JPH09329605A - Scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning probe microscope having high reproducbility and sensitivity by enhancing the spatial resolution through an analytical method when different information is obtained from the same pixel. SOLUTION: When a voltage is applied from a bias voltage supply circuit 18 to a sample 15 and a micro cantilever 21 approaches the surface of the sample 15 from above, reflected light from the micro cantilever 21 is detected by a displacement detection system 23. Electrical information of the sample 15 is obtained based on the surface profile of the sample 15 and the output from a current/voltage conversion circuit 22 through the displacement detection system 23. Furthermore, the sample 15 is irradiated with a laser light from a laser light source 17 through a critical angle prism 16 simultaneously with the measurement. When the probe 20 of the micro cantilever 21 comes into contact with an evanescent field 25 on the surface of the sample 15, an evanescent light is emitted and inputted to a photomultiplier 24 which produces optical information of the sample 15.

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 typified by an atomic force microscope. More specifically, when obtaining different kinds of information from the same pixel, spatial resolution can be improved through an analytical method. The present invention relates to a scanning probe microscope having improved and high reproducibility and high sensitivity.

[0002]

2. Description of the Related Art A scanning probe microscope (SPM) which has been used conventionally detects an interaction acting between a probe and a sample surface which are in close proximity to each other while scanning the probe to obtain surface information of the sample. Is a device for obtaining. Among them, the AC mode atomic force microscope (AFM) measures the surface shape of the sample while controlling the positional relationship between the probe and the sample so that the vibration amplitude signal of the cantilever becomes constant. No. 63-309803.

FIG. 9 is a block diagram of an AC mode device used for conventional SPM measurement. In this device, a sample, which is an object to be examined, is placed on a piezoelectric stage, and the sample is scanned with a cantilever having a probe that repeats a constant vibration amplitude, thereby detecting information such as the surface shape of the sample. It makes it possible.

In FIG. 9, a sample 3 is placed on a stage 2 on a piezoelectric body 1 which is movable in the XYZ directions. The piezoelectric body 1 is formed in a hollow cylindrical shape, and divided electrodes for driving the piezoelectric body are attached to the outer periphery thereof.

Above the sample 3, a cantilever 5 having a sharply pointed probe 4 at the sample-side tip is fixed to the excitation piezoelectric body 6 so as to face the sample 3. The excitation piezoelectric body 6 is connected to an excitation signal generator 8. Furthermore,
The excitation signal generator 8 generates a signal for vibrating the excitation piezoelectric body 6 based on the instruction signal from the computer 9.

Above the cantilever 5, an optical displacement detection system 7 for optically detecting the displacement of the cantilever 5 is provided. This optical displacement detection system 7 is connected to an amplitude detector 10 that detects the displacement amplitude of the cylinder value cantilever 5. The amplitude detector 10 is for performing a predetermined process on the displacement amplitude of the cantilever 5. The amplitude detector 10 is also connected to the servo circuit 11 and the computer 9.

The computer 9 outputs a signal for vibrating the cantilever 5 to the excitation signal generator 8 and a displacement amplitude signal of the cantilever 5 detected by the optical displacement detection system 7 via the amplitude detector 10. recognize. Further, the computer 9 scans the piezoelectric body 1 in the XY directions via the high-voltage amplifier 12, and recognizes the drive signal in the Z direction based on the output signal of the servo circuit 11. This Z
A sample surface image is formed based on the direction driving signal and the XY direction scanning signal.

Next, the operation of the SPM thus constructed will be described. First, the operation for keeping the vibration of the cantilever 5 constant while no force (for example, atomic force, frictional force, contact force, adhesive force, etc.) is acting between the probe 4 and the sample 3. , As follows.

In response to an instruction signal from the computer 9, the excitation signal generator 8 outputs a signal for vibrating the excitation piezoelectric body 6. Then, based on this signal, the excitation piezoelectric body 6
Vibrates, and this vibration is propagated to the cantilever 5, and the cantilever 5 vibrates.

The vibration of the cantilever 5 is detected by the optical displacement detection system 7, and the amplitude thereof is detected by the amplitude detector 10. This amplitude is input to the computer 9, and the instruction signal from the computer 9 to the excitation signal generator 8 is controlled so that the cantilever 5 is controlled to have a constant amplitude. The amplitude of the cantilever 5 is preferably oscillated constantly at a frequency near the resonance point peculiar to the cantilever 5 used.

Next, after the amplitude of the cantilever 5 is stabilized, the probe 4 and the sample 3 are brought close to or in contact with each other, and when a force is exerted between the two, comparison is made with the case where no force is exerted as described above. Thus, the position of the resonance point of the vibration of the cantilever 5 is moved (shifted). This is because the natural frequency of the cantilever 5 changes depending on the force acting between the probe 4 and the sample 3.

