Scanning probe microscope and method

Abstract

A technique for improving the accuracy of a sample elastic modulus calculation is provided. A control section of a scanning probe microscope having a displacement detector for detecting probe displacement generates a first force curve that is a measurement result of the probe displacement accompanying a change in the distance between the probe and the sample, using the detection output of the displacement detector with respect to the sample. Furthermore, the control section generates a second force curve by excluding a region shorter than the distance of an inflection point in the first force curve from the first force curve. Then, the control section calculates the elastic modulus of the sample based on the second force curve and a theoretical formula.

Description

Technical Field

[0001] This invention relates to the calculation of the elastic modulus of a sample using SPM (Scanning Probe Microscope). Background Technology

[0002] The SPM has a cantilever with a probe at its front end. The SPM acquires information about the sample surface by bringing the probe close to the sample and generates an observation image based on that information. Japanese Patent Application Publication No. 2022-013401 (Patent Document 1) mentions using an SPM to calculate the elastic modulus of a sample.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2022-013401 Summary of the Invention The technical problem that the invention aims to solve The elastic modulus is an indicator of the hardness of a sample, but in the prior art, sometimes the elastic modulus value is calculated to deviate from the value expected based on the actual hardness of the sample.

[0004] In view of the above facts, the present invention aims to provide a technique for improving the accuracy of calculating the elastic modulus of a sample.

[0005] Solution to the above technical problems According to one aspect of this disclosure, a scanning probe microscope comprises: a sample stage on which a sample is mounted; a cantilever fixed at its base and having a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, characterized in that the control unit is configured to: generate a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector, wherein the first force curve determines a jump... A first region, starting from the -in portion and corresponding to a range shorter than the jump-in portion, in which the probe begins to be attracted by the sample in response to the shortening distance, the control unit in the first region determines the region from the first inflection point closest to the jump-in portion among one or more inflection points in the first region to the jump-in portion as a basic region, and determines the region other than the basic region as an exclusion region, generates a second force curve by excluding the exclusion region from the first force curve, and calculates the elastic modulus of the sample based on the second force curve and a theoretical formula.

[0006] A scanning probe microscope according to one aspect of this disclosure comprises: a sample stage on which a sample is placed; a cantilever with its base fixed and a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, characterized in that the control unit is configured to: generate a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector; generate a second force curve by excluding regions from the first force curve whose distances are shorter than the inflection points in the first force curve; and calculate the elastic modulus of the sample based on the second force curve and a theoretical formula.

[0007] According to one aspect of this disclosure, a method for calculating the elastic modulus of a sample using a scanning probe microscope, the scanning probe microscope comprising: a sample stage on which a sample is placed; a cantilever fixed at its base and having a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, the method comprising: generating a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector; and controlling the first force curve by... The steps are as follows: 1) excluding regions shorter than the inflection point from the curve to generate a second force curve; and 2) calculating the elastic modulus of the sample based on the second force curve and a theoretical formula. The step of generating the second force curve includes, within the first force curve, determining a first region starting from the jump-in portion and corresponding to a range shorter than the jump-in portion, in which the probe begins to experience attraction from the sample in response to the shortening distance. The step of generating the second force curve also includes, within the first region, determining the inflection point closest to the jump-in portion among one or more inflection points in the first region as the inflection point.

[0008] A method according to one aspect of this disclosure is a method for calculating the elastic modulus of a sample using a scanning probe microscope, the scanning probe microscope comprising: a sample stage on which a sample is placed; a cantilever fixed at its base and having a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, the method comprising: generating a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector; generating a second force curve by excluding regions shorter than the inflection point from the first force curve; and calculating the elastic modulus of the sample based on the second force curve and a theoretical formula.

[0009] Invention Effects According to one aspect of this disclosure, a technique for improving the accuracy of calculating the elastic modulus of a sample is provided. Attached Figure Description

[0010]

【 Figure 1 [Illustrated diagram] is a schematic diagram showing the structure of the SPM100 according to the embodiment.

[0011]

【 Figure 2 The figure shown is an example of the hardware structure of the information processing device 20.

[0012]

【 Figure 3 The diagram illustrates the mechanical model upon which the JKR (Johnson, Kendall, Roberts) method is based.

[0013]

【 Figure 4 The figure shown is an example of a force curve obtained by measurement when the sample has adhesion.

[0014]

【 Figure 5 The figure shown is an example of a load-displacement curve.

[0015]

【 Figure 6 The diagram shows the state of probe 3 and sample of cantilever 2 at the equilibrium point and the maximum adhesion point.

[0016]

【 Figure 7 The figure shown is an example of a force curve obtained through measurements unaffected by adhesion.

[0017]

【 Figure 8 The figure above represents the contact theory model in the Hertz method.

[0018]

Figure 9 The symbol

[0019]

【 Figure 10 The diagram above is a schematic representation of the mechanical model upon which the Sneddon method is based.

[0020]

【 Figure 11 The figure shown is an example of a force curve obtained through measurements unaffected by adhesion.

[0021]

【 Figure 12 The figure above represents the contact theory model in the Sneddon method.

[0022]

Figure 13 The symbol

[0023]

【 Figure 14 The figure shown is an example of a force curve generated based on the measurement results of the sample.

[0024]

【 Figure 15 The figure shown is a specific example of a force curve.

[0025]

Figure 16

[0026]

【 Figure 17 [] is used for explanation Figure 15 A graph showing the correction of the force curve.

[0027]

【 Figure 18 The figure shown is a specific example of a force curve.

[0028]

Figure 19

[0029]

【 Figure 20 The graph shown is the corrected force curve.

[0030]

【 Figure 21 This is a flowchart of the process performed by the information processing device 20 to calculate the elastic modulus. Detailed Implementation

[0031] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, identical or equivalent parts in the drawings are given the same reference numerals, and their descriptions are omitted.

[0032] [Structure of a scanning probe microscope] Figure 1This is a schematic diagram illustrating the structure of the SPM100 according to the embodiment. The SPM100 is an atomic force microscope (AFM) that observes a sample S by utilizing interatomic forces (attraction or repulsion) acting between a probe and the surface of the sample S.

[0033] Reference Figure 1 The SPM100 includes an observation device 80, an information processing device 20, a display device 26, and an input device 28. The observation device 80 includes an optical system 1, a cantilever 2, a scanner 10, a sample stage 12, a drive unit 16, a computing unit 17, and a control unit 18.

[0034] The scanner 10 is a moving device used to change the relative positional relationship between the sample S and the probe 3. The sample S is held on the sample stage 12 placed on the scanner 10. The scanner 10 has an XY scanner that scans the sample S in mutually orthogonal X and Y axis directions, and a Z scanner that micro-moves the sample S in the Z axis direction. The XY and Z scanners are composed of piezoelectric elements that deform according to the voltage applied from the drive unit 16. The scanner 10 scans in three dimensions (X-axis, Y-axis, and Z-axis directions) according to the voltage applied to the piezoelectric elements. Thus, the relative positional relationship between the sample S and the probe 3 placed on the scanner 10 can be changed in three dimensions.

