JP6842754B2 - Scanning probe microscope - Google Patents

Description

The present invention relates to a scanning probe microscope that observes a sample while scanning the probe.

A scanning probe microscope is a microscope that obtains physical information on the surface of a sample such as irregularities or chemical properties of a sample as a signal by scanning the probe with respect to the sample.

Scanning probe microscopes include, for example, an atomic force microscope (AFM), a scanning tunneling microscope (STM), a scanning magnetic force microscope (MFM), a scanning electrocapacity microscope (SCaM), and a scanning proximity field light microscope (SCaM). There are a scanning thermal microscope (SThM), a scanning ion electric microscope (SICM), and the like. In these scanning probe microscopes, the physics of a sample is obtained by scanning the probe or sample in the horizontal direction (XY direction) and the vertical direction (Z direction) and sequentially displaying the physical information or chemical properties of the obtained sample. It represents information or chemical properties as an image.

The scanning probe microscope is provided with a scanning mechanism (X scanner, Y scanner, Z scanner) that can move in each of the X, Y, and Z directions in order to scan the probe or sample in the horizontal and vertical directions (X scanner, Y scanner, Z scanner). For example, see Patent Document 1). The scanning probe microscope described in Patent Document 1 includes a piezoelectric element as a scanning mechanism for horizontal two-dimensional raster scanning. In the scanning probe microscope, for example, for scanning in the X direction, the probe or sample is driven in the X direction by applying a triangular wave voltage (high frequency voltage) whose amplitude changes at a constant cycle to the X scanner from the piezoelectric element. doing.

Japanese Unexamined Patent Publication No. 2009-276318

However, in the high-speed drive of the X scanner by the voltage of the triangular wave described above, the piezoelectric element does not follow the voltage of the triangular wave at the peak or valley of the triangular wave, the observed image is distorted, and a so-called mirror image is generated at the edge of the observed image. Is occurring.

In view of the above problems, an object of the present invention is to provide a scanning probe microscope capable of suppressing distortion of an observed image.

In order to solve the above problems, the scanning probe microscope according to one aspect of the present invention includes a sample stage on which an observation sample is placed, a probe for observing the surface state or dynamics of the observation sample, and the sample stage. includes a scanner for driving, and a control unit for controlling the operation of the scanner, the control unit, a scanning voltage to repeat increase and decrease in a predetermined cycle is applied to the scanner, the scanning voltage is increased immediately after the start first acceleration of increase that put the period is a positive value der of is, and, the slope of the increase following the first period is constant.

As a result, the speed of voltage increase at the start of voltage increase can be increased as compared with the case where the speed of voltage increase of the scanning voltage is constant. Therefore, it is possible to increase the scanning speed of the cantilever with respect to the sample at one end side of the observation area in the scanning outward path of the observation area of the sample. Therefore, when scanning the cantilever relative to the sample from one end to the other end of the observation area of the sample, when the scanning direction is switched on one end side of the observation area, one end side of the observation area is affected by the response delay of the scanner. It is possible to suppress the occurrence of distortion in the observed image in the vicinity.

Also, the scan voltage is a second reduced-small acceleration is negative that put the period reduced small immediately before the end, and the slope of the decrease in the previous than the second period be constant Good.

As a result, the voltage reduction speed at the end of the voltage reduction can be slowed down as compared with the case where the voltage reduction speed of the scanning voltage is constant. Therefore, in the scanning return path of the observation area, the scanning speed of the cantilever on the sample at one end side of the observation area can be slowed down.

Further, the probe microscope includes an image processing unit that displays the surface state or dynamics of the observed sample detected by the probe as an image having a predetermined number of pixels, and the first period is the amplitude of the scanning voltage. The period may be 5% or more and 10% or less of the number of pixels corresponding to the half cycle of the predetermined period from the start of the increase.

As a result, in the scanning outbound route of the observation region of the sample, in the region of the set number of pixels (5% or more and 10% or less of the number of pixels in the X direction) on one end side where scanning is started, the sample is steeper to the other end than the other regions. It can scan to and in other areas at a constant speed. Therefore, it is possible to suppress the occurrence of distortion in the observed image.

Further, the scanning voltage in the first period may be increased by a power function.

As a result, the speed of voltage increase at the start of voltage increase can be sharply increased as compared with the case where the speed of voltage increase of the scanning voltage is constant. Therefore, in the scanning outward path of the observation area of the sample, the scanning speed of the cantilever on the sample at one end side of the observation area can be sharply increased.

