CN113588989A - Scanning Casimir force microscope and method of use - Google Patents
Scanning Casimir force microscope and method of use Download PDFInfo
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- CN113588989A CN113588989A CN202110855322.4A CN202110855322A CN113588989A CN 113588989 A CN113588989 A CN 113588989A CN 202110855322 A CN202110855322 A CN 202110855322A CN 113588989 A CN113588989 A CN 113588989A
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- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
- G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
- G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
- G01Q60/38—Probes, their manufacture, or their related instrumentation, e.g. holders
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q70/00—General aspects of SPM probes, their manufacture or their related instrumentation, insofar as they are not specially adapted to a single SPM technique covered by group G01Q60/00
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Abstract
一种扫描卡西米尔力显微镜及使用方法，该扫描卡西米尔力显微镜，包括：扫描管，用于放置样品；样品控制器，用于发出控制扫描管的移动的控制信号；计算机控制系统，用于接收控制信号并依此控制扫描管的移动；激光器，用于发出激光；卡西米尔力探针，包括悬臂梁和位于悬臂梁端部的球状测量针尖，悬臂梁上设有反射面，用于反射激光器发出的激光；测量针尖用于与样品产生卡西米尔效应；四象限接收器，用于接收悬臂梁的反射面反射的激光以及将激光转换成电压信号；以及四象限信号读出器，用于读取四象限接收器的电压信号从而确定卡西米尔力的大小。
A scanning Casimir force microscope and using method, the scanning Casimir force microscope comprises: a scanning tube for placing a sample; a sample controller for sending out control signals for controlling the movement of the scanning tube; a computer control system, It is used to receive the control signal and control the movement of the scanning tube accordingly; the laser is used to emit laser light; the Casimir force probe includes a cantilever beam and a spherical measuring tip at the end of the cantilever beam, and the cantilever beam is provided with a reflective surface, Used to reflect the laser light emitted by the laser; the measuring tip is used to generate the Casimir effect with the sample; the four-quadrant receiver is used to receive the reflected laser light from the reflecting surface of the cantilever beam and convert the laser light into a voltage signal; and the four-quadrant signal readout The device is used to read the voltage signal of the four-quadrant receiver to determine the magnitude of the Casimir force.
Description
Technical Field
The invention relates to the field of microscope devices and the field of precision mechanics detection, in particular to a scanning Casimilar force microscope and a using method thereof.
Background
In recent years, as the demand for measuring physical properties of materials has increased, more and more scanning probe microscopes have been used in the research of materials. The scanning probe microscopes currently used for sample characterization are mainly the following: (1) atomic Force Microscope (AFM); (2) electrostatic Force Microscopy (EFM); (3) magnetic Force Microscope (MFM); (4) a Lateral Force Microscope (LFM), and the like.
With the development of the era, more and more physical properties can be detected by scanning techniques, such as Tip Enhanced Raman Scattering Microscope (TERSM), Magnetic Force Microscope (MFM), Microwave Impedance Microscope (MIM), and the like, to achieve spatially resolved detection of physical properties.
In the middle of the last century, the netherlands physicist cassimel (Casimir) proposed that due to vacuum zero electromagnetic fluctuations, there would be attraction between two parallel ideal uncharged conductor plates, and thereafter the soviet physicist Lifshitz (Lifshitz) developed a correction of the cassimel effect in the subsequent medium environment, taking into account the influence of the dielectric function and permeability of the medium material on the Casimir effect. Dermagin et al have also studied the effect of object shape on the Casimilar effect since then, and these theories of work lay a solid foundation for the subsequent development of the Casimilar effect.
Although the current measurement of the Casimir effect can be carried out in various medium environments and different materials, only samples with known conductivity and permeability can be measured, and samples with unknown parameters such as conductivity and permeability cannot be directly measured, so that the method has a large gap from practical application research. At the same time, these associated microscopes can cause more or less damage to the sample during the measurement, especially when measuring softer materials, which can cause significant resistance to continued use of the sample.
Disclosure of Invention
In view of the above, it is a primary object of the present invention to provide a scanning cassimeial force microscope and method of use that at least partially solves at least one of the above mentioned technical problems.