[0035] The cantilever 2 has a surface opposite to the sample S and a back surface opposite to that surface. One end of the cantilever 2 is supported by a support 4. The cantilever 2 has a probe 3 on the surface of its free end, i.e., the front end. The probe 3 is configured to be opposite to the sample S. As the probe 3 moves along the surface of the sample S, the cantilever 2 is displaced due to the interatomic forces acting between the probe 3 and the sample S.

[0036] An optical system 1 for detecting the displacement of the cantilever 2 in the Z-axis direction is provided above the cantilever 2. When observing the sample S, the optical system 1 illuminates the back of the cantilever 2 with a laser beam and detects the laser beam reflected from the back of the cantilever 2. The optical system 1 includes a laser source 6, a beam splitter 5, a reflector 7, and a photodetector 8.

[0037] The laser source 6 has a laser oscillator that emits a laser beam. The photodetector 8 has a four-quadrant photodiode that detects the incident laser beam. The laser beam LA emitted from the laser source 6 is reflected by the beam splitter 5 and illuminates the back side of the cantilever 2.

[0038] The cantilever 2 is made of silicon or silicon nitride and can reflect the laser beam incident from the optical system 1 onto the back of the cantilever 2. The laser beam reflected from the back of the cantilever 2 is then reflected by the mirror 7 and incident on the photodetector 8. The displacement of the cantilever 2 can be detected by detecting the laser beam through the photodetector 8.

[0039] Specifically, the photodetector 8 has multiple (usually two) light-receiving surfaces divided in the displacement direction (Z-axis direction) of the cantilever 2. Alternatively, the photodetector 8 has four light-receiving surfaces divided in the Z-axis and Y-axis directions. When the cantilever 2 is displaced, the proportion of light irradiated onto these multiple light-receiving surfaces changes. The photodetector 8 outputs a detection signal corresponding to the multiple light irradiations to the arithmetic unit 17. After receiving the detection signal, the arithmetic unit 17 calculates the displacement of the cantilever 2 based on the detection signal. The arithmetic unit 17 controls the Z-axis position of the sample S so that the interatomic force between the probe 3 and the surface of the sample S remains constant. The arithmetic unit 17 calculates the voltage value that causes the scanner 10 to be displaced in the Z-axis direction based on the displacement of the cantilever 2 and outputs it to the scanner 10.

[0040] Furthermore, the arithmetic unit 17 outputs the detection signal to the control unit 18. The control unit 18 generates a control signal based on the detection signal and outputs the control signal to the information processing device 20.

[0041] The information processing device 20 is communicatively connected to the control unit 18, the display device 26, and the input device 28. The information processing device 20 generates image data (contour data) based on control signals from the control unit 18.

[0042] The information processing device 20 displays the observed image on the display device 26 based on the generated image data. The observed image is an image representing the surface of the sample S. Furthermore, the information processing device 20 controls the drive unit 16 via the control unit 18 to drive the scanner 10 in a three-dimensional direction.

[0043] Input device 28 receives user input. Input device 28 outputs a signal corresponding to the user's operation to information processing device 20. Information processing device 20 outputs this signal to control unit 18. Control unit 18 performs control on observation device 80 based on this signal. Input device 28 can be a touch panel mounted on display device 26, or it can be a dedicated operation button, mouse, or physical operation key such as a keyboard.

[0044] [Hardware structure of information processing device] Figure 2This diagram illustrates an example of the hardware structure of the information processing device 20. The main components of the information processing device 20 include: a CPU (Central Processing Unit) 160, a ROM (Read Only Memory) 162, a RAM (Random Access Memory) 164, a HDD (Hard Disk Drive) 166, a communication I / F (Interface) 168, a display I / F 170, and an input I / F 172. These components are interconnected via a data bus.

[0045] Communication I / F168 is an interface for communicating with observation device 80. Display I / F170 is an interface for communicating with display device 26. Input I / F172 is an interface for communicating with input device 28.

[0046] ROM 162 stores the program executed by CPU 160. RAM 164 can temporarily store data generated by the program executed by CPU 160, as well as data input via communication I / F 168. RAM 164 can be used as temporary data storage for the working area. HDD 166 is a non-volatile storage device. Alternatively, semiconductor storage devices such as flash memory can be used instead of HDD 166.

[0047] Furthermore, the program stored in ROM 162 can be stored on a storage medium and distributed as a program product. Alternatively, the program can be provided by an information provider as a program product that can be downloaded via the Internet or the like. The information processing device 20 reads the program provided by the storage medium or the Internet. The information processing device 20 stores the read program in a designated storage area (e.g., ROM 162). The CPU 160 performs the aforementioned display processing by executing the stored program.

[0048] The storage medium is not limited to DVD-ROM (Digital Versatile Disk Read Only Memory), CD-ROM (compact disc read-only memory), FD (Flexible Disk), and hard disk, but can also be a medium that permanently carries a program, such as magnetic tape, cassette tape, optical disc (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), optical card, mask ROM, EPROM (Electronically Programmable Read-Only Memory), EEPROM (Electronically Erasable Programmable Read-Only Memory), flash memory ROM, etc. Furthermore, the recording medium is a non-transitory medium that can be read by a computer. At least one of ROM162, RAM164, and HDD166 corresponds to the "memory" of this disclosure. That is, the memory stores information used by the information processing device.

[0049] [Calculation of the elastic modulus of the sample] In the SPM100, the information processing device 20 uses a force curve when calculating the elastic modulus of a sample. At this time, the information processing device 20 performs a force curve measurement. A force curve measurement refers to changing the distance between the sample and the cantilever 2 by scanning the cantilever 2 in a direction perpendicular to the sample (Z-direction) and measuring the force acting on the cantilever 2 during this process. Through force curve measurement, the relationship between the distance between the base of the cantilever and the sample and the force acting on the cantilever 2 can be obtained. The graph representing this relationship is called a "force curve".

[0050] The elastic modulus is calculated using theoretical formulas. Below, we will illustrate three theoretical formulas with specific examples.