Further, the scanning voltage in the first period may be increased by a fifth-order or sixth-order function.

As a result, the voltage increase speed at the start of the voltage increase of the scanning voltage can be further increased. Therefore, in the scanning outward path of the observation area, the scanning speed of the cantilever on the sample at one end side of the observation area can be increased more steeply.

Further, the scanning voltage in the second period may be reduced by a quadratic function.

As a result, the voltage reduction speed at the end of the voltage reduction of the scanning voltage can be made slower. Therefore, in the scanning return path of the observation region, the scanning speed of the cantilever on the sample at one end side of the observation region can be further reduced.

Further, the image processing unit may output the output signal corresponding to the scanning voltage after delaying the output signal corresponding to the scanning voltage by a third period from the timing of the scanning voltage.

As a result, the mirror area where the observed image is distorted can be distributed to both ends of the observation area. Therefore, the distortion of the observed image can be further suppressed.

Further, the third period may be a period for the number of pixels within 5% of the number of pixels corresponding to a half cycle of the predetermined cycle from the start of the increase in the amplitude of the scanning voltage.

As a result, the mirror areas allocated to both ends of the observation area can be made inconspicuous. Therefore, the distortion of the observed image can be further suppressed.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a scanning probe microscope capable of suppressing the occurrence of distortion in an observed image.

A block diagram showing a configuration of a scanning probe microscope according to an embodiment. The figure which shows the scanning direction of the scanning probe microscope which concerns on embodiment. The figure which shows the relationship between the scanning signal of the scanning probe microscope which concerns on embodiment, and the movement amount of a scanner. The figure which shows the scanning signal before correction of the scanning probe microscope which concerns on embodiment. The figure which shows the scanning signal after correction of the scanning probe microscope which concerns on embodiment. The figure which shows the sample observation image before correction of the scanning probe microscope which concerns on embodiment. The figure which shows the sample observation image after correction of the scanning probe microscope which concerns on embodiment. The figure which shows an example of the sample observation image at the time of pixel-shifting about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image at the time of pixel-shifting about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image at the time of pixel-shifting about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image at the time of pixel-shifting about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image before changing the signal velocity about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image when the signal speed is changed about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image when the signal speed is changed about the sample observation image of the scanning probe microscope which concerns on the modification of embodiment. The figure which shows an example of the sample observation image when the signal velocity is changed and the pixel shift is combined with respect to the sample observation image of the scanning probe microscope which concerns on the modification of embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following embodiment, an atomic force microscope (AFM) will be described as an example as a scanning probe microscope. In the drawings, the components with the same reference numerals indicate the same or the same type of components.

Moreover, the embodiment described below shows a preferable specific example of the present invention. Numerical values, shapes, materials, components, arrangement positions of components, connection forms, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Further, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept of the present invention will be described as arbitrary components constituting the more desirable form.

(Embodiment)
[Structure of scanning probe microscope]
First, the configuration of the scanning probe microscope 1 according to the present embodiment will be described. FIG. 1 is a block diagram showing a configuration of a scanning probe microscope 1 according to the present embodiment.

The scanning probe microscope 1 is a microscope for observing the surface state, dynamics, etc. of the sample 20 to be observed. The scanning probe microscope 1 may be a contact-type microscope in which the tip of the probe 10a of the cantilever 10 is brought into contact with the sample 20 for scanning, or the tip of the probe 10a of the cantilever 10 is intermittently in contact with the sample 20. It may be an intermittent contact method, or it may be a non-contact microscope that scans at a predetermined interval from the tip of the probe 10a of the cantilever 10.

As shown in FIG. 1, the scanning probe microscope 1 is a scanner that scans the cantilever 10, the sample stage 22 on which the sample 20 is placed, and the sample stage 22 in three-dimensional directions (X direction, Y direction, Z direction). 24, a laser unit 30, a sensor 31, an amplitude detection unit 33, a feedback control unit 34, a computer 35, an oscillator 36, and a monitor 37 are provided. Here, the XY direction is a direction orthogonal to each other on the horizontal plane. Further, the Z direction is a vertical direction, which is a concave-convex direction (height direction) of the sample 20.

