JPH0954097A - Scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a probe to approach the surface of a sample at a high speed and to eliminate the possibility of the probe colliding with the sample. SOLUTION: A sample stage 1 is formed by a quartz oscillator. A circuit 6, together with the sample stage 1, constitutes a quartz oscillator circuit and causes the sample stage 1 to oscillate at a resonance frequency represented by the formula F0 =f0 +Δf0 . Using a reference frequency oscillator 7, a mixer 8, a low-pass filter 9, and an F/V converter 10, a voltage signal at a level proportional to an amount of change Δf from the resonance frequency f0 when a probe 2 has moved away can be obtained from the output of the F/V converter 10. A control part 11 controls a probe drive 3 so that the probe 2 approaches the sample in response to a command from an operating part 12. The control part 11 stops the operation of the probe drive 3 when the level of a signal output from the F/V converter 10 has reached a predetermined level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope for measuring predetermined information of a sample while scanning a probe on the sample surface.

[0002]

2. Description of the Related Art A scanning probe microscope is an apparatus capable of observing a sample surface with a resolution on the order of nanometers.

Typical examples include a scanning tunneling microscope (STM), an atomic force microscope (AFM) and a scanning near field optical microscope (SNOM).

In the STM, a bias voltage is applied between a probe having a sharpened tip and a sample to bring them close to each other within tens of angstroms, and a tunnel current flowing between the probe and the sample is detected. Then, for example, when the probe is scanned on the sample surface while applying feedback so that the tunnel current becomes constant, the probe moves along the shape of the sample surface, so that the surface shape of the sample can be measured. .

In the AFM, generally, a cantilever having a probe at its tip is brought close to the sample surface, and the bending of the cantilever due to the atomic force from the sample is detected. Since this amount of bending is proportional to the atomic force acting between the probe and the sample surface,
For example, the shape of the sample surface can be measured by scanning the sample surface with the probe while applying feedback so that the amount of deflection becomes constant.

In SNOM, when the light is guided to a probe (optical probe) having an opening smaller than the wavelength of the light to be irradiated on the sample, an evanescent wave exists near the opening. The optical information of the sample can be measured by scanning the sample surface with the probe. Further, in SNOM, even when the irradiation light is made incident from the back surface of the sample so that the total reflection condition is satisfied, an evanescent wave exists on the sample surface. Therefore, a probe (probe) for detecting this is used as a sample. By scanning the surface, the optical information of the sample can be measured.

A scanning near-field optical microscope as disclosed in Japanese Patent Laid-Open No. 59-121310 will be described as an example of a conventional scanning probe microscope with reference to FIG. FIG. 4 is a schematic configuration diagram showing this conventional scanning near-field optical microscope.

In FIG. 4, reference numeral 101 denotes a base, which is structured so as not to be subjected to external vibration by a vibration isolation device (not shown). Reference numeral 102 denotes a sample table which is arranged on the base 101 and on which the sample 103 is mounted. The sample table 102 is moved by an unillustrated moving device (driving device) in X and Y directions (in the X and Y directions, the sample (measured Object) 103 in a plane parallel to the surface of the object 103) and orthogonal to each other.). 104 is the base 1
Reference numeral 105 denotes a light source attached to the tip arm portion 104A of the support column 104 via a vertical adjusting device (moving device capable of moving in the Z direction orthogonal to the surface of the sample 103) 106. Reference numeral 105 is a semiconductor laser or the like. By moving the sample 103 in the X and Y directions, the probe 107 having an opening at the tip relatively scans the surface of the sample 103. Reference numeral 113 denotes a sensor that detects reflected light that is emitted from the light source 105, passes through the opening of the probe 107, and is reflected by the surface of the sample 103. The reflected light that enters the sensor 113 is detected by the optical fiber 110 by the photodetector 111.
And converted into an electric signal.

According to this scanning type near-field optical microscope, the vertical adjustment device 106 is operated in advance at the start of measurement to make the probe 1
07 is brought close to the surface of the sample 103, and the evanescent wave at each point on the surface of the sample 103 is moved while moving the sample 103 in the X and Y directions with the position of the probe 107 in the Z direction fixed. It is possible to obtain the optical state of the sample surface with high resolution by measuring the intensity of the reflected light and reconstructing it with a display device or the like not shown.

[0010]

However, in the conventional scanning near-field optical microscope, the probe 1 is used at the start of measurement.
When the sample 07 is brought close to the surface of the sample 103 in advance, the probe 1
There is a defect that 07 may collide with the sample 103 and it takes time to approach.