The shift amount of the resonance point of the cantilever 5 at this time is detected by the optical displacement detection system 7 and input to the computer 9 via the amplitude detector 10. The observer selects a desired shift amount of the cantilever 5 from the input signal. That is, the force acting between the probe 4 and the sample 3 is determined. This shift amount is set in the computer 9 and becomes a reference shift amount for scanning the sample 3 with the probe 4. After the reference shift amount is determined, a scanning signal is output from the computer 9 to the piezoelectric body 1 via the high voltage amplifier 12, and the sample 3 is scanned in the XY directions.

The distance between the probe 4 and the sample 3 changes according to the unevenness of the surface of the sample 3 scanned in the XY directions. The resonance point of the cantilever 5 changes as the distance changes.
The change in the resonance point is detected by the optical displacement detection system 7 and input to the servo circuit 11 via the amplitude detector 10. The servo circuit 11 creates and outputs a signal for correcting the change in the shift amount based on the change in the reference shift amount and the amplitude set in the computer 9. This output signal is input to the piezoelectric body 1 and the distance between the probe 4 and the sample 3 is adjusted. That is, the piezoelectric body 1 is driven in the Z direction.

The output signal from the servo circuit 11 is
It is input to the computer 9 and used for image formation of the surface shape of the sample together with the XY scanning signal. Thus, by repeating the operation of controlling the piezoelectric body 1 in the Z direction so as to maintain the reference shift amount on the XY plane,
An image such as the surface shape of the sample 3 is formed.

Further, the AFM is the A as shown in FIG.
In addition to the C mode, for example, the excitation piezoelectric body 6 of FIG.
A device configuration without the excitation signal generator 8 and the amplitude detector 10 is conceivable. In this structure, the following control is performed.

When the probe 4 and the sample 3 come close to or in contact with each other, a force (primitive force, contact force, etc.) acts between them, and the cantilever 5 bends based on the force. This deflection amount is detected by the optical displacement detection system 7, and a displacement signal based on this deflection amount is input to the servo circuit 11 and the computer 9. In the computer 9, as in the case of the above-mentioned reference shift amount, a desired flexure amount serving as a reference is determined in advance, and in the servo circuit 11, a signal for keeping the flexure amount of the cantilever 5 at the reference flexure amount, that is, the flexure amount is constant. A servo signal for maintaining

The output signal of the servo circuit 11 is input to the computer 9 as surface information of the sample and is also given to the piezoelectric body 1 via the high-voltage amplifier 12 as a signal for driving the piezoelectric body 1 in the Z direction. Used. The piezoelectric body 1 is driven in the Z direction, and the amount of bending of the cantilever 5 is kept constant.

In the AFM, keeping the amount of bending constant means keeping the force (primitive force, contact force, etc.) acting between the probe 4 and the sample 3 constant. Further, since the primitive force has a distance dependency, it can be said that keeping the amount of bending constant also keeps the distance between the probe 4 and the sample 3 constant.

Further, "the probe and the sample are in close proximity to or in contact with each other" means that the above-mentioned AFM including the AC mode is included.
This is because there are variations such as a non-contact mode in which the sample surface and the probe are in close proximity but not in contact with each other, and a contact mode in which the sample surface and the probe are in contact with each other.

Further, a bias voltage is applied to the sample, a conductive probe is brought close to the sample, a tunnel current flowing between the sample and the probe is detected, and the tunnel current is kept at a constant value. A scanning tunneling microscope (STM) is known in which a piezoelectric body holding a sample or a probe is controlled in the Z direction (STM feedback), and this control signal is imaged as a tunnel image of the sample.

Further, the sample surface is scanned with the probe formed at the free end of the cantilever in contact with the sample surface, and the amount of twist of the cantilever caused by this scanning is detected. As a result, the sample surface A friction force measurement microscope (LFM) for measuring friction force, and "OPTICAL LET"
TERS February 1, 1994 / Vo
l. 19, no. 3 P 159-161 "," Near-Field scanning ".
optical microscope witha
Like a metallic probe tip ", a probe is brought into contact with an evanescent field formed on the sample surface, and scattered light generated at this time is detected using a photodetector such as a photomultiplier phototube (PMT),
Scanning near-field light microscope (SN
OM) and the like are also known.

In recent years, using a cantilever having such a probe, a probe microscope for detecting surface information in a very limited region of a sample has been combined, and the above-mentioned A is used.
Devices based on FM and having functions of STM, LFM, and SNOM have been developed.

Thus, since the AFM using the cantilever was developed (G. Binnig, C. et al.
F. Quate and Ch. Gerber: Phy
s. Rev. Lett. , 56'86, 930), AF
Since the observation target of M is not limited to one having conductivity, it has spread to many research and development fields. The physical quantity to be detected is not limited to atomic force, but is extended to magnetic force, intermolecular force, frictional force, evanescent light, etc., and various ideas have been made for its detection mechanism and measurement mode (for example,
Y. Martin, H .; K. Wickramasing
he: Appl. Phys. Lett. 50,145
5'87 etc.).

In addition, the cantilever is made electrically conductive and
Compound microscopes having the functions of M and STM have also appeared (Y. Sugawara, T. Ishizaka an.
dS. Morita: Jpn. J. Appl. Phys
s. 29'90 1533).