The cantilever 10 is made of, for example, silicon nitride. The cantilever 10 has a probe 10a and a beam portion 10b. The probe 10a is provided on one side of the beam portion 10b on one end side, and is formed in a shape with a sharp tip. In the cantilever 10, the root portion of the beam portion 10b on the side opposite to the side on which the probe 10a is formed is supported by a support portion (not shown), and the beam portion 10b on the side on which the probe 10a of the cantilever 10 is arranged is arranged. It is a free end. The probe 10a is arranged so as to face the sample stage 22 on which the sample 20 is arranged. In the case of a contact-type scanning probe microscope, the probe 10a is in contact with the sample 20, and in the case of an intermittent contact-type scanning probe microscope, the beam portion 10b vibrates, so that the probe 10a is a sample. Intermittent contact with 20 is scanned.

The sample stage 22 is a sample holder for holding the sample 20 toward the probe side of the cantilever 10. The sample stage 22 is mounted on the scanner 24. Further, the sample stage 22 may adsorb and hold the sample 20 by, for example, providing an adsorption mechanism (not shown). The sample 20 may be adhered to the sample stage 22.

The scanner 24 is a scanning mechanism for scanning the sample 20 relative to the probe 10a by moving the sample stage 22 in the X direction, the Y direction, and the Z direction. The scanner 24 is composed of, for example, a columnar piezoelectric element (piezo element) having a diameter of about 2 mm and a height of about 2 mm. Scanning in the X and Y directions of the scanner 24 is controlled by the computer 35, and scanning in the Z direction is controlled by the feedback control unit 34, which will be described in detail later.

Specifically, the scanning of the scanner 24 in the X and Y directions is amplified by supplying an X scanning signal and a Y scanning signal (also referred to as an XY scanning signal) from the computer 35 to a scanner driver (not shown). Is supplied to the scanner 24. Further, in the scanning in the Z direction of the scanner 24, a feedback signal (FB signal) is supplied from the feedback control unit 34 to the scanner driver (not shown), amplified, and supplied to the scanner 24. The X scanning signal and the Y scanning signal are voltage signals. This voltage signal is called a scanning voltage. The scanning voltage is a voltage that repeatedly increases and decreases the amplitude in a predetermined cycle. The XY scanning signal will be described in detail later.

The laser unit 30 and the sensor 31 form an optical lever type displacement sensor. The laser unit 30 is a laser light emitting device for irradiating the cantilever 10 with laser light. The laser beam emitted from the laser unit 30 is reflected by a surface near the free end of the beam portion 10b of the cantilever 10 and opposite to the surface on which the probe 10a is provided. Since the cantilever 10 vibrates according to the state or dynamics of the surface of the sample 20, the reflection position and the reflection intensity of the laser beam reflected near the free end of the beam portion 10b also change according to the state or dynamics of the surface of the sample 20. Will be done.

The sensor 31 is, for example, a light receiving sensor composed of a photodiode. The laser beam reflected by the cantilever 10 is received by the sensor 31. That is, the sensor 31 detects the displacement signal corresponding to the state or dynamics of the surface of the sample 20 by receiving the laser beam reflected by the cantilever 10.

The oscillator 36 is an oscillator for applying a sine wave (sin2πft) having a frequency f to the piezoelectric element installed in the cantilever 10. Here, the frequency f is set in the vicinity of the resonance frequency of the cantilever 10, and the cantilever 10 vibrates at the frequency f due to the vibration of the piezoelectric element. When the probe 10a comes into contact with the sample, the displacement or amplitude signal of the beam portion 10b changes. Based on this displacement signal, feedback control of the movement of the scanner 24 in the Z direction is performed as described later.

The amplitude detection unit 33 is an amplitude detection unit that detects an amplitude change among the displacement signals detected by the sensor 31. The signal detected by the amplitude detection unit 33 is supplied to the feedback control unit 34.

The feedback control unit 34 controls the scanner 24 in the Z direction so that the amplitude continues to match the preset set point (target value). The feedback control unit 34 has, for example, a subtractor that generates a deviation signal by subtracting a set point from the amplitude and a PID circuit that amplifies the deviation signal, and generates an FB signal for controlling the scanner 24. The FB signal is supplied to the computer 35.