That is, the signal intensity for detecting the evanescent wave sharply decreases as the probe 103 moves away from the sample 103. The signal strength for detecting the evanescent wave is about 1 pW to 1 mW, which is very weak. Therefore, when the probe 107 is moved closer to the surface of the sample 103 by the vertical adjustment device 106 and the probe 107 is automatically stopped based on the signal intensity obtained from the photodetector 111, the probe 107 is moved to the sample 103. May cause a collision. In this way, the probe 10
When 7 collides with the sample 103, not only the sample 103 but also the probe 107 is often damaged. Therefore, in order to avoid such a collision, the probe 107
The approach speed of the sample 103 to the sample 103 was sufficiently slowed, but in this case, rapid measurement of the sample 103 cannot be performed. Moreover, even if the approach speed is sufficiently slowed, the signal intensity obtained from the photodetector 11 is
7 reflects the optical state of the sample 103 as well as the distance between the surface of the sample 103 and the surface of the sample 103. Therefore, the approach state of the probe 107 is detected from the signal of the photodetector 111. Therefore, depending on the optical state of the surface of the sample 103, the signal of the photodetector 107 may cause
Since the approaching state of 07 cannot be detected, the probe 107 inevitably collides with the sample 103.

The circumstances described above are the same in various other scanning probe microscopes such as STM. For example, in the STM, the signal intensity for detecting the tunnel current sharply decreases as the probe moves away from the sample, and is from pA to several nA, which is very weak. Further, in the STM, the magnitude of the tunnel current not only reflects the distance between the probe and the sample, but also changes depending on the state of conductivity of the sample. It cannot detect the approach state to the sample.

In the conventional scanning near-field optical microscope, the detection signal obtained by the photodetector 111 is, as described above, the optical state of the sample 103 and the probe 107.
It reflects both the distance between the sample and the sample 103. That is, the light intensity detected by the photodetector 111 depends not only on the local optical properties (refractive index, absorbance, etc.) on the surface of the sample 103, but also largely on the distance from the sample surface to the opening. The two pieces of information, the surface shape and the optical properties of the, are not separated. For example, factors that decrease the detection signal intensity may include a change in the shape of the surface of the observation region that is recessed and an optical change such that the refractive index is high or the absorbance is high. Therefore, the conventional scanning near-field optical microscope has a drawback in that only optical information of the sample cannot be obtained separately from the shape information.

In this respect, a cantilever with a probe employed in an atomic force microscope is used, and the probe is configured so that it can also be used as a probe of a scanning near-field optical microscope. A microscope that combines the functions of an optical microscope and an atomic force microscope has been proposed.

In this case, however, a probe suitable for a scanning near-field optical microscope has to be formed on the cantilever, and the probe that can be provided on the cantilever is structurally limited, and a usable probe can be used. The drawback is that the needles are very limited.

Such a situation was also the same in various other scanning probe microscopes such as STM.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to bring the probe closer to the sample surface automatically at a high speed, and further, the probe may collide with the sample. It is an object to provide a scanning probe microscope that does not have a laser beam.

Another object of the present invention is to provide a scanning probe microscope capable of obtaining only desired information separated from shape information of a sample without being restricted by the type of probe. .

[0019]

In order to solve the above-mentioned problems, a scanning probe microscope according to the first aspect of the present invention has a sample stage on which a sample is mounted, a probe, and a direction substantially perpendicular to the sample surface. First moving means for moving the probe relative to the sample, and second moving means for moving the probe relative to the sample in the direction of a plane substantially parallel to the sample surface. In the scanning probe microscope including a moving unit, the sample stage is made of a crystal oscillator, a vibrating unit that vibrates the sample stage at a resonance frequency of the sample stage, and a signal corresponding to the resonance frequency of the sample stage. And a frequency detecting means for outputting the signal, and controlling the first moving means so that the probe relatively approaches the sample in response to a command signal, and based on the output signal of the frequency detecting means. The resonance circumference of the sample table When the number reaches a predetermined frequency, in which close to said sample of said probe is further comprising a control means for controlling the first moving means so as to stop, the.

A scanning probe microscope according to a second aspect of the present invention is a sample stage on which a sample is mounted, a probe, and the probe relative to the sample in a direction substantially perpendicular to the sample surface. A scanning probe microscope comprising: first moving means for moving; and second moving means for moving the probe relative to the sample in a direction of a plane substantially parallel to the surface of the sample, The sample stage is made of a crystal oscillator, a vibrating means for vibrating the sample stage at a predetermined frequency near the resonance frequency of the sample stage, an impedance detecting means for outputting a signal according to the impedance of the sample stage, and a command signal In response to the control of the first moving means so that the probe relatively approaches the sample, and based on the output signal of the impedance detecting means, the impeller of the sample stage is controlled. When the scan reaches a predetermined impedance, in which close to said sample of said probe is further comprising a control means for controlling the first moving means so as to stop, the.

