Atomic force microscope operation method

Abstract

The invention provides an atomic force microscope operation method. The method comprises the following steps: selecting a sample, and setting an atomic force microscope detection mode; setting initial scanning parameters; scanning the surface topography, and calculating the resolution of a scanning result; scanning parameters are modified, scanning is carried out for multiple times, the abrasion loss of the probe is calculated, and scanning is ended when a certain duration is reached; according to the resolution ratio and the probe abrasion loss, the better scanning parameters are obtained, the corresponding scanning parameter combination can be determined according to the requirements of the resolution ratio and the probe abrasion loss, the high resolution ratio and the high detection effect are achieved, meanwhile, the abrasion of the probe is reduced, and the service life of the probe is prolonged.

Description

Technical Field

[0001] The invention belongs to the field of scanning probe measurement, relates to an atomic force microscope, and in particular to an atomic force microscope operating method. Background Art

[0002] Atomic force microscopy is a high-resolution microscope designed based on scanning tunneling microscopy. Atomic force microscopy generates an interaction force between the probe and the sample surface, and detects the interaction force by detecting the position and deformation of the probe, thereby generating an image or other characterization data of the sample surface.

[0003] The detection effect of atomic force microscopy varies greatly under different scanning parameters, so before scanning, it is necessary to optimize the scanning parameters to obtain better imaging effects. However, the existing scanning parameter optimization method mainly determines the better scanning parameters before the start of scanning, and does not take into account the wear of the probe tip during the scanning process. The wear of the probe tip is usually judged by experience or evaluated when the effect is significantly reduced. This will affect the reliability of the data before the wear reaches a significant level, thereby affecting the detection effect. In addition, the probe, as the core component of the atomic force microscope detection, is prone to wear. Unreasonable scanning parameters will greatly accelerate the wear of the probe tip, thereby affecting the detection effect.

[0004] Therefore, there is an urgent need for a scanning parameter optimization method for an atomic force microscope to obtain better detection effects and reduce probe wear.

[0005] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0006] In order to provide a scanning probe optimization method to obtain better detection effect and reduce the wear of the probe, the present invention provides an atomic force microscope operation method, comprising: S1: Determine that the detection position is set to a sample with a known surface structure; set the atomic force microscope to tapping mode; S2: Set the scanning parameters of the atomic force microscope; S3: enabling the probe to scan the surface of the sample for a preset time and a preset path, obtaining the surface morphology of the sample by scanning, and calculating the resolution of the surface morphology; S4: modify the scanning parameters, keep the preset time length and preset path unchanged, and perform S3 again; calculate the wear amount of the needle tip according to at least two groups of the surface morphologies obtained in S3; when the wear amount is greater than or equal to a preset threshold, enter S5; S5: According to the resolution and the wear amount, the corresponding scanning parameters are selected as scanning parameters of the atomic force microscope.

[0007] Preferably, the operation method further comprises: S6: determining that the detection position is set to a sample with an unknown surface structure, and after replacing the probe, using the scanning parameters obtained in S5 to scan the sample with an unknown surface structure.

[0008] Preferably, the scanning parameters include at least one of a free amplitude, a scanning frequency, and a set point.

[0009] Preferably, in S3, the preset path includes at least one straight line segment, and the probe scans the sample along the straight line segment to obtain a morphology curve; in S4, the wear amount of the probe is calculated based on the information of at least the peak of the morphology curve obtained by the adjacent S3.

[0010] Further preferably, the shape of the wave peak is used as the needle tip morphology of the probe, and the wear amount is calculated based on the needle tip morphology.

[0011] Optionally, the preset path includes multiple sub-paths, and at least two of the sub-paths are the same.

[0012] Preferably, the S3 further comprises: calculating the elastic coefficient of the probe during the scanning process; and the S4 further comprises: modifying the scanning parameters according to the elastic coefficient.

[0013] Preferably, the S3 further comprises: calculating the roughness of the surface topography, and calculating the resolution of the surface topography according to the roughness.

[0014] The present invention also provides an atomic force microscope, comprising: an operation unit and a storage unit, wherein the operation unit is communicatively connected to the storage unit, and the storage unit stores instructions that can be executed by the operation unit, so that the operation unit can execute the aforementioned atomic force microscope operation method.

[0015] The present invention also provides a non-volatile computer storage medium, wherein the non-volatile computer-readable storage medium stores at least one program, each of which includes instructions, which, when executed by a terminal, enable the terminal to execute the aforementioned atomic force microscope operation method.