[0051] <Theoretical formula following the JKR method> Model Overview The JKR method is based on a mechanical model that includes the following three assumptions: the indenter is assumed to be spherical, the sample is assumed to be planar, and the indenter tip makes spherical contact with the sample surface. The following explanations can be found in the following three references: • Experimental Physics Science Series 6, *Scanning Probe Microscope*, co-authored by Shigekawa, Yoshimura, and Kawazu, published by Kyoritsu Publishing, ISBN: 9784320033818 •Ken NAKAJIMA, Hao LIU, Makiko ITO, So FUJINAMI, J. Vac. Soc. Jpn., 2013, 56, 258 •Sae NAGAI, So FUJINAMI, Ken NAKAJIMA, Toshio NISHI (Nihon ReorojiGakkaishi, 2008, 36, 99) Figure 3 This is a diagram illustrating the mechanical model upon which the JKR method is based. In this mechanical model, as... Figure 3 As shown, the tip of the indenter 200 makes spherical contact with the surface of the sample 201. When in spherical contact, there is a relationship between the radius of curvature R of the indenter 200 tip and the sample deformation δ, where R > δ. Sample adhesion is considered in this model.

[0052] Applicable force curves Figure 4 This is a graph showing an example of a force curve obtained by measurement in the presence of adhesion in the sample. Figure 4 In the diagram, the horizontal axis represents the distance between the base of cantilever 2 and the sample as the "Z position". The vertical axis represents the displacement of cantilever 2 ("cantilever displacement") as an index equivalent to the force acting on cantilever 2. Furthermore, the displacement of cantilever 2 represents the displacement of probe 3 caused by the force acting on cantilever 2.

[0053] exist Figure 4 In the force curve shown, during the approach process, the data moves towards the direction where the Z-position value decreases over time. Figure 4 Add data in the direction to the right of the Z position. During the release process, as time progresses, data is added in the direction where the Z position value increases (…). Figure 4 Add (to the left).

[0054] During the approach, a jump phenomenon can be observed where the cantilever displacement changes drastically near the sample surface. After the jump, the sample continues to move closer to the cantilever (e.g., the Z-scanner is driven to decrease the Z-position value). As a result, the value of the cantilever displacement changes from negative (due to attraction, probe 3 bends towards the sample) to positive (due to repulsion, probe 3 bends in the opposite direction to the sample) after passing through an equilibrium point.

[0055] During the detachment process, even if the distance between the base of cantilever 2 and the sample increases, exceeding the point where the jump occurs (even if the Z-position value increases, exceeding the point where the jump occurs), cantilever 2 continues to be subjected to adhesive force. Then, after being subjected to the maximum adhesive force, a jump phenomenon with a sharp change in cantilever displacement can be observed.

[0056] Furthermore, the equilibrium point represents the point where the elastic force applied to cantilever 2 (probe 3) balances with the adhesive force generated by the sample, resulting in a net force of zero. The maximum adhesion point represents the point where, during detachment, the force applied to the cantilever reaches its maximum value in the Z-axis direction due to sample adhesion.

[0057] The JKR method is applicable to the force curve that reflects the sample adhesion as described above (i.e., the force curve in which the cantilever displacement changes with the Z position).

[0058] Figure 4 The force curve shown is for a relatively soft sample. On the other hand, if the sample is sufficiently hard, then... Figure 4 As shown by the dashed line, the cantilever displacement changes linearly with the Z-position. That is, the sample deformation (the difference between the solid and dashed lines at each Z-position) becomes extremely small. In the JKR method, the sample deformation is used to calculate the elastic modulus. Therefore, when the sample deformation is extremely small, the JKR method is not suitable for calculating the elastic modulus.

[0059] exist Figure 4 In this context, dZ represents the piezoelectric Z-displacement (the scanner control quantity from the jump to the end of the press). dΔ represents the value of the cantilever displacement corresponding to the piezoelectric Z-displacement. The sample deformation dδ, the piezoelectric Z-displacement dZ, and the cantilever displacement dΔ corresponding to the piezoelectric Z-displacement are related by the following equation (1).

[0060]

Number 1

[0061] ≪Precautions during measurement≫ When determining the elastic modulus, the following points should be noted when obtaining the force curves used in conjunction with the theoretical formulas following the JKR method.

[0062] • Make the probe indentation less than the radius of curvature of the probe tip so that the probe tip makes spherical contact with the sample surface.

[0063] • Use a cantilever with an appropriate spring constant.

[0064] (If the spring constant of the cantilever is too large, the indentation of a soft sample during approach may be excessive. On the other hand, if the spring constant is too small, the indentation of a hard sample during approach may not be guaranteed.) ≪Analytical Methods≫ To calculate the elastic modulus from the obtained force curve, the force curve needs to be redrawn as a load-displacement curve (F-δ curve) representing the relationship between the force F applied to the cantilever and the sample deformation δ to generate a theoretical F-δ curve, which is then fitted by superimposing the theoretical F-δ curve onto the measured F-δ curve.

[0065] Figure 5 This is a graph showing an example of a load-displacement curve. In Figure 5 In the curve, the horizontal axis represents Figure 4 The sample deformation in the force curve. In one implementation example, the displacement of probe 3 is used as the sample deformation. Figure 4 The value of the cantilever displacement). The vertical axis represents the force applied to cantilever 2. The force applied to cantilever 2 is calculated as the product of the deflection of cantilever 2 and the spring constant. Figure 5 In, with Figure 4 Similarly, the curve for a softer sample is represented by a solid line, while the curve for a sufficiently hard sample is represented by a dashed line.

[0066] In the JKR method, the relationship between F and δ is expressed by the following equations (2) and (3) through the contact circle radius a between the tip of probe 3 and the sample surface. w represents the adhesion energy, R represents the radius of curvature of probe 3, and K represents the elastic coefficient of the sample.

[0067]

Number 2

[0068]

Number 3

[0069] Equations (2) and (3) are very cumbersome. Therefore, even if the theoretical F-δ curve is obtained by eliminating 'a' from equations (2) and (3) and rewriting them as expressions containing only F and δ, and then superimposing this theoretical F-δ curve onto... Figure 5 Fitting the load-displacement curve is also difficult.

[0070] Therefore, use Figure 5 The elastic modulus is calculated by finding the equilibrium point and the point of maximum adhesion. This method is also known as the "two-point method".

[0071] Figure 6 This is a diagram that schematically represents the state of probe 3 and sample of cantilever 2 at the equilibrium point and the maximum adhesion point. For the force F applied to the cantilever, the sample deformation δ, and the contact circle radius a between the tip of probe 3 and the sample surface, the values ​​at the equilibrium point are appended with a subscript "0", and the values ​​at the maximum adhesion point are appended with a subscript "1".

[0072] In addition, Figure 4 In this context, dZ represents the scanner control quantity from the jump in to the push-in end point. On the other hand, in... Figure 6 In this context, dZ represents the difference between the Z-position value of the equilibrium point and the Z-position value of the maximum adhesion point.

[0073] The following describes the steps for obtaining F and δ at two points and then calculating the elastic modulus.

[0074] First, consider the maximum adhesion point. At the maximum adhesion point, probe 3 is about to break off from the sample surface. Therefore, the contact circle radius a1 reaches its minimum. Thus, the value within the square root of equation (2), as shown in equation (4), is 0.