A scanning probe microscope according to the third aspect of the present invention is a sample stage on which a sample is mounted, a probe, and the probe relative to the sample in a direction substantially perpendicular to the sample surface. A scanning probe microscope comprising: first moving means for moving; and second moving means for moving the probe relative to the sample in a direction of a plane substantially parallel to the surface of the sample, The sample stage is made of a crystal oscillator, and vibrating means for vibrating the sample stage at the resonance frequency of the sample stage, frequency detecting means for outputting a signal according to the resonance frequency of the sample stage, and the frequency detecting means The probe scans the sample surface in the direction of a plane substantially parallel to the sample surface while controlling the first moving means so that the resonance frequency of the sample stage becomes a predetermined frequency based on the output signal. As said second moving means And control means for controlling, in which further comprising a.

A scanning probe microscope according to a fourth aspect of the present invention is a sample stage on which a sample is mounted, a probe, and the probe relative to the sample in a direction substantially perpendicular to the sample surface. A scanning probe microscope comprising: first moving means for moving; and second moving means for moving the probe relative to the sample in a direction of a plane substantially parallel to the surface of the sample, The sample stage is made of a crystal oscillator, a vibrating means for vibrating the sample stage at a predetermined frequency near the resonance frequency of the sample stage, an impedance detecting means for outputting a signal according to the impedance of the sample stage, and the impedance While controlling the first moving means so that the impedance of the sample stage becomes a predetermined impedance based on the output signal of the detecting means, the impedance is moved in a direction substantially parallel to the sample surface. Control means for the needle to control the second moving means so as to scan the sample surface, in which further comprising a.

A scanning probe microscope according to a fifth aspect of the present invention is the scanning probe microscope according to the third or fourth aspect, wherein the sample surface of the probe is in a direction substantially parallel to the sample surface. And means for obtaining information on the relative position of the probe with respect to the sample surface in a direction substantially perpendicular to the sample surface according to the relative position with respect to the sample surface.

In the present specification, "the sample stage is made of a crystal oscillator" means not only the case where the entire sample stage is made up of the crystal oscillator only, but also the case where the sample stage is made up of the crystal oscillator and the crystal oscillator. It also includes a case where it is composed of a plate-like member provided on the surface.

According to the first aspect, the sample stage made of the crystal oscillator is vibrated at the resonance frequency of the sample stage by the vibrating means, and the sample mounted on the sample stage also vibrates accordingly. When the probe approaches the sample, the resonance frequency of the sample table changes due to the interatomic force acting between the probe and the sample. The Q value of the crystal unit is high, and even if a weak force is applied, the resonance frequency changes greatly. Therefore, the approach state of the probe to the sample can be detected with high sensitivity from the signal corresponding to the resonance frequency of the sample stage output by the frequency detection means. Therefore, even if the speed of approach of the probe to the sample is increased,
There is no risk of collision between the probe and the sample. Further, the signal obtained from the frequency detecting means depends on the interatomic force acting between the probe and the sample, and reflects only the distance between the probe and the sample. It is possible to detect the approach state of the probe to the sample regardless of the state of conductivity and the like. As a result, according to the first aspect, the control unit controls the first moving unit so that the probe relatively approaches the sample, and based on the output signal of the frequency detecting unit. Since the first moving means is controlled so that the approach of the probe to the sample is stopped when the resonance frequency of the sample table reaches a predetermined frequency, the probe is moved relatively quickly to the sample surface. The probe can be automatically approached, and there is no risk of the probe colliding with the sample.