The computer 35 is composed of, for example, a personal computer or the like, and controls the entire scanning probe microscope 1. The computer 35 also provides a user interface function. When various instructions from the user are input to the computer 35, the computer 35 controls the probe microscope 1 according to the user's input. Further, the computer 35 is a control unit that controls the movement of the scanner 24 in the X direction and the Y direction. Further, the computer 35 generates an image of the sample surface based on the amplitude signal supplied from the feedback control unit 34, is an image processing unit, and outputs the generated image to the monitor 37.

The monitor 37 is a display unit that displays an image based on the supplied signal, and displays information on the surface state or dynamics of the sample output from the computer 35 as an image.

[Operation of scanning probe microscope]
Next, the operation of the scanning probe microscope 1 will be described. Hereinafter, the operation of the intermittent contact type scanning probe microscope 1 will be described. FIG. 2 is a diagram showing the scanning direction of the scanning probe microscope 1 according to the present embodiment. FIG. 3 is a diagram showing the relationship between the scanning signal of the scanning probe microscope 1 and the movement amount of the scanner according to the present embodiment. FIG. 4A is a diagram showing a scanning signal of the scanning probe microscope 1 according to the present embodiment before correction. FIG. 4B is a diagram showing a corrected scanning signal of the scanning probe microscope 1 according to the present embodiment.

First, the sample 20 and the cantilever 10 to be observed are placed at predetermined positions. The sample 20 is placed on the sample stage 22. At this time, the sample 20 may be fixed to the sample stage 22 by an adsorption mechanism, an adhesive, or the like. Then, the cantilever 10 is arranged at a position at a predetermined height from the surface of the sample 20. In the case of the contact-type scanning probe microscope 1, the cantilever 10 may be brought into contact with the surface of the sample 20.

After the sample 20 and the cantilever 10 are placed, the scanner 24 is controlled by the computer 35 to move the sample stage 22 in the XY directions. As a result, the sample stage 22 is scanned in the XY direction with respect to the cantilever 10. That is, the cantilever 10 is scanned in the XY directions relative to the sample 20, for example, as shown in the locus P and the locus Q shown in FIG. In FIG. 2, the scanning of the scanner 24 indicated by the locus P is referred to as a scanning outward path, and the scanning of the scanner 24 indicated by the locus Q is referred to as a scanning return path. Further, the start side of the locus P is referred to as one end side of the observation region of the sample 20, and the end side of the locus P is referred to as the other end side of the observation region of the sample 20.

The relative position of the cantilever 10 with respect to the sample 20 in the XY direction is controlled by the computer 35. The computer 35 supplies the scanner 24 with an X scanning signal whose amplitude changes at a predetermined cycle for scanning in the X direction. Here, the predetermined period is a scanning period that makes one round trip between one end and the other end of the observation region of the sample 20, and is, for example, 6.7 ms, as will be described later. The amplitude is the amplitude of the voltage applied to the scanner 24, and is, for example, 5 Vpp (−2.5 V or more and 2.5 V or less). As shown in FIG. 3, the X scanning signal is a voltage signal that repeats an increase in amplitude for a certain period (period A) and a decrease in amplitude for a certain period (period B). The X scanning signal will be described in detail later. As a result, as shown in FIG. 2, for example, the scanner 24 moves in the positive direction in the X direction during the period A in which the amplitude increases, and moves in the negative direction in the X direction in the period B in which the amplitude decreases. The scanning of the scanner 24 in the period A is the scanning outward path described above, and the scanning of the scanner 24 in the period B is the scanning return path described above. Further, as shown in FIG. 3, a certain delay time occurs until the X scanning signal is applied to the scanner 24 and the scanning is actually completed. The constant delay time is, for example, about 0.2 ms.

During period B, when the amplitude decreases, the computer 35 moves the scanner 24 in the negative direction in the X direction as well as in the positive direction in the Y direction. That is, in the period B, the computer 35 scans Y in addition to the X scan signal so that the cantilever 10 is scanned relative to the sample 20 in the X and Y directions as shown in the locus Q shown in FIG. The signal is supplied to the scanner 24. The Y scanning signal is a signal that simultaneously moves the scanner 24 in the Y direction by a predetermined distance when scanning from the other end to one end of the sample 20 after the scanning in the X direction from one end to the other end of the sample 20 is completed for one line. Is. Here, the predetermined distance is a distance corresponding to one pixel in the sample observation image of the sample 20.

