Method for detecting pollution degree of probe of atomic force microscope and cleaning pollutants of probe of atomic force microscope

Abstract

The invention relates to the field of atomic force microscopes, and provides a method for detecting the pollution degree of an atomic force microscope probe and cleaning pollutants of the atomic force microscope probe, and the detection method comprises the steps: obtaining a first fluorescence signal of a probe insertion section when the probe is inserted, and obtaining a second fluorescence signal of a termination section; and comparing the first fluorescence signal with the second fluorescence signal, and determining the pollution degree of the probe. According to the detection method, the pollution degree of the atomic force microscope probe can be accurately judged, the pollution degree of the probe can be known only by inserting the probe once, the efficiency is high, quantitative comparison is facilitated, the method can be used for real-time monitoring of the pollution degree of the probe, and the detection accuracy is improved. Therefore, the cleaning opportunity of the probe is automatically judged, and the end point of the probe cleaning operation is automatically judged.

Description

Technical Field

[0001] The present invention relates to the field of atomic force microscopy, and in particular to a method for detecting the degree of contamination of an atomic force microscope probe and cleaning contaminants from the atomic force microscope probe. Background Art

[0002] Atomic force microscopy (AFM) is a high-resolution scanning probe microscopy technique widely used in materials science, nanotechnology, biology, and physics. AFM uses the interaction between the probe and the sample surface to obtain information about the surface morphology and physical properties of the sample.

[0003] In practical AFM applications, the probe is susceptible to contamination during the scanning process. For example, when scanning samples containing organic molecules (such as proteins, lipids, and polysaccharides) or biomolecules, these molecules will adsorb to the probe surface. When residual moisture remains on the sample surface, dissolved substances in the water (such as salts and minerals) will deposit on the probe. When scanning soft materials such as polymers and gels, molecules or fragments on the sample surface will transfer to the probe tip. Metal or metal oxide particles can also adhere to the probe during scanning, especially when the sample surface is uneven or has rough areas. Under extreme temperature conditions, the chemical properties of the sample surface change, causing more contaminants to adhere to the probe. Contaminants on the AFM probe tip typically include organic contaminants (such as organic solvent residues, oils and fats, biomolecules, and organic coatings), inorganic contaminants (such as metal ions, oxide particles, and mineral salts), residual moisture on the sample surface, electrolytes in the water (such as sodium, potassium, and calcium ions), and nanoparticles (such as carbon nanotubes, graphene sheets, and metal nanoparticles).

[0004] However, the detection method for the degree of contamination of atomic force microscope probes still needs to be studied. Summary of the Invention

[0005] The present application aims to solve the technical problems existing in the prior art at least to a certain extent. To this end, the present application proposes a method for detecting the degree of contamination of an atomic force microscope probe and cleaning contaminants in an atomic force microscope probe. The detection method of the present application can accurately determine the degree of contamination of the atomic force microscope probe. Only one needle insertion is required to understand the degree of contamination of the probe. It is highly efficient and convenient for quantitative comparison. It can be used for real-time monitoring of the degree of contamination of the probe, thereby automatically determining the timing of cleaning the probe and the end point of the probe cleaning operation. In this way, it is ensured that the probe can provide accurate and reliable data in subsequent measurement and imaging tasks, thereby improving the overall performance of the atomic force microscope and the credibility of the experimental results.

[0006] In one aspect, the present application provides a method for detecting the degree of contamination of an atomic force microscope probe. According to an embodiment of the present application, the method includes: acquiring a first fluorescent signal during the insertion phase and a second fluorescent signal during the termination phase of the probe; and comparing the first and second fluorescent signals to determine the degree of contamination of the probe.

[0007] The presence of contaminants on the probe surface can alter the physical and chemical properties of the interaction between the probe and the sample, thereby affecting changes in fluorescence intensity. By comparing the changes in the fluorescence signal during the probe's insertion and termination phases, the degree of probe contamination can be accurately determined, ensuring that the probe provides accurate and reliable data in subsequent measurement and imaging tasks, thereby improving the overall performance of the atomic force microscope and the credibility of experimental results.

[0008] According to an embodiment of the present application, the probe is selected from transparent probes with fluorescent light-emitting substances inside.

[0009] According to an embodiment of the present application, the fluorescent light-emitting object is an NV color center.

[0010] According to an embodiment of the present application, the atomic force microscope is selected from a scanning NV probe microscope.

[0011] According to an embodiment of the present application, the first fluorescent signal and the second fluorescent signal each independently include a curve of a change in fluorescence intensity value relative to time.

[0012] According to an embodiment of the present application, the comparison of the first fluorescence signal and the second fluorescence signal includes: obtaining a first change curve of the fluorescence intensity value of the probe relative to time in an uncontaminated state, obtaining a second change curve of the current fluorescence intensity value of the probe relative to time, and comparing the first change curve and the second change curve.

