阅读说明：本技术 原子力显微镜探针及其制作方法 (Atomic force microscope probe and manufacturing method thereof ) 是由 丁喜冬 罗永震 陈弟虎 黄臻成 林国淙 文锦辉 于 2020-06-30 设计创作，主要内容包括：本申请涉及一种原子力显微镜探针及其制作方法。包括获取原子力显微镜探针的Q值随针尖长度的变化曲线。变化曲线中包含了QTF不同的振动模式。根据变化曲线,确定针尖长度的取值范围,实现了根据附加质量和振动模式对AFM中QTF探针在不同针尖长度下的Q值变化规律对探针结构的优化。根据针尖长度的取值范围,确定音叉的尺寸参数和平衡调节装置的尺寸参数。将针尖固定于音叉的第一叉臂的自由端,并将平衡调节装置固定于音叉的第二叉臂的自由端。本申请巧妙地利用了QTF的机械共振的特征和变化规律并采用适当的方法实现了Q值的调控,可在探针针尖的长度较长时仍能够获得其Q值的极大值,从而得到振动特性优良的AFM探针。(The application relates to an atomic force microscope probe and a manufacturing method thereof. The method comprises the step of obtaining a change curve of the Q value of the atomic force microscope probe along with the length of a needle tip. The variation curve contains different vibration modes of the QTF. And determining the value range of the tip length according to the change curve, and realizing the optimization of the Q value change rule of the QTF probe in the AFM under different tip lengths according to the additional mass and the vibration mode. And determining the size parameter of the tuning fork and the size parameter of the balance adjusting device according to the value range of the needle tip length. The needle tip is fixed to the free end of a first prong of the tuning fork, and the balance adjustment device is fixed to the free end of a second prong of the tuning fork. The method skillfully utilizes the characteristics and the change rule of the mechanical resonance of the QTF and adopts a proper method to realize the regulation and control of the Q value, and the maximum value of the Q value can be obtained when the length of the probe tip is longer, so that the AFM probe with excellent vibration characteristics is obtained.)

1. A method for manufacturing an atomic force microscope probe is characterized by comprising the following steps:

obtaining a change curve of the Q value of the atomic force microscope probe along with the length of the needle tip;

determining the value range of the needle tip length according to the change curve;

determining the size parameter of the tuning fork and the size parameter of the balance adjusting device according to the value range of the needle tip length;

and fixing the needle tip to the free end of the first prong of the tuning fork, and fixing the balance adjusting device to the free end of the second prong of the tuning fork.

2. The method for manufacturing the afm probe according to claim 1, wherein the step of determining the value range of the tip length according to the variation curve includes:

and acquiring an abnormal Q value descending section and a normal section of the atomic force microscope probe according to the change curve so as to enable the value range of the needle tip length to be in the normal section.

3. The method of claim 2, wherein the tip is made of a metal material and the length of the tip is 2.5mm to 4.0 mm.

4. The method of claim 1, wherein the first arm of the tuning fork has a mass 10 to 25 times that of the tip, and the balance adjustment device has a mass the same as or similar to that of the tip.

5. The method for fabricating an afm probe according to claim 1, wherein the step of fixing the tip to the free end of the first arm of the tuning fork and the balance adjustment device to the free end of the second arm of the tuning fork is followed by:

and carrying out micro-regulation on the balance regulating device until the Q value of the atomic force microscope probe reaches a preset value.

6. The method for fabricating the AFM probe of claim 5, wherein the step of fine-tuning the balance adjustment mechanism comprises:

and intercepting the balance adjusting device to a preset length.

7. The method for fabricating the AFM probe of claim 5, wherein the step of fine-tuning the balance adjustment mechanism comprises:

adding a preset amount of curing glue to the free end of the second fork arm of the tuning fork.