As a result, the cantilever 10 is scanned in the positive direction in the X direction from one end to the other end of the sample 20 as shown in the locus P shown in FIG. 2, and then in the negative direction in the X direction as shown in the locus Q shown in FIG. And moved in the positive direction of the Y direction. By repeating the scanning in the X direction and the Y direction, the cantilever 10 can be relatively scanned in a predetermined region of the sample 20.

Here, the X scanning signal in the present embodiment is a non-linear, amplitude increase and decrease as shown in FIG. 4B by applying a predetermined correction to the linear triangular wave shown in FIG. 4A that repeatedly increases and decreases its amplitude. It is a repeating substantially triangular wave signal.

As shown in FIG. 4A, the uncorrected triangular wave signal is a voltage signal having the same absolute value of the slope of the increase and decrease of the amplitude. That is, the rate of increase and decrease of the amplitude of the voltage applied to the scanner 24 is the same. Therefore, the moving speed of the scanner 24 in the positive direction and the moving speed in the negative direction of the scanner 24 are constant and the same.

For example, the triangular wave shown in FIG. 4A is a triangular wave having a minimum amplitude value of −2.5 V and a maximum amplitude value of 2.5 V, and the amplitude is repeatedly increased / decreased in a cycle of 6.7 ms. In this triangular wave, the rate of increase and decrease of voltage is almost constant at 0.37 V / ms.

On the other hand, as shown in FIG. 4B, in the corrected scanning probe microscope 1, in the triangular wave shown in FIG. 4A, the increase in amplitude in the first period immediately after the start of increase in the X scanning signal (scanning voltage) The acceleration is a positive value. Here, the first period is, for example, a period in which the number of pixels is 5% of the number of pixels corresponding to a half cycle of the cycle of increase / decrease of the X scanning signal from the start of increase in the voltage amplitude of the X scanning signal. That is, it is a period having 5% of the number of pixels corresponding to the period A shown in FIG. For example, when the total number of pixels in the period A is 256 pixels, the first period is a period of 13 pixels on one end side of the sample observation image.

Further, the acceleration of the increase in the amplitude of the X scanning signal in the first period is represented by a power function (exponential function).

As a result, in the scanning outward path of the observation region, the speed of increase in the amplitude of the X scanning signal in the first period immediately after the start of the voltage increase can be increased, so that the region on one end side (one end side) of the observation region of the sample 20 can be increased. The sample 20 can be scanned toward the other end more steeply than the other regions in the region (with a pixel count of 5%).

The power function is, for example, a fifth-order function. By setting the order of the power function to the fifth order, the speed of increasing the amplitude in the first period immediately after the start of increasing the amplitude of the X scanning signal can be further increased. Therefore, in the scanning outward path of the observation region, the scanning speed of the cantilever 10 with respect to the sample 20 on one end side of the observation region can be increased more steeply.

The order of the power function is not limited to the fifth order and may be the sixth order or another order. The higher the order of the power function, the steeper the scanning speed of the cantilever 10 with respect to the sample 20 at one end side of the observation region.

Further, as shown in FIG. 4B, in the corrected scanning probe microscope 1, the acceleration of the decrease in the amplitude of the X scanning signal is set to a negative value in the second period immediately before the end of the decrease in the amplitude of the X scanning signal. .. Here, the second period is, for example, a period in which the number of pixels is 10% of the number of pixels corresponding to half the cycle of the increase / decrease of the X scanning signal from the start of the increase in the voltage amplitude of the X scanning signal. That is, it is a period of 10% of the number of pixels corresponding to the period B shown in FIG. For example, when the total number of pixels in the period B is 256 pixels, the region at the end of the voltage decrease is a region of about 25 pixels on one end side of the sample observation image.

Further, the acceleration of the decrease in the amplitude of the X scanning signal in the second period can be expressed by a power function. The function to be concerned can be represented by, for example, a quadratic function.

As a result, in the scanning return path of the scanning region, the reduction speed of the amplitude of the X scanning signal in the second period immediately before the end of the voltage reduction can be reduced, so that the region on one end side (one end side) of the observation region of the sample 20 can be reduced. In the region (with 10% of the number of pixels), the sample 20 can be scanned to one end side at a slower speed than the other regions. In addition, in the region other than the region on one end side of the sample 20, scanning can be performed at a constant speed.