According to the second aspect, the sample stage made of a crystal oscillator is vibrated at a predetermined frequency near the resonance frequency of the sample stage by the vibrating means, and the sample mounted on the sample stage accordingly. Vibrate. When the probe approaches the sample, the resonance frequency of the sample table changes due to the interatomic force acting between the probe and the sample, and the impedance of the sample table changes. The Q value of the crystal unit is high, and even if a weak force is applied, the change of the resonance frequency is large, and the change of the impedance of the sample stage is large. Therefore, the approaching state of the probe to the sample can be detected with high sensitivity from the signal output from the impedance detecting means according to the impedance of the sample stage. Therefore, even if the approaching speed of the probe to the sample is increased, there is no possibility of collision between the probe and the sample. Further, the signal obtained from the impedance detecting means depends on the interatomic force acting between the probe and the sample, and reflects only the distance between the probe and the sample. It is possible to detect the approach state of the probe to the sample regardless of the state of conductivity and the like. As a result, according to the second aspect, the control means controls the first moving means so that the probe relatively approaches the sample, and based on the output signal of the frequency detecting means. , The first moving means is controlled so that the approach of the probe to the sample is stopped when the impedance of the sample table reaches a predetermined impedance, so that the probe is automatically moved at a high speed relative to the sample surface. In addition, the probe can be prevented from colliding with the sample, and damage to both the probe and the sample can be prevented.

Further, according to the third aspect, the first
As in the case of (1), a signal indicating only the distance between the probe and the sample can be obtained from the frequency detecting means. Further, according to the fourth aspect, similarly to the second aspect, a signal indicating only the distance between the probe and the sample can be obtained from the frequency detecting means. Therefore, the third and fourth
In this mode, the probe controls the sample surface in a direction substantially parallel to the sample surface while keeping the distance between the probe and the sample constant by following the unevenness of the sample surface by the control of the control means. Will be scanned. Therefore, according to the third and fourth aspects, desired information due to the probe separated from the shape information of the sample (for example, optical information of the sample in SNOM).
Can be obtained separately from the shape information, and
Since it is not necessary to provide the probe on the cantilever, there is no restriction on the type of probe.

According to the third and fourth aspects, since the movement control of the probe similar to the so-called non-contact mode in the atomic force microscope is realized, the relative movement as in the fifth aspect is performed. By obtaining the information on the position, it is possible to obtain the shape data of the unevenness of the sample surface,
It is more preferable for observing the sample.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION A scanning probe microscope according to the present invention will be described below with reference to the drawings.

(Embodiment 1) First, a scanning near-field optical microscope according to a first embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a schematic configuration diagram schematically showing the scanning near-field optical microscope according to the present embodiment. Further, FIG. 3 is a diagram showing impedance characteristics of the crystal unit.

The scanning near-field optical microscope according to the present embodiment comprises a sample table 1 on which a sample (not shown) is mounted, a probe (optical probe) 2 having an opening 2a at the tip, and a sample table 1
Probe drive device 3 for moving the probe 2 in the Z direction perpendicular to the surface of the sample table 1, and the sample table 1 independently in the X direction and the Y direction, which are directions of a plane parallel to the surface of the sample table 1 and are orthogonal to each other. And a sample table drive device 4 for moving.

In the present embodiment, the probe driving device 3 constitutes moving means for moving the probe 2 relative to the sample in a direction substantially perpendicular to the sample surface, and the sample table driving device 4 A moving means for moving the probe 2 relative to the sample in the direction of a surface substantially parallel to the surface is configured. However, these moving means may move either the probe 2 or the sample table 4.

Further, the scanning near-field optical microscope according to the present embodiment includes a light source (not shown) for irradiating the probe 2 with light to generate an evanescent wave from the opening 2a of the probe 2, and an evanescent light. The photodetector 5 for detecting the reflected light reflected by the surface of the sample due to the wave, and the reflected light corresponding to the sensor 113 and the optical fiber 110 in FIG.
And a means (not shown) for guiding to. However,
Irradiation light is made incident from the back surface of the sample table 2 so as to satisfy the condition of total reflection, and an evanescent wave is generated from the sample surface,
The evanescent wave detected by the opening 2 a of the probe 2 may be guided to the photodetector 5.

Then, in the present embodiment, the sample table 1
Is composed of a crystal oscillator and has electrodes 1a and 1b on its upper and lower surfaces, respectively. The crystal oscillator constituting the sample stage 1 is adapted to vibrate in the Z direction according to the voltage applied between the electrodes 1a and 1b. In the present embodiment, the sample stage 1 is composed of only the crystal unit, but a flat plate or the like may be provided on the sample-side surface of the crystal unit if necessary. However, since the Q value is lowered by providing such a flat plate or the like, it is preferable to mount the sample directly on the surface of the crystal oscillator.

Further, as shown in FIG. 1, the scanning near-field optical microscope according to this embodiment has a circuit 6 and a mixer 8.
, A low-pass filter 9, an F / V converter 10,
Control unit 11, operation unit 12, processing unit 13, and display unit 1
4 is provided.

