JP2009115550A - Scanning probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning probe microscope for measuring the strength of a force as an object to be measured, in addition to ω<SB>0</SB>and Q<SB>0</SB>, in a sate where a cantilever is vibrated at all times and continuously with a fixed amplitude. <P>SOLUTION: In the scanning probe microscope, a probe scans a sample in a state where the probe attached to a leading end of the cantilever approaches the sample; change in the force received from the sample by the probe is detected by the excitation of the cantilever, while a force modulator modulates the force applied between the probe and the sample; and sample image in a micro region is rendered, based on its changed value, while the change is fed back to the excited amplitude of the cantilever by an automatic gain amplifier. The automatic gain amplifier is driven at an input amplification rate for vibrating the cantilever at a fixed amplitude, at all times. The excited amplitude of the cantilever is controlled so as to be fixed. The sample image in the micro region is rendered, by taking into consideration the index as a change in the exciting force which is received from the sample by the cantilever, which is obtained from the change in the input amplification rate that controls the amplification rate of the automatic gain amplifier. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a scanning probe microscope that scans a probe or a sample to observe a sample image of a minute region.

  The scanning probe microscope generates a local stimulus from the probe to the sample when the probe is scanned relative to the sample in a state where the probe and the sample are brought close to each other, and from the sample surface to the stimulus. It is the microscope which observes the surface of a sample by measuring the local response of.

  Scanning probe microscopes are classified into two types based on the difference in response. The first is a scanning tunneling microscope. In this method, the probe is a metal probe, the stimulus is a tunnel voltage, and the response is a tunnel current. The second is a scanning atomic force microscope. In this method, the probe is a force detection cantilever, the stimulus is an atomic force, and the response is a displacement of the cantilever by force.

  The apparatus to which the present invention is applied is limited to the latter scanning atomic force microscope. As a microscope derived from a scanning atomic force microscope, a scanning magnetic force microscope (probe: cantilever with a magnet attached to the probe, stimulation: magnetic force), a scanning electrostatic force microscope (probe: probe) A cantilever that works as an electrode, stimulation: electrostatic force), a scanning magnetic resonance force microscope (probe: cantilever with a magnet attached to the probe, stimulation: magnetic force), and the like have been developed. These are all considered to be microscopes that observe force as a response, and belong to the category of scanning atomic force microscopes.

  There are two types of scanning atomic force microscopes (hereinafter abbreviated as AFM), a contact-type measurement mode and a non-contact-type measurement mode, due to differences in measurement conditions. The contact measurement mode is a method of observing a force while bringing the probe and the sample surface into contact with a strong repulsive force generated between the probe and the sample surface as a stimulus. On the other hand, the non-contact measurement mode is a measurement method in which a force is observed without bringing the probe and the sample into contact by using a weak attractive force generated between the probe and the sample surface as a stimulus.

  The present invention is effective only in the latter non-contact measurement mode.

  AFM can provide a concavo-convex image of the sample surface with high spatial resolution by observing the weak atomic force generated between the probe and the atoms on the sample. The features and technologies of AFM are widely known. For example, the book “Scanning Probe Microscopy Basics and Future Prediction” written by Seizo Morita, published by Maruzen Co., Ltd. (2000), and the book “Scanning Probe Microscopy” The Lab on a Tip "Ernst Meyer, Hans Josef Hug, Roaland Bennewitz Springer (2004).

The present invention is expected to be effective only in the force detection method using the non-contact measurement mode in the AFM. First, the force detection method will be described. The force to be measured in the AFM is generally detected by using a cantilever which is a cantilever spring. The amount x by which the cantilever bends by the force F applied to the tip attached to the tip of the cantilever or the force f The induced vibration amount A of the cantilever can be observed from a precise position displacement meter and evaluated from F = kx or f = kA / Q ₀ , respectively. Here, k is a spring constant, and Q ₀ represents the Q value of the cantilever.

  The force acting on the tip attached to the tip of the cantilever is an atomic force, electrostatic force, magnetic force (in this case, the tip must be a magnetic tip) due to the interaction between the sample surface and its vicinity. It becomes a target.