In the SPM having a single function considering the measurement mode, STM, contact mode AFM, AC mode AF
M, non-contact AFM and the like. Further, in the case of the two types of composite types, contact (non-contact) mode STM / AFM, AFM / LFM, AFM / SNOM and the like can be mentioned.

[0026]

By the way, in the case where the AFM or STM unit is separately used to measure the same portion of the sample separately, conventionally, one unit is used for the measurement and then the other unit is used for the measurement. Was going on. However, with this measurement method, it is difficult to correctly align the different units when setting them on the sample, and the reproducibility of the measurement results at the same location on the same sample cannot be said to be high. In other words, it is possible that an observer intends to measure the same point on the sample using a different unit, but may measure another point.

In addition to the displacement signal of the cantilever (AFM signal, LFM signal, etc.), even when the optical signal (SNOM signal) or current signal (STM signal) is obtained as the second channel, Since different physical quantities are detected, not all physical quantities can be detected with high sensitivity. For example, in the case of STM feedback in simultaneous STM / AFM measurement, that is, in the mechanism that keeps the tunnel current value flowing between the sample and the probe constant,
The tunnel current value changes based on the local difference in conductivity of the sample, and the distance between the sample and the probe changes even if the sample has no unevenness. As a result, the displacement of the cantilever changes even if the tunnel current value is kept constant. Therefore, in such a configuration, ST
Although the electrical characteristics of the sample can be detected by M, the surface shape of the sample cannot always be detected by AFM at the same time.

Further, the AC mode AFM / SNOM is
It is controlled based on the signal of the AFM. That is, the control signal when the sample surface is scanned by this control reflects the sample surface shape. However, since the evanescent field formed on the sample has a distance dependency of weakening in the direction away from the sample, when the distance between the sample and the probe changes, the scattered light to be detected fluctuates. It is known to do. And in the SNOM measurement,
Since the value obtained by time-integrating the scattered light detected at each measurement point is the effective value (detected light),
In the C mode AFM / SNOM, only the average scattered light value is obtained with respect to the vibration of the cantilever. The present invention has been made in view of the above problems, and an object thereof is to provide a scanning probe microscope having high reproducibility and high sensitivity when different kinds of information are obtained from the same pixel.

[0029]

That is, according to the present invention, a cantilever which is arranged so as to be able to scan facing a sample to be measured, has a probe at its tip and is held at its free end, and the displacement of this cantilever. It is provided with a first detecting means for detecting a signal to obtain the surface shape of the sample, and a second detecting means for detecting information other than the surface shape of the sample at the same time as the detection of the first detecting means. , The first detecting means and the second
The surface information of the sample is obtained based on the detection result of the detection means.

In the scanning probe microscope of the present invention, as shown as a typical example in FIG. 1, simultaneous measurement using a micro cantilever 21 capable of detecting a plurality of signals from the same pixel, for example, conductivity. In order to obtain the above, a micro cantilever 21 coated with a conductive material or doped is used. Alternatively, as shown in FIG. 3, it has a feedback mechanism that reflects the unevenness of the sample 15. Further, as shown in FIG. 5, a structure is provided in which a laser input at the time of detecting an optical signal and a bias voltage application at the time of detecting an electric signal are synchronized with the vibration of the micro cantilever 21. This allows
It is possible to improve S / N at the time of detecting a plurality of signals and perform signal analysis and image processing.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, and is a view showing a schematic configuration of a compound microscope having an STM / AFM / SNOM function (conductivity, high refractive index probe). .

In FIG. 1, a critical angle prism 16 is provided below a sample 15 which is a subject, and a laser light source is provided so that the sample 15 is irradiated with laser light from the outside of the critical angle prism 16. 17 are arranged. Also,
The sample 15 is provided with a transparent conductive layer (for example, ITO; indium / Ti) not shown so that a predetermined voltage is applied.
bias voltage supply circuit 18 via
Is connected.

On the sample 15, a micro cantilever 21 for observing the shape of the surface of the sample 15 and having a probe 20 at the tip is arranged. The micro cantilever 21 has conductivity and a refractive index higher than that of the sample or air. For example, the lever portion is made of gold-plated stainless steel, and the probe portion is a diamond tip and is conductive to the lever. It is fixed with a flexible adhesive.

A current-voltage conversion circuit 22 is connected to the micro cantilever 21, and the probe 20 and the sample 1 are connected.
Electrical information from the sample 15 such as a contact current when 5 comes into contact with or a tunnel current when approaching the tunnel region is obtained. Further, above the micro cantilever 21, similarly to a normal atomic force microscope, a displacement detection system 2 for detecting the reflected light of the laser light from the optical system (not shown) by the micro cantilever 21.
3 are arranged. Furthermore, the micro cantilever 21
Near the photomultiplier photocell (Photomaru)
24 is provided so that scattered light generated when the probe 20 is brought into contact with the evanescent field 25 generated on the surface of the sample 15 is detected.

In such a structure, when the sample 15 is scanned using the probe 20, the same feedback operation as in the conventional AFM is performed. That is, the displacement detection system 23 determines the amount of bending of the microphone cantilever 21 caused by the force acting between the sample 15 and the probe 20 (in this case, mainly the primitive force).
And the distance between the sample 15 and the probe 20 is controlled so that this deflection amount is maintained at the reference deflection amount. Also,
At the same time, from the bias voltage supply circuit 18 to the sample 15
Is applied to the current, and the tunnel current detected by the probe 20 is input to the current-voltage conversion circuit 22.

As a result, the shape of the surface of the sample 15 (AFM information) and the current-voltage conversion circuit 2 are detected via the displacement detection system 23.
The electrical information (STM information) of the sample 15 can be obtained from the output of 2.

Simultaneously with the above measurement, the laser light source 17 irradiates the sample 15 with laser light through the critical angle prism 16, and an evanescent field 25 is formed on the surface of the sample 15. Then, scattered light is generated by the contact between the probe 20 and the evanescent field 25 on the surface of the sample 15, and this is detected by the photo-mulch 24. The optical information (AFM information) of the sample 15 can be obtained from the output of the photomultiplier 24.

Therefore, from the displacement detection system 23 to the sample 15
Of the surface shape (AFM information), electrical information (STM information) of the sample 15 from the current-voltage conversion circuit 22, and optical information (SNOM information) of the sample 15 from the photomultiplier 24.
But they are obtained at the same time.

Further, the AFM feedback in the above-mentioned embodiment is based on the inter-primitive force and is a so-called non-contact mode AFM feedback, but the present embodiment is not limited to this. Absent.
For example, AFM feedback in the contact mode may be used. In this case, the amount of deflection of the micro cantilever 21 due to the contact force rather than the inter-primitive force is detected as the AFM information. Further, as STM information, not the tunnel current but the contact current is accurately detected. However, the amount of flexure of the micro cantilever 21 indicates the surface shape of the sample 15, and the contact current shows electric characteristics based on the conductivity of the sample 15. Therefore,
Even in the AFM feedback in the contact mode as described above, the same information detection as in the present embodiment can be performed.

Next, with reference to FIG. 2, an example of interpretation of an image as a result of detecting a plurality of signals will be described based on the operation of the first embodiment. Now, it is considered that the sample 15 has a shape as shown in FIG. This sample 15
There is no clear difference in shape, but non-equivalent A site 15
a, B site 15b, and C site 15c. The A site 15a has higher conductivity than the other two sites, and the B site 15b has the other two sites.
It is assumed that the transmittance is higher than that of one site.

In such a case, the micro cantilever 2
The surface shape of the sample 15 is shown in FIG.
Is obtained as shown in. Then, the electrical information is shown in FIG.
The optical information obtained as shown in FIG.
Obtained as shown in (c).

As described above, according to the first embodiment,
From the images obtained at the same time, it is possible to identify even if they are the same in shape. That is, it is possible to perform various evaluations on the surface by folding in known information and inferring from a plurality of information. In this sense, the in-plane resolution can be improved as compared with the SPM having a single function.

Since a plurality of pieces of information can be detected by scanning once, it is possible to improve the reproducibility of the measurement result at the same location on the same sample. Further, in the present embodiment, although AFM feedback is used, the distance between the probe 20 and the sample 15 is always kept constant because the micro cantilever 21 is not vibrated. Therefore, SNOM information can be detected at a constant distance on the sample, and stable optical information based on scattered light can be detected.

Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a schematic configuration of the second embodiment, and this embodiment shows an example of a compound microscope having a function of simultaneous STM / AFM measurement using a conductive micro cantilever. It is a thing.

In this embodiment, contact mode AFM feedback is performed to detect the amount of flexure of the microcantilever 21, and this is used as the surface shape (AFM information). Further, the STM information detection is performed by using bias feedback, which is different from the STM feedback that is normally performed. Normal STM
Feedback is a control method of expanding and contracting the piezoelectric body 26 so as to make the tunnel current constant during sample scanning, and bias feedback keeps the amount of deflection of the micro cantilever 21 constant during sample scanning (AFM feedback). This is a control method in which the bias voltage is changed so as to keep the tunnel current constant.

In FIG. 3, the sample 15 is placed on a piezoelectric body 26 capable of scanning in the XYZ directions, and is composed of an α site 27 having a small resistance value and a β site 28 having a large resistance value, as will be described later. It is assumed that Micro cantilever 21 having probe 20 provided on this sample 15
Is configured to have conductivity, as in the first embodiment described above. A displacement detection system 23 is provided above the micro cantilever 21.

Next, a control system for performing bias feedback will be described. The micro cantilever 21 is connected to the current / voltage conversion circuit 22. The current-voltage conversion circuit 22 is connected to the differential amplifier 29,
Further, this differential amplifier 29 is provided with the current-voltage conversion circuit 2 in advance.
2 is connected to a current value setting circuit 32 for setting and storing the contact current value to be detected. Further, the differential amplifier 29 is connected to the adding circuit 31 via the feedback circuit 30. The adder circuit 31 is connected to the bias voltage supply circuit 18 and the sample 15, and the bias voltage supply circuit 18 generates a bias voltage to be supplied to the sample 15.