8. The method for fabricating an afm probe according to claim 1, wherein the step of fixing the tip to the free end of the first arm of the tuning fork and the balance adjustment device to the free end of the second arm of the tuning fork is followed by:

providing a support substrate;

and fixing the base of the tuning fork on the support substrate.

9. The method for fabricating the AFM probe of claim 1, wherein the tip is fixed to the free end of the first arm of the tuning fork in a vertical force mode, a shear force mode, or a fixed mode at a predetermined angle.

10. An atomic force microscope probe, characterized by being manufactured by the method for manufacturing an atomic force microscope probe according to any one of claims 1 to 9.

Technical Field

The application relates to the technical field of atomic force microscopy, in particular to an atomic force microscope probe and a manufacturing method thereof.

Background

Atomic Force Microscopy (AFM) typically uses a flexible microcantilever fixed at one end and having a tip at the other end to detect the topography or other surface properties of a sample. When the sample or the needle tip scans, the interaction force between the needle tip samples related to the distance can cause the micro-cantilever to deform. A laser beam irradiates the back of the micro-cantilever to reflect the laser beam to a photoelectric detector, and the laser intensity difference values received by different quadrants of the detector and the deformation quantity of the micro-cantilever form a certain proportional relation, so that the force can be detected. At present, the AFM in the atmospheric environment generally uses a micro-cantilever probe based on laser position detection, and the detection device is precise, high in cost and complex to operate.

Compared with the micro-cantilever probe based on laser position detection, the self-induction AFM probe based on the Quartz Tuning Fork (QTF) has the characteristics of self excitation and self detection, so the structure is simple and the use is convenient. In QTF-based AFM probes, the tip used for force measurement is typically formed as a sharp tip using a tungsten (W) or platinum/iridium (PtIr) metal filament, typically electrochemically etched, and then bonded to the free end of one arm of the QTF. In order to obtain high sensitivity in surface profiling, the mechanical vibration of the AFM probe must have a high quality factor (Q value).

In conventional solutions, if the quality of the needle tip (including the amount of viscose) is small (e.g., using fibers to make the needle tip), and the rebalancing technique is used, the Q value of the QTF probe can be improved to some extent (e.g., up to 2000 or higher). However, when the tip of the QTF probe is made of metal, the length of the probe tip cannot be larger than 1.5 mm. When the tip length is long (e.g., about 3.5mm), how to obtain an AFM probe with excellent vibration characteristics (Q value is 1000 or more) is currently lacking in an effective technique or manufacturing method.

Disclosure of Invention

Accordingly, the present application provides an atomic force microscope probe and a method for fabricating the same, so that an AFM probe having excellent vibration characteristics can be obtained even when the length of the probe tip is long.

A method for manufacturing an atomic force microscope probe comprises the following steps:

obtaining a change curve of the Q value of the atomic force microscope probe along with the length of the needle tip;

determining the value range of the needle tip length according to the change curve;

determining the size parameter of the tuning fork and the size parameter of the balance adjusting device according to the value range of the needle tip length;

and fixing the needle tip to the free end of the first prong of the tuning fork, and fixing the balance adjusting device to the free end of the second prong of the tuning fork.

In one embodiment, the step of determining the value range of the tip length according to the variation curve includes:

and acquiring an abnormal Q value descending section and a normal section of the atomic force microscope probe according to the change curve so as to enable the value range of the needle tip length to be in the normal section.

In one embodiment, the needle tip is made of a metal material, and the length of the needle tip is 2.5mm to 4.0 mm.

In one embodiment, the mass of the first arm of the tuning fork is 10 to 25 times the mass of the needle tip, and the mass of the balance adjustment device is the same as or similar to the mass of the needle tip.

In one embodiment, the step of fixing the needle tip to the free end of the first arm of the tuning fork and the balance adjustment device to the free end of the second arm of the tuning fork is followed by:

and carrying out micro-regulation on the balance regulating device until the Q value of the atomic force microscope probe reaches a preset value.