When the cantilever 10 is scanned relative to the sample 20 between one end side and the other end side of the observation region of the sample 20 by using the X scanning signal as described above, the scanning direction is set on one end side of the observation region. At the time of switching, it is possible to suppress distortion of the sample observation image in the vicinity of one end side of the observation region due to the response delay of the scanner 24 (piezoelectric element) when the scanning direction of the scanner 24 is switched.

The first period and the second period are not limited to 5% of the total number of pixels corresponding to the entire period of voltage increase or voltage decrease, but may be 4% or may be changed as appropriate. Further, in the X scanning signal shown in FIGS. 4A and 4B, reverse transmission correction may be performed to correct the vibration generated when the scanning direction is reversed at both ends of the observation region of the sample 20. ..

During scanning in the XY directions, the sensor 31 detects the vibration signal of the cantilever 10 by detecting the reflected light emitted from the laser unit 30 and reflected by the cantilever 10. Then, the sensor 31 supplies the detected vibration amplitude to the amplitude detection unit 33. That is, when the cantilever 10 is scanned in the positive direction of the X direction with respect to the sample 20, the change in the vibration amplitude of the cantilever 10, that is, the detection of the unevenness information on the surface of the sample 20 is performed.

The amplitude detection unit 33 detects the amplitude from the supplied displacement signal and supplies it to the feedback control unit 34. The feedback control unit 34 performs feedback control in the Z direction of the scanner 24 so that the supplied amplitude matches the set point. The set point is a predetermined target value of amplitude.

The feedback control unit 34 generates a feedback signal according to the difference between the amplitude and the set point, and supplies the feedback signal to the scanner 24. The scanner 24 operates in the Z direction according to the feedback signal. More specifically, a scanner driver (not shown) drives the scanner 24 according to the feedback signal.

Further, the amplitude changes according to the distance between the cantilever 10 and the sample 20. Therefore, the feedback control keeps the distance between the cantilever 10 and the sample 20 constant.

In this way, the XY scan is performed while keeping the distance between the cantilever 10 and the sample constant. The feedback signal is also supplied to the computer 35. The feedback signal is a signal that drives the scanner 24 in the Z direction, and corresponds to the height of the sample 20 in the Z direction. Therefore, by obtaining the feedback signal, information on the state of the surface of the sample 20 (concavo-convex information) can be obtained.

Further, the computer 35 generates the unevenness information of the sample surface as an image based on the control data of the XY scanning and the input feedback signal, and supplies the information to the monitor 37. As a result, the unevenness information on the sample surface is displayed on the monitor 37 as a three-dimensional image.

[Observation example using scanning probe microscope]
Here, an observation example using the scanning probe microscope 1 is shown. In the observations shown below, silicon having a grid of constant irregularities formed on the surface was used as the sample 20. On the surface of sample 20, the grid is formed with a period of 1 μm. The size of the recess of the grid is 0.5 μm as an example. The sample 20 is not limited to silicon, and may be any material such as a biological sample, a polymer, and a semiconductor. Further, when forming a grid having a certain unevenness on the surface of the sample 20, the size and period of the grid may be appropriately changed.

FIG. 5A is a diagram showing a sample observation image before correction of the scanning probe microscope 1 according to the embodiment. FIG. 5B is a diagram showing a corrected sample observation image of the scanning probe microscope 1 according to the embodiment. In FIGS. 5A and 5B, the observation region is a region of 15 μm × 15 μm. Further, in FIGS. 5A and 5B, observation and display are performed at 256 × 256 pixels. The X scanning signal for the sample 20 of the cantilever 10 at the time of observation is the X scanning signal shown in FIGS. 4A and 4B, and the scanning speed is 7.8 ms per line.

In the case of the scanning probe microscope 1 using the X scanning signal (see FIG. 4A) in which the applied triangular wave voltage is not corrected, as shown in the region of the broken line in FIG. 5A, one end side of the sample observation image of the sample 20, that is, In the first period immediately after the start of the increase in the amplitude of the triangular wave described above, a region (mirror region) in which the sample observation image is distorted appears. On the other hand, as shown in FIG. 5B, in the scanning probe microscope 1 using the X scanning signal (see FIG. 4B) corrected for the applied triangular wave voltage, a mirror region appears on one end side of the sample observation image of the sample 20. Not. From this, as described above, by operating the scanner 24 using the X scanning signal shown in FIG. 4B, when the scanning direction is switched at one end of the observation region, the sample observation image is formed in the vicinity of one end of the observation region. It can be seen that the generation of the mirror region is suppressed.