[0013] According to an embodiment of the present application, the first change curve and the second change curve independently and sequentially include a needle insertion segment, a characteristic segment and a termination segment, the needle insertion segment corresponds to the time period when the probe is inserted into the needle in a non-contaminated state, the termination segment corresponds to the time period after the probe terminates the insertion of the needle in the non-contaminated state, and the characteristic segment is the critical time period between the needle insertion segment and the termination segment; the characteristic segment contains a characteristic peak, and the peak value of the characteristic peak is greater than the peak values of the needle insertion segment and the termination segment.

[0014] According to an embodiment of the present application, the method includes: obtaining a first change curve of the fluorescence intensity value of the probe relative to time in a non-contaminated state, and obtaining a second change curve of the current fluorescence intensity value of the probe relative to time; obtaining the difference in the average fluorescence intensity between the needle insertion segment and the terminal segment of the first change curve, recorded as the first difference; obtaining the difference in the average fluorescence intensity between the needle insertion segment and the terminal segment of the second change curve, recorded as the second difference; determining the degree of contamination of the probe based on the difference or ratio of the first difference and the second difference.

[0015] According to an embodiment of the present application, when the difference or ratio between the first difference and the second difference is greater than or equal to a first threshold, it is determined that the probe is not contaminated; when the difference or ratio between the first difference and the second difference is less than or equal to a second threshold, it is determined that the probe is contaminated.

[0016] According to an embodiment of the present application, the method includes: obtaining a first change curve of the fluorescence intensity value of the probe in a non-contaminated state relative to time, and obtaining a second change curve of the current fluorescence intensity value of the probe relative to time; based on the first change curve, judging whether the characteristic segment appears in the second change curve, and determining the degree of contamination of the probe.

[0017] According to an embodiment of the present application, when the characteristic segment does not appear in the second variation curve, it is determined that the probe is contaminated.

[0018] In another aspect of the present application, a method for cleaning contaminants from an atomic force microscope probe is provided. According to an embodiment of the present application, the method comprises: providing a cleaning object having a tip and an atomic force microscope (AFM) loaded with a probe, the probe having been previously determined to be contaminated using the aforementioned method for detecting the degree of contamination of the AFM probe, and the tip diameter of the cleaning object being no larger than the tip diameter of the probe; activating the AFM to cause relative motion between the probe and the cleaning object, with the tip of the cleaning object directed toward the tip of the probe, and the tip of the cleaning object interacting with the tip of the probe to remove contaminants from the probe tip.

[0019] According to an embodiment of the present application, the tip diameter of the probe is 0.1 μm~1.0 μm; and / or the tip diameter of the cleaning object is 50 nm~500 nm; and / or the Mohs hardness of the cleaning object is greater than or equal to 7; and / or the material of the cleaning object includes at least one of silicon-based material, corundum, silicon nitride and diamond.

[0020] In another aspect, the present application provides a computer-readable storage medium. According to an embodiment of the present application, the computer-readable storage medium stores one or more programs, which can be executed by one or more processors to implement the aforementioned method for detecting the degree of contamination of an atomic force microscope probe and / or the aforementioned method for cleaning contaminants from an atomic force microscope probe.

[0021] In another aspect of the present application, an atomic force microscope is provided. According to an embodiment of the present application, the atomic force microscope includes the aforementioned computer-readable storage medium, or the atomic force microscope can operate according to the aforementioned method for detecting the degree of contamination of an atomic force microscope probe and / or the aforementioned method for cleaning contaminants from an atomic force microscope probe.

[0022] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 The fluorescence intensity-time curves of the probe tip before contamination, when slightly contaminated, and after cleaning are shown. (a) shows the fluorescence intensity-time curve of the probe tip before contamination (the contact distance between the probe and the sample is less than 100 nm); (b) shows the fluorescence intensity-time curve of the probe tip with slight contamination (the contact distance between the probe and the sample is approximately 100 nm); (c) shows a partial magnified view of the fluorescence intensity-time curve of the probe tip after cleaning (the contact distance between the probe and the sample is less than 100 nm); Figure 2 Shows images of the same area scanned before and after probe contamination: (A) uncontaminated, (B) contaminated, and (C) cleaned. Figure 3 Shows the images of the same area scanned before and after probe contamination, (A) uncontaminated, (B) slightly contaminated, (C) heavily contaminated, and (D) cleaned; Figure 4 Shows the changes in ODMR CW spectrum contrast, (A) uncontaminated, (B) contaminated, and (C) cleaned; Figure 5 Electron micrographs showing the probe after contamination and after cleaning; Figure 6 The ODMR signal diagrams of the needle when the probe is contaminated and after cleaning are shown. (a) shows the ODMR signal diagram of the needle when the probe is contaminated; (b) shows the ODMR signal diagram of the needle after cleaning. Figure 7 The fluorescence intensity-time curves of the probe when it is contaminated and after cleaning without inserting the needle are shown. (a) The fluorescence intensity-time curve of the probe when it is contaminated without inserting the needle is shown (fluorescence counts are approximately 210k); (b) The fluorescence intensity-time curve of the probe when it is cleaned without inserting the needle is shown (fluorescence counts are approximately 260k). Figure 8 Schematic diagram showing the sample surface microstructure after cleaning the probe tip of contaminants. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0025] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of this application, unless otherwise specified, "plurality" means two or more.