In one embodiment, the step of micro-regulating the balance adjustment device comprises:

and intercepting the balance adjusting device to a preset length.

In one embodiment, the step of micro-regulating the balance adjustment device comprises:

adding a preset amount of curing glue to the free end of the second fork arm of the tuning fork.

In one embodiment, the step of fixing the needle tip to the free end of the first arm of the tuning fork and the balance adjustment device to the free end of the second arm of the tuning fork is followed by:

providing a support substrate;

and fixing the base of the tuning fork on the support substrate.

In one embodiment, the manner of fixing the needle tip to the free end of the first arm of the tuning fork is a vertical force mode, a shear force mode or a fixed mode with a preset angle.

An afm probe is manufactured by the method for manufacturing an afm probe according to any one of the embodiments.

The manufacturing method of the atomic force microscope probe comprises the step of obtaining a change curve of the Q value of the atomic force microscope probe along with the length of the needle tip. The variation curve comprises different vibration modes of the QTF. And determining the value range of the tip length according to the change curve, thereby realizing the optimization of the Q value change rule of the QTF probe in the AFM under different tip lengths according to the additional mass and the vibration mode. And determining the size parameter of the tuning fork and the size parameter of the balance adjusting device according to the value range of the needle tip length. And fixing the needle tip to the free end of the first prong of the tuning fork, and fixing the balance adjusting device to the free end of the second prong of the tuning fork. The method skillfully utilizes the characteristics and the change rule of the mechanical resonance of the QTF and adopts a proper method to realize the regulation and control of the Q value, and the maximum value of the Q value can be obtained when the length of the probe tip is longer, so that the AFM probe with excellent vibration characteristics is obtained.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of a method for fabricating an AFM probe according to an embodiment of the present disclosure;

FIG. 2 is a graph of Q versus tip length provided in accordance with another embodiment of the present application;

FIG. 3 is a schematic structural diagram of an AFM probe according to an embodiment of the present disclosure;

FIG. 4 is a schematic view of a probe tip bonding method according to an embodiment of the present application;

fig. 5 is a Q-value adjustment effect test chart according to an embodiment of the present application.

Description of the main element reference numerals

10. A needle tip; 20. a tuning fork; 21. a first yoke; 22. a second prong; 23. a base; 30. a balance adjustment device; 31. curing glue; 40. a support substrate; 50. and an electrode lead.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.

It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a first acquisition module may be referred to as a second acquisition module, and similarly, a second acquisition module may be referred to as a first acquisition module, without departing from the scope of the present application. The first acquisition module and the second acquisition module are both acquisition modules, but are not the same acquisition module.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, the present application provides a method for fabricating an atomic force microscope probe. The manufacturing method of the atomic force microscope probe comprises the following steps:

and S10, acquiring a change curve of the Q value of the atomic force microscope probe along with the length of the needle tip.

In step S10, according to existing relevant theory and general knowledge, the quartz tuning fork should exhibit the best performance of mechanical vibration (i.e., the maximum value of Q value) under its most balanced condition. However, from said curves we have found that the occurrence of the best performance of the rebalancing tuning fork probe in the experiment always deviates from the above-mentioned cognitive results. In other words, tuning fork probes do not always achieve the highest Q performance in their most symmetric case; in particular, in the case of a large tip mass, the probe does not achieve the highest Q performance at its most symmetrical condition. For example, where the tip is short (e.g. less than 1mm), it is possible to say that the highest Q performance is obtained in substantially (within experimental error) the most symmetrical case. For example, as shown in FIG. 2, the Q values of all QTF probes drop significantly under certain tip add-on mass conditions (e.g., at a tip 10 length of 2.1 mm), regardless of the add-on mass of the tip 10 on the other side (even in the ideal equilibrium case). That is, as long as the needle tip 10 reaches a certain length on either side, such a sharp decrease in the Q value occurs. The occurrence of the special point of sharp drop here is determined by the properties of the tuning fork 20 itself. The Q value variation of the tuning fork probe shows a piecewise characteristic (non-monotonic function). The resonant frequency of each segment of data will also exhibit a piecewise characteristic (non-monotonic function). Therefore, the phenomenon in this experiment includes different vibration modes of the QTF, and each vibration mode corresponds to a section of curve (the change rule of the frequency is different). It can be seen that there is degeneracy of the mechanical vibration modes between the QTF vibration modes, resulting in changes in vibration performance, manifested as abrupt and abnormal decreases in the Q-value change curve in the figure (within the interval of 1.6-2.2mm in length of the needle tip 10). The curve can now be divided into an abnormally falling segment and a normal segment.