[0075]

Number 4

[0076] Solving equation (4), we can obtain that F1 is represented by equation (5).

[0077]

Number 5

[0078] Substituting equation (5) into equation (2), we obtain equation (6).

[0079]

Number 6

[0080] Substituting equation (6) into equation (3), we obtain equation (7).

[0081]

Number 7

[0082] Next, consider the equilibrium point. At the equilibrium point, F0 = 0. Substituting F0 = 0 into equation (2), we get equation (8).

[0083]

Number 8

[0084] Substituting equation (8) into equation (3), we obtain equation (9).

[0085]

Number 9

[0086] Using equations (7) and (9), we obtain equation (10).

[0087]

Number 10

[0088] Transform equation (10) to obtain equation (11).

[0089]

Number 11

[0090] The elastic modulus E of the sample, if the Poisson's ratio of the sample is ν, is expressed by equation (12).

[0091]

Number 12

[0092] Substituting equation (11) into equation (12), we obtain equation (13).

[0093]

Number 13

[0094] According to equation (13), the elastic modulus E of the sample can be calculated using the sample's Poisson's ratio ν, the force F1 applied to the cantilever at the point of maximum adhesion, the sample deformation δ0 at the equilibrium point, and the sample deformation δ1 at the point of maximum adhesion. In this sense, equation (13) constitutes an example of a theoretical formula for calculating the elastic modulus.

[0095] <Theoretical formula following Hertz's method> Model Overview The Hertz method is based on a mechanical model that includes the following three assumptions: the indenter is spherical, the sample is planar, and the indenter tip makes spherical contact with the sample surface. The following explanations can be found in the following three references: • Experimental Physics Science Series 6, *Scanning Probe Microscope*, co-authored by Shigekawa, Yoshimura, and Kawazu, published by Kyoritsu Publishing, ISBN: 9784320033818 •Ken NAKAJIMA, Hao LIU, Makiko ITO, So FUJINAMI, J. Vac. Soc. Jpn., 2013, 56, 258 • Manufacturing Textbook - Practical • Mechanics of Materials (Nikkei Manufacturing Textbook), Chapter 24, by Toshiyuki Sawa, Nikkei BP, ISBN: 9784822218997 The mechanical model upon which Hertz's method is based is the same as that upon which JKR's method is based, derived from... Figure 3 The pattern is illustrated. However, in the mechanical model upon which the Hertz method is based, sample adhesion is not considered.

[0096] Applicable force curves Figure 7 This is a graph illustrating an example of a force curve obtained through measurements unaffected by adhesion. For instance, when the force curve measurement is performed in a liquid, the Hertz method may be applicable to this force curve because no ingress or egress occurs. Figure 7 In the graph, the horizontal axis (probe-sample distance) represents the Z-position. The vertical axis represents the cantilever displacement.

[0097] exist Figure 7 In the diagram, the solid line represents the force curve when the sample is relatively soft, and the dashed line represents the force curve when the sample is sufficiently hard. Figure 7In the force curves shown, no abrupt change in cantilever displacement near the sample surface was observed during the approach process. Because the Hertz method does not consider adhesive forces, it is applicable for calculating the elastic modulus using force curves that show no abrupt change in displacement.

[0098] exist Figure 7 In the example, the relationship shown in equation (1) also holds between the sample deformation dδ, the piezoelectric Z displacement dZ, and the cantilever displacement dΔ corresponding to the piezoelectric Z displacement.

[0099] ≪Precautions during measurement≫ When determining the elastic modulus, the following points should be noted when obtaining the force curve (a non-jump force curve) used in conjunction with the theoretical formula following the Hertz method.

[0100] • Make the indentation of probe 3 less than the radius of curvature of the probe tip so that the probe tip makes spherical contact with the sample surface.

[0101] • To suppress jumps, use cantilever arms with large spring constants.

[0102] • To suppress jumping in, measurements are taken in water.

[0103] ≪Analytical Methods≫ Figure 8 This represents the contact theory model in the Hertz method. Figure 8 The diagram illustrates the contact between object 211 and object 212. R1 represents the radius of curvature of object 211, and R2 represents the radius of curvature of object 212. E1 represents the elastic modulus of object 211, and E2 represents the elastic modulus of object 212. ν1 represents the Poisson's ratio of object 211, and ν2 represents the Poisson's ratio of object 212.

[0104] According to Hertz contact theory, when two spheres are in contact under a force F, the sample deformation δ is given by equation (14). * This represents the combined elastic modulus of objects 211 and 212.

[0105]

Number 14

[0106] In addition, the composite elastic modulus E * If elastic moduli E1 and E2 and Poisson's ratios ν1 and ν2 are used, it can be expressed as Equation (15).

[0107]

Number 15

[0108] In actual measurements, R2 is much larger than R1. Therefore, under the assumption that R2→∞ (plane approximation), equation (14) is transformed into equation (16).

[0109]

Number 16

[0110] Furthermore, if we assume that the elastic modulus of the cantilever 2 is much greater than that of the sample, then equation (15) can be transformed into equation (17).

[0111]

Number 17

[0112] Substituting equation (17) into equation (16), we derive the relationship between F and δ (18).

[0113]

Number 18

[0114] To calculate the elastic modulus from the force curve obtained from the measurement, the force curve needs to be redrawn as a load-displacement curve (F-δ curve) representing the relationship between the force F applied to cantilever 2 and the sample deformation δ, and the theoretical F-δ curve of the applicable model needs to be fitted.

[0115] Figure 9 This shows how to redraw Figure 7 The load-displacement curve is obtained by plotting the force curve. Figure 9 In the middle, the horizontal axis represents Figure 7 The sample deformation in the force curve, with the vertical axis representing the force applied to the cantilever calculated as the product of the cantilever deflection and the spring constant.

[0116] according to Figure 9 The load-displacement curve shown is given by equation (19). The force F applied to the cantilever 2 can be approximated as being proportional to the 3 / 2 power of the sample deformation δ.

[0117]

Number 19

[0118] Taking the logarithm of both sides of equation (19) yields equation (20). Furthermore, in equation (20), the base can be arbitrary, for example, it can be "10".

[0119]

Number 20

[0120] Equation (20) has the form of a linear function, namely Y = aX + b. Therefore, the regression line can be calculated by applying the least squares method to equation (20) obtained from the measurement results. The theoretical slope of the regression line is log in equation (20).10 The coefficient of δ is 3 / 2. Then, as shown in equation (21), the elastic modulus E2 of object 212 is derived using the intercept b of the above regression line.

[0121]

Number 21

[0122] When object 211 is cantilever 2 and object 212 is sample, the elastic modulus E2 is derived as the elastic modulus of the sample.