[0026] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0027] In this document, the terms "include" or "comprising" are open expressions, that is, including the contents specified in this application, but not excluding other contents.

[0028] The present application proposes a method for detecting the degree of contamination of an atomic force microscope probe, cleaning contaminants from the atomic force microscope probe, a computer-readable storage medium, and an atomic force microscope, which will be described in detail below.

[0029] Method for detecting the contamination degree of atomic force microscope probe In one aspect, the present application provides a method for detecting the degree of contamination of an atomic force microscope probe. According to an embodiment of the present application, the method includes: acquiring a first fluorescent signal during the insertion phase and a second fluorescent signal during the termination phase of the probe; and comparing the first and second fluorescent signals to determine the degree of contamination of the probe.

[0030] The presence of contaminants on the probe surface can alter the physical and chemical properties of the interaction between the probe and the sample, thereby affecting changes in fluorescence intensity. By comparing the changes in the fluorescence signal during the probe's insertion and termination phases, the degree of probe contamination can be accurately determined, ensuring that the probe provides accurate and reliable data in subsequent measurement and imaging tasks, thereby improving the overall performance of the atomic force microscope and the credibility of experimental results.

[0031] According to an embodiment of the present application, the probe is selected from a transparent probe with a fluorescent light-emitting object inside. Thus, the degree of contamination of the probe can be determined by the fluorescent signal emitted by the probe. Compared with scanning images, contrast and electron microscope images, fluorescence signals are helpful to quantify the degree of contamination of the probe, facilitate understanding the degree of contamination of the probe, automatically start the cleaning operation, reduce manual regular cleaning based on experience, and facilitate comparison of the cleaning effects between different cleaning methods; and facilitate understanding the effect of the cleaning operation, thereby controlling the end point of the cleaning operation in real time. In some embodiments, the fluorescent light-emitting object is an NV color center, and the atomic force microscope is selected from a scanning NV probe microscope.

[0032] According to an embodiment of the present application, the method includes: determining the degree of contamination of the probe based on changes in fluorescence intensity values obtained when the probe is inserted. Exemplarily, the first fluorescence signal and the second fluorescence signal each independently include a curve of changes in fluorescence intensity values relative to time.

[0033] According to an embodiment of the present application, the comparison of the first fluorescence signal and the second fluorescence signal includes: obtaining a first change curve of the fluorescence intensity value of the probe relative to time in an uncontaminated state, obtaining a second change curve of the current fluorescence intensity value of the probe relative to time, and comparing the first change curve and the second change curve.

[0034] In this article, the term "probe in an uncontaminated state," also referred to as a "contamination-free probe," refers to the state of the current probe under test (also referred to as the "probe to be tested") when no detectable contaminants (such as organic molecules, metal particles, nanoparticles, etc.) are present on its surface. Specifically, a probe to be tested is considered "contamination-free" when it is brand new and unused, or has been thoroughly cleaned and verified to have ideal surface cleanliness. The fluorescence intensity changes of this uncontaminated probe can be used as a reference standard for comparative analysis with the fluorescence intensity changes of the probe to be tested. By comparing the difference between these two curves, the contamination status of the probe to be tested can be accurately determined.

[0035] According to an embodiment of the present application, the first change curve and the second change curve independently and sequentially include a needle insertion segment, a characteristic segment and a termination segment, the needle insertion segment corresponds to the time period when the probe is inserted into the needle in a non-contaminated state, the termination segment corresponds to the time period after the probe terminates the insertion of the needle in the non-contaminated state, and the characteristic segment is the critical time period between the needle insertion segment and the termination segment; the characteristic segment contains a characteristic peak, and the peak value of the characteristic peak is greater than the peak values of the needle insertion segment and the termination segment.

[0036] For ease of understanding, the following takes the cleaning of SNVM probes on a silicon-based sample with a sharp protrusion tip (diameter 50-100 nm) as an example to explain in detail the signal changes and principles of the entire process of needle insertion and withdrawal of the SNVM probe before and after cleaning.

[0037] Since SNVM is a device developed based on atomic force microscopy, according to the principle of atomic force microscopy, when the probe is contaminated, the contaminant will approach the sample and generate an interaction force between atoms, thereby changing the vibration frequency of the probe cantilever (tuning fork), which will be fed back to the closed-loop control system to indicate the end point of the needle insertion (i.e., determining that the probe and the sample have contacted); and because SNVM is also a device developed based on NV color centers and ODMR technology (optical detection magnetic resonance technology), Figure 1 Middle (a), Figure 1 (b) and Figure 1 Taking (c) as an example, its signal is based on the ODMR signal of the NV center. Therefore, different degrees of contamination of the probe will cause the contact distance between the NV center and the sample to change at the end point of the needle insertion. The change in contact distance will cause the NV center to feel different magnetic fields on the sample surface, which can also characterize the contact distance between the NV center and the sample, thereby indirectly characterizing the degree of contamination of the probe. Figure 1 Middle (a), Figure 1 The rise in the tail end curve in (c) is caused by the probe withdrawing (i.e., leaving the sample surface).