In such a structure, the distance between the sample 15 and the probe 20 (the micro cantilever 21
AFM feedback is performed so as to keep the amount of flexure) constant. Then, the contact current flowing between the sample 15 and the probe 20 is detected. This contact current is applied to the current-voltage conversion circuit 2
The signal is converted in 2 and then input to the differential amplifier 29.
In the differential amplifier 29, the contact current signal detected by the sample 15 and the contact current signal set in the current value setting circuit 32 are compared, and the difference signal is input to the feedback circuit 30. In the feedback circuit 30, the bias voltage to be supplied to the sample 15, that is, the voltage to be supplied to the sample 15 for keeping the contact current constant is calculated based on the difference signal, and the calculation result is supplied to the adding circuit 31. To be done. In the adding circuit 31, the voltage supplied from the bias voltage supply circuit 18 is adjusted based on the calculation result of the feedback circuit 30, and the voltage is applied to the sample 15. This makes it possible to feed back the bias voltage so that the detected current of the micro cantilever 21 becomes the set value current.

Here, consider a case where AFM feedback in the contact mode is performed, and further STM feedback is performed as in the conventional case. When measuring a sample 15 composed of an α site 27 having a small resistance value and a β site 28 having a large resistance value as shown in FIG. 4A, when the contact current exceeds the set value, the piezoelectric body 26 is The image is displaced so as to keep the current value constant, and an image as shown in FIG. 4B is obtained. At this time, the piezoelectric body 26 displaces the sample 15 in the direction of separating from the micro cantilever 21. here,
It is known that in the measurement environment in air, the surface of the sample 15 has an extremely thin film of water and a viscosity peculiar to the sample. The cantilever 21 is retracted downward or is excessively retracted and jumps upward. Here, the displacement of the micro cantilever 21 does not reflect the actual surface shape of the sample 15.

On the other hand, in the case of the second embodiment, the displacement of the micro cantilever 21 is detected by the deflection amount of the micro cantilever 21 based on the AFM feedback, and the sample as shown in FIG. There are 15 surface shapes. On the other hand, the output of the bias voltage applied to the sample 15 to which the bias feedback is applied is shown in FIG.
As shown in (c), the information reflects the amount of constant current value, that is, the resistance value of the surface of the sample 15.

As described above, according to the second embodiment,
The surface shape can be obtained by keeping the amount of bending of the micro cantilever 21 constant, and at the same time, electrical information can be obtained by keeping the contact current at that time constant.
Therefore, it is possible to identify the images having the same shape from the images obtained at the same time. That is, it is possible to perform various evaluations on the surface by folding in known information and inferring from a plurality of information. In this sense,
The in-plane resolution can be improved over the single-function SPM.

Since a plurality of pieces of information can be detected by scanning once, the reproducibility of the measurement result at the same location on the same sample can be improved. Further, in the present embodiment, the contact current is detected by using the contact mode AFM, and the bias feedback is performed. However, the tunnel current is detected by using the non-contact mode AFM and the bias feedback is performed. Needless to say, the same effect can be obtained.

Next explained is the third embodiment of the invention. In the third embodiment, the AFM in AC mode is used.
As an example of a device for performing simultaneous / SNOM measurement with high accuracy, a compound microscope having a configuration in which laser emission is synchronized so that an evanescent field is formed on the sample surface only when the probe comes closest to the sample Show.

FIG. 5 is a block diagram showing a schematic structure of a compound microscope according to the third embodiment. In FIG. 5, a critical angle prism 16 and a laser light source 17 are arranged below the sample 15. On the sample 15, the probe 2
The microcantilever 21 having 0 is the piezoelectric body 3 for vibration.
4 is fixed. The vibration of the vibrating piezoelectric body 34 is
This is performed based on the output signal from the connected oscillator 35. Above the micro cantilever 21, the amplitude of the vibrating micro cantilever 21 is detected, and
A displacement detection system 23 for detecting the surface shape of the sample 15 based on the change in the amplitude is provided. In addition, in the vicinity of the micro cantilever 21, an evanescent field 25
A photo lens 24 for detecting scattered light generated when the probe 20 comes into contact with is provided.

Further, there is provided a laser output adjusting mechanism circuit 36 for adjusting the timing at which the laser light source 17 makes the laser enter the critical angle prism 16. The input to the laser output adjusting mechanism circuit 36 is a signal synchronized with the output of the oscillator 25 or the displacement detection system 23, and the probe 2
Considering that the displacement of 0 is reflected, it is preferable to use the output of the displacement detection system 23.

The surface information detected in this embodiment is the same as that in the conventional AC mode detection method. In such a configuration, the vibrating piezoelectric body 34 is driven according to the output signal from the oscillator 35, and the microcantilever 21 starts vibrating. And the probe 2
In the state where 0 is close to the sample 15 to the extent that an atomic force is generated, laser light is incident on the critical angle prism 16 from the laser light source 17, and scattered light based on the evanescent field 25 is detected by the photomal 24. To verify that.

Next, in synchronization with the output signal of the displacement detection system 23, the laser output adjusting mechanism circuit 36 calculates the emission timing of the laser light emitted from the laser light source 17. Then, the laser light source 17 is made to blink at the timing. The emission timing of this laser light can be arbitrarily set by the observer, but when the scattered light becomes the maximum, that is,
The moment when the probe 20 comes closest to the sample 15 is preferable. This is because this moment does not detect the most external noise.

By the above operation, the scattered light generated by the contact between the probe 20 and the evanescent field 25 on the surface of the sample 15 is input to the photomultiplier 24. The optical information of the sample 15 can be obtained from the output of the photomultiplier 24.

Here, referring to FIG. 6, a case where the surface shape and the optical information are simultaneously obtained in the AC mode will be described. The output obtained by converting the evanescent field 25 localized on the surface of the sample 15 into the propagating light (scattered light) by the probe 20 is the vibration as shown in FIG. 6A when the vibration is sufficiently repeated on each pixel. At some time, it is detected by the photomultiplier 24 as an output signal as shown in FIG. This output signal shows the distribution of the output signal of the scattered light that is actually obtained. Figure 6
When (a) and FIG. 6 (b) are compared, the probe 20 shows the sample 1
It can be seen that the scattered light is the strongest at the moment when it comes closest to 5. In the present embodiment, as a result of the above-mentioned operation, FIG.
As shown in (c), the micro cantilever 21
Laser light is output in synchronization only at the lowest point of the (probe 20) when it vibrates.

By irradiating the sample 15 with the laser light in this way, the optical information is detected only at the moment when the intensity of the scattered light is strongest in the photomultiplier 24, and the influence of external noise can be reduced. Then, by scanning the sample 15 with the probe 20, it becomes possible to detect surface information and at the same time detect optical information.

Therefore, since a plurality of pieces of information can be detected by one scanning, it is possible to improve the reproducibility of the measurement result at the same location on the same sample. Moreover, the positional relationship between the probe 20 and the sample 15 is clear, and the optical information in the positional relationship can be detected. Further, it is possible to reduce the influence of external noise and detect optical information in a good S / N state.

In the above description, the laser light source 17 is driven in synchronization with the output of the displacement detection system 23, but the laser light source is driven in synchronization with the output signal of the oscillator 35. Is also good.

Further, in the third embodiment, when the current signal is detected, the bias voltage is set to be the same as that of the laser light incident on the laser light source 17 by using the conductive micro cantilever 21 and the probe 20. Sample 15 at the timing of
The same effect can be obtained by applying the voltage.

In the AC mode AFM, the microcantilever 21 normally vibrates in a frequency range of about 50 to 200 KHz in accordance with its own resonance frequency. Therefore, it is physically difficult to emit a laser beam at each moment when the probe 21 comes closest to the sample 15, and in actual measurement, the probe 21 comes close to the sample 15 at any measurement point. It suffices to emit laser light only at the moment.

Next explained is the fourth embodiment of the invention. The fourth embodiment is a modification of the above-described third embodiment, and is a simultaneous AFM / SNOM measurement.
In this example, the light receiving surface of the photomultiplier is turned on when the probe comes closest to the sample.

In FIG. 7, a critical angle prism 16 and a laser light source 17 are provided below the sample 15. A bias voltage supply circuit 18 is connected to the sample 15 so that a predetermined voltage is applied.

On the sample 15, a micro cantilever 21 having a probe 20 is fixed to a vibrating piezoelectric body 34. The vibration of the vibrating piezoelectric body 34 is performed based on the output signal from the connected oscillator 35. Above the micro cantilever 21, a displacement detection system 23 is provided for detecting the amplitude of the vibrating micro cantilever 21 and detecting the surface shape of the sample 15 based on the change in the amplitude. In the vicinity of the micro cantilever 21, a photomultiplier 2 for detecting scattered light generated when the probe 20 contacts the evanescent field 25.
4 are provided. A shutter 37 is provided on the light receiving surface of the photomultiplier 24, and is opened / closed by a drive circuit 38 connected to the displacement detection system 23.

The surface information detected in this embodiment is the same as that in the conventional detection method in the AC mode. In such a configuration, the vibrating piezoelectric body 34 is driven according to the output signal from the oscillator 35, and the microcantilever 21 starts vibrating. And the probe 20
However, the laser light is incident on the critical angle prism 16 from the laser light source 17 in a state of being close to the sample 15 to the extent that an atomic force is generated, and the scattered light based on the evanescent field 25 is detected by the photomal 24. Make sure that.

Next, in synchronization with the output signal of the displacement detection system 23, the drive circuit 38 calculates the emission timing of the laser light emitted from the laser light source 17. Then, the shutter 37 is opened and closed according to the timing. An observer can arbitrarily set the opening / closing timing of the shutter 37,
The time when the scattered light becomes maximum, that is, the moment when the probe 20 comes closest to the sample 15 is preferable. This is because this moment does not detect the most external noise.