It will be appreciated that a plurality of abnormally decreasing segments may be included in the curve. When the materials of the needle tips 10 are different, the lengths of the needle tips 10 corresponding to the abnormal descent sections are also different.

And S20, determining the value range of the length of the needle tip 10 according to the change curve.

In step S20, the abnormal Q-value descending section and the normal section of the afm probe may be determined according to the variation curve, and further, when the length of the tip 10 is selected, the length of the tip 10 corresponding to the normal section is selected.

Alternatively, the tip 10 is typically made of metal, and is made of a thin wire (about 0.05mm to 0.1mm in cross-sectional diameter) of tungsten (W) or platinum/iridium (PtIr). The sharp point is usually formed by electrochemical etching, and the sharp point 10 front end can also be formed by mechanical shearing. When the needle tip 10 is made of a metal material, the length of the needle tip is 2.5mm to 4.0 mm. In one alternative embodiment, when the tip 10 is a tungsten wire with a diameter of 0.1mm, the tip 10 is 3mm to 4mm long. Preferably, the needle tip 10 is 3.5mm in length. Of course, the material of the needle tip 10 may also be glass or other materials.

And S30, determining the size parameter of the tuning fork 20 and the size parameter of the balance adjusting device 30 according to the value range of the length of the needle tip 10.

In step S30, the tuning fork 20 includes a first prong 21, a second prong 22, and a base 23. The QTF probe realizes the interconversion of mechanical vibration and an oscillating electric signal by utilizing the piezoelectric effect of the tuning fork 20, has very good frequency stability and also has extremely high quality factor (namely Q value). The piezoelectric effect of the tuning fork 20 can complete the conversion between the mechanical vibration and the electrical signal, and the optical lever method is not needed for detecting the surface information of the sample, thereby omitting the optical devices and the optical path calibration process. The QTF has the piezoelectric effect, so that a piezoelectric oscillator required by the cantilever probe can be omitted, and self-excitation and self-induction driving can be realized through a circuit.

In an alternative embodiment, the raw material of the quartz tuning fork used in the present application for making the QTF probe is a cylindrical quartz crystal oscillator with a center frequency of 32.768kHz, which is commonly used in electronic watches. The outer diameter of the crystal oscillator before shelling is 3mm, and the length of the crystal oscillator is 8 mm. After the crystal oscillator is shelled, the width is 1.52mm, the thickness is 0.38mm, and the length is 6.02 mm. From the commercial QTF used (32.768kHz, 10ppm, YT-38, YXC) and the main dimensional parameters of the tungsten needle tip 10, the mass of the tuning fork arm and the probe tip 10 can be estimated. Typically, the mass of the prongs needs to be significantly greater than the mass of the tip 10, up to about 20 times different. Optionally, the mass of the first prong 21 of the tuning fork 20 is 10 times to 25 times the mass of the needle tip 10. The tuning fork is thus the main body of vibration, and the vibrator under vibration study will still be based primarily on the tuning fork. The modification of the probe to vibration may be approximately equivalent to adding a small additional mass to the tuning fork arms.

The balance adjusting means 30 may be a balance wire. To achieve mass rebalancing, the gauge (material, straightness, length, etc.) of the metal filament used is generally about the same as the gauge of the metal tip 10 after the tip treatment is completed. The balance adjustment device 30 may be replaced by resin glue of equal mass instead of wire, as long as the same mass rebalancing effect can be achieved.