[0038] by Figure 1 Middle (a), Figure 1 (b) and Figure 1 Taking (c) as an example, during the needle insertion process, the ODMR signal exhibits a phenomenon of "gradual fluctuation, substantial increase, then significant decrease and remaining stable at a low level". This "gradual fluctuation, substantial increase, then significant decrease" phase can be called the "needle insertion segment", of which the "substantial increase, then significant decrease" can be called the "characteristic segment", and the "maintaining low stability" can be called the "termination segment". The explanation for the above phenomenon is: The fluorescence emitted by the NV color center has different emission angles with the diamond crystal, depending on the emission direction. As a result, some fluorescence will be totally reflected inside the diamond crystal, while some fluorescence will be refracted outside the diamond crystal. As the probe approaches the sample, the fluorescence refracted outside the diamond crystal will be reflected back into the diamond crystal by the sample surface and collected by the fluorescence signal collection device. Since the fluorescence reflected from the sample surface, the fluorescence totally reflected from the diamond interior, and the fluorescence directly toward the NV color center have different optical paths to the fluorescence signal collection device, there is a phase difference and they are mutually coherent lights. Therefore, as the distance between the probe and the sample gradually decreases, the phase difference of the coherent light will gradually change, resulting in a "gradual fluctuation" phenomenon. When the phase difference of the coherent light is 0, the fluorescence signal intensity "significantly increases". When the distance between the probe and sample reaches approximately 100 nm, the fluorescence signal intensity "drops significantly again and remains stable at a low level." The smaller the distance between the probe and sample, the greater the drop in fluorescence signal intensity. This may be because the sample and probe are close enough that the optical-medium interface of the diamond crystal is no longer a simple diamond-air interface, but has become a diamond-sample interface (air is only a component and influencing factor of this interface). The refractive index of the sample is generally greater than that of air. Therefore, fluorescence originally totally reflected within the diamond crystal is refracted out of the diamond crystal, resulting in a decrease in fluorescence signal intensity. The closer the distance between the sample and probe, the greater the proportion of totally reflected fluorescence lost, resulting in a greater drop in fluorescence signal intensity. Since the distance between the probe and sample at the end of needle insertion depends on the degree of probe contamination, this phenomenon can be used to accurately determine the distance between the probe and sample, and thus the degree of probe contamination.

[0039] According to an embodiment of the present application, the method includes: obtaining a first change curve of the fluorescence intensity value of the probe relative to time in a non-contaminated state, and obtaining a second change curve of the fluorescence intensity value of the probe relative to time; obtaining the difference in the average value of the fluorescence intensity between the needle insertion section and the terminal section of the first change curve, recorded as the first difference; obtaining the difference in the average value of the fluorescence intensity between the needle insertion section and the terminal section of the second change curve, recorded as the second difference; determining the degree of contamination of the probe based on the difference or ratio of the first difference and the second difference. In some embodiments, when the difference or ratio of the first difference and the second difference is greater than or equal to a first threshold, it is determined that the probe is not contaminated; when the difference or ratio of the first difference and the second difference is less than or equal to a second threshold, it is determined that the probe is contaminated.

[0040] It should be noted that the "difference in average fluorescence intensity" in this application should be understood in a broad sense. It can be the value of the average fluorescence intensity of the needle insertion segment (referred to as "needle insertion segment value") minus the average fluorescence intensity of the termination segment (referred to as "termination segment value"), or the value of the average fluorescence intensity of the termination segment minus the average fluorescence intensity of the needle insertion segment. However, which of the needle insertion segment value and the termination segment value is used as the subtrahend and which is used as the minuend is consistent between contaminant-free probes and probes. For example, if the needle insertion segment value minus the termination segment value of the contaminant-free probe is recorded as the first difference, then the needle insertion segment value minus the termination segment value of the probe is recorded as the second difference; conversely, if the termination segment value minus the needle insertion segment value of the contaminant-free probe is recorded as the first difference, then the termination segment value minus the needle insertion segment value of the probe is recorded as the second difference.

[0041] The difference or ratio between the first difference and the second difference is consistent with the preset method of the first threshold or the second threshold. For example, if the first threshold is preset by subtracting the value of the probe from the value of the clean probe, then when determining the degree of probe contamination, the value of the first difference minus the second difference is compared with the first threshold.

[0042] According to an embodiment of the present application, the method includes: obtaining a first curve showing the fluorescence intensity of the probe in an uncontaminated state relative to time, and obtaining a second curve showing the current fluorescence intensity of the probe relative to time; based on the first curve, determining whether the second curve contains a characteristic segment to determine the degree of contamination of the probe. If the second curve does not contain the characteristic segment, the probe is determined to be contaminated.

[0043] by Figure 1 Middle (a), Figure 1 (b) and Figure 1 Taking (c) as an example, if the ODMR signal is terminated before reaching the "substantial increase" stage (i.e., no characteristic segment appears) during the needle insertion process, or if the ODMR signal reaches the stage of "significantly decreasing again and maintaining a low and stable level" (i.e., reaching the termination segment), but the ratio or difference of the fluorescence intensity after the decrease compared to the fluorescence signal intensity when the probe is away from the sample (i.e., the termination segment of the uncontaminated probe) is greater than or equal to the first threshold a, then it indicates that the probe is highly contaminated.