To achieve the above object, as a first aspect of the present invention, there is provided a scanning cassimel force microscope comprising: the scanning tube is used for placing a sample; a sample controller for sending a control signal for controlling the movement of the scanning tube; the computer control system is used for receiving the control signal and controlling the movement of the scanning tube according to the control signal; a laser for emitting laser light; the Casimir force probe comprises a cantilever beam and a spherical measuring needle point positioned at the end part of the cantilever beam, wherein the cantilever beam is provided with a reflecting surface for reflecting laser emitted by the laser; the measuring needle tip is used for generating a Casimir effect with the sample; the four-quadrant receiver is used for receiving the laser reflected by the reflecting surface of the cantilever beam; and converting the laser light into a voltage signal; and a four-quadrant signal reader for reading the voltage signal of the four-quadrant receiver to determine the magnitude of the Cassimmer force.
As a second aspect of the present invention, there is also provided a method of using a scanning cassimei force microscope as described above, comprising:
placing a sample on a scanning tube; measuring the inclination of the sample surface for slope correction; the measuring needle tip is contacted with a sample on a scanning tube and then separated from the sample, the relation between the voltage value applied to the scanning tube in the vertical direction and the distance between the measuring needle tip and the sample is determined, and the height of the measuring needle tip is kept fixed; sending a signal for controlling the movement of the scanning tube by using a sample controller, and acting on a computer control system to enable the computer control system to control the scanning tube to move according to the inclination of the inclined plane, so that the measuring needle tip scans the upper part of the surface of the sample; during scanning, laser emitted by the laser is reflected to the four-quadrant receiver through the cantilever beam and converted into a voltage signal, and the voltage signal is read by the four-quadrant signal reader, so that the Casimir force is determined through the voltage signal.
According to the technical scheme, the scanning Casimilar force microscope and the using method have one or part of the following beneficial effects:
(1) the invention relates to a scanning Casimir force microscope, which utilizes a sample controller to send out a control signal for controlling the movement of a scanning tube and acts the signal on a computer control system, wherein the computer system comprises a computer host and a microscope controller, the computer host sends out an instruction to the microscope controller after receiving the control signal of the sample controller, and the microscope controller controls the movement of the scanning tube by applying voltage to the scanning tube.
(2) The scanning Casimir force microscope is provided with the four-quadrant signal reader, the four-quadrant signal reader can directly read the voltage signal of the four-quadrant receiver, and the voltage signal is in direct proportion to the Casimir force, so that the Casimir force can be determined.
(3) The measuring needle point in the scanning Casimilar force microscope is a ball with a metal surface, and the Casimilar effect is generated between the metal ball and a sample, so that the Casimilar force is measured.
Drawings
FIG. 1 is a schematic structural view of a scanning Casimilar force microscope in example 1 of the present invention;
FIG. 2 is a schematic view showing the structure of a Casimilar force probe in a scanning Casimilar force microscope in example 1 of the present invention;
FIG. 3 is a graph comparing a Casimir force measured by a scanning Casimir force microscope in example 2 of the present invention with a theoretical curve;
FIG. 4 is a graph of the Casimilar force experimentally measured before the electrostatic force is not eliminated by the scanning Casimilar force microscope in example 2 of the present invention;
FIG. 5 is a comparison of the Casimilar force plus trip point correction curve measured by the scanning Casimilar force microscope in example 2 of the present invention with the theoretical curve;
FIG. 6 shows the Casimilar force signal measured from a one-dimensional scanning peak sample when the distance between the fixed sample and the measuring tip is 3.7 nm in example 3 of the present invention;
FIG. 7 shows the Casimir force signal measured from a two-dimensional scanning peak sample at a distance of 11.1 nm from the fixed sample to the measuring tip in example 3 of the present invention;
FIG. 8 is a method of using the scanning Casimilar force microscope of the present invention.