  Hereinafter, Non-Patent Document 1 will be described as an example of AFM using the force detection method. Non-Patent Document 1 describes a magnetic resonance force microscope apparatus using a force detection method.

  FIG. 1 shows a block diagram depicting components. The magnetic resonance force microscope scans the stage 002 on which the sample 001 is placed, and collects data of magnetic resonance force applied to the cantilever 003 at each position. Then, a magnetic resonance force map is acquired, and appropriate image processing is performed to image information on the spin density distribution of the sample. In the following, the explanation will be continued focusing on the operation for evaluating the force intensity.

  First, a magnetic force is generated between the spin included in the sample 001 and the magnet placed on the tip of the cantilever 003. The force acts on the cantilever 003. Further, the modulation signal generated by the force modulation oscillator 006 is supplied to the force modulation device 004 via the driver 005, and is included in the sample 001 using the force modulation device 004 based on the widely known magnetic resonance principle. Manipulate some spins to constantly modulate the magnetic force.

Let the modulation amplitude of the force be f. When the modulation frequency is matched with the mechanical resonance angular frequency ω ₀ of the cantilever 003, the cantilever 003 resonates with an amplitude A = fQ ₀ / k. The behavior that the cantilever 003 resonates is detected by the cantilever displacement detector 007. The detected signal is detected by a lock-in amplifier 008 using a sine wave that is a modulation source as a reference signal, and an amplitude value A of the cantilever 003 is obtained.

In Non-Patent Document 1, as a more realistic problem, the fact that the resonance frequency ω ₀ of the cantilever 003 changes during measurement is taken into account, and the process of always matching the oscillation frequency of the force modulation oscillator 006 with this change is taken into account. Yes.

  Eventually, a process as shown in FIG. 2 is performed to evaluate the force intensity.

  A01: Move the stage 002.

  A02: In order to obtain the resonance frequency of the cantilever 003, the cantilever 003 is vibrated using the cantilever exciter 009 and the cantilever exciting driver 010.

  A03: Based on the vibration behavior of the cantilever 003 detected by the cantilever displacement detector 007, the frequency is measured by the frequency adjuster 011 for the sine wave oscillator.

  A04: The output of the cantilever excitation driver 010 is stopped, and the excitation of the cantilever 003 is stopped.

  A05: The frequency of the force modulation oscillator 006 is matched with the frequency measured by the sine wave oscillator frequency adjuster 011.

  A06: After confirming that the cantilever 003 is not vibrated and is oscillating in a natural state, the force modulation device 004 modulates the spin of the sample 001, and as a result, the measurement target generated in the sample The magnetic resonance force is applied to the cantilever.

  A07: The vibration of the cantilever 003 is observed using the cantilever displacement detector 007 and the lock-in amplifier 008.

  A08: The force modulation device 004 is stopped, and the magnetic resonance force that is the measurement target is stopped. And it returns to A01 again and repeats the same procedure.

  FIG. 3 shows an illustration of how the vibration of the cantilever 003 behaves in the operations from step A01 to step A08. The cantilever 003 is configured to alternately repeat excitation by the cantilever exciter 009 and the cantilever excitation driver 010 and excitation by the magnetic resonance force of the sample 001.

K. Wago, D. Botkin, CS Yannoni and D. Ruger, “Paramagnetic and magnetic resonance imaging with a tip-on-cantilever magnetic resonance force microscope”, Appl. Phys. Lett., Vol. 72, pp. 2757-2759 (1998) Lee E. Harrell, Kent R. Thurber and Doran D. Smith, “Cantilever noise in off-cantilever-resonance force-detected nuclear magnetic resonance”, J. Appl. Phys., Vol. 95, pp. 2577-2581 (2004 ) T. R. Albrecht, P. Grutter, D. Horne and D. Ruger, “Frequency modulation detection using high-Q cantilevers for enhanced force microscope sensitivity”, J. Appl. Phys., Vol. 69, pp. 668-673 (1991) JP 2007-85955 A JP 2005-241539 A JP 2005-114580 A JP 2003-294602 A JP 2003-28773 A JP 2001-242231 A

By the way, in order to quantitatively evaluate the force acting on the cantilever from the vibration displacement of the cantilever, it is necessary to know the resonance angular frequency ω ₀ and the Q value Q ₀ of the cantilever. As pointed out in Non-Patent Document 1, if ω ₀ changes when the relative position of the sample with respect to the probe is moved by the stage, ω ₀ is sequentially measured each time the stage is moved. It is necessary to continue.