[0016] The present invention has at least the following beneficial effects: it can obtain a more optimal combination of atomic force microscope scanning parameters, so that the user can determine the corresponding combination of scanning parameters according to the requirements of resolution and probe wear, thereby reducing probe wear and extending the probe life while having higher resolution and detection effect. DETAILED DESCRIPTION

[0017] To make the purpose and features of the present invention more obvious and understandable, the specific embodiments of the present invention are further described below. It should be noted that very simplified forms and inaccurate ratios are used only for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0018] The present invention provides an operation method of an atomic force microscope. Specifically, the operation method comprises: S1: Determine that the detection position is set to a sample with a known surface structure; set the atomic force microscope to tapping mode. More specifically, in order to make the surface structure of the detection position known, a sample with a known surface structure can be selected, or a partial area can be selected, and the detection position and subsequent scanning path are both located within the known area. Usually, a standard sample can be selected, or a sample that has been tested in other surface structure detection equipment can be selected. For the atomic force microscope, it can be an atomic force microscope that can only implement the tapping mode, or it can be an atomic force microscope with multiple scanning modes.

[0019] S2: Set the scanning parameters of the atomic force microscope. More specifically, when the atomic force microscope selects the tapping mode, the scanning parameters of the atomic force microscope include at least one of the free amplitude, scanning frequency, and set point. Among them, the free amplitude refers to the vibration amplitude of the probe when it is not in contact with the sample surface in the tapping mode; the scanning frequency refers to the frequency when the probe moves on the sample surface, that is, how many times the probe completes the scanning line process in a given time; the set point refers to the target value of the probe amplitude. When the needle is inserted, the atomic force microscope will bring the probe close to the sample until the probe amplitude decays from the free amplitude to the set point.

[0020] In addition, in some cases, the atomic force microscope can also be calibrated accordingly, for example, adjusting the laser beam so that it accurately illuminates the back of the probe; adjusting the position of the detector so that the laser spot is in the center of the sensitive area of ​​the detector, etc.

[0021] S3: The probe is made to scan the surface of the sample for a preset time and a preset path, the surface morphology of the sample is acquired through scanning, and the resolution of the surface morphology is calculated.

[0022] S4: modify the scanning parameters, keep the preset time length and preset path unchanged, and perform S3 again; calculate the wear amount of the needle tip based on at least two groups of the surface morphologies obtained in S3; when the wear amount is greater than or equal to a preset threshold, enter S5.

[0023] When the probe scans the surface of the object to be measured, the probe will gradually wear out. The data during the scanning process can be recorded to analyze the wear of the probe. More specifically, since the object to be measured with a known surface structure has been used as the detection object in S1, and the surface morphology of the object to be measured can be generally regarded as unchanged, the change in the surface morphology of the sample obtained by S3 mainly comes from the wear of the probe tip. More specifically, in the surface morphology image of the object to be measured obtained by scanning, the area such as the peak in the image can reflect the morphology of the probe tip, so that the morphology of the probe tip can be obtained based on this, and then by performing S3 multiple times and comparing the morphology of the probe tip, the amount of wear of the probe can be determined.

[0024] The preset threshold of the amount of wear can be set to one-fifth of the wear life of the probe. On the one hand, different scanning parameters can be tested before the performance of the probe has significantly decreased to find the best combination of scanning parameters. On the other hand, the wear of the probe tip is more obvious, so the wear is more significant in the early period of the probe's service life. When the probe is not used for a long time, the wear of the probe is difficult to measure. Therefore, a preset time of not less than one-fifth of the wear life of the probe is used, so that the wear of the probe can be detected during the rapid wear stage of the probe, and the wear data can be easily measured to reduce the error of the amount of wear. In addition, the amount of wear can be measured by the needle tip diameter of the probe, and correspondingly, the preset threshold can be expressed by the needle tip diameter of the probe. Of course, the corresponding preset threshold can also be set as needed, which will not be repeated here.

[0025] S5: According to the resolution and the amount of wear, the corresponding scanning parameters are selected as the scanning parameters of the atomic force microscope. More specifically, the aforementioned scanning parameters can be adjusted multiple times to directly obtain a parameter combination with better resolution and less wear, or the correlation between each scanning parameter and the amount of wear of the probe can be fitted, and the parameter combination with better resolution and less wear can be calculated based on the correlation. More specifically, the trade-off between resolution and wear can be determined by the user. For example, when the detection accuracy is higher, a higher resolution can be selected, and the wear can be minimized as much as possible on this basis.