[0044] If, during the needle insertion process, the ODMR signal reaches the stage of "significantly decreasing again and maintaining a low and stable level", and the ratio or difference of the fluorescence intensity after the decrease compared to the fluorescence signal intensity when the probe is away from the sample (i.e., the end section of the uncontaminated probe) is less than or equal to the second threshold value b, it indicates that the degree of probe contamination is low.

[0045] The value of the first threshold a can be determined based on the image clarity and spectral signal contrast that the experiment can accept under different degrees of probe contamination; the larger the value of the first threshold a, the longer the probe can work continuously, indicating that the experiment has a high degree of acceptance of probe contamination; the smaller the value of the first threshold a, the shorter the probe can work continuously, indicating that the experiment has a low degree of acceptance of probe contamination.

[0046] The value of the second threshold b can be any value smaller than the first threshold a; if the value of the second threshold b is closer to 0, the cleaning operation time is longer and the degree of contamination of the probe after cleaning is lower; if the value of the second threshold b is closer to the first threshold a, the cleaning operation time is shorter, but the degree of contamination of the probe after cleaning is higher.

[0047] When the ODMR signal reaches the critical position of "substantially increasing" and "significantly decreasing and maintaining low stability", the exact distance between the probe and the sample depends on factors such as the position of the NV center at the probe tip and the ambient temperature. For the commonly used SNVM probe and at room temperature, the exact distance between the probe and the sample at the critical position is 80-150nm.

[0048] The above-mentioned method of detecting the degree of contamination of the atomic force microscope probe through the change of the fluorescence intensity value only requires one needle insertion to understand the degree of contamination of the probe, without the need to scan and image the sample and then judge the imaging effect, or sweep the frequency to produce the ODMR CW spectrum to calculate the contrast, or use a scanning electron microscope to observe the probe contamination. It is highly efficient and convenient for quantitative comparison. It can be used for real-time monitoring of the probe contamination, thereby automatically determining the timing of cleaning the probe and automatically determining the end point of the probe cleaning operation.

[0049] Methods for Cleaning Contaminants from Atomic Force Microscope Probes In another aspect of the present application, a method for cleaning contaminants from an atomic force microscope probe is provided. According to an embodiment of the present application, the method comprises: providing a cleaning object having a tip and an atomic force microscope (AFM) loaded with a probe, the probe having been previously determined to be contaminated using the aforementioned method for detecting the degree of contamination of the AFM probe, and the tip diameter of the cleaning object being no larger than the tip diameter of the probe; activating the AFM to cause relative motion between the probe and the cleaning object, with the tip of the cleaning object directed toward the tip of the probe, and the tip of the cleaning object interacting with the tip of the probe to remove contaminants from the probe tip.

[0050] According to the method of the present application, a cleaning object with a pointed end is selected as a sample, and the sample is scanned using an atomic force microscope loaded with a probe to be cleaned. During the scanning process, the tip of the cleaning object interacts with the tip of the probe to remove contaminants on the probe surface, thereby improving the cleanliness of the probe.

[0051] The following is a detailed explanation of the principles by which this application can achieve the above beneficial effects: Figure 8 A schematic diagram of the sample and probe positions is shown. Using a cleaning material with sharp protrusions as the sample, during the scanning process, as the distance between the probe and the cleaning material decreases, the interatomic interaction force between the two increases accordingly. This interaction can promote the shedding of contaminants on the probe surface, thereby improving the cleanliness of the probe. Specifically, the tip diameter d of the cleaning material protrusion should be no larger than the probe tip diameter D to achieve a better cleaning effect. Conversely, when the tip diameter of the cleaning material protrusion is larger than the probe tip diameter, the cleaning effect is weak or even non-existent.

[0052] According to an embodiment of the present application, the tip diameter of the probe is 0.1 μm to 1.0 μm, for example, 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, or 1.0 μm. Thus, when interacting with the tip of the cleaning material, contaminants on the probe tip can be effectively removed. Furthermore, a probe with this tip diameter has excellent resolution, enabling more precise scanning of microstructures on the sample surface. It also reduces the contact area between the probe and the sample, thereby reducing the risk of damage caused by contact and extending the probe's service life.

[0053] According to an embodiment of the present application, the tip diameter of the cleaning material is 50 nm to 500 nm, for example, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm. Thus, when interacting with the probe tip, contaminants at the probe tip can be effectively removed. Furthermore, excessive wear or damage to the probe tip can be avoided, thereby extending the service life of the probe.

[0054] According to an embodiment of the present application, the cleaning material has a Mohs hardness of greater than or equal to 7, for example, 7, 7.5, 8, 8.5, 9, 9.5, or 10, which can be measured using a Mohs hardness tester. Thus, the cleaning material can provide sufficient mechanical strength when interacting with the probe tip to scrape off or loosen contaminants attached to the probe surface. Furthermore, the cleaning material having the above Mohs hardness can more effectively remove stubborn contaminants without damaging the probe tip, thereby improving cleaning efficiency and the cleanliness of the probe, ensuring that the probe is restored to good working condition and extending its service life.