S40, fixing the needle tip 10 to the free end of the first prong 21 of the tuning fork 20, and fixing the balance adjusting device 30 to the free end of the second prong 22 of the tuning fork 20.

In step S40, the needle tip 10 is bonded to the free end of one of the tuning fork arms of the QTF using epoxy or other adhesive. In one alternative embodiment, the manner of fixing the needle tip 10 to the free end of the first prong 21 of the tuning fork 20 is a vertical force mode, a shear force mode, or a fixed mode at a preset angle. To achieve additional mass rebalancing of the two prongs, a length of metal wire is epoxied to the prong to which the needle tip 10 is not attached.

In this embodiment, the method for manufacturing the afm probe includes obtaining a variation curve of the Q value of the afm probe along with the length of the tip 10. The variation curve comprises different vibration modes of the QTF. And determining the value range of the length of the needle tip 10 according to the change curve, so that the optimization of the Q value change rule of the QTF probe in the AFM under different lengths of the needle tip 10 according to the additional mass and the vibration mode is realized. According to the value range of the length of the needle tip 10, the size parameters of the tuning fork 20 and the size parameters of the balance adjusting device 30 are determined. The needle tip 10 is fixed to the free end of the first prong 21 of the tuning fork 20, and the balance adjusting device 30 is fixed to the free end of the second prong 22 of the tuning fork 20. The method skillfully utilizes the characteristics and the change rule of the mechanical resonance of the QTF and adopts a proper method to realize the regulation and control of the Q value, and the maximum value of the Q value can be obtained when the length of the probe tip 10 is longer, so that the AFM probe with excellent vibration characteristics is obtained.

In one embodiment, step S40 is followed by:

and carrying out micro regulation and control on the balance regulating device 30 until the Q value of the atomic force microscope probe reaches a preset value. Alternatively, one method of micro-regulation is to intercept to a preset length on the balance adjustment device 30. I.e. to regulate the length of the balancing wire. Carefully remove a small piece (about 0.1mm) each time on the end of the balance wire, changing its length and effective mass; then monitoring the Q value of the mechanical resonance of the tuning fork 20 probe; if the Q value meets the requirement, the regulation can be finished, otherwise, a small section is cut off again until the Q value meets the requirement.

Alternatively, another method of micro-tuning is to add a preset amount of curing glue 31 to the free end of the second arm 22 of the tuning fork 20. Namely, the effect of adjusting and rebalancing the additional mass of the tuning fork 20 is achieved by adjusting and controlling the amount of the curing adhesive 31. One typical approach is to use a photo-curable glue. The specific method comprises the following steps: the liquid photo-curing glue is injected to a specific position of the second prong 22 by using a micro-injector, and the quality of the glue added is controlled each time, for example, the glue is added by about 10ug each time. Then monitoring the Q value of the mechanical resonance of the tuning fork 20 probe; if the Q value meets the requirement, the regulation can be finished, otherwise, the glue dosage is added again until the Q value meets the requirement. Another typical method is to use a heat-curable glue. The concrete method is similar to that of photo-curing glue, and aims to accelerate the curing of the glue by heating so as to be beneficial to the rapid regulation and control of the Q value.

In one embodiment, step S40 is followed by:

a support substrate 40 is provided. Fixing the base 23 of the tuning fork 20 to the support substrate 40. The support substrate 40 is a specially-made circuit board. The support substrate 40 is used for fixing and supporting the tuning fork 20. The support substrate 40 may be fixed to the base 23 of the tuning fork 20 by epoxy, and may also support the tuning fork 20 by the electrode lead 50 or both. The carrier substrate 40 has 2-4 electrical connections for communicating two or more electrical signals.

The present application provides an atomic force microscope probe. The atomic force microscope probe is manufactured by the method for manufacturing the atomic force microscope probe according to any one of the embodiments.