The electrodes 1a and 1b of the crystal oscillator (sample stage) 1 are connected to the two terminals 6a and 6b of the circuit 6, respectively, and the circuit 6 together with the crystal oscillator 1 is a well-known crystal such as Hartley type or Colpitts type. It constitutes an oscillation circuit, and the crystal unit 1 vibrates at its resonance frequency F ₀ (see FIG. 3). Therefore, in the present embodiment, the circuit 6
However, it constitutes a vibrating means for vibrating the sample table 1 at the resonance frequency F ₀ of the sample table 1. Since the configuration itself of the circuit 6 is well known, its detailed description is omitted. Terminal 6c of circuit 6
Is an output terminal of the crystal oscillation circuit, and an oscillation output whose frequency is the resonance frequency F ₀ is obtained from the terminal 6c.

The reference frequency oscillator 7 has a reference frequency (in the present embodiment, the crystal oscillator 1 in a state where the probe 2 is away from the sample surface and no atomic force acts between the probe 2 and the sample surface). there is a frequency f ₀ is the resonant frequency F ₀ of but not necessarily to output a reference frequency signal having not limited.) this frequency. The mixer 8 mixes the oscillation output from the terminal 6c of the circuit 6 and the reference frequency signal from the reference frequency oscillator 7 to obtain the sum and difference of the frequency F _{0 of the} oscillation output and the frequency f ₀ of the reference frequency signal. An output signal having a frequency component is output. The low-pass filter 9 filters and outputs only the signal having the frequency component of the difference among the output signals of the mixer 8. The F / V converter 10 is
A voltage having a level proportional to the frequency of the output signal of the mixer 8 is output.

Now, assuming that the resonance frequency F ₀ of the crystal unit 1 changes from f ₀ to f ₀ + Δf ₀ , the output signal of the mixer 8 has a frequency component of 2f ₀ + Δf _{0 and} a frequency component of Δf _0. The low-pass filter 9 outputs only a signal having a frequency component of Δf ₀ , and the output of the F / V converter 10 is Δ
The voltage has a level proportional to f ₀ . Where Δf ₀ is
Crystal oscillator 1 in a state in which the probe 2 is away from the sample surface and no atomic force acts between the probe 2 and the sample surface
For the frequency f ₀ is the resonant frequency F ₀ of the resonant frequency F ₀ of the crystal oscillator 1 of the actual state frequency f ₀ + Delta] f
_Since the change amount is ₀ , the output of the F / V converter 10 indicates the change amount Δf ₀ , and eventually becomes a signal corresponding to the resonance frequency F ₀ of the crystal resonator 1.

As can be seen from the above description, in the present embodiment, the mixer 8, the low-pass filter 9 and the F / V converter 10 are provided with frequency detecting means for outputting a signal corresponding to the resonance frequency F ₀ of the sample stage 1. I am configuring. However, the configuration of the frequency detecting means is not limited to this.

The operation unit 12 is composed of a mouse, a keyboard and the like, and has a command (hereinafter, referred to as "approach command") to bring the probe 2 closer to the sample at the start of measurement and a measurement start according to the operation of the measurer. Input commands to various commands.

The control unit 11 controls the probe driving device 3 so that the probe 2 approaches the sample in response to the approach command from the operation unit 12. Then, the control unit 11 controls the F /
Based on the output signal of the V converter 10, the probe driving device 3 is controlled so that the approach of the probe 2 to the sample is stopped when the resonance frequency F ₀ of the sample table 1 reaches a predetermined frequency. That is, in the present embodiment, the control unit 11
Stops the operation of the probe drive device 3 when the level of the output signal of the F / V converter 10 reaches a predetermined level. This predetermined level is set to a level obtained when the distance between the probe 2 and the sample reaches a desired approach distance.

Further, in this embodiment, the control unit 11 is
In response to the measurement start command from the operation unit 12 given after the approach of the probe 2 to the sample is completed, the level of the output signal of the F / V converter 10 is set to a predetermined level based on the output signal of the F / V converter 10. While controlling the probe driving device 3 so as to be as follows, the sample table driving device 3 is controlled so that the probe 2 scans the sample surface in the X direction and the Y direction.

From the control unit 11 to the probe driving device 3
The control signal given to the
It indicates the relative position of the direction. Further, the control signal given from the control unit 11 to the probe driving device 3 is the probe 2
Indicates the relative position in the X and Y directions with respect to the sample surface.