Description of the reference numerals
1 laser
2 Casimir force measuring probe
21 measuring tip 22 cantilever
3 Probe holder
4 samples
5 scanning tube
6 microscope base
7 microscope probe
8 four-quadrant receiver
9 four-quadrant signal reader
10 computer control system
11 sample controller
12 computer display
Detailed Description
In recent decades, many experiments for measuring the Casimilar effect between materials emerge, and particularly, a method for measuring the Casimilar effect between a metal ball and a metal plate based on an atomic force microscope device provides an important experimental basis for the subsequent research on the Casimilar effect. The method uses a special gold ball probe to measure the relationship between the cassimel force of the gold ball and the gold plate as a function of distance.
In the process of implementing the invention, it is found that the Casimilar force can be measured by designing the measuring tip in the scanning Casimilar force microscope as a ball with a metal surface and utilizing the Casimilar effect generated between the metal ball and the sample. When the measuring needle tip scans on the surface of a sample, the sample controller sends out a control signal for controlling the movement of the scanning tube, and the signal is acted on a computer control system to further control the movement of the scanning tube. In addition, a four-quadrant signal reader is designed, so that the voltage signal of the four-quadrant receiver can be directly read, and the Casimir force can be further determined.
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
According to an embodiment of the present invention, there is provided a scanning cassimei force microscope including: the scanning tube is used for placing a sample; the sample controller is used for sending out a control signal for controlling the movement of the scanning tube; the computer control system is used for receiving the control signal and controlling the movement of the scanning tube according to the control signal; a laser for emitting laser light; the Casimir force probe comprises a cantilever beam and a spherical measuring needle tip positioned at the end part of the cantilever beam, wherein the cantilever beam is provided with a reflecting surface for reflecting laser emitted by a laser; the measuring needle tip is used for generating a Casimir effect with the sample; the four-quadrant receiver is used for receiving the laser reflected by the reflecting surface of the cantilever beam and converting the laser into a voltage signal; and a four-quadrant signal reader for reading the voltage signal of the four-quadrant receiver to determine the magnitude of the Cassimmer force.
The voltage signal read by the four-quadrant signal reader, i.e., the (Up-Down) signal, has a voltage value proportional to the cassimel force, and thus, the magnitude of the cassimel force can be determined based on the voltage signal. The computer control system comprises a computer host and a microscope controller, wherein the computer host sends an instruction to the microscope controller after receiving a control signal of the sample controller, and the microscope controller controls the movement of the scanning tube by applying voltage to the scanning tube.
The relationship between Casimilar force and Up-Down signal is: casimilar force F ═ K/K1)VmWherein F is Casimir force, K is the expansion coefficient of the drawing tube in the vertical direction, Vm is Up-Down signal, K is1The proportionality coefficient of the Up-Down signal and the deformation quantity of the cantilever beam is shown.
According to an embodiment of the invention, the scanning cassimei force microscope further comprises: the microscope probe is used for observing the positions of the measuring needle point, the sample and the laser spot in real time; the microscope base is used for placing and fixing the scanning tube; and a computer display for displaying the program of the control signal received by the computer control system.
According to an embodiment of the invention, the measuring tip is a ball with a metal surface, in particular a gold-plated polystyrene ball, the diameter of which is between 20 and 100 micrometers.
According to the embodiment of the invention, the elastic coefficient of the cantilever beam is between 0.02N/m and 0.06N/m, and the material of the cantilever beam is SiN.
There is also provided, in accordance with an embodiment of the present invention, a method of using a scanning Casimilar force microscope as above. FIG. 8 is a method of using the scanning Casimilar force microscope of the present invention. As shown in fig. 8, the using method includes: placing a sample on a scanning tube; measuring the inclination of the surface of the sample to perform slope correction; the measuring needle point is contacted with a sample on the scanning tube and then separated from the sample, the relation between the voltage value applied to the scanning tube in the vertical direction and the distance between the measuring needle point and the sample is determined, and the height of the measuring needle point is kept fixed; a sample controller is used for sending a signal for controlling the movement of the scanning tube and acting on a computer control system, so that the computer control system controls the scanning tube to move according to the inclination of the inclined plane, and the measuring needle point scans the upper part of the surface of the sample; during scanning, laser emitted by the laser is reflected to the four-quadrant receiver through the cantilever beam and converted into a voltage signal, and then the voltage signal is read by the four-quadrant signal reader, so that the Casimir force is determined through the voltage signal.