[0123] <Theoretical formula following Sneddon's method> Model Overview The Sneddon method is based on a mechanical model that includes the following three assumptions: the indenter is conical, the sample is planar, and the indenter tip contacts the sample surface via a conical surface. The following explanations can be found in, for example, the following literature: • Manufacturing Textbook - Practical • Mechanics of Materials (Nikkei Manufacturing Textbook), Chapter 24, by Toshiyuki Sawa, Nikkei BP, ISBN: 9784822218997 Figure 10 This is a diagram illustrating the mechanical model upon which the Sneddon method is based. (Example) Figure 10 As shown, in the mechanical model of the Sneddon method, the indenter 221 in contact with the sample 222 is conical in shape. Figure 10 In this equation, R represents the radius of curvature of the indenter 221, and δ represents the sample deformation. There is a relationship between R and δ: R > δ. In the mechanical model upon which the Sneddon method is based, sample adhesion is not considered.

[0124] Applicable force curves Figure 11 This is a graph illustrating an example of a force curve obtained through measurements unaffected by adhesion. Figure 11 In the graph, the horizontal axis (probe-sample distance) represents the Z-position. The vertical axis represents the cantilever displacement.

[0125] exist Figure 11 In the diagram, the solid line represents the force curve when the sample is relatively soft, and the dashed line represents the force curve when the sample is sufficiently hard. Figure 11 In the force curves shown, no abrupt change in cantilever displacement near the sample surface was observed during the approach process. Because the Sneddon method does not consider adhesive forces, it is applicable for calculating the elastic modulus using force curves that show no abrupt change in displacement.

[0126] exist Figure 11In the example, the relationship shown in equation (1) also holds between the sample deformation dδ, the piezoelectric Z displacement dZ, and the cantilever displacement dΔ corresponding to the piezoelectric Z displacement.

[0127] ≪Precautions during measurement≫ When determining the elastic modulus, the following points should be noted when obtaining the force curve (without jump) used in conjunction with the theoretical formula following the Sneddon method.

[0128] • Make the indentation of probe 3 less than the radius of curvature of the probe tip so that the probe tip contacts the sample surface in a conical manner.

[0129] • To suppress jumps, use cantilever arms with large spring constants.

[0130] • To suppress jumping in, measurements are taken in water.

[0131] ≪Analytical Methods≫ Figure 12 This represents the contact theory model in the Sneddon method. Figure 12 The contact between the indenter 221 and the sample 222 is shown. R1 represents the radius of curvature of the indenter 221, and R2 represents the radius of curvature of the sample 222. E1 represents the elastic modulus of the indenter 221, and E2 represents the elastic modulus of the sample 222. ν1 represents the Poisson's ratio of the indenter 221, and ν2 represents the Poisson's ratio of the sample 222.

[0132] According to Sneddon's contact theory, when two spheres are in contact under a force F, the sample deformation δ is given by equation (22). * This represents the composite elastic modulus of the indenter 221 and the sample 222. α represents the half-apex angle of the indenter 221.

[0133]

Number 22

[0134] In addition, the composite elastic modulus E * If elastic moduli E1 and E2 and Poisson's ratios ν1 and ν2 are used, it can be expressed as equation (23).

[0135]

Number 23

[0136] If we assume that the elastic modulus of cantilever 2 is much greater than that of the sample, then equation (23) can be transformed into equation (24).

[0137]

Number 24

[0138] Substituting equation (24) into equation (22), we derive the relationship between F and δ (25).

[0139]

Number 25

[0140] To calculate the elastic modulus from the force curve obtained from the measurement, the force curve needs to be redrawn as a load-displacement curve (F-δ curve) representing the relationship between the force F applied to cantilever 2 and the sample deformation δ, and the theoretical F-δ curve of the applicable model needs to be fitted.

[0141] Figure 13 This shows how to redraw Figure 11 The load-displacement curve is obtained by plotting the force curve. Figure 13 In the middle, the horizontal axis represents Figure 11 The sample deformation in the force curve, with the vertical axis representing the force applied to the cantilever calculated as the product of the cantilever deflection and the spring constant.

[0142] according to Figure 13 The load-displacement curve shown is given by equation (26). The force F applied to the cantilever 2 can be approximated as being proportional to the square of the sample deformation δ.

[0143]

Number 26

[0144] Taking the logarithm of both sides of equation (26) yields equation (27). Furthermore, in equation (27), the base can be arbitrary, for example, it can be "10".

[0145]

Number 27

[0146] Equation (27) has the form of a linear function, namely Y = aX + b. Therefore, the regression line can be calculated by applying the least squares method to equation (27) obtained from the measurement results. The theoretical slope of the regression line is log in equation (27). 10 The coefficient of δ is 2. Then, as shown in equation (28), the elastic modulus E2 of sample 222 is derived using the intercept b of the above regression line.

[0147]

Number 28

[0148] [Correction of force curve] <Correction of force curves for theoretical formulas following the JKR method> Figure 14 This is a graph showing an example of a force curve generated based on the measurement results of the sample. Furthermore, in Figure 14 In this example, the sample is placed on a substrate. Figure 14In the diagram, the dashed line represents the sensitivity line obtained from the force curve of the substrate alone. The slope of the sensitivity line is the sensitivity S of the cantilever. Furthermore, sensitivity S is a coefficient used when converting the deflection of cantilever 2 from a voltage value (V) to a distance (nm). The sensitivity line is set to have a slope of sensitivity S and passes through the minimum value (point A) of the cantilever displacement upon jump, and is superimposed on... Figure 14 superior.

[0149] exist Figure 14 In the example, the force curve is used to determine δ0 (sample deformation at the equilibrium point) and δ1 (sample deformation at the point of maximum adhesion) applicable to the theoretical formula above. More specifically, δ0 is determined as the difference between the sensitivity line and the force curve at the equilibrium point. δ1 is determined as the difference between the force curve and the sensitivity line at the point of maximum adhesion.

[0150] When the sample mounted on the substrate is sufficiently thick (e.g., tens of μm or more), the influence of the substrate can be neglected in the force profile. However, when the sample is a thin film, the force profile is affected by the substrate hardness. If the elastic modulus is calculated using a force profile affected by substrate hardness, the elastic modulus may deviate from the value expected based on the original hardness of the sample. More specifically, the aforementioned effect is less likely to occur during indentation after approaching the equilibrium point, but is expected to occur between the indentation and the equilibrium point.

[0151] Therefore, in this embodiment, the force curve can be corrected to reduce the influence of the substrate.

[0152] Figure 15 This is a diagram showing a specific example of a force curve. Figure 15 The image shows dot patterns consisting of triangular markers acquired during the approach phase and dot patterns consisting of circular markers acquired during the disengagement phase. During the approach phase, the markers changed from... Figure 15 Add from the left to the right. During the detachment process, over time, the markers move from... Figure 15 Add from the right to the left. Line L1 indicates that... Figure 15 The baseline is determined in the force curve.