In response to the measurement start command, the processing unit 13 takes in each control signal from the control unit 11 and the detection signal of the photodetector 5 and makes the probe 2 relative to the sample surface in the X and Y directions. Information about the level of the detection signal of the photodetector 5 according to the position (that is, optical information of the sample) is obtained, and the probe 2 according to the relative position of the probe 2 in the X and Y directions with respect to the sample surface is obtained. Information about the relative position in the Z direction with respect to the sample surface (that is, sample shape information) is obtained. Then, these pieces of information are displayed as images on the display unit 14 such as a CRT.

According to the scanning near-field optical microscope of the present embodiment, the sample stage 1 made of a crystal oscillator is vibrated at the resonance frequency F ₀ of the sample stage 1 by the circuit 6, and the sample stage 1 is mounted on the sample stage 1 accordingly. The sample subjected to vibration also vibrates.

In response to the approach command from the operating section 12, when the probe driving device 3 operates and the probe 2 approaches the sample, the atomic force acting between the probe 2 and the sample causes the sample stage 1 to move.
The resonance frequency F _{0 of} is shifted to the low frequency side. As a result,
The level of the output voltage of the F / V converter 10 changes.
Then, when the level of the output voltage of the F / V converter 10 reaches a predetermined level, the control unit 11 stops the operation of the probe driving device 3 and automatically stops the approach of the probe 2 to the sample.

The crystal resonator has a high Q value, and even if a weak force is applied, the resonance frequency F ₀ changes greatly. For this reason,
The approach state of the probe 2 to the sample can be detected with high sensitivity from the output of the F / V converter 10. Therefore,
Even if the approach speed of the probe 2 to the sample is increased, there is no possibility of collision between the probe 2 and the sample. Further, the output of the F / V converter 10 depends on the interatomic force acting between the probe 2 and the sample, and reflects only the distance between the probe 2 and the sample. The approach state of the probe 2 to the sample can be detected regardless of the state. Therefore, from this point as well, there is no possibility of collision between the probe 2 and the sample.

Further, according to the present embodiment, the output signal of the F / V converter 10 reflects only the distance between the probe 2 and the sample. Then, as described above, the operation unit 12
In response to the measurement start command from the control unit 11, the control unit 11 controls the F / V
While controlling the probe driving device 3 so that the level of the output signal of the F / V converter 10 becomes a predetermined level based on the output signal of the converter 10, the probe 2 scans the sample surface in the X and Y directions. Then, the sample stage drive device 3 is controlled. Therefore, under the control of the control unit 11, the probe 2 follows the unevenness of the sample surface and the distance between the probe 2 and the sample is kept constant, while the probe 2 moves in a direction substantially parallel to the sample surface. Will be scanned. That is, the movement control of the probe similar to the so-called non-contact mode in the atomic force microscope is realized. Therefore, the optical information of the sample obtained by the processing unit 13 is separated from the shape information of the sample.

Furthermore, in the present embodiment, the processing unit 13 also obtains the shape information of the sample, which is preferable for observing the sample. However, in the present invention, it is not always necessary to obtain the shape information of the sample.

(Second Embodiment) Next, a scanning type near-field optical microscope according to a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 2 is a schematic configuration diagram schematically showing the scanning near-field optical microscope according to this embodiment. 2, constituent elements that are the same as or correspond to the constituent elements in FIG. 1 are assigned the same reference numerals, and descriptions thereof will be omitted.

The scanning near-field optical microscope according to the present embodiment differs from the scanning near-field optical microscope according to the first embodiment in that the circuit 6, mixer 8, low-pass filter 9 and F in FIG. / V converter 10 is deleted,
Instead, the oscillator 21, the resistor 22, and the lock-in amplifier 23 are provided.

One electrode 1b of the crystal oscillator 1 is grounded, and the other electrode 1a of the crystal oscillator 1 is connected to the output terminal of the oscillator 21 via the resistor 22. The oscillator 21 outputs an oscillation output having a predetermined frequency f _A near the oscillation frequency F ₀ of the crystal unit 1 to an output terminal. Therefore, in the present embodiment, the oscillator 21 and the resistor 22 constitute a vibrating means for vibrating the sample table 1 at a predetermined frequency f _A near the oscillation frequency F ₀ of the sample table 1. In the present embodiment, unlike the first embodiment, the crystal unit 1 does not oscillate at its own resonance frequency, but is always forcedly excited by the oscillator 21 at the predetermined frequency f _A. Of.