Referring to fig. 3, the afm probe includes a tuning fork 20, a tip 10, a balance adjustment device 30, a support substrate 40, and an electrode lead 50. The needle tip 10 is 3mm to 4mm in length. Optionally, the needle tip 10 is 3.5mm in length. The tuning fork 20 comprises a first prong 21, a second prong 22 and a base 23. The balance adjusting means 30 may be a balance wire. The needle tip 10 is bonded to the free end of the first prong 21 of the tuning fork 20 using epoxy or other adhesive. The balance adjustment means 30 is bonded to the free end of the second arm 22 of the tuning fork 20 using epoxy or other adhesive. The support substrate 40 is fixedly connected to the base 23 of the tuning fork 20 through a curing adhesive 31. And the support substrate 40 is connected to the base 23 of the tuning fork 20 by an electrode lead 50.

In this embodiment, the atomic force microscope probe obtains a variation curve of the Q value of the atomic force microscope probe with the length of the tip 10. The variation curve comprises different vibration modes of the QTF. And determining the value range of the length of the needle tip 10 according to the change curve, so that the optimization of the Q value change rule of the QTF probe in the AFM under different lengths of the needle tip 10 according to the additional mass and the vibration mode is realized. According to the value range of the length of the needle tip 10, the size parameters of the tuning fork 20 and the size parameters of the balance adjusting device 30 are determined. The needle tip 10 is fixed to the free end of the first prong 21 of the tuning fork 20, and the balance adjusting device 30 is fixed to the free end of the second prong 22 of the tuning fork 20. The method skillfully utilizes the characteristics and the change rule of the mechanical resonance of the QTF and adopts a proper method to realize the regulation and control of the Q value, and the maximum value of the Q value can be obtained when the length of the probe tip 10 is longer, so that the AFM probe with excellent vibration characteristics is obtained.

In one embodiment, the application provides a method for manufacturing an atomic force microscope probe based on a quartz tuning fork. The fabrication of the atomic force microscope probe based on the quartz tuning fork is divided into the following 5 steps.

Step 1, preparing a Quartz Tuning Fork (QTF) and a bracket:

the Quartz Tuning Fork (QTF) adopts quartz crystal as a material and can be obtained by customization; the crystal can also be obtained by shelling the existing cylindrical crystal oscillator product with the center frequency of 32.768 kHz. Selecting a crystal oscillator with the outer diameter of 3mm and the length of 8mm, and removing the shell. If the tuning fork 20 is smaller in size (e.g., using a crystal oscillator with an outer diameter of 2mm and a length of 6 mm), an AFM probe that meets the requirements cannot be prepared. In the embodiment, the basic manufacturing materials of all tuning fork probes are quartz tuning forks with model numbers YT-38 produced by YXC company (Shenzhen Yangxing technology); the dimensions of the QTF tuning fork 20 used in the examples are as in table 1:

TABLE 1 Experimental Quartz tuning forks and tip 10 size isoparametric

Next, the electrode leads 50 of the QTF were soldered to the mount substrate 40 such that the QTF plane was perpendicular to the mount substrate 40. In one embodiment, a carrier substrate 40 is a circuit board of about 12mm by 9mm by 0.6 mm. In order to make the connection between the support substrate 40 and the QTF more stable, epoxy resin may be used to bond the groove position on the side of the support substrate 40 and the base 23 of the tuning fork 20 (including the position of the electrode lead 50 and the bottom side of the tuning fork 20). 2-4 electrical connection devices are arranged on the support substrate 40 and can lead out electrodes of the QTF; if necessary, an electrode signal of the probe tip 10 or other electrode signals may be extracted together.