According to an embodiment of the present invention, the computer system controls the movement of the scanning tube by controlling the voltage applied to the scanning tube.
According to an embodiment of the invention, a method for performing slope correction on a sample surface comprises: the measuring needle point is separated from the sample after contacting, and the distance H between the measuring needle point and the sample is obtained1(ii) a Horizontally moving the sample for a distance L, and contacting the sample with the measuring tipThe distance between the sample and the measuring needle tip after the sample moves horizontally is H2(ii) a The slope of the sample surface was (H)1-H2)/L。
The sample controller of the scanning Casimir force microscope of the invention sends out a control signal for controlling the movement of the scanning tube based on a preset program, and after a host of a computer control system receives the control signal, the host regulates and controls the voltage applied to the scanning tube through the microscope controller so as to control the movement of the scanning tube.
According to the embodiment of the invention, the distance between the measuring tip and the sample is less than 1000nm, and the frequency of the sample scanned by the measuring tip is 0.1Hz-1 Hz.
The technical solution of the present invention will be described in detail below with reference to specific examples. It should be noted that the following specific examples are only for illustration and are not intended to limit the invention.
Example 1
FIG. 1 is a schematic diagram of a scanning Casimilar force microscope in an embodiment of the present invention. FIG. 2 is a schematic diagram of the structure of the Casimilar force probe in the scanning Casimilar force microscope in an embodiment of the present invention.
As shown in fig. 1 and 2, the structure of the scanning cassimei force microscope of the present invention includes:
a scanning tube 5 for placing a sample 4;
a sample controller 11 for sending a control signal for controlling the movement of the scanning tube 5;
a computer control system 10 for receiving control signals from the sample controller 11 and controlling the movement of the scanning tube 5; the computer control system 10 includes a host computer and a microscope controller, the host computer sends an instruction to the microscope controller after receiving the control signal from the sample controller 11, and the microscope controller controls the movement of the scanning tube by applying a voltage to the scanning tube.
A laser 1 for emitting laser light;
the Casimilar force probe 2 comprises a cantilever beam 22 and a spherical measuring tip 21 positioned at the end part of the cantilever beam 22, wherein the measuring tip 21 is a gold-plated polystyrene sphere with the diameter of 100 microns, the measuring tip 21 is arranged at the end part of the cantilever beam 22, and in the embodiment of the disclosure, the cantilever beam 22 is in a triangular structure as shown in FIG. 2; the cantilever beam 22 is provided with a reflecting surface for reflecting the laser emitted by the laser 1; the spherical measuring needle point 21 is used for generating a Casimir effect with a sample;
the four-quadrant receiver 8 is used for receiving the laser reflected by the reflecting surface of the cantilever beam 22 and converting the laser into a voltage signal; and
a four-quadrant signal reader 9 for reading a voltage signal of the four-quadrant receiver 8, the voltage signal being used to determine the magnitude of the cassimel force;
the microscope probe 7 is an atomic force microscope probe and is used for observing the relative position of the Casimir force probe 2 and the sample and the position of the laser in real time;
the microscope base 6 is an atomic force microscope base and is used for placing and fixing the scanning tube 5; and
a computer display 12 for displaying the program of the control signal received by the computer control system 10.
Example 2
In this embodiment, the fixed point in the sample is detected to verify that the cassimell force can be measured using the cassimell force microscope of the present invention as described above, and the specific steps are as follows:
step 1: the cassimell effect probe 2 (cantilever 22 is SiN, the measuring tip 21 is 100 micron polystyrene bead, and Au with a thickness of 100 nm is plated on the surface) is installed in the apparatus, and the scanning tube 5 with a range of 100 microns is installed and the sample 4 is fixed.
Step 2: the measuring tip 21 and the sample 4 are connected to ground, while the ion blower is activated for eliminating the influence of electrostatic force.
And step 3: the contact mode is selected and the position of the laser is observed using the microscope probe 7, centering the laser spot at the center of the sample and the small circle in the center of the four quadrant window on the computer display, ensuring that the four quadrant reader signals Up-Down and Left-Right read a value of 0.