[0026] According to the aforementioned atomic force microscope operation method, a more optimal combination of atomic force microscope scanning parameters can be obtained by systematically adjusting the scanning parameters and evaluating the detection resolution and probe wear, so that the user can determine the corresponding combination of scanning parameters according to the requirements of resolution and probe wear, thereby reducing probe wear and extending the probe life while obtaining high resolution and better detection effects, thereby achieving a high-efficiency and high-stability detection or imaging process.

[0027] The operation method further includes: S6: determining that the sample with unknown surface structure is set at the detection position, and after replacing the probe, using the scanning parameters obtained in S5 to scan the sample with unknown surface structure. When replacing the same type of probe for detection, the data obtained by the operation method provided by the present invention can be used to adjust the corresponding scanning parameter combination, or directly use the better scanning parameter combination obtained in S5, without having to find the appropriate parameters again, which greatly saves the experimental preparation time, and can also improve the detection accuracy and reduce the wear of the probe; in addition, since there is no need to try and error to find the better parameters, the damage to the sample surface can be reduced, especially for fragile or soft materials.

[0028] In S3, the preset path includes at least one straight line segment, and the probe scans the sample along the straight line segment to obtain a morphology curve; in S4, the morphology curve includes at least information of peaks obtained according to the adjacent S3, wherein, for a sample with a known surface morphology, the peaks can be used to determine the tip morphology of the probe in the surface morphology obtained by testing it, and then the wear amount of the probe can be calculated by comparing the tip morphology of the probe.

[0029] In addition, based on the surface topography image of the object to be measured, a straight line can be selected in the image, and the peak in the direction of the straight line can be obtained, and the topography of the probe tip can be calculated through the peak. In other words, a two-dimensional surface topography image can be obtained based on the three-dimensional surface topography image of the object to be measured, and the probe tip topography can be obtained using the two-dimensional image, and then the probe tip wear can be obtained by comparing the probe tip topography.

[0030] In some cases, the shape of the peak can be used as the tip morphology of the probe.

[0031] In order to improve the acquisition accuracy of the surface morphology image of the object to be measured, the preset path in S3 can also include multiple sub-paths, and at least two sub-paths can be made the same to avoid random errors in the probe detection process, and then avoid errors in the surface morphology data, so as to reduce the error in calculating the probe tip wear.

[0032] The S3 also includes: calculating the elastic coefficient of the probe during the scanning process. In an atomic force microscope, the elastic coefficient of the probe affects the mechanical response when the probe interacts with the sample, thereby affecting the detection result. When an atomic force microscope is actually used, in some cases, there is a certain difference between the actual elastic coefficient of the probe and the marked elastic coefficient, so it is necessary to correct the elastic coefficient of the probe. For a specific correction method, at least the following methods can be used: the signal of the light spot reflected by the probe and irradiated on the four-quadrant detector is collected, and the power spectrum of the voltage signal of the four-quadrant detector collected is calculated according to the preset sampling rate, minimum frequency resolution, sensitivity parameter, and frequency range, and then the elastic coefficient is calculated by the fitting parameters obtained after the power spectrum is Lorentz fitted. Of course, the elastic coefficient of the probe can also be corrected in other ways to obtain the actual elastic coefficient of the probe.

[0033] When S3 includes a step of acquiring or correcting the actual elastic coefficient of the probe, S4 may further include: modifying the scanning parameters according to the elastic coefficient obtained in S3 to further obtain a better combination of scanning parameters.

[0034] The S3 also includes: calculating the roughness of the surface topography, and calculating the resolution of the surface topography according to the roughness. The average height change of the surface of the object to be measured, that is, the average roughness, is calculated through the surface topography data of the object to be measured. More specifically, the average roughness is the average value of the absolute values ​​of all vertical deviations over a given length. When a known object to be measured is used as a standard sample, a relatively obvious mapping relationship can be generated between the roughness and the resolution. Specifically, the calculation result of the roughness is roughly proportional to the vertical resolution.

[0035] The present invention also provides an atomic force microscope, comprising: an operation unit and a storage unit, wherein the operation unit is communicatively connected to the storage unit, and the storage unit stores instructions that can be executed by the operation unit, so that the operation unit can execute the aforementioned atomic force microscope operation method.