Further, in the present embodiment, the oscillator 21
Of the lock-in amplifier 23 is connected to the reference input terminal 23a of the lock-in amplifier 23, the input terminal 23b of the lock-in amplifier 23 is connected to the electrode 1a of the crystal unit 1, and the output terminal 23c of the lock-in amplifier 23 is connected to the control unit 11. It is connected. The lock-in amplifier 23 outputs, to the output terminal 23c, a DC voltage having a level proportional to the amplitude of the same frequency component as the frequency of the signal input to the reference input terminal 23a among the frequency components of the signal input to the input terminal 23b. It is a thing. Therefore, assuming that the crystal oscillator impedance is Z and the oscillator voltage is V, {Z / (Z + R)} is output from the output terminal 23c of the lock-in amplifier 23.
A DC voltage proportional to V is obtained, and a voltage of a level corresponding to the impedance of the crystal unit 1 is obtained. As can be seen from the above description, in the present embodiment,
The lock-in amplifier 23 constitutes impedance detecting means for outputting a signal corresponding to the impedance of the crystal unit 1. However, in the present invention, the configuration of the impedance detecting means is not limited to this.

Further, in the present embodiment, the control unit 11
Controls the probe driving device 3 based on the output signal of the lock-in amplifier 23 so that the probe 2 stops approaching the sample when the impedance of the sample table 1 reaches a predetermined frequency. That is, in the present embodiment, the control unit 11 stops the operation of the probe driving device 3 when the level of the output signal of the lock-in amplifier 23 reaches the predetermined level. This predetermined level is set to a level obtained when the distance between the probe 2 and the sample reaches a desired approach distance.

Further, in this embodiment, the control unit 11 is
The level of the output signal of the lock-in amplifier 23 becomes a predetermined level based on the output signal of the lock-in amplifier 23 in response to the measurement start command given from the operation unit 12 after the approach of the probe 2 to the sample is completed. While controlling the probe driving device 3 in this manner, the sample stage driving device 3 is controlled so that the probe 2 scans the sample surface in the X and Y directions.

Except for the points described above, this embodiment is exactly the same as the first embodiment.

According to the scanning near-field optical microscope of the present embodiment, the sample stage 1 made of a crystal oscillator is vibrated at a predetermined frequency f _A near the resonance frequency F ₀ of the sample stage 1 by the oscillator 21 and the resistor 22. The sample mounted on the sample table 1 also vibrates accordingly.

In response to the approach command from the operation unit 12, when the probe driving device 3 operates and the probe 2 approaches the sample, the atomic force acting between the probe 2 and the sample causes the sample table 1 to move.
The resonance frequency F _{0 of} is shifted to the low frequency side. That is,
The impedance of the crystal unit 1 changes. As a result,
The level of the output voltage of the lock-in amplifier 23 changes.
Then, when the level of the output voltage of the lock-in amplifier 23 reaches a predetermined level, the control unit 11 stops the operation of the probe driving device 3 and automatically stops the approach of the probe 2 to the sample.

The Q value of the crystal unit is high, the change in the resonance frequency F ₀ is large even when a weak force is applied, and the change in the impedance of the sample stage 1 is large. Therefore, the approach state of the probe 2 to the sample can be detected with high sensitivity from the output of the lock-in amplifier 23. Therefore, even if the approach speed of the probe 2 to the sample is increased, there is no possibility of collision between the probe 2 and the sample. The output of the lock-in amplifier 23 depends on the interatomic force acting between the probe 2 and the sample, and reflects only the distance between the probe 2 and the sample. However, it is possible to detect the approach state of the probe 2 to the sample. Therefore, from this point as well, there is no possibility of collision between the probe 2 and the sample.

Further, according to the present embodiment, the output signal of the lock-in amplifier 23 reflects only the distance between the probe 2 and the sample. Then, as described above, the operation unit 12
In response to the measurement start command from the control unit 11, the control unit 11 controls the probe drive device 3 so that the level of the output signal of the lock-in amplifier 23 becomes a predetermined level based on the output signal of the lock-in amplifier 23. The sample stage drive device 3 is controlled so that the probe 2 scans the sample surface in the X and Y directions. Therefore, under the control of the control unit 11, the probe 2 follows the unevenness of the sample surface and the distance between the probe 2 and the sample is kept constant, while the probe 2 moves in a direction substantially parallel to the sample surface. Will be scanned. That is, the movement control of the probe similar to the so-called non-contact mode in the atomic force microscope is realized. Therefore, the optical information of the sample obtained by the processing unit 13 is separated from the shape information of the sample.

Further, also in the present embodiment, the shape information of the sample is obtained by the processing unit 13, which is preferable for observing the sample.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

For example, in each of the above-described embodiments, both acquisition of the shape information of the sample and optical information of the separated sample and automatic approach of the probe 3 are achieved at the same time.
The present invention may achieve only one of them.