[0153] exist Figure 15 In the example, point P11 represents the point of maximum adhesion. Point P12 represents the equilibrium point. The equilibrium point is determined as the intersection of the trace and the baseline during the approach (or detachment) process.

[0154] However, in Figure 15 In the force curve, between point P11 and point P12, the curvature of the curve formed by the point traces is not constant during the approach and disengagement processes.

[0155] Figure 16 It shows the accompanying markings. Figure 15 A graph of the force curve. (e.g.) Figure 16 As shown, the curvature of the force curve changes at point P13, between points P11 and P12. More specifically, in Figure 16 In the example, the force curve from point P11 to point P13 is a curve, while the section from point P13 to point P12 is a straight line. Figure 16 In the diagram, point P14 represents the minimum displacement of the cantilever during the jump.

[0156] In this embodiment, the information processing device 20 corrects the force curve.

[0157] In the correction of the force curve, the information processing device 20 first determines the minimum value of the cantilever displacement at the moment of entry.

[0158] Then, the information processing device 20 operates in a region where the probe-sample distance is shorter than the aforementioned minimum value ( Figure 15 and Figure 16 The inflection point is searched in the right-hand side of the force curve. The search for the inflection point can be performed in the portion of the force curve obtained from the approach process or in the portion obtained from the disengagement process.

[0159] Then, the information processing device 20 determines the inflection point closest to the aforementioned minimum value from among the more than one inflection point obtained as search results. Figure 16 In the example, point P13 was determined as the inflection point closest to the aforementioned minimum value.

[0160] Then, the information processing device 20 deletes regions corresponding to probe-sample distances shorter than the inflection points determined above. Figure 15 and Figure 16 The right side of the curve is used to correct the force curve.

[0161] Figure 17 It is used for explanation Figure 15 A graph showing the correction of the force curve. Figure 17 In the force curve shown, with Figure 15 Compared to the force curve shown, the part to the right of point P13 has been deleted.

[0162] Information processing device 20 Figure 17 In the force curve shown, the data from point P14 to point P13 are extrapolated using either a straight line or a curve. Figure 17 In the diagram, the line obtained by extrapolation is represented as line L2.

[0163] Then, the intersection point of the straight line or curve (line L2) obtained through the above extrapolation and the baseline (line L1) is determined as the equilibrium point. Figure 17 In the equation, the equilibrium point determined using the corrected baseline is denoted as point P15.

[0164] To calculate the elastic modulus of the sample, the information processing device 20 generates a force curve for the sample and uses the force curve to determine δ0 (sample deformation at the equilibrium point) and δ1 (sample deformation at the point of maximum adhesion). Furthermore, the information processing device 20 determines the force applied to the cantilever at the point of maximum adhesion as F1. The information processing device 20 also obtains the Poisson's ratio ν of the sample. The Poisson's ratio ν of the sample is input by the user, for example, via the input device 28. Then, the information processing device 20 applies these values ​​to the theoretical formula shown in equation (13) to calculate the elastic modulus of the sample.

[0165] When using from Figure 15 The elastic modulus is 1299.1 kPa when δ0 and δ1 are determined by the force curve shown. On the other hand, when using from Figure 17 The elastic modulus is 469.7 kPa at δ0 and δ1 as determined by the force curve shown (the corrected force curve). That is, the final elastic modulus value has changed by using the corrected force curve.

[0166] In this embodiment, Figure 15 The force curve shown constitutes an example of the first force curve as a measurement result. Figure 17 The force curve shown is an example of a second force curve generated by deleting data from a given region of the first force curve.

[0167] Furthermore, in this embodiment, Figure 15 In the force curve shown, point P11 and the portion to the right of point P11 constitute an example of the first region (starting from the jump-in portion and corresponding to a range where the distance between the probe and the sample is shorter than that jump-in portion). Furthermore, the jump-in portion refers to the part of the force curve where the cantilever displacement value changes drastically due to the jump-in.

[0168] In this embodiment, for Figure 15 An inflection point search was performed on the portion to the right of point P11 of the force curve shown. Thus, point P13 was determined as the inflection point within the portion to the right of point P11. Through point P13, the portion to the right of point P11 was divided into a portion from point P11 to point P13 and a portion from point P13 to point P12.

[0169] The portion from point P11 to point P13 constitutes an example of a basic region (the region connected to the leap portion). The portion from point P13 to point P12 constitutes an example of an excluded region (the region with curvature lower than that of the basic region).

[0170] exist Figure 15In the force curves shown, it is speculated that the portion from point P11 to point P13 mainly reflects the influence of sample properties, while the portion from point P13 to point P12 mainly reflects the influence of substrate properties. More specifically, the substrate is harder than the sample; therefore, during the approach process, after the initial insertion, when the probe-sample distance is sufficiently short, it is speculated that the cantilever displacement will increase linearly. This is because when the sample is softer, before the probe-sample distance is sufficiently short, the sample will deform before the cantilever displacement value changes as cantilever 2 is pressed in. On the other hand, when the probe-sample distance is sufficiently short, and the sample deformation is sufficient to accommodate the cantilever 2 indentation, the cantilever displacement value will change with the cantilever 2 indentation. Furthermore, it is speculated that the change in cantilever displacement value after the sample deformation is sufficient to accommodate the cantilever 2 indentation will exhibit the aforementioned linear increase.

[0171] Therefore, the information processing device 20 can divide the portion to the right of point P11 into a curved portion and a straight portion, and determine the straight portion as an exclusion region. Then, the information processing device 20 can determine the portion that is closer to point P11 than the portion determined as the exclusion region as the basic region.

[0172] <Correction of force curves following theoretical formulas of Hertz and Sneddon methods> Figure 18 This is a diagram showing a specific example of a force curve. Figure 18 The image shows the points acquired during the approach process. During the approach process, data is generated over time from... Figure 18 Add from the right to the left (i.e., in the direction where the probe-sample distance value decreases).

[0173] Figure 19 It shows the accompanying markings. Figure 18 A graph of the force curve. (e.g.) Figure 19 As shown, the curvature of the force curve changes at point P21. More specifically, in Figure 19 In the example, the part to the right of point P21 in the force curve is a curve, while the part to the left of point P21 is a straight line.

[0174] exist Figure 19 In the force curves shown, it is speculated that the portion to the right of point P21 mainly reflects the influence of sample properties, while the portion to the left of point P21 mainly reflects the influence of substrate properties. The reasoning is that when the sample is relatively soft, before the probe-sample distance is sufficiently short, the sample will deform before the cantilever displacement changes as cantilever 2 is pressed in. On the other hand, when the probe-sample distance is sufficiently short to accommodate the sample deformation after the cantilever 2 has been pressed in, the cantilever displacement will change with the pressing in of cantilever 2. Furthermore, it is speculated that the change in cantilever displacement after the sample deformation is complete and can accommodate the cantilever 2's pressing in exhibits the aforementioned linear increase.