And 4, step 4: measuring the needle point 21, selecting proper 'reference point' and 'integral gain' and 'proportional gain' in the computer control system 10 (respectively set to 0.2, 200 and 200) and selecting to start needle insertion, and ending needle insertion when the voltage applied to the piezoelectric ceramic (i.e. the scanning tube 5) is suddenly changed from 180V to about 0V.
And 5: the distance between the measuring needle point 21 and the sample 4 is gradually reduced by using the sample controller 11 and the computer control system 10 until the Up-Down signal suddenly jumps, the value of the Up-Down signal (which is a voltage signal) and the voltage value loaded on the piezoelectric ceramic (i.e. the scanning tube 5) are recorded in real time in the process, and the distance between the sample 4 and the measuring needle point 21 at the corresponding moment is obtained according to the voltage value loaded on the piezoelectric ceramic (i.e. the scanning tube 5). The Casimir force is determined from the value of the Up-Down signal, and the relationship between the distance between the sample 4 and the measuring tip 21 and the Casimir force can be obtained.
In order to improve the measurement and data analysis accuracy, jump correction needs to be performed on the data of the measurement data of the scanning Casimilar force microscope. When the distance between the measuring tip 21 and the sample 4 is very close, the restoring moment of the cantilever beam 22 is not enough to overcome the external moment caused by the cassimel force, so that the measuring tip 21 suddenly jumps to be in contact with the gold plate, and therefore, the measured cassimel force needs to be corrected by using a jump point so as to improve the fitting precision of a theoretical curve to experimental data. That is, the measured cassimei force-distance curve is moved in the positive X direction to correct the distance at which the measuring tip 21 jumps into contact with the sample 4. Typically the value of the jump correction is in the range of 50 nm to 100 nm.
FIG. 3 is a graph comparing Casimir force measured by a scanning Casimir force microscope with a theoretical curve in an example of the invention. As shown in fig. 3, in order to verify the feasibility of the scanning cassimel force microscope of the present invention, an experiment was performed based on the cassimel force scanning microscope, and the force-distance curve of the measured scanning cassimel force microscope was compared with the theoretical curve, and the experiment was performed at room temperature. It can be seen from fig. 3 that the force-distance curve of the microscope measured in this example corresponds well to the theoretical curve.
FIG. 4 is a graph of Casimilar force experimentally measured with a scanning Casimilar force microscope prior to eliminating the electrostatic force in an embodiment of the present invention. As shown in FIG. 4, the Casimilar force-distance curve measured for sample 4, which was a 300nm gold (Au) -plated silicon plate before the electrostatic force was eliminated, was significantly different from the theoretical curve.
FIG. 5 is a comparison of the Casimilar force plus trip point correction curve measured by a scanning Casimilar force microscope and the theoretical curve. As shown in fig. 5, the force-distance curve of the microscope measured experimentally with the trip point correction added is closer to the theoretical curve.
Example 3
The method for using the Casimilar force microscope comprises the following steps of 1-7:
step 1: the cassimell effect probe 2 (cantilever 22 is SiN, the measuring tip 21 is 100 micron polystyrene bead, and Au with a thickness of 100 nm is plated on the surface) is installed in the apparatus, and the scanning tube 5 with a range of 100 microns is installed and the sample 4 is fixed.
Step 2: the measuring tip 21 and the sample 4 are connected to ground, while the ion blower is activated for eliminating the influence of electrostatic force.
And step 3: the contact mode is selected and the position of the laser is observed using the microscope probe 7, centering the laser spot at the center of the sample and the small circle in the center of the four quadrant window on the computer display, ensuring that the four quadrant reader signals Up-Down and Left-Right read a value of 0.
And 4, step 4: measuring the needle point 21, selecting proper 'reference point' and 'integral gain' and 'proportional gain' in the computer control system 12 (respectively set to 0.2, 200 and 200) and selecting to start the needle insertion, when the voltage applied on the piezoelectric ceramic (namely the scanning tube 5) is suddenly changed from 180V to about 0V, the needle insertion is ended.