[0055] According to an embodiment of the present application, the material of the cleaning material includes at least one of silicon-based materials, corundum, silicon nitride and diamond.

[0056] In some embodiments, a silicon-based sample having a sharp protrusion (the tip diameter of the protrusion is about 50-500 nm) can be obtained by purchasing a commercially available product that meets the requirements (e.g., a grating product used to measure the diameter of an atomic force microscope scanning probe), or can be prepared by micro-nano processing. The general steps are as follows: 1. Making a mask: Using electron beam lithography to make a mask; 2. Photoresist coating: Spin-coat several spots of positive electron beam resist (such as PMMA) on the silicon substrate; 3. Exposure: Expose the sample using a mask with a dot array; 4. Development: Place the exposed sample in a developer to remove the resist from the exposed area, exposing the silicon substrate. 5. Etching: Dry etching (e.g., reactive ion etching, RIE): Adjust the etching conditions and control the lateral etching rate to produce a silicon tip array that meets the requirements for cleaning the SNVM probe tip. Wet etching: Utilize the anisotropy of silicon to etch the silicon tip array. Surface oxidation and hydrofluoric acid etching are then used to trim the silicon tip shape to obtain a silicon tip array that meets the requirements. 6. Coating: Coating SiO2 on the silicon tip array to increase strength.

[0057] In some embodiments, a sample having a pointed protrusion (the tip diameter of the protrusion is 50-500 nm) and made of diamond can be prepared by inductively coupled plasma (ICP) etching. The general steps are as follows: 1. Make a mask: Use electron beam lithography to make a mask; 2. Coating: Diamond substrate is chrome-plated to increase conductivity; 3. Apply photoresist: Use negative electron beam photoresist (such as HSQ); 4. Exposure: Expose the sample using a mask with a dot array; 5. Development: Place the exposed sample in a developer to remove the resist from the unexposed area. 6. Etching: Using inductively coupled plasma (ICP) etching, adjusting etching conditions and controlling the lateral etching rate to produce a silicon tip array suitable for cleaning the AFM probe tip; 7. Use focused ion beam (FIB) to further adjust, etch or repair the sample surface microstructure so that the diamond sample meets the microstructure requirements for cleaning the AFM probe tip.

[0058] According to an embodiment of the present application, the atomic force microscope (AFM) includes a scanning NV probe microscope (SNVM), a scanning probe Raman microscope (SPRM), and the like.

[0059] Placing a diamond containing a single-spin NV color center system at the tip of an atomic force microscope (AFM) probe and combining NV color center quantum sensing technology based on optically detected magnetic resonance with atomic force microscopy scanning technology enables high-resolution magnetic imaging and detection of other physical quantities. The instrument using this technology is called a scanning NV probe microscope (SNVM). For SNVM, the scanning parameters can be optimized to ensure both the efficiency and effectiveness of the cleaning operation. Specifically, when performing probe tip contamination cleaning operations, the SNVM parameters are: 1. Mechanical parameters Spring constant representing the rigidity of the cantilever: 20 kN / m.

[0060] Natural vibration frequency (resonance frequency) of the cantilever: 32 kHz.

[0061] 2. Scan parameters Scan speed: 200 ms / pixel.

[0062] 3. Feedback control parameters Tapping mode (the probe is gently vibrated above the sample surface, and the probe height is controlled by changes in the cantilever amplitude).

[0063] Cantilever set amplitude (adjust the probe height according to the difference between the actual cantilever amplitude and the set amplitude): the actual amplitude is about 1nm.

[0064] Probe vibration amplitude in tapping mode: The threshold is set between 80% and 99% of the free amplitude.

[0065] During the probe cleaning operation, 50 points are scanned with a scanning range of 5 microns.

[0066] Computer-readable storage medium and atomic force microscope In another aspect, the present application provides a computer-readable storage medium. According to an embodiment of the present application, the computer-readable storage medium stores one or more programs, which can be executed by one or more processors to implement the aforementioned method for detecting the degree of contamination of an atomic force microscope probe and / or the aforementioned method for cleaning contaminants from an atomic force microscope probe.

[0067] A computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, device, or apparatus. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media may include an electrical connection based on one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0068] In another aspect of the present application, an atomic force microscope is provided. According to an embodiment of the present application, the atomic force microscope includes the aforementioned computer-readable storage medium, or the atomic force microscope can operate according to the aforementioned method for detecting the degree of contamination of an atomic force microscope probe and / or the aforementioned method for cleaning contaminants from an atomic force microscope probe.

[0069] Below in conjunction with embodiment, the scheme of the application will be explained. Those skilled in the art will appreciate that the following examples are merely for illustration of the application and should not be considered as limiting the scope of the application. Where specific techniques or conditions are not indicated in the examples, they are carried out according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents used or instruments not indicated by the manufacturer are conventional products that can be obtained commercially.