Step 2, bonding the metal needle tip 10:

a metal filament is adhered to one arm of the tuning fork 20 as a needle tip 10. The needle tip 10 is made of tungsten or platinum iridium wire with the diameter of 0.05-0.1 mm; the initial length is about 5-6mm (about 2mm longer than the actual length after tip treatment to facilitate its tip treatment). The tungsten tipped filaments in the examples had a diameter of 0.1mm and a length of about 5 mm. The front end of the tungsten wire may be treated without any treatment before bonding. The adhesive used for bonding is an epoxy (generally non-conductive). In order to reduce the amount of glue used in bonding, the section to which the metal wire strip is bonded is first glued and then placed still on the tuning fork arm to wait for bonding. If it is desired to reduce the adhesion time, a photosensitive or thermosensitive type resin may be used in order to accelerate the adhesion by means of light or heat.

Bonding method of the needle tip 10: typically, a vertical force mode (probe tip orientation perpendicular or nearly perpendicular to the tuning fork) is used, but a shear force mode (probe tip orientation parallel to the tuning fork) or an adhesive mode in which the tip 10 is at an angle to the tuning fork may also be used. As shown in fig. 4.

In an embodiment, the initial length of the needle tip 10 is about 5.5mm and the diameter is 0.1 mm.

Step 3, yoke rebalancing treatment:

a length of wire is attached to the prong without the needle tip 10 attached by epoxy. To achieve mass rebalancing, the gauge (material, straightness, length, etc.) of the metal filament used is generally about the same as the gauge of the metal tip 10 after the tip treatment is completed. The adhesive can be the same as that used for bonding the needle tip 10, i.e., epoxy resin is also used; other means of bonding may also be used. Instead of wires, resin glues of approximately equal mass can be used instead, to achieve the same mass-rebalancing effect.

The bonding direction and position of the rebalancing metal filament must be kept symmetrical with the bonding direction and position of the probe tip, i.e. at a symmetrical position rotated 180 degrees with respect to the axial centers of the two tuning fork arms (i.e. the connecting line of the bonding regions on the two arms respectively just passes through the axial center of the QTF). This makes it possible to make the mechanical vibration modes used in the measurement by the probe as symmetrical as possible, thereby facilitating the improvement of the Q value thereof.

Step 4, processing the front end of the needle tip 10;

electrochemical mechanical shearing may be used to sharpen the forward end of the tip 10 or to obtain the desired shape and characteristics of the tip 10. For topographic imaging by Atomic Force Microscopy (AFM), the tip 10 is typically tapered at its forward end and approximately hemispherical at its forward-most end, with the radius of curvature of the hemispherical forward end typically being about 15 nm, in the range of 5-30 nm. Mechanical shearing may also be used to change the leading end to a chamfer at an angle of about 30 degrees to the axis of the wire.

Another purpose of the front end processing of the tip 10 is to achieve a specific requirement for the additional mass and shape of the probe tip to facilitate its Q value increase. In particular, for a needle tip 10 of 0.1mm in diameter, the optimal length is about 3.5 mm; acceptable lengths range from about 3.0mm to 4.0mm with a final Q value greater than 1500; the accuracy of the length adjustment needs to reach about 0.1mm, otherwise the difficulty of adjusting the Q value of the subsequent tuning fork 20 is increased significantly, and even the required Q value cannot be reached.

It should be noted that, for different metal tips 10, different diameters of the tips 10, different bonding methods or different shapes of the tips 10, the optimal length will usually be different, but in most cases the optimal length or additional mass can be found; the optimal values and ranges can be determined by theoretical analysis, simulation calculation or experiments.

And 5, adjusting the Q value of the tuning fork 20.

The Q value adjustment of the tuning fork 20 is to adjust the additional mass or the mass center of the other tuning fork arm in a micro-adjustment manner, so as to achieve the effects of Q value adjustment and calibration. The Q value can be adjusted by the following 2 methods, or by any alternation or combination of the two methods.

The first method of adjusting the Q value of the tuning fork 20 is to adjust the length of the wire for rebalancing. In this method, the initial length of the metal filament for rebalancing is preferably slightly longer than the length of the tip 10 of the probe, but if used in combination with the second method, the initial length is preferably shorter (e.g., half the length) than the length of the tip 10 of the probe. Carefully removing a small piece (about 0.1mm) each time on the end of the wire for rebalancing, changing its length and effective mass; then monitoring the Q value of the tuning fork probe mechanical resonance; if the Q value meets the requirement, the regulation can be finished, otherwise, a small section is cut off again until the Q value meets the requirement.

The second method for adjusting the Q value of the tuning fork 20 is to adjust and rebalance the additional mass of the tuning fork by adjusting and controlling the amount of the curing adhesive 31. One typical approach is to use a photo-curable glue. The specific method comprises the following steps: and injecting the liquid light-cured glue to the specific position of the rebalancing tuning fork arm by using a micro injector, and controlling the mass of the glue added each time, such as adding about 10ug each time. Then monitoring the Q value of the tuning fork probe mechanical resonance; if the Q value meets the requirement, the regulation can be finished, otherwise, the glue dosage is added again until the Q value meets the requirement. Another typical method is to use a heat-curable glue. The concrete method is similar to that of photo-curing glue, and aims to accelerate the curing of the glue by heating so as to be beneficial to the rapid regulation and control of the Q value.

In the examples, Q of QTF-based AFM probes was increased to about 1800 using a method of modulating the length of the rebalancing wire. In this embodiment, the tip 10 is a tungsten wire of 0.1mm diameter and about 3mm in length. The tuning fork 20 used has a Q value of about 8000 in an original state; the Q value of the probe tip 10 having a length of 3.5mm bonded thereto was about 500 before the fork re-balancing process was not performed and the Q value of the tuning fork 20 was not adjusted. Therefore, the Q value of the quartz tuning fork probe can be improved by about 3.5 times by the method.

In another embodiment, the Q-value adjusting effect of the tip 10 from 1mm to 4.5mm in length was tested by using a tungsten wire having a diameter of 0.1mm as the tip 10 to adjust the length of the metal filament for rebalancing. The results are shown in FIG. 5. The open circles in the figure indicate the adjusted Q values. Except that the Q value decreased with increasing probe length, the results show that: after rebalancing and Q-value adjustment, the QTF probe has a significantly higher Q-value than a common QTF probe. A particular decrease in Q was observed at probe tips less than about 2.1mm in length. In addition, as the probe tip length becomes longer, the difference between the Q values of the two probes becomes larger, so that the Q value adjustment effect is better when the probe is relatively long. In general, the Q value of the tuning fork probe with the long tip 10 stuck thereon is relatively low, which means that the tuning fork probe with the long tip 10 tends to have a larger lift space. Therefore, the preparation method of the present application will be more effective for the application scenario of long tips such as 3.5 mm). An unregulated long tip reduces the Q of a QTF probe below 500, which is not possible for AFM imaging of high quality. After the preparation method is adopted, the performance of the long-needle-point tuning fork probe (particularly for a tungsten wire probe with the length of about 3.5mm) can be obviously improved.

In this embodiment, when the tip 10 of the probe is made of a metal material and has a long length (e.g., a length in the range of 3-4 mm), the prepared QTF probe can still achieve a high Q value (e.g., over 1000). In principle, the preparation method can remarkably enhance the mechanical vibration of the opposite-phase vibration mode of the QTF probe, thereby showing a larger Q value.

The AFM probe with the slender tip 10 provided by the technical means is particularly suitable for measurement imaging of Electrostatic Force in an Electrostatic Force Microscope (EFM). This is because the slender tip 10 structure can significantly increase the contribution of the local part of the front end of the tip 10 of the probe to the detection of the electrostatic force, and reduce or avoid the influence of stray capacitance generated by the rest of the probe (such as tuning fork arms or cantilever beams), thereby improving the spatial resolution of the EFM measurement imaging.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.