Although the above-described embodiments are examples in which the present invention is applied to the scanning near-field optical microscope, the present invention is applied to the scanning tunnel microscope and other various scanning probe microscopes. You can also

[0067]

As described above, according to the present invention,
The probe can be brought relatively close to the sample surface automatically at high speed, and there is no risk of the probe colliding with the sample.

Further, according to the present invention, it is possible to obtain only desired information separated from the shape information of the sample without being restricted by the type of the probe.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram schematically showing a scanning near-field optical microscope according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram schematically showing a scanning near-field optical microscope according to a second embodiment of the present invention.

FIG. 3 is a diagram showing impedance characteristics of a crystal unit.

FIG. 4 is a schematic configuration diagram showing a conventional scanning near-field optical microscope.

[Explanation of symbols]

 1 sample stage (quartz oscillator) 2 probe 3 probe drive device 4 sample stage drive device 5 photodetector 6 circuit 7 reference frequency oscillator 8 mixer 9 low-pass filter 10 F / V converter 11 control unit 12 operation unit 13 processing unit 14 Display 21 Oscillator 22 Resistor 23 Lock-in amplifier

Claims (5)

[Claims] 1. A sample stage on which a sample is mounted, a probe, first moving means for moving the probe relative to the sample in a direction substantially perpendicular to the sample surface, and the sample surface. A second moving means for moving the probe relative to the sample in a direction substantially parallel to the sample, wherein the sample stage is made of a quartz oscillator, Vibrating means for vibrating the stage at the resonance frequency of the sample stage, frequency detecting means for outputting a signal according to the resonance frequency of the sample stage, and the probe relative to the sample in response to a command signal. The first moving means is controlled so as to approach the sample, and the probe approaches the sample when the resonance frequency of the sample table reaches a predetermined frequency based on the output signal of the frequency detecting means. Said to stop Scanning probe microscope for and control means for controlling the moving means, and further comprising a. 2. A sample stage on which a sample is mounted, a probe, first moving means for moving the probe relative to the sample in a direction substantially perpendicular to the sample surface, and the sample surface. A second moving means for moving the probe relative to the sample in a direction substantially parallel to the sample, wherein the sample stage is made of a quartz oscillator, Vibrating means for vibrating the table at a predetermined frequency near the resonance frequency of the sample table, impedance detecting means for outputting a signal corresponding to the impedance of the sample table, and the probe with respect to the sample in response to a command signal. The first moving means so as to relatively approach each other, and when the impedance of the sample stage reaches a predetermined impedance based on the output signal of the impedance detecting means, Scanning probe microscope characterized in that the approach with respect to the sample needle is further provided with a control means for controlling the first moving means so as to stop, the. 3. A sample stage on which a sample is mounted, a probe, first moving means for moving the probe relative to the sample in a direction substantially perpendicular to the sample surface, and the sample surface. A second moving means for moving the probe relative to the sample in a direction substantially parallel to the sample, wherein the sample stage is made of a quartz oscillator, A vibrating unit that vibrates the table at the resonance frequency of the sample table, a frequency detecting unit that outputs a signal corresponding to the resonance frequency of the sample table, and a resonance frequency of the sample table based on the output signal of the frequency detecting unit. Control for controlling the second moving means so that the probe scans the sample surface in a direction substantially parallel to the sample surface while controlling the first moving means so as to have a predetermined frequency. Characterized by further comprising: Scanning probe microscope. 4. A sample stage on which a sample is mounted, a probe, first moving means for moving the probe relatively to the sample in a direction substantially perpendicular to the sample surface, and the sample surface. A second moving means for moving the probe relative to the sample in a direction substantially parallel to the sample, wherein the sample stage is made of a quartz oscillator, Vibrating means for vibrating the table at a predetermined frequency near the resonance frequency of the sample table, impedance detecting means for outputting a signal according to the impedance of the sample table, and the sample table of the sample table based on the output signal of the impedance detecting means. While controlling the first moving means so that the impedance becomes a predetermined impedance, the second movement is performed so that the probe scans the sample surface in a direction of a plane substantially parallel to the sample surface. Scanning probe microscope characterized in that it further comprises a control means for controlling the stage, the. 5. According to the relative position of the probe with respect to the sample surface in the direction of a plane substantially parallel to the sample surface,
5. The scanning probe microscope according to claim 3, further comprising means for obtaining information on a relative position of the probe with respect to the sample surface in a direction substantially perpendicular to the sample surface.