[0070] Example 1 A probe with a tip diameter of 500 nm was used as a sample (equivalent to a sample with a protrusion tip diameter of 500 nm and made of diamond). Another SNVM probe with a tip diameter of 500 nm was cleaned. The SNVM parameters were: 1. Mechanical parameters Spring constant representing the rigidity of the cantilever: 20 kN / m.

[0071] Natural vibration frequency (resonance frequency) of the cantilever: 32 kHz.

[0072] 2. Scan parameters Scan speed: 200 ms / pixel.

[0073] 3. Feedback control parameters Tapping mode (the probe is gently vibrated above the sample surface, and the probe height is controlled by changes in the cantilever amplitude).

[0074] Cantilever set amplitude (adjust the probe height according to the difference between the actual cantilever amplitude and the set amplitude): the actual amplitude is about 1nm.

[0075] Probe vibration amplitude in tapping mode: The threshold is set between 80% and 99% of the free amplitude.

[0076] During the probe cleaning operation, 50 points are scanned with a scanning range of 5 microns.

[0077] SNVM scans were performed on the contaminated probe and the cleaned probe, and the results were as follows: Figure 6 Middle (a), Figure 6 Middle (b), Figure 7 (a) and Figure 7 As shown in (b), the probe after cleaning is considered uncontaminated. After probe contamination, the distance between the probe and the sample's insertion endpoint is approximately 120 nm, marking the early stages of "significantly decreasing and remaining stable at a low level." The maximum fluorescence value barely decreases, dropping from a peak of 276 kJ to 259 kJ. In contrast, the fluorescence count when the probe is not inserted (i.e., away from the sample) is approximately 210 kJ. After the probe is cleaned, the distance between the probe and the sample's insertion endpoint is slightly less than 100 nm, marking the mid-stage of "significantly decreasing and remaining stable at a low level." The maximum fluorescence value decreases from a peak of 303 kJ to 233 kJ. In contrast, the fluorescence count when the probe is not inserted is approximately 260 kJ.

[0078] Assuming that the probe is free of contaminants, the average difference in fluorescence intensity between the insertion and termination segments of the first curve (the first difference) is 40k. When determining whether cleaning is necessary: After the probe is contaminated, the difference in fluorescence counts between the insertion and termination sections of the probe is 210k-259k=-49k, where -49k is the second difference. The first difference minus the second difference is 40k-(-49k)=89k. If the first threshold is 89k, the probe is currently contaminated and needs to be cleaned; Because contamination will cause the average intensity of the fluorescence signal in the termination segment to increase, the second difference will continue to decrease as the degree of contamination continues to deepen, and the result of subtracting the second difference from the first difference will continue to increase; therefore, if the first threshold is 100k, the probe can continue to work for a period of time in its current contamination state.

[0079] When determining whether it is clean: After the probe is cleaned, the difference in fluorescence counts between the insertion and termination sections of the probe is 260k-233k=27k, where 27k is the second difference. The first difference minus the second difference is 40k-27k=13k. If the second threshold is 13k, the probe is currently contaminated and needs to be cleaned; Because cleaning will reduce the average intensity of the fluorescent signal in the termination segment, the second difference will continue to increase as the cleanliness level continues to increase, and the result of subtracting the second difference from the first difference will continue to decrease; therefore, if the second threshold is 5k, the probe still needs to be cleaned for a while.

[0080] Under different probes, different samples, and different working parameters, the fluorescence count distributions of the probe insertion section and the termination section in the first and second change curves are different. Figure 6 Middle (a), Figure 6 In the example of (b), the second difference is positive when the surface is clean and negative when the surface is polluted, so the difference judgment method is suitable.

[0081] If Figure 1 As shown in the figure, it is not difficult to see that the second difference is positive whether it is clean or contaminated. Therefore, the ratio of the first difference to the second difference can be used to determine whether the probe needs to be cleaned and whether the probe is clean. The specific method is the same as Figure 6 Middle (a), Figure 6 The example in (b) is similar and will not be repeated here.

[0082] Example 2 A silicon-based sample with a tip (50-100 nm in diameter) was used to clean contaminants from the tip of the SNVM probe (500 nm in diameter). The parameters of the SNVM were the same as those in Example 1.

[0083] The scan results are as follows Figure 2 and Figure 3 shown. Figure 2 and Figure 3 The scanning images of different SNVM probes can intuitively show the impact of probe contamination and the effect of the probe cleaning method provided by this application.

[0084] Figure 4 From top to bottom, the contrast changes of the ODMR (optical detection magnetic resonance) CW spectra (referring to the optical detection magnetic resonance signal obtained under continuous wave conditions. In this mode, the microwave source continuously irradiates the sample within a scanning frequency range and records the changes in the sample's luminescence intensity) under the same measurement conditions before contamination, after contamination, and after cleaning: before the probe is uncontaminated, the contrast is about 23%; after the probe is contaminated, the contrast is about 13%; after the probe is cleaned, the contrast is about 20%.

[0085] Figure 5 The morphology of the probe after contamination and cleaning was obtained by scanning electron microscopy.

[0086] It can be seen that the use of a cleaning object with a protruding tip can effectively clean contaminants on the probe surface.