[0036] More specifically, the operation unit usually refers to a microprocessor or a central processing unit, which can at least perform functions including controlling the scanning state and process of the atomic force microscope, data acquisition, image processing, roughness calculation, resolution evaluation and other analysis functions. The storage unit refers to the hardware used to store data and instructions, which can be a memory, a hard disk drive, a solid-state drive or any type of non-volatile storage medium. In an atomic force microscope, the storage unit is mainly used to store the operating system, application programs, measurement data and software instructions required to perform related operations. The communication connection between the operation unit and the storage unit ensures that data and instructions can be efficiently transmitted between the two. This connection can be achieved through a data bus, an interface or a network.

[0037] The present invention also provides a non-volatile computer storage medium, wherein the non-volatile computer-readable storage medium stores at least one program, each of which includes instructions, which, when executed by a terminal, enable the terminal to execute the aforementioned atomic force microscope operation method.

[0038] More specifically, when the program on the non-volatile computer storage medium is executed by the terminal, the following functions can be implemented: performing the scanning process of the atomic force microscope according to the scanning parameters set by the user, or the adjusted or optimized scanning parameters; processing the raw data collected by the atomic force microscope, and performing necessary analysis according to the built-in algorithm, for example, analyzing the surface morphology of the sample, the amount of probe wear, etc.; in some cases, the processed and analyzed data can also be displayed to the user in the form of graphics, text or reports, so that the user can plan corresponding operations, such as adjusting optimization parameters, etc.; in addition, in other cases, the operating status and operating mode of the atomic force microscope can also be adjusted according to the user's input.

[0039] The above shows and describes the basic principles, main features and advantages of the present invention, so the above is only an embodiment of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention also includes various equivalent changes and improvements, which will fall within the scope of the present invention to be protected.

Claims

1. A method for operating an atomic force microscope, characterized in that: include: S1: Determine that the detection position is set to a sample with a known surface structure; Set the AFM to tapping mode; S2: Set the scanning parameters of the atomic force microscope; S3: enabling the probe to scan the surface of the sample for a preset time and a preset path, obtaining the surface morphology of the sample by scanning, and calculating the resolution of the surface morphology; S4: modify the scanning parameters, keep the preset time length and preset path unchanged, and perform S3 again; calculate the wear amount of the needle tip according to at least two groups of the surface morphologies obtained in S3; when the wear amount is greater than or equal to a preset threshold, enter S5; S5: According to the resolution and the wear amount, the corresponding scanning parameters are selected as scanning parameters of the atomic force microscope.

2. The method for operating an atomic force microscope according to claim 1, characterized in that: The operation method further includes: S6: determining that the detection position is set to a sample with an unknown surface structure, and after replacing the probe, using the scanning parameters obtained in S5 to scan the sample with an unknown surface structure.

3. The method for operating an atomic force microscope according to claim 1, wherein: The scanning parameters include at least one of a free amplitude, a scanning frequency, and a set point.

4. The method for operating an atomic force microscope according to claim 1, wherein: In S3, the preset path includes at least one straight line segment, and the probe scans the sample along the straight line segment to obtain a topography curve; in S4, the wear amount of the probe is calculated based on the information of at least the peak of the topography curve obtained by the adjacent S3.

5. The method for operating an atomic force microscope according to claim 4, characterized in that: The shape of the wave peak is used as the needle tip morphology of the probe, and the wear amount is calculated according to the needle tip morphology.

6. The method for operating an atomic force microscope according to claim 1, wherein: The preset path includes multiple sub-paths, and at least two of the sub-paths are the same.

7. The method for operating an atomic force microscope according to claim 1, characterized in that: The S3 further includes: calculating the elastic coefficient of the probe during the scanning process; The S4 further includes: modifying the scanning parameters according to the elastic coefficient.

8. The method for operating an atomic force microscope according to claim 1, wherein: The S3 further includes: calculating the roughness of the surface topography, and calculating the resolution of the surface topography according to the roughness.

9. An atomic force microscope, characterized in that: include: An operation unit and a storage unit, wherein the operation unit is communicatively connected to the storage unit, and the storage unit stores instructions that can be executed by the operation unit, so that the operation unit can execute an atomic force microscope operation method according to any one of claims 1-8.

10. A non-volatile computer storage medium, characterized in that: The non-volatile computer-readable storage medium stores at least one program, each of which includes instructions, and when the instructions are executed by the terminal, the terminal executes an atomic force microscope operating method according to any one of claims 1-8.