method based on a scanning probe microscope according to any one of claims 1 to 8, characterized in that: The pre-tested frequency response function of the probe is a function tested by pre-calibrating the modal parameters of the probe.

10. A surface potential measurement device based on a scanning probe microscope, characterized in that: The device comprises: A vibration signal acquisition module is used to acquire a time-domain vibration signal of a probe on a scanning probe microscope when it vibrates on the surface of a sample to be measured; wherein, after receiving a trigger signal from the scanning probe microscope, the signal generating device generates an excitation signal, which is transmitted to the scanning probe microscope and applied to the probe to generate vibration, and the generated periodic voltage signal is applied to the sample to be measured; A frequency domain transformation module, configured to perform frequency domain transformation processing on the time domain vibration signal to obtain a frequency domain vibration signal representing the vibration spectrum characteristics; a denoising module, configured to perform a first denoising process on the frequency domain vibration signal to obtain a denoised frequency domain vibration signal, and perform a filtering process on the denoised frequency domain vibration signal through a bandpass filter to obtain a filtered frequency domain vibration signal; The surface potential measurement module is used to calculate the electrostatic force on the probe according to the filtered frequency domain vibration signal and the pre-tested frequency response function of the probe, and determine the surface potential of the sample to be tested based on the electrostatic force.

Images