[0087] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for detecting the contamination degree of an atomic force microscope probe, characterized in that: The method comprises: When the probe is inserted into the needle, a first fluorescent signal of the insertion section is obtained, and a second fluorescent signal of the termination section is obtained; The first fluorescent signal and the second fluorescent signal are compared to determine the contamination degree of the probe.

2. The method for detecting the contamination degree of an atomic force microscope probe according to claim 1, characterized in that: The probe is selected from transparent probes with fluorescent light emitters inside.

3. The method for detecting the contamination degree of an atomic force microscope probe according to claim 2, characterized in that: The fluorescent light-emitting object is an NV color center.

4. The method for detecting the contamination degree of an atomic force microscope probe according to claim 1, wherein: The atomic force microscope is selected from a scanning NV probe microscope.

5. The method for detecting the contamination degree of an atomic force microscope probe according to claim 1, wherein: The first fluorescent signal and the second fluorescent signal each independently include a curve of changes in fluorescence intensity value relative to time.

6. The method for detecting the contamination degree of an atomic force microscope probe according to any one of claims 1 to 5, characterized in that: The comparison of the first fluorescence signal and the second fluorescence signal includes: obtaining a first change curve of the fluorescence intensity value of the probe relative to time in an uncontaminated state, obtaining a second change curve of the current fluorescence intensity value of the probe relative to time, and comparing the first change curve and the second change curve.

7. The method for detecting the contamination degree of an atomic force microscope probe according to claim 6, characterized in that: The first change curve and the second change curve independently and sequentially include a needle insertion segment, a characteristic segment, and a termination segment, wherein the needle insertion segment corresponds to a time period during which the probe is inserted into the needle in a non-contaminated state, the termination segment corresponds to a time period after the probe terminates the insertion of the needle in the non-contaminated state, and the characteristic segment is a critical time period between the needle insertion segment and the termination segment; The characteristic segment includes a characteristic peak, and the peak value of the characteristic peak is greater than the peak values of the needle insertion segment and the terminal segment.

8. The method for detecting the contamination degree of an atomic force microscope probe according to claim 7, characterized in that: The method comprises: obtaining a first change curve of the fluorescence intensity value of the probe in a non-contaminated state relative to time, and obtaining a second change curve of the current fluorescence intensity value of the probe relative to time; Obtaining a difference in the average fluorescence intensity between the needle insertion segment and the terminal segment of the first change curve, recorded as a first difference; obtaining a difference in the average fluorescence intensity between the needle insertion segment and the terminal segment of the second change curve, recorded as a second difference; The contamination level of the probe is determined based on the difference or ratio of the first difference and the second difference.

9. The method for detecting the contamination degree of an atomic force microscope probe according to claim 8, characterized in that: When the difference or ratio of the first difference value to the second difference value is greater than or equal to a first threshold value, it is determined that the probe is not contaminated; When the difference or ratio of the first difference value to the second difference value is less than or equal to a second threshold value, it is determined that the probe is contaminated.

10. The method for detecting the contamination degree of an atomic force microscope probe according to claim 8, characterized in that: The method comprises: obtaining a first change curve of the fluorescence intensity value of the probe in a non-contaminated state relative to time, and obtaining a second change curve of the current fluorescence intensity value of the probe relative to time; Based on the first change curve, it is determined whether the second change curve has the characteristic segment, and the contamination degree of the probe is determined.

11. The method for detecting the contamination degree of an atomic force microscope probe according to claim 10, characterized in that: When the characteristic segment does not appear in the second variation curve, it is determined that the probe is contaminated.

12. A method for cleaning contaminants from an atomic force microscope probe, characterized in that: include: An atomic force microscope (AFM) is provided with a cleaning object having a tip and a probe, wherein the probe is previously determined to be contaminated by the method for detecting the degree of contamination of an AFM probe according to any one of claims 1 to 11, and the diameter of the tip of the cleaning object is no greater than the diameter of the probe tip. The atomic force microscope is started to cause relative movement between the probe and the cleaning object, with the tip of the cleaning object facing the tip of the probe. The tip of the cleaning object interacts with the tip of the probe to remove contaminants on the tip of the probe.

13. The method for cleaning contaminants from an atomic force microscope probe according to claim 12, wherein: The tip diameter of the probe is 0.1 μm to 1.0 μm; And / or, the tip diameter of the cleaning object is 50 nm to 500 nm; And / or, the Mohs hardness of the cleaning material is greater than or equal to 7; And / or, the material of the cleaning material includes at least one of silicon-based materials, corundum, silicon nitride and diamond.

14. A computer-readable storage medium, characterized in that The computer-readable storage medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the method for detecting the degree of contamination of an atomic force microscope probe as described in any one of claims 1 to 11 and / or the method for cleaning contaminants of an atomic force microscope probe as described in claim 12 or 13.

15. An atomic force microscope, characterized in that: The atomic force microscope includes the computer-readable storage medium according to claim 14, or the atomic force microscope can operate according to the method for detecting the degree of contamination of an atomic force microscope probe according to any one of claims 1 to 11 and / or the method for cleaning contaminants of an atomic force microscope probe according to claim 12 or 13.

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