And 5: utilizing the sample controller 11 and the computer control system 10, starting the scanning function in the x and y directions to measure the inclination of the surface of the sample 4, and obtaining the inclination of the surface of the sample 4, which specifically comprises:
and measuring the height difference of two positions with a certain distance, dividing the height difference by the distance difference according to the distance of the two points in the horizontal direction to obtain the slope of the sample along the direction, and finishing the process of slope correction. That is, the measuring tip 21 is brought into contact with the sample 4 and then separated therefrom, and the distance H between the measuring tip 21 and the sample 4 at this time is recorded1(ii) a Horizontally moving the sample 4 for a distance L, and then contacting the sample 4 with the measuring needle point 21 to obtain the distance H between the sample and the measuring needle point after the sample moves horizontally2The slope of the sample surface is (H)1-H2) And L. The microscope controller regulates and controls the voltage applied to the scanning tube 5 so as to control the movement of the scanning tube 5, and the program of the control signal is preset, so that the real-time voltage value applied to the scanning tube 5 can be known, and the voltage value and the movement distance of the scanning tube have a functional relation, so that the movement distance of the sample can be determined according to the voltage value.
Step 6: the method comprises the following steps of (1) introducing voltage to piezoelectric ceramics in the z direction, contacting the measuring needle point 21 with the sample 4, then separating the contact, and obtaining the distance between the measuring needle point 21 and the sample 4 according to a voltage value in the vertical direction of the scanning tube 5, wherein the method comprises the following specific steps:
the voltage applied to the vertical direction of the scanning tube 5 at the initial scanning time is set, so that the descending height of the sample is calculated. By scanning for one cycle, the sample 4 is corrected to be raised by a certain height, and the raising of the height is stopped when the sample 4 comes into contact with the measuring tip 21. The distance between the measuring tip 21 and the sample 4 is determined by the number of cycles scanned determining the value of the voltage applied in the vertical direction of the scanning tube 5.
And 7: fixing the height position of the measuring needle point 21, slowing down the speed of the measuring needle point 21 and finely scanning the sample 4, wherein laser emitted by the laser 1 is reflected to the four-quadrant receiver 8 through the cantilever arm 22 during scanning to be converted into a voltage signal, the voltage signal is read out by the four-quadrant signal reader 9, and the Casimir force is determined according to the relationship between the voltage signal and the Casimir force, and the method comprises the following specific steps:
the voltage value added in the vertical direction of the scanning tube 5 is set according to the set distance between the measuring needle point 21 and the sample 4 through the relationship between the voltage value added in the vertical direction of the scanning tube 5 and the distance between the measuring needle point 21 and the sample 4, the scanning frequency is set, fine scanning is carried out, and the numerical value of the Cassimmer force between the sample 4 and the measuring needle point is obtained by collecting the voltage signal of the four-quadrant signal reader 9.
In order to improve the measurement and data analysis accuracy, jump correction needs to be performed on the data of the measurement data of the scanning Casimilar force microscope. When the distance between the measuring tip 21 and the sample 4 is very close, the restoring moment of the cantilever beam 22 is not enough to overcome the external moment caused by the cassimel force, so that the measuring tip 21 suddenly jumps to be in contact with the gold plate, and therefore, the measured cassimel force needs to be corrected by using a jump point so as to improve the fitting precision of a theoretical curve to experimental data. That is, the measured cassimei force-distance curve is moved in the positive X direction to correct the distance at which the measuring tip 21 jumps into contact with the sample 4. Typically the value of the jump correction is in the range of 50 nm to 100 nm.
FIG. 6 is a Casimilar force signal measured from a one-dimensional scan peak sample at a fixed sample tip distance of 3.7 nm in an example of the present invention. As shown in fig. 6, the sample 4 is a silicon plate with a peak (convex) Au plating on the surface, and the sample is scanned in one dimension by the scanning cassimel force microscope of the present invention, and it can be seen from fig. 6 that the cassimel force value read by the four-quadrant signal reader 9 is significantly decreased at the convex portion of the sample because the convex portion of the sample is closer to the measuring probe, and the third power of the distance between the sample and the measuring probe is inversely proportional to the cassimel force value read by the four-quadrant signal reader.