[Effects, etc.]
As described above, according to the scanning probe microscope according to the present embodiment, by using the X scanning signal corrected as described above, the cantilever 10 is relative to the sample 20 from one end to the other end of the observation region of the sample 20. When the scanning direction is switched at one end of the observation area during scanning, it is possible to suppress distortion of the sample observation image in the vicinity of one end of the observation area due to the influence of the switching of the scanning direction of the scanner 24.

(Modification example 1)
In the scanning probe microscope 1, the computer 35 may display the output signal corresponding to the triangular wave on the monitor 37 with a delay of a third period from the timing of the triangular wave. Here, the third period is, for example, the number of pixels within 5% of the number of pixels corresponding to the period of increase in the amplitude of the X scanning signal, that is, the half cycle of the amplitude increase / decrease cycle from the start of the increase in the amplitude of the X scanning signal. The period of minutes. Delaying the monitor display during the third period is called pixel shift. For example, the pixel shift of 10% means that 10% of the number of pixels corresponding to the half cycle of the amplitude increase / decrease cycle is delayed from the start of the amplitude increase of the X scanning signal and displayed on the monitor 37.

6A to 6D are examples of a sample observation image when a lipid bilayer film is used as the sample 20 and the sample observation image when the surface of the sample 20 is observed by the probe microscope 1 is pixel-shifted.

6A to 6D show sample observation images when the imaging rate is 0.5 s / frame and the pixel shifts are 0%, 5%, 10%, and 15%, respectively.

When the pixel shift is 0%, a mirror region appears on one end side of the sample observation image of the sample 20 as shown in the region of the broken line in FIG. 6B.

When the pixel shift is 5%, as shown in FIG. 6B, the mirror region on one end side of the sample observation image of the sample 20 is narrowed. This is because, in the sample observation image of the sample 20, the above-mentioned mirror region is divided into one end side and the other end side of the sample observation image in the X direction. That is, since the mirror regions are dispersed at both ends in the X direction and each mirror region is small, it is possible to suppress the conspicuousness of the mirror region and display a sample observation image without a sense of discomfort.

Further, when the pixel shift is 10%, as shown in FIG. 6C, the mirror region on the other end side of the sample observation image of the sample 20 appears larger than when the pixel shift is 5%.

Further, when the pixel shift is 15%, as shown in FIG. 6D, the mirror region on the other end side of the sample observation image of the sample 20 appears larger than when the pixel shift is 10%.

By pixel-shifting the sample observation image, the above-mentioned mirror region can be distributed to both ends of the sample observation image in the X direction in the sample observation image of the sample 20, so that distortion of the sample observation image is further suppressed. can do. As described above, when the third period is larger than 5% of the period of increase in the amplitude of the X scanning signal, the mirror regions distributed on both sides of the sample observation image become conspicuous. Therefore, the third period is preferably within 5% of the period of increase in the amplitude of the X scanning signal, for example, about 3%.

Further, in FIGS. 7A to 7D, the increase and decrease rates of the scanning signal voltage are changed with respect to the sample observation image when the surface of the sample 20 is observed by the probe microscope 1 using the lipid bilayer as the sample 20, and further. This is an example of a sample observation image when pixel shift is combined.

In FIGS. 7A to 7D, the imaging rate (signal velocity) is set to 0.2 s / frame, and when the scanning signal voltage is increased, the voltage is increased by a fifth-order power function at 8% of the 200 pixels of the operation signal, that is, 16 pixels. It shows a sample observation image when accelerated, decelerated by a quadratic function when the scanning voltage decreases, stopped at 6% of the number of pixels, that is, 12 pixels, and when the pixel shift is 5%. ..

As shown in FIG. 7A, when the imaging rate is 0.2 s / frame (before the imaging rate is changed), as shown in the dashed area of FIG. 7A, a mirror is placed on one end side of the sample observation image of the sample 20. The area is appearing.

When the rate of increase of the scanning signal voltage is accelerated by a fifth-order power function at 8% of the number of scanning pixels of 200, that is, 16 pixels in the outward path of the scanning signal, the sample observation of the sample 20 is shown as shown by the broken line in FIG. 7B. The mirror area appearing on one end side of the image is narrower than that in FIG. 7A.