In general, Q ₀ may change as the stage moves. In this case, it is necessary to continuously measure Q ₀ every time the stage is moved.

When Dissipation force microscopy is a microscopic widely known as one of the AFM, the image which the microscope is provided considering that correspond to the image depicting the change in Q _0, Q ₀ when the scanning It can be said that the change is not special.

In the method exemplified in the background art, a method is described in which the cantilever is vibrated each time the stage is scanned, ω ₀ is measured during the scanning, and the oscillation frequency of the oscillator is continuously updated. Non-Patent Document 1 does not mention updating Q ₀ . However, as a method of updating ω _0, the method of vibrating a cantilever described in Non-Patent Document 1 can measure not only ω ₀ but also Q _{0 when the} ring-down method, which is one of the methods, is taken up, for example. Needless to say, this is a technique that can update both ω ₀ and Q ₀ .

However, in the method described in the background art, when detecting the force applied to the cantilever, it is necessary to measure the vibration amplitude of the cantilever excited by the force to be measured, and the purpose is to measure ω ₀ and Q ₀ . The influence of vibration must be negligible.

For example, when a weak force is targeted, if the force required for vibration is 100 times larger than the force to be measured, 4.6 × 2Q ₀ until the influence of vibration does not appear in the vibration of the cantilever. / ω You have to wait for ₀ time. If Q ₀ = 1000 and ω ₀ = 2π [1000 Hz], then 4.6 × 2Q ₀ / ω ₀ = 1.5 seconds or so.

Thus, in response to the problem that both the update of ω ₀ and Q ₀ and the measurement of force intensity are necessary, the amplitude of the cantilever is observed and the cantilever is vibrated and stopped, as in the prior art. In a situation where the above must be repeated, the measurement time becomes longer by the waiting time.

  Non-Patent Document 2 proposes a method that does not change the frequency of the force modulation oscillator even when the resonance frequency of the cantilever changes, in response to the above-described problem.

In this method, it is stated that S / N is observed as the output of the apparatus. Assuming that the transfer function of the cantilever is G (ω ₀ , Q ₀ ), the vibration amount induced by the force f, which is the measured amount, is fG, the vibration amount excited by the thermal noise force N is NG, and S / N Is given by f / N and does not include G as a variable.

However, this method is not appropriate when ω ₀ or Q ₀ changes greatly. The first reason is, omega is omega ₀ when large extent from the G (ω _0, Q ₀₎ is significantly reduced, it becomes the main different measurement noise and NG compared to NG Noise exacerbates the S / N Because it will end up. The second reason is that N is a parameter that depends on ω ₀ , Q ₀ , and the spring constant k of the cantilever from statistical mechanics considerations, and the value of N changes when these numerical values change.

An object of the present invention is to provide a scanning type capable of measuring not only ω ₀ and Q ₀ but also the strength of a force to be measured in a situation where the cantilever is continuously vibrated with a constant amplitude in view of the above points. It is to provide a probe microscope.

In order to achieve this object, a scanning probe microscope according to the present invention includes:
The sample is scanned from the sample while the probe attached to the tip of the cantilever and the sample are brought close to each other, and the force acting between the probe and the sample is modulated by a force modulator. Changes in the force received by the probe are detected by excitation of the cantilever, and the change is fed back to the excitation amplitude of the cantilever by an automatic gain amplifier, and a sample image of a minute region is drawn based on the value of the change. In a scanning probe microscope,
The automatic gain amplifier is driven at an input amplification factor such that the cantilever always vibrates with a constant amplitude, the excitation amplitude of the cantilever is controlled to be constant, and the amplification factor of the automatic gain amplifier is controlled. It is characterized in that a sample image of a minute region can be drawn by using, as an index, a change in excitation force received from the sample by the cantilever which can be understood from a change in the value of the input amplification factor.