By the above operation, the scattered light generated by the contact between the probe 20 and the evanescent field 25 on the surface of the sample 15 is input to the photo-mulch 24. The optical information of the sample 15 can be obtained from the output of the photomultiplier 24.

As a result, the evanescent field 25 on the surface of the sample 15 is converted into the probe 20 of the micro cantilever 21.
The output converted into propagating light by the micro cantilever 2
Photomar 24 only when 1 comes closest to the surface of sample 15.
It becomes possible to receive light. The fourth embodiment has the same effects as the above-described third embodiment.

Further, in the AC mode AFM, the microcantilever 21 normally vibrates in a frequency range of about 50 to 200 KHz in accordance with its own resonance frequency. Therefore, it is physically difficult to open and close the shutter 37 at each moment when the probe 21 comes closest to the sample 15, and in actual measurement, the probe 21 comes close to the sample 15 at any point for each measurement point. The shutter 37 may be opened and closed only at the moment.

Next explained is the fifth embodiment of the invention. The fifth embodiment is an example of detection of a current signal for simultaneous STM / AFM measurement (lock-in method).

In FIG. 8, the sample 15 to which the adding circuit 32 is connected is placed on the piezoelectric body 26. And
A micro cantilever 21 having a probe 20 is provided on the sample 15 so as to be fixed to a vibrating piezoelectric body 34. The output of the built-in oscillator of the lock-in amplifier 40 is supplied to the vibrating piezoelectric body 34 via the amplifier 39. The output of the current-voltage conversion circuit 22 connected to the micro cantilever 21 is input to the lock-in amplifier 40. Further, the output of the displacement detection system 23 provided above the micro cantilever 21 is also supplied to the lock-in amplifier 40.

The surface information detected in this embodiment is the same as that in the conventional AC mode detection method. In such a configuration, the vibrating piezoelectric body 34 is driven according to the output signal from the amplifier 39, and the micro cantilever 21 starts vibrating. At the same time, a bias voltage is applied from the bias voltage supply circuit 18 to the sample 15.

Further, the probe 20 and the sample 15 are kept close to each other to the extent that an atomic force is generated between the sample 15 and the sample 15.
It is confirmed by the current-voltage conversion circuit 22 that the tunnel current is flowing between 0 and 0.

Next, the lock-in amplifier 40 detects the output signal of the displacement detection system 23. Then, the tunnel current in the current-voltage conversion circuit 22 is detected at the detection timing of the lock-in amplifier 40. The timing of detecting the tunnel current can be arbitrarily set by the observer, but it is preferable that the tunnel current becomes maximum, that is, the moment when the probe 20 comes closest to the sample 15. This is because the most sensitive detection is possible at this moment.

By such an operation, the probe 20 and the sample 1 are
The current-voltage conversion circuit 22 detects the tunnel current flowing between the surface and the surface. The electrical information of the sample 15 can be obtained from the output of the current-voltage conversion circuit 22. The tunnel current detected in this way is extracted in the same manner as in FIG. 6C from only the most sensitive portion of the tunnel current having the same distribution as the evanescent field described in FIG. 6B. ing.

Further, specifically, when the resonance frequency of the microcantilever 21 is fo, the self-constant (τ) of the lock-in amplifier 40 uptake is set to about 10 / fo. At the same time, the scanning frequency is set to fo / (10 × 2 × 512) by capturing 512 points on one line, so that a current signal in response to the resonance frequency of the microcantilever 21 can be obtained.

As described above, according to the fifth embodiment,
In the simultaneous STM / AFM measurement, a plurality of pieces of information can be detected by one scan, so that the reproducibility of the measurement result at the same location of the same sample can be improved. In addition, it is possible to detect a tunnel current signal having a good S / N in response to the resonance frequency of the microcantilever 21, rather than simply detecting the average tunnel current output.

According to the above embodiment of the present invention, the following constitution can be obtained. (1) A micro cantilever that is arranged so as to be able to scan facing a sample to be measured, has a probe at its tip and is held at its free end, and the displacement signal of this micro cantilever is detected to detect the surface of the sample. A first detecting means for obtaining a shape; and a second detecting means for detecting information other than the surface shape of the sample simultaneously with the detection by the first detecting means. 2. A scanning probe microscope, wherein the surface information of the sample is obtained based on the detection result of the second detection means.

(2) The second detecting means detects the input timing of external information to the sample in order to obtain information other than the surface shape of the sample. Scanning probe microscope.

(3) In the above-mentioned (1), the second detecting means constitutes a feedback circuit to the bias voltage at the time of measuring the current in order to obtain information other than the surface shape of the sample. Scanning probe microscope.

(4) A micro cantilever, which is arranged so as to face a sample to be measured so as to be scannable, has a probe at its tip and is held at its free end, and a displacement signal of this micro cantilever is detected to detect the above. First to obtain the surface shape of the sample
And the second detection means for detecting electrical information of the sample at the same time as the detection of the first detection means, and the optical information of the sample by the first and second detection means. A scanning probe microscope, comprising: a third detection means for detecting at the same time as the detection, wherein the surface information of the sample is obtained based on the surface shape, electrical information and optical information of the sample.

(5) A micro cantilever which is arranged so as to be able to scan facing a sample to be measured, has a probe at its tip and is held at its free end, and a displacement signal of this micro cantilever is detected to detect the above. First to obtain the surface shape of the sample
Detecting means and second detecting means for detecting electrical information of the sample simultaneously with the detection of the first detecting means. Based on the surface shape of the sample and the electrical information of the sample, A scanning probe microscope characterized by obtaining surface information.

(6) The scanning probe microscope according to the above (5), wherein the second detecting means constitutes a feedback circuit to the bias voltage at the time of measuring the current. (7) The surface of the sample, which is arranged so as to be able to scan facing the sample to be measured, has a probe at the tip and is held at the free end, and the displacement signal of this microcantilever is detected. A first detecting means for obtaining a shape and a second detecting means for detecting the optical information of the sample at the same time as the detection by the first detecting means are provided. A scanning probe microscope, wherein the surface information of the sample is obtained based on the scanning probe microscope.

(8) The second detecting means detects the input timing of external information to the sample in order to obtain information other than the surface shape of the sample. Scanning probe microscope.

(9) The scanning probe microscope according to the above (8), wherein the second detecting means has a transmitting means for determining the input timing of the optical information of the sample.

(10) The second detecting means has an input permitting means for permitting the input of the optical information in synchronization with the input timing of the optical information of the sample. The scanning probe microscope according to 1.

(11) A microcantilever which is arranged so as to be able to scan facing a sample to be measured, has a probe at its tip and is held at its free end, and the displacement signal of this microcantilever is detected to detect the above. First detection means for obtaining the surface shape of the sample and electrical information of the sample are detected at the same time as the detection by the first detection means, and the electrical information of the sample at the time of current measurement according to the scanning frequency of the micro cantilever is detected. Second with feedback circuit to micro cantilever
And a detecting means for obtaining the surface information of the sample based on the surface shape and electrical information of the sample.

[0091]

As described above, according to the present invention, when the different signals (information) are obtained from the same pixel, a micro cantilever capable of detecting a plurality of signals is used, and a feedback system in which the detection sensitivity is improved. -By adopting the signal detection method, it becomes possible to improve the spatial resolution through an analytical method and provide a scanning probe microscope with high reproducibility.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention, in which S
It is the figure which showed the schematic structure of the compound microscope which has the function of TM / AFM / SNOM (conductivity and the probe of a high refractive index).

FIG. 2 is a diagram showing an example of image interpretation of a result of detecting a plurality of signals.

FIG. 3 is a block diagram of a compound microscope having a function of simultaneous contact mode STM / AFM (bias feedback method) measurement using a conductive micro-cantilever, showing a schematic configuration of a second embodiment. Is.

FIG. 4 is a diagram showing an example of an image by a bias feedback method in contact mode STM / AFM simultaneous measurement.

FIG. 5 is a block diagram showing a schematic configuration of a compound microscope according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an example of the timing of laser incidence for simultaneous AFM / SNOM measurement.

FIG. 7 shows a fourth embodiment of the present invention, in which A
It is a block diagram which shows the schematic structure of the compound microscope which has the function of ON / OFF of the photomultiplier of FM / SNOM simultaneous measurement.

FIG. 8 shows a schematic configuration of a fifth embodiment of the present invention, and is a block diagram of a compound microscope having a function of lock-in detection of a current signal for simultaneous STM / AFM measurement.

FIG. 9 is a configuration diagram of an AC mode device used for conventional SPM measurement.

[Explanation of symbols]

 15 sample, 16 critical angle prism, 17 laser light source, 18 bias voltage supply circuit, 20 probe, 21 micro cantilever, 22 current-voltage conversion circuit, 23 displacement detection system, 24 photomultiplier photoelectric tube (photomul), 25 evanescent field , 26 piezoelectric body, 29 differential amplifier, 30 feedback circuit, 31 addition circuit, 32 current value setting circuit, 34 vibration piezoelectric body, 35 oscillator, 36 laser output adjusting mechanism circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Hori 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (3)

[Claims] 1. A microcantilever, which is arranged so as to be capable of scanning in opposition to a sample to be measured, has a probe at its tip and is held at its free end, and the sample by detecting a displacement signal of the microcantilever. The first detection means for obtaining the surface shape of the sample and the second detection means for detecting information other than the surface shape of the sample simultaneously with the detection of the first detection means. And a scanning probe microscope, wherein surface information of the sample is obtained based on the detection result of the second detection means. 2. The scanning type according to claim 1, wherein the second detecting means detects the input timing of external information to the sample in order to obtain information other than the surface shape of the sample. Probe microscope. 3. The scanning according to claim 1, wherein the second detecting means constitutes a feedback circuit to the bias voltage at the time of measuring the current in order to obtain information other than the surface shape of the sample. Type probe microscope.