Further, in the return path of the scanning signal, when the scanning voltage is decelerated by a quadratic function and the scanning is stopped at 6% of the number of pixels, that is, 12 pixels, one end of the sample observation image of the sample 20 as shown in FIG. 7C. The mirror area that appears on the side is even narrower.

Further, when the pixel shift of 5% is further combined, as shown in FIG. 7D, the mirror area does not appear large and becomes inconspicuous.

In this way, by combining the reciprocating shape change of the X scanning signal and the pixel shift, it is possible to suppress the appearance of mirror regions at both ends of the sample observation image.

(Other embodiments)
Although the scanning probe microscope according to the present invention has been described above based on the embodiment, the present invention is not limited to the embodiment. The present invention also includes a form obtained by subjecting an embodiment to a modification that a person skilled in the art can think of, and another form realized by arbitrarily combining components in a plurality of embodiments.

For example, in the above-described embodiment, the locus P is taken in the X direction as shown in FIG. 2, and when the cantilever is scanned in the X direction with respect to the sample, the unevenness information in the Z direction is detected as an observation image. Not limited to this, when the locus P is taken in the Y direction and the cantilever is scanned in the Y direction with respect to the sample, the unevenness information in the Z direction may be detected as an observation image.

Further, in the above-described embodiment, the probe microscope provided with the cantilever as the probe has been described, but the probe is not limited to the cantilever and may be a probe having another configuration. Further, the surface of the sample may be scanned by means other than the probe.

Further, at the start of the increase in the scanning voltage, the acceleration of the voltage increase may be a power function. Further, the order of the power function may be 5th order as described above, and may be 6th order or another order as well as 5th order. The higher the order of the power function, the steeper the scanning speed of the cantilever 10 with respect to the sample 20 at one end side of the observation region.

Further, at the end of the decrease in the scanning voltage, the acceleration of the voltage decrease may be a power function.

Further, the order of the power function may be a quadratic power function or another order. The higher the order of the power function, the slower the scanning speed of the cantilever 10 with respect to the sample 20 at one end of the observation region.

Further, the size and the number of pixels of the observation area are not limited to the above-mentioned size and the number of pixels, and may be appropriately changed according to the observation sample.

Further, the configuration of the scanning probe microscope is not limited to the above, and may be appropriately changed depending on the type of the scanning probe microscope.

The scanning probe microscope according to the present invention is useful for a scanning probe microscope or a probe scanning device for observing physical information on a sample surface or chemical properties of a sample at high speed.

1 Scanning probe microscope 10 Cantilever (probe)
10a probe 10b beam part 20 sample (observation sample)
22 Sample stage 24 Scanner 30 Laser unit 31 Sensor 33 Amplitude detection unit 34 Feedback control unit 35 Computer (control unit)
36 oscillator 37 monitor

Claims (7)

A sample stage on which the observation sample is placed and
A probe for observing the surface state or dynamics of the observed sample,
The scanner that drives the sample stage and
A control unit that controls the operation of the scanner is provided.
Wherein the controller applies a scan voltage to repeat increase and decrease in a predetermined cycle to said scanner,
The scan voltage is increased starting first acceleration of increase that put the period immediately after Ri positive value der and slope of increase following the first period is constant,
The scanning voltage is a scanning probe microscope in which the acceleration of decrease in the second period immediately before the end of decrease is a negative value and the slope of decrease before the second period is constant. The probe microscope includes an image processing unit that displays the surface state or dynamics of the observed sample detected by the probe as an image having a predetermined number of pixels.
Wherein the first period, according to claim 1 wherein from 5% to 10% or less of the period of several minutes pixels of said number of pixels from the increase start corresponding to the half cycle of the predetermined period of the scanning voltage Scanning probe microscope. The scanning probe microscope according to claim 1, wherein the scanning voltage in the first period increases with a power function. The scanning probe microscope according to claim 3, wherein the scanning voltage in the first period increases with a fifth-order or sixth-order function. The scanning probe microscope according to claim 1 , wherein the scanning voltage in the second period decreases by a quadratic function. The scanning probe microscope according to claim 2, wherein the image processing unit outputs an output signal corresponding to the scanning voltage with a delay of a third period from the timing of the scanning voltage. The third period is a scanning probe microscope according to claim 6 increase the start of the scan voltage is a period of a few minutes pixels within 5% of the number of the pixels corresponding to the half cycle of the predetermined cycle ..