  The input amplification factor is obtained by detecting a change in amplitude of the cantilever with a lock-in amplifier using the excitation signal of the force modulation device as a reference signal.

  The force acting between the probe and the sample is a magnetic resonance force.

According to the scanning probe microscope of the present invention,
The sample is scanned from the sample while the probe attached to the tip of the cantilever and the sample are brought close to each other, and the force acting between the probe and the sample is modulated by a force modulator. Changes in the force received by the probe are detected by excitation of the cantilever, and the change is fed back to the excitation amplitude of the cantilever by an automatic gain amplifier, and a sample image of a minute region is drawn based on the value of the change. In a scanning probe microscope,
The automatic gain amplifier is driven at an input amplification factor such that the cantilever always vibrates with a constant amplitude, the excitation amplitude of the cantilever is controlled to be constant, and the amplification factor of the automatic gain amplifier is controlled. Since the cantilever that can be seen from the change in the value of the input amplification factor is the change in the excitation force received from the sample, the sample image of the minute region is drawn,
It is possible to provide a scanning probe microscope capable of measuring not only ω ₀ and Q ₀ but also the strength of the force to be measured in a situation where the cantilever is constantly vibrated with a constant amplitude.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 4 shows an embodiment of a scanning probe microscope according to the present invention. In the figure, reference numeral 101 denotes a sample. The stage 102 on which the sample 101 is placed is scanned, and data on the strength of the force applied to the cantilever 103 with a probe at each position is collected and imaged. Alternatively, the stage 102 on which the sample 101 is placed is scanned in the XY direction while adjusting in the Z direction so that the force intensity is constant, and data on the Z position is collected and imaged for each XY position.

At this time, the self-excitation of the cantilever 103 eliminates the need to update ω ₀ and Q ₀ , and the force intensity is evaluated from the power change of the exciter that excites the cantilever 103.

  FIG. 5 is a flowchart showing a procedure for collecting and imaging force intensity data.

  B01: The self-excitation loop of the cantilever described below is turned ON in advance. Non-Patent Document 3 proposes a self-excitation loop for stably exciting a cantilever.

In the cantilever displacement detector 107, the vibration behavior x (t) of the cantilever is measured. In the automatic gain amplifier 112, when the amplitude value of x (t) is small, the amplification factor is increased with respect to the input x (t) so that the amplitude of x (t) becomes the specified value A ₀ , and x (t When the amplitude value of t) is large, the output is reduced with respect to the input x (t).

  The amplitude of x (t) is calculated by detecting x (t) with the lock-in amplifier 108. As the reference signal (REF) of the lock-in amplifier 108, an oscillation signal of a self-excitation loop supplied via the amplitude adjuster 106 and the phase shifter 111 is used.

The differentiating circuit 113 enables αdx (t) / dt to be output with respect to αx (t) (α is a proportional constant). The cantilever exciter driver 110 amplifies and transmits the differential signal to the cantilever exciter 109 so that the cantilever 103 can be excited by the differential signal output from the differentiation circuit 113. By this loop, the amplitude value of the cantilever 103 is kept at a constant value A ₀ .

  The motion x (t) of the cantilever 103 is described by the following equation.

d ² x / dt ² + (ω ₀ / Q ₀ ) dx / dt + ω ₀ ² x = {(ω ₀ ² F _ex / k) / v} dx / dt
Here F _ex is the force cantilever exciter 109 provides the cantilever 103, v (= Aω ₀₎ represents the amplitude value of dx / dt. That the amplitude value of the cantilever 103 is a constant value is realized when the second term on the left side of the above equation is equal to the term on the right side. At this time, the following equation is obtained.

F _ex = kA ₀ / Q ₀
Here, A ₀ is known. k is k = mω ₀ (m is the total mass of the cantilever) and can be evaluated from the value of the resonance frequency ω ₀ . Therefore, the above equation suggests that Q ₀ can be derived if F _ex can be known.

The magnitude of F _ex is controlled by the amplification factor of the automatic gain amplifier 112, which is in a proportional relationship. Calibration of the proportionality factor is possible as follows.

When the tip of the cantilever 103 does not approach the vicinity of the sample 101, for example, when free vibration occurs, Q ₀ can be obtained from measurement of the vibration noise spectrum of the cantilever 103 or the like. At this time, _Fex can be evaluated from the above equation. When the gain is zero, if it is recognized that F _ex is zero, the proportionality coefficient can be evaluated from the ratio between the evaluated F _ex and the gain of the automatic gain amplifier 112 at that time.

Therefore, if the amplification factor of the automatic gain amplifier 112 is known when the amplitude of the signal oscillated in the self-excitation loop is stabilized, information on Q ₀ is obtained.

  B02: The stage 102 is moved, and a local portion to be measured near the surface of the sample 101 is brought close to the tip of the cantilever 103.

B03: The gain (information of Q ₀ ) of the automatic gain amplifier 112 and the frequency ω ₀ generated in the self-excitation loop measured by the frequency demodulator 114 are recorded.

  B04: It is assumed that some force is generated between a local portion near the surface of the sample 101 and the tip of the cantilever 103, and that force acts on the cantilever 103. Further, it is assumed that the force modulation device 104 can be used to modulate the force. For example, if the atomic force is a target, a device that varies the position of the stage 102 in the Z direction applies to the force modulation device 104. If the electrostatic force is a target, a device that changes the potential difference of the cantilever 103 with respect to the sample 101 or the stage 102 applies to the force modulation device 104.

  As a result, the electric signal (1 / v) dx (t) / dt taken out from the differentiation circuit 113 of the self-excitation loop and obtained through the amplitude adjuster 106 is received by the force modulation device 104 via the driver 105. , Force change with time f (t) = (f / t) dx (t) / dt. Here, f is an unknown and is a parameter to be evaluated.

B05: The amplitude of the cantilever 103 is A ₀ -A due to the force fluctuation f (t) derived from the force modulation device 104. Here, A = fQ ₀ / k. In the self-excitation loop, the automatic gain amplifier 112 automatically adjusts the amplification factor so that the amplitude is A _0. Therefore, the force transmitted to the cantilever exciter 109 is changed from F _ex → F _ex + Ak / Q _0. become.

Therefore, it is possible to obtain the F _ex when the measured force which had been measured in B03 process does not work, the F _ex + by obtaining the difference between _{Ak / Q 0, Ak / Q} 0 when working.

  B06: The output of the force modulation device 104 is stopped. And it returns to process B02 and repeats the procedure from process B02 to process B06.

  FIG. 6 shows an illustration of how the vibration of the cantilever 103 and the amplification factor of the automatic gain amplifier 112 behave in the operation from the process B02 to the process B06.

  As a supplement to the above, the generation of the force to be measured in the process B04, the force measurement in the process B05, and the force stop in the process B06 are performed, but the series of operations from the process B04 to the process B06 is constantly changed. It doesn't matter. That is, the force ON / OFF may be constantly and periodically changed, and the intensity modulation of the cantilever caused by the periodically changing force may be detected.

  FIG. 7 shows an embodiment of a scanning probe microscope according to the present invention. In the figure, 201 is a sample. The stage 202 on which the sample 201 is placed is scanned, and data on the force intensity applied to the cantilever 203 with a probe at each position is collected and imaged. Alternatively, the stage 202 on which the sample 201 is placed is scanned in the XY direction while adjusting in the Z direction so that the force intensity is constant, and data on the Z position is collected and imaged for each XY position.

At this time, the self-excitation of the cantilever 203 eliminates the need to update ω ₀ and Q ₀ , and the force intensity is evaluated from the power change of the exciter that excites the cantilever 203.

  FIG. 8 is a flowchart showing a procedure for collecting and imaging force intensity data.

  C01: The cantilever self-excitation loop described below is turned ON in advance. Non-Patent Document 3 proposes a self-excitation loop for stably exciting a cantilever.

The cantilever displacement detector 207 measures the vibration behavior x (t) of the cantilever. In the automatic gain amplifier 212, when the amplitude value of x (t) is small so that the amplitude of x (t) becomes the specified value A ₀ , the amplification factor is increased with respect to the input x (t) and output, and x (t When the amplitude value of t) is large, the output is reduced with respect to the input x (t).

  The amplitude of x (t) is calculated by detecting x (t) with the lock-in amplifier 208. As a reference signal (REF) of the lock-in amplifier 208, an oscillation signal of a self-excited loop supplied via the amplitude adjuster 206 and the phase shifter 211 is used.

The differentiation circuit 213 can output αdx (t) / dt with respect to αx (t) (α is a proportional constant). The cantilever exciter driver 210 amplifies and transmits the differential signal to the cantilever exciter 209 so that the cantilever 203 can be excited by the differential signal output from the differentiation circuit 213. By this loop, the amplitude value of the cantilever 203 is kept at a constant value A ₀ .

  The motion x (t) of the cantilever 203 is described by the following equation.

d ² x / dt ² + (ω ₀ / Q ₀ ) dx / dt + ω ₀ ² x = {(ω ₀ ² F _ex / k) / v} dx / dt
Here F _ex is the force cantilever exciter 209 provides the cantilever 203, v (= Aω ₀₎ represents the amplitude value of dx / dt. The fact that the amplitude value of the cantilever 203 becomes a constant value is realized when the second term on the left side of the above equation is equal to the term on the right side. At this time, the following equation is obtained.

F _ex = kA ₀ / Q ₀
Here, A ₀ is known. k is k = mω ₀ (m is the total mass of the cantilever) and can be evaluated from the value of the resonance frequency ω ₀ . Therefore, the above equation suggests that Q ₀ can be derived if F _ex can be known.

The magnitude of F _ex is controlled by the amplification factor of the automatic gain amplifier 212, which is in a proportional relationship. Calibration of the proportionality factor is possible as follows.

For example, when the tip of the cantilever 203 is not approaching the vicinity of the sample 201 and is in free vibration, Q ₀ can be obtained from measurement of the vibration noise spectrum of the cantilever 203 or the like. At this time, _Fex can be evaluated from the above equation. When it is recognized that F _ex is zero when the amplification factor is zero, the proportionality coefficient can be evaluated from the ratio between the evaluated F _ex and the amplification factor of the automatic gain amplifier 212 at that time.

Therefore, if the amplification factor of the automatic gain amplifier 212 is known when the amplitude of the signal oscillated in the self-excitation loop is stabilized, the information of Q ₀ is obtained.

  C02: The stage 202 is moved to bring the local portion to be measured near the surface of the sample 201 closer to the tip of the cantilever 203.

C03: The gain (information of Q ₀ ) of the automatic gain amplifier 212 and the change in the resonance frequency of the cantilever 203 generated in the self-excitation loop measured by the frequency demodulator 214 are recorded.

  C04: It is assumed that some force is generated between a local portion in the vicinity of the surface of the sample 201 and the tip of the cantilever 203, and that force acts on the cantilever 203. Further, it is assumed that the force modulation device 204 can be used to modulate the force. For example, if the atomic force is a target, a device that varies the position of the stage 202 in the Z direction applies to the force modulation device 204. If the electrostatic force is a target, a device that changes the potential difference of the cantilever 203 with respect to the sample 201 and the stage 202 applies to the force modulation device 204.

As a result, the electric signal (1 / A ₀ ) x (t) taken out from the self-excitation loop and obtained through the amplitude adjuster 206 is received by the force modulator 204 through the driver 205, and the time change of the force It is assumed that f (t) = (f / A ₀ ) x (t). Here, f is an unknown and is a parameter to be evaluated.

C05: The resonance frequency of the cantilever 203 becomes √ (ω ₀ ² −f / A ₀ ) due to the force fluctuation f (t) derived from the force modulation device 204. That frequency becomes the frequency of the signal generated in the self-excited loop. The frequency is measured by the frequency demodulator 14.

Therefore, the difference between the square frequency ω ₀ ² when the measured force measured in step C03 does not work and the square of the angular frequency when it works (ω ₀ ² −f / A ₀ ) By obtaining, f / A ₀ can be obtained.

  C06: The output of the force modulation device 204 is stopped. And it returns to process C02 and repeats the procedure from process C02 to process C06.

  FIG. 9 illustrates how the vibration of the cantilever 203, the amplification factor of the automatic gain amplifier 212, and the resonance frequency of the cantilever (the output of the frequency demodulator 214) behave in the operations from step C02 to step C06. It showed in.

  As a supplement to the above, the force to be measured is generated in step C04, the force is measured in step C05, and the force is stopped in step C06. The series of operations from step C04 to step C06 is changed as follows. It is also possible. That is, the force ON / OFF is periodically and periodically changed, and the frequency modulation amount of the cantilever caused by the periodically changing force is detected with respect to the frequency measurement amount read by the frequency demodulator 214. It doesn't matter.

  It can be widely used for scanning probe microscopes such as magnetic resonance force microscopes.

It is a figure which shows an example of the conventional scanning probe microscope. It is an example of the figure which shows the flow of a measurement in the conventional scanning probe microscope. It is an example of the figure which shows the vibration of the cantilever during measurement in the conventional scanning probe microscope. It is a figure which shows one Example of the scanning probe microscope concerning this invention. It is one Example of the figure which shows the flow of a measurement in the scanning probe microscope concerning this invention. It is one Example of the figure which shows the vibration of the cantilever under measurement in the scanning probe microscope concerning this invention. It is a figure which shows another Example of the scanning probe microscope concerning this invention. It is another Example of the figure which shows the flow of a measurement in the scanning probe microscope concerning this invention. It is another Example of the figure which shows the vibration of the cantilever under measurement in the scanning probe microscope concerning this invention.

Explanation of symbols

001: Sample, 002: Stage, 003: Cantilever with probe, 004: Force modulation device (modulation magnetic field generator), 005: Driver for driving the force modulation device, 006: Oscillator for force modulation, 007: Cantilever displacement detector , 008: Lock-in amplifier, 009: Cantilever exciter, 010: Driver for cantilever excitation, 011: Frequency adjuster for sine wave oscillator, 101: Sample, 102: Stage, 103: Cantilever with probe, 104: Force modulator (Modulated magnetic field generator), 105: Driver for driving the force modulator, 106: Amplitude adjuster, 107: Cantilever displacement detector, 108: Lock-in amplifier, 109: Cantilever exciter, 010: Driver for cantilever excitation, 111 : Phase shifter, 112: automatic gain amplifier, 113: fine Circuit: 114: Frequency demodulator, 201: Sample, 202: Stage, 203: Cantilever with probe, 204: Force modulation device (modulation magnetic field generator), 205: Driver for driving the force modulation device, 206: Amplitude adjuster 207: Cantilever displacement detector 208: Lock-in amplifier 209: Cantilever exciter 210: Cantilever excitation driver 211: Phase shifter 212: Automatic gain amplifier 213: Differentiation circuit 214: Frequency demodulator

Claims (3)

The sample is scanned from the sample while the probe attached to the tip of the cantilever and the sample are brought close to each other, and the force acting between the probe and the sample is modulated by a force modulator. Changes in the force received by the probe are detected by excitation of the cantilever, and the change is fed back to the excitation amplitude of the cantilever by an automatic gain amplifier, and a sample image of a minute region is drawn based on the value of the change. In a scanning probe microscope,
The automatic gain amplifier is driven at an input amplification factor such that the cantilever always vibrates with a constant amplitude, the excitation amplitude of the cantilever is controlled to be constant, and the amplification factor of the automatic gain amplifier is controlled. A scanning probe microscope characterized in that a sample image of a minute region can be drawn by using, as an index, a change in excitation force received from the sample by the cantilever, which is known from a change in input amplification factor. The scanning probe microscope according to claim 1, wherein the input amplification factor is obtained by detecting a change in amplitude of the cantilever with a lock-in amplifier using an excitation signal of the force modulation device as a reference signal. 2. The scanning probe microscope according to claim 1, wherein the force acting between the probe and the sample is a magnetic resonance force.

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