[0175] Therefore, the information processing device 20 determines the inflection point in the force curve and corrects the force curve to remove portions of the probe-sample distance that are shorter than the determined inflection point. Figure 20 This is a graph showing the corrected force curve. (Referring to...) Figures 18 to 20 In the example provided, Figure 18 or Figure 19 The force curve shown constitutes an example of the first force curve. Furthermore, Figure 20 The force curve shown is obtained by correction. Figure 18 or Figure 19 The force curve generated from the force curve shown constitutes an example of the second force curve.

[0176] When calculating the elastic modulus of the sample, the information processing device 20 uses the corrected force curve. More specifically, in the case of the Hertz method, the information processing device 20 redraws the corrected force curve as a load-displacement curve. Figure 9 The relationship between the force F applied to the cantilever 2 and the sample deformation δ, as shown in equation (19), is obtained. Then, the information processing device 20 uses equation (19) to determine the intercept value of equation (20). Then, the information processing device 20 uses the obtained intercept value to calculate the elastic modulus of the sample, as explained with reference to equation (21).

[0177] In the case of the Sneddon method, the information processing device 20 redraws the corrected force curve as a load-displacement curve. Figure 13 The relationship between the force F applied to the cantilever 2 and the sample deformation δ, as shown in equation (26), is obtained. Then, the information processing device 20 uses equation (26) to determine the intercept value of equation (27). Then, the information processing device 20 uses the obtained intercept value to calculate the elastic modulus of the sample, as explained with reference to equation (28).

[0178] [Processing Flow] Figure 21 This is a flowchart of the process performed by the information processing device 20 to calculate the elastic modulus. Figure 21 The processing begins, for example, when an application executing in the information processing device 20 instructs the calculation of the elastic modulus. Furthermore, in one implementation example, Figure 21 The processing was performed on the sample whose elastic modulus to be calculated had already been measured and used to generate the force curve. (Refer to...) Figure 21 Explain the content of the above processing.

[0179] In step S10, the information processing device 20 reads the specification of the theoretical formula to be used. More specifically, the user inputs the specification of the theoretical formula to be used (following the JKR method, Hertz method, or Sneddon method, or other methods) into the information processing device 20 (the application running in it). The information processing device 20 reads the input specification. That is, the information processing device 20 is configured to calculate the elastic modulus using multiple theoretical formulas, and in step S10, it selects the theoretical formula for calculating the elastic modulus from these multiple theoretical formulas.

[0180] In step S12, the information processing device 20 generates a first force curve based on the results obtained in the above measurement.

[0181] In step S14, the information processing device 20 generates a second force curve by deleting a portion of the first force curve as described above.

[0182] In step S16, the information processing device 20 calculates the elastic modulus of the sample using the second force curve and the theoretical formula determined by the specification read in step S10.

[0183] In step S18, the information processing device 20 outputs the elastic modulus calculated in step S16 and ends the process. Figure 21 The processing of the elastic modulus is achieved, for example, by displaying it on the display device 26.

[0184] In the above-described processing, when using theoretical formulas following the JKR method, Hertz method, or Sneddon method, an inflection point is required in the generation of the second force curve in step S14 (if it is the JKR method, then it is...). Figure 16 Point P13; if using Hertz's method or Sneddon's method, then it is... Figure 19 (Point P21). In one implementation example, the JKR method can be selected for soft samples such as polymers or biological materials; the Hertz method can be selected when the sample is a harder material and / or when no jump is observed in the liquid.

[0185] In the above process, the inflection point can be determined by the information processing device 20 or by the user. When the inflection point is determined by the user, the user inputs the inflection point into the information processing device 20 (the application running in it). At this time, the information processing device 20 can display the first force curve on the display device 26. The user can input the given point as the inflection point into the information processing device 20 by touching a given point on the displayed first force curve.

[0186] When the information processing device 20 reads the specified theoretical formula in step S10, it can receive input information about sample hardness (sample type, sample hardness, etc.). The information processing device 20 can store a database that associates information about sample hardness with the type of theoretical formula used. The information processing device 20 can process the type of theoretical formula corresponding to the input "information about hardness" as the specified "theoretical formula used".

[0187] The information processing device 20 can also be used as a comparison to calculate the elastic modulus using the first force curve and the theoretical formula determined by the specification read in step S10, and output it as a comparison value together with the elastic modulus calculated using the second force curve and the above-mentioned theoretical formula.

[0188] [Way] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following approaches.

[0189] (First item) A scanning probe microscope according to one embodiment comprises: a sample stage on which a sample is placed; a cantilever with its base fixed and a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, characterized in that the control unit is configured to: generate a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector, wherein the first force curve determines the displacement from the entry point... A first region, which begins at a distance shorter than the jump-in portion, is defined as the first region in which the probe begins to experience attraction from the sample in response to the shortening distance. Within this first region, the control unit determines a base region from the first inflection point closest to the jump-in portion among one or more inflection points in the first region to the jump-in portion, and determines regions other than the base region as exclusion regions. A second force curve is generated by excluding the exclusion regions from the first force curve, and the elastic modulus of the sample is calculated based on the second force curve and a theoretical formula.

[0190] (Second item) In the scanning probe microscope described in the first item, the control unit is configured to: determine the one or more inflection points in the first region, and determine the first inflection point from the one or more inflection points.

[0191] (Third item) In the scanning probe microscope described in the first or second item, the control unit is configured to determine the region with zero curvature as the exclusion region.

[0192] (Fourth item) A scanning probe microscope according to one method comprises: a sample stage on which a sample is placed; a cantilever with its base fixed and a probe provided at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, characterized in that the control unit is configured to: generate a first force curve as a measurement result of the displacement accompanying the change in distance between the probe and the sample using the detection output of the displacement detector; generate a second force curve by excluding regions from the first force curve whose distances are shorter than the inflection points in the first force curve; and calculate the elastic modulus of the sample based on the second force curve and a theoretical formula.

[0193] (Fifth item) In any one of the first to fourth items of the scanning probe microscope, the control unit is configured to receive a specification regarding the type of theoretical formula, and select the theoretical formula from two or more theoretical formulas according to the specification.

[0194] (Sixth item) In any one of the first to fifth items of the scanning probe microscope, the control unit is configured to receive a specification regarding the hardness of the sample and, based on the specification, select the theoretical formula from two or more theoretical formulas.

[0195] (Seventh item) In any one of the first to sixth items of the scanning probe microscope, the control unit is further configured to: calculate the elastic modulus of the sample as a comparison value based on the first force curve and the theoretical formula.

[0196] (Eighth item) A method according to one approach is a method for calculating the elastic modulus of a sample using a scanning probe microscope, the scanning probe microscope comprising: a sample stage on which a sample is placed; a cantilever fixed at its base and having a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, the method comprising: generating a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector; and measuring the displacement using the first force curve... The method comprises the steps of excluding regions shorter than the inflection point in the first force curve to generate a second force curve; and the steps of calculating the elastic modulus of the sample based on the second force curve and a theoretical formula, characterized in that the step of generating the second force curve includes, within the first force curve, determining a first region starting from the jump portion and corresponding to a range shorter than the jump portion, in which the probe begins to be subjected to an attractive force from the sample in response to the shortening distance, and the step of generating the second force curve further includes, within the first region, determining the inflection point closest to the jump portion among one or more inflection points in the first region as the inflection point.

[0197] (Ninth item) A method according to one approach is a method for calculating the elastic modulus of a sample using a scanning probe microscope, the scanning probe microscope comprising: a sample stage on which a sample is placed; a cantilever fixed at its base and having a probe at its front end; a moving mechanism for relatively changing the positional relationship between the sample stage and the base; a displacement detector for detecting the displacement of the probe relative to the base; and a control unit for controlling the moving mechanism, the method comprising: generating a first force curve as a measurement result of the displacement accompanying a change in the distance between the probe and the sample using the detection output of the displacement detector; generating a second force curve by excluding regions shorter than the inflection point from the first force curve; and calculating the elastic modulus of the sample based on the second force curve and a theoretical formula.

[0198] The embodiments disclosed herein should be considered exemplary and not restrictive in all respects. The scope of this disclosure is defined not by the description of the embodiments above, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Furthermore, it is intended that the techniques in the embodiments can be implemented individually or in combination with other techniques in the embodiments as needed.

[0199] Explanation of reference numerals in the attached figures 1 Optical system, 2 Cantilever, 3 Probe, 4 Support, 5 Beam splitter, 6 Laser source, 7 Mirror, 8 Photodetector, 10 Scanner, 12 Sample stage, 16 Drive unit, 17 Computing unit, 18 Control unit, 20 Information processing device, 26 Display device, 28 Input device, 80 Observation device, 100 SPM, 162 ROM, 164 RAM, 200, 221 Indenter, 201, 222, S Sample, 211, 212 Object.

Claims

1. A scanning probe microscope, characterized in that, have: A sample stage on which a sample is placed; A cantilever, with its base fixed and a probe at its front end; A moving mechanism for relatively changing the position of the sample stage and the base end; A displacement detector is used to detect the displacement of the probe relative to the base end; as well as The control unit is used to control the moving mechanism. The control unit is configured as follows: The detection output of the displacement detector is used to generate a first force curve, which is a measurement result of the displacement accompanying the change in the distance between the probe and the sample. In the first force curve, a first region is determined that starts from the jump-in portion and corresponds to a range shorter than the jump-in portion. In the leap-in section, the probe begins to experience an attractive force from the sample in response to the shortening distance. The control unit In the first region, a region extending from the first inflection point closest to the leap portion among one or more inflection points in the first region to the leap portion is determined as a basic region, and regions other than the basic region are determined as exclusion regions. A second force curve is generated by excluding the exclusion region from the first force curve. Based on the second force curve and the theoretical formula, the elastic modulus of the sample is calculated.

2. The scanning probe microscope according to claim 1, characterized in that, The control unit is configured to: determine one or more inflection points in the first region, and determine the first inflection point from the one or more inflection points.

3. The scanning probe microscope according to claim 1 or claim 2, characterized in that, The control unit is configured to define the region with zero curvature as the exclusion region.

4. A scanning probe microscope, characterized in that, have: A sample stage on which a sample is placed; A cantilever, with its base fixed and a probe at its front end; A moving mechanism for relatively changing the position of the sample stage and the base end; A displacement detector is used to detect the displacement of the probe relative to the base end; as well as The control unit is used to control the moving mechanism. The control unit is configured as follows: The detection output of the displacement detector is used to generate a first force curve, which is a measurement result of the displacement accompanying the change in the distance between the probe and the sample. A second force curve is generated by excluding regions from the first force curve that are shorter than the distance to the inflection point in the first force curve. Based on the second force curve and the theoretical formula, the elastic modulus of the sample is calculated.

5. The scanning probe microscope according to claim 1 or claim 4, characterized in that, The control unit is configured as follows: Receives a specification regarding the type of theoretical formula. And, according to the specified method, select the theoretical formula from two or more theoretical formulas.

6. The scanning probe microscope according to claim 1 or claim 4, characterized in that, The control unit is configured as follows: Receive specifications regarding sample hardness. And, according to the specified method, select the theoretical formula from two or more theoretical formulas.

7. The scanning probe microscope according to claim 1 or claim 4, characterized in that, The control unit is further configured to calculate the elastic modulus of the sample as a comparison value based on the first force curve and the theoretical formula.

8. A method for calculating the elastic modulus of a sample using a scanning probe microscope, characterized in that, The scanning probe microscope includes: A sample stage on which a sample is placed; A cantilever, with its base fixed and a probe at its front end; A moving mechanism for relatively changing the position of the sample stage and the base end; A displacement detector for detecting the displacement of the probe relative to the base end; and The control unit is used to control the moving mechanism. This method has the following characteristics: The step of generating a first force curve as a measurement result of the displacement accompanying the change in distance between the probe and the sample using the detection output of the displacement detector; The step of generating a second force curve by excluding regions shorter than the inflection point from the first force curve; as well as The step of calculating the elastic modulus of the sample based on the second force curve and theoretical formula is as follows: The step of generating the second force curve includes: In the first force curve, a first region is determined that starts from the jump-in portion and corresponds to a range shorter than the jump-in portion. In the leap-in section, the probe begins to experience an attractive force from the sample in response to the shortening distance. The step of generating the second force curve further includes: In the first region, the inflection point closest to the leap-in portion among one or more inflection points in the first region is determined as the inflection point.

9. A method for calculating the elastic modulus of a sample using a scanning probe microscope, characterized in that, The scanning probe microscope includes: A sample stage on which a sample is placed; A cantilever, with its base fixed and a probe at its front end; A moving mechanism for relatively changing the position of the sample stage and the base end; A displacement detector for detecting the displacement of the probe relative to the base end; and The control unit is used to control the moving mechanism. This method has the following characteristics: The step of generating a first force curve as a measurement result of the displacement accompanying the change in distance between the probe and the sample using the detection output of the displacement detector; The step of generating a second force curve by excluding regions shorter than the inflection point from the first force curve; as well as The step of calculating the elastic modulus of the sample based on the second force curve and theoretical formula.

Images