FIG. 7 shows the Casimilar force signal measured from a two-dimensional scanning peak sample at a distance of 11.1 nm from the stationary sample tip in an example of the present invention. Fig. 7 is a result of two-dimensional scanning of the sample 4 of fig. 6, wherein the sample is at a distance of 11.1 nm from the measuring tip 21. The shade of the color indicates the strength of the Casimilar force. As can be seen from fig. 7, the value of the cassimel force read by the four-quadrant signal reader 9 is significantly decreased at the convex portion of the sample 4.
The cassimell microscope of the present invention can work in atmospheric, vacuum and liquid medium environments. The method can also be used for detecting the Casimir effect of dielectric materials such as gold, silicon dioxide, graphene and the like, researching the influence of plasmons on the Casimir effect, and simultaneously obtaining the surface morphology of the sample.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A scanning cassimei force microscope comprising:
the scanning tube is used for placing a sample;
the sample controller is used for sending out a control signal for controlling the movement of the scanning tube;
the computer control system is used for receiving the control signal and controlling the movement of the scanning tube according to the control signal;
a laser for emitting laser light;
the Casimir force probe comprises a cantilever beam and a spherical measuring needle point positioned at the end part of the cantilever beam, wherein the cantilever beam is provided with a reflecting surface for reflecting laser emitted by the laser; the measuring needle tip is used for generating a Casimir effect with the sample;
the four-quadrant receiver is used for receiving the laser reflected by the reflecting surface of the cantilever beam and converting the laser into a voltage signal; and
a four-quadrant signal reader for reading the voltage signal of the four-quadrant receiver to determine the magnitude of the Cassimmer force.
2. The scanning cassimeiil force microscope of claim 1, wherein the scanning cassimeiil force microscope further comprises:
the microscope probe is used for observing the positions of the measuring needle point, the sample and the laser spot in real time;
the microscope base is used for placing and fixing the scanning tube; and
and the computer display is used for displaying the program of the control signal received by the computer control system.
3. The scanning cassimeiil force microscope of claim 1, wherein the measuring tip is a sphere whose surface is metal;
the ball with the metal surface is a polystyrene ball with gold-plated surface.
4. The scanning Casimilar force microscope of claim 3, wherein the polystyrene spheres are between 20 microns and 100 microns in diameter.
5. The scanning cassimei force microscope of claim 1, wherein the cantilever beam has a spring rate between 0.02N/m and 0.06N/m.
6. The scanning cassimei force microscope of claim 1, wherein the cantilever beam is of SiN.
7. A method of using the scanning cassimeiil force microscope of any one of claims 1-6, comprising:
placing a sample on a scanning tube;
measuring the inclination of the sample surface for slope correction;
the measuring needle tip is contacted with a sample on a scanning tube and then separated from the sample, the relation between the voltage value applied to the scanning tube in the vertical direction and the distance between the measuring needle tip and the sample is determined, and the height of the measuring needle tip is kept fixed;
sending a signal for controlling the movement of the scanning tube by using a sample controller, and acting on a computer control system to enable the computer control system to control the scanning tube to move according to the inclination of the inclined plane, so that the measuring needle tip scans the upper part of the surface of the sample;
during scanning, laser emitted by the laser is reflected to the four-quadrant receiver through the cantilever beam and converted into a voltage signal, and the voltage signal is read by the four-quadrant signal reader, so that the Casimir force is determined through the voltage signal.
8. The use of claim 7, wherein the computer system controls the movement of the scanning tube by controlling the voltage applied to the scanning tube.
9. The method of use of claim 7, wherein the method of performing slope correction on the sample surface comprises:
separating the measuring needle tip from the sample after contacting the sample to obtain the distance H between the measuring needle tip and the sample1；
Horizontally moving the sample for a distance L, and then contacting the sample with the measuring needle point to obtain the distance H between the sample and the measuring needle point after the sample is horizontally moved2；
The slope of the sample surface is (H)1-H2)/L。
10. The use of claim 7, wherein the distance between the measuring tip and the sample is less than 1000 nm;
the frequency of the sample scanned by the measuring needle tip is 0.1Hz-1 Hz.
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