JP2001305037A - Scanning probe microscope, light absorbing material detecting method using it, and microspectroscopy method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new device/method for directly detecting a light absorbing material by a nano-scale by means of a scanning tunnel microscope STM probe. SOLUTION: A chopper 6 intermittently radiates a gap beam (a wavelength 788 nm, 12 mW/mm2) at an incident angle 45 deg. onto a p-GaAs 10 surface with a high modulation frequency beyond follow-up by a constant current control of the STM. A lock-in amplifier 3 lock-in detects a modulated tunnel current waveform. It so as to find a tunnel current amplitude ΔI. In a two-dimensional distribution image based on this, a bright contrast part not existing in an ordinary STM topographic image is observed. This is because heat locally generated by non-light emission recombination in an isolated defect beneath the sample 10 surface is dispersed to the circumference and causes a great thermal expansion displacement on the surface around the defect specially. In this way, a defect in the sample 10 can be detected.

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 performing measurement using a phenomenon such as photothermal expansion, a method for detecting a light absorbing substance using the same, and a microspectroscopic method.

[0002]

2. Description of the Related Art An apparatus for observing a sample surface using a tunnel current flowing between a probe and a sample (Scanning T).
unning Microscopy, hereafter "ST
M ”) is known.

[0003] The STM is a device capable of detecting information on the shape and electronic state of a sample surface at an atomic order spatial resolution by utilizing the electron tunneling phenomenon. Application to similar devices such as devices is possible.

[0004] In the STM, a measurement signal is detected by controlling a distance by using a tunnel current generated when the distance between the probe and the sample is several nm or less as a servo signal while scanning the surface of the sample with a pointed probe. are doing.

[0005] A conventional technique of STM will be described. FIG.
0 is an STM disclosed in JP-A-6-137810.
3 is a functional block diagram of FIG.

In FIG. 10, reference numeral 51 denotes a probe having a sharp tip, and 52 denotes a sample arranged opposite to the probe 51. The sample is provided in an XY-axis direction by an XY scanning signal generating circuit and an XY scanning driving mechanism (not shown). Scanned. A probe control actuator 53 moves the probe 51 in the Z-axis direction. 5
Reference numeral 4 denotes a bias circuit that applies a voltage between the probe and the sample. Reference numeral 55 denotes a current-to-voltage converter that detects a tunnel current generated when the probe 51 and the sample 52 approach each other in a bias applied state and converts the tunnel current into a voltage. A circuit 56 is a logarithmic conversion circuit for further logarithmically converting the converted voltage and outputting the same. 57 is a difference circuit for setting a desired tunnel current value as a set value and detecting a difference signal from the input. Remove high frequency components,
A low-pass filter 58 for outputting a topo signal is a probe Z control signal generation circuit, which forms a servo signal from the output of the LPF 59 and outputs it to the probe control actuator 53 to control the distance between the probe samples. Let Reference numeral 61 denotes a topo (Topograph Imag) output from the low-pass filter 59.
e) A signal 62 is a current signal output from the logarithmic conversion circuit 56 and is used as a screen information signal.

When a bias is applied between the probe 51 having a sharp tip and the sample 52 by the bias circuit 54 and the probe 51 is moved close to 1 nm to the sample surface, a tunnel current flows between the probe and the sample. Start flowing. This tunnel current is converted to a voltage by a current-voltage conversion circuit 55, and a difference signal from a desired set tunnel current value is detected by a difference circuit 57 via a logarithmic conversion circuit 56, and a low-pass filter 59, a probe Z control signal generation circuit A servo signal is formed through 58. This servo signal is input to a probe control actuator 53 composed of a piezoelectric element or the like to control the distance, and at the same time, an XY scanning signal is input by an XY scanning signal generation circuit (not shown), and scanning is performed along the in-plane direction of the sample. The topography signal 61 formed via the difference circuit 57 and the low-pass filter 59 or the current signal 62 which is the output signal of the logarithmic conversion circuit 56 is monitored and subjected to image processing to reflect the shape of the sample surface and the electronic state. Observation image can be obtained.

[0008]

Incidentally, it is required that a semiconductor used in a semiconductor device has no defect. Attention has been paid to prevent defects from occurring in the semiconductor manufacturing process, and inspection of semiconductors after manufacturing to find defects has been performed.

Various problems arise when there are crystal defects. For example, Japanese Patent Application Laid-Open No. Hei 10-135567 discloses a "semiconductor laser device" as follows. In a semiconductor laser device, Mg and Z which are conventionally used Group II elements are used.
With a p-type dopant such as n or Be, there is a problem that high-concentration doping cannot be performed due to a large diffusion coefficient.
This is because, when diffusion occurs to the active layer, a non-emission center is formed inside the active layer, thereby lowering the luminous efficiency, adversely affecting reliability, and lowering the carrier concentration due to diffusion from the contact layer. Causes a problem of an increase in operating voltage. Further, carbon having a small diffusion coefficient as a p-type dopant needs to be grown at a low temperature in order to increase the diffusion efficiency. However, in that case, there is a problem that a crystal defect occurs in the semiconductor, so that a non-emission center is formed.

Although such a non-emission center can be detected by the STM when it is on the sample surface, it is difficult to detect when it is inside the sample. Also, it has been difficult to directly detect non-luminescent centers on a nanoscale.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a scanning probe microscope capable of directly detecting a defect in a semiconductor on a nanoscale, and a non-light-emitting center or more generally a light-absorbing material using the same. It is an object of the present invention to provide a method for detecting Another object of the present invention is to provide a novel nano-resolution microspectroscopy method.

[0012]

A scanning probe microscope according to the present invention includes a probe provided near a sample and a tunnel current generated when the probe approaches the surface of the sample. A negative feedback controller that controls a distance between the probe and the sample so as to maintain a constant tunnel current; a light source; a modulator that transmits light emitted from the light source at predetermined time intervals; and A spectroscope for extracting light of a predetermined wavelength from the emitted light, an irradiating unit for irradiating the sample with the emitted light of the spectroscope, and detecting the amplitude of the tunnel current by synchronizing with a modulation signal of the modulator. And an amplifier for outputting the output.

Preferably, the apparatus further comprises a detecting section for detecting a light absorbing substance in the sample based on an output of the amplifier, wherein the detecting section uses a photothermal expansion effect accompanying light absorption in the light absorbing substance in the sample. I do.

Preferably, the detecting section determines that the light-absorbing substance is present when the tunnel current amplitude is larger than a normal tunnel current amplitude.

Preferably, there is provided an image processing unit for generating a two-dimensional distribution image based on the output of the amplifier, and the detection unit determines a high contrast portion in the two-dimensional distribution image as a light absorbing substance.

[0016] Preferably, the detecting section comprises a light-absorbing material when a modulation frequency of the modulator is increased, a tunnel current amplitude is reduced, and a high-contrast portion in the two-dimensional distribution image is reduced. Is determined.

Preferably, a detector is provided for detecting a light-absorbing substance in the sample based on the output of the amplifier, and the detector uses a change in charge of the light-absorbing substance in the sample accompanying light irradiation. Perform detection.

Preferably, the apparatus further comprises a detecting section for detecting a light absorbing substance in the sample based on an output of the amplifier, wherein the detecting section detects the light absorbing substance in the sample by utilizing the contraction of the sample accompanying the irradiation of light. I do.

Preferably, a detector is provided for detecting a light-absorbing substance in the sample based on an output of the amplifier, and the detector detects a bistability defect due to a temperature rise accompanying light irradiation on the light-absorbing substance in the sample. The detection is performed using the displacement caused by increasing the stay time in the metastable structure.

[0020] Preferably, the spectroscope scans a wavelength to be extracted in a predetermined range.

The method for detecting a light absorbing substance according to the present invention comprises:
Irradiating the sample with modulated light of a predetermined wavelength; causing thermal expansion displacement on a surface of the sample near the light absorbing substance; bringing a probe close to the sample; Detecting and outputting the amplitude of the tunnel current by synchronizing the tunnel current generated by the thermal expansion displacement with the modulation signal when approaching the surface of the sample, and light absorption in the sample based on the amplitude of the tunnel current. Detecting a substance.

The method for detecting a light absorbing substance according to the present invention comprises:
Irradiating the sample with modulated light of a predetermined wavelength, causing a change in charge due to irradiation of light on the surface near the light absorbing material of the sample, and bringing a probe close to the sample, Detecting and outputting an amplitude of the tunnel current by synchronizing a tunnel current generated by a change in charge accompanying the light irradiation with a modulation signal when the probe approaches the surface of the sample; and Detecting the light absorbing substance in the sample based on the amplitude of the current.

The method for detecting a light-absorbing substance according to the present invention comprises:
Irradiating the sample with modulated light having a predetermined wavelength, causing the sample to shrink with the irradiation of light on the surface of the sample near the light absorbing material, and bringing a probe close to the sample, Detecting and outputting the amplitude of the tunnel current by synchronizing the tunnel current generated by the sample contraction with the light irradiation with the modulation signal when the needle approaches the surface of the sample, and outputting the tunnel current. Detecting a light-absorbing substance in the sample based on the amplitude.

The method for detecting a light absorbing substance according to the present invention comprises:
Irradiating the sample with a modulated light of a predetermined wavelength, and increasing the temperature due to the irradiation of light on the surface of the sample near the light absorbing substance increases the residence time of the bistable defect in the metastable structure. Causing the probe to approach the sample, and synchronizing a tunnel current caused by the displacement with a modulation signal when the probe approaches the surface of the sample, thereby obtaining an amplitude of the tunnel current. And outputting a light-absorbing substance in the sample based on the amplitude of the tunnel current.

In the microspectroscopy method according to the present invention, a step of irradiating a sample with a modulated light of a predetermined wavelength, a step of directly exciting a light absorbing substance of the sample, a step of bringing a probe close to the sample, A step of detecting and outputting the amplitude of the tunnel current by synchronizing a tunnel current generated when the probe approaches the surface of the sample with a modulation signal, and setting a wavelength of the light in a predetermined range. The method includes a step of repeating the above steps while scanning, and a step of obtaining characteristics of the amplitude and wavelength of the tunnel current.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, a light-absorbing substance is referred to as a "defect" for convenience and used for description. FIG. 1 is a configuration diagram of a nanospectroscopic microscope using a phenomenon such as photothermal expansion according to an embodiment of the present invention.

Reference numeral 1 denotes an ultra-high pressure scanning tunneling microscope (U
HV-STM), 2 is a feedback circuit.
The UHV-STM1 includes the probe 51, the probe control actuator 53, and the bias circuit 54 shown in FIG. Feedback circuit 2
Includes a current-voltage conversion circuit 55, a logarithmic conversion circuit 56, a difference circuit 57, a probe Z control signal generation circuit 58 and an LPF 59 shown in FIG.

When the probe is brought close to the surface of the sample to about 1 nm, a tunnel current starts flowing between the probe and the sample, and this tunnel current is converted into a probe Z by a current-voltage conversion circuit, a logarithmic conversion circuit, a difference circuit, and an LPF. The control signal generation circuit generates a feedback signal to control the position of the probe in the Z direction. An XY scanning signal is input by an XY scanning signal generating circuit (not shown), a top signal which is an output signal of the feedback circuit 2 is monitored while scanning along an in-plane direction of the sample, and a shape of the sample surface is obtained by performing image processing. Observed images reflecting the electronic state can be obtained.

Reference numeral 3 denotes a lock-in amplifier, reference numeral 4 denotes a halogen lamp as a light source, reference numeral 5 denotes a lens, reference numeral 6 denotes a chopper for intermittently intermitting light beams, and reference numeral 7
Is a monochromator for separating light of a specific narrow wavelength band from the light of the halogen lamp 4,
Reference numeral 8 denotes an optical fiber for guiding light from the monochromator 7, and reference numeral 9 denotes a condenser lens for condensing the light emitted from the optical fiber 8 onto the sample 10. The lock-in amplifier 3
An amplifier for performing synchronous detection with an external reference signal,
A signal modulated with a reference frequency can be detected and measured from very high noise levels. The lock-in amplifier 3 captures the tunnel current signal It using the intermittent frequency signal f of the chopper 6 as a reference signal, and outputs an amplitude image (A
mplitude image) signal.

When only a two-dimensional image of current amplitude is obtained by monochromatic light, a monochromatic light source capable of emitting intermittent light of an appropriate wavelength is used instead of the halogen lamp 4, lens 5, chopper 6, and monochromator 7 in the above. For example, laser) may be used.

The optical fiber 8 and the lens 9 in FIG. 1 may be replaced by a suitable optical system for guiding light from a light source to a sample.

The intermittent frequency of the irradiation light is set sufficiently higher than the response frequency of the feedback circuit for keeping the tunnel current constant, so that the modulation signal accompanying the light irradiation appears in the tunnel current.

The intermittent frequency of the irradiation light is set high enough to sufficiently smooth the macroscopic thermal expansion of the probe and the sample irradiated with the light.

The apparatus shown in FIG. 1 is provided with a condensing optical system for condensing light of a specific wavelength on the sample 10 at regular intervals.
Tunneling current signal I using intermittent frequency signal f as a reference signal
It is different from the conventional STM in that it has a lock-in amplifier 3 that takes in t and outputs it as an amplitude image signal. By providing the lock-in amplifier 3 with the condensing optical system including the halogen lamp 4, the lens 5, the chopper 6, the monochromator 7, the optical fiber 8, and the condensing lens 9, the non-emission light in the sample (for example, a semiconductor) is provided. Binding centers can be detected directly at the nanoscale.

Next, the apparatus / method according to the embodiment of the present invention will be described with reference to the flowchart of FIG. 2, the operation principle of FIG. 3, the modulation tunnel current waveform of FIG. 4, and the modulation frequency of FIG. Graph of tunnel current amplitude ΔI and FIG.
Will be described based on a schematic diagram of a two-dimensional distribution image of the current amplitude ΔI.

As shown in FIG. 2, first, the sample is irradiated with intermittent light having a predetermined wavelength (S1). For example, using a semiconductor laser on the (110) surface of the p-GaAs sample 10, a wavelength of 788 is used.
A gap light of 12 mW / mm ² is intermittently irradiated at an incident angle of 45 °. The irradiated light is modulated by the chopper 6 at a modulation frequency that is too high for the constant current control of the STM to follow.

By irradiating the sample with predetermined light, a thermal expansion displacement occurs on the surface of the sample 10 near the defect (S
2). When the light is applied, as shown in FIG.
Non-radiative recombination locally generates heat at an isolated defect below the surface of the substrate, and this heat diffuses to the surroundings, causing a particularly large thermal expansion displacement on the surface near the defect. Since the tunnel current changes due to the thermal expansion displacement, thermal expansion, that is, the presence of a defect can be detected by observing the change.

Observed by STM, the modulated tunnel current waveform (see FIG. 4) is lock-in detected by the lock-in amplifier 3, and the current amplitude ΔI is obtained (S3). FIG. 5 shows a graph of the tunnel current amplitude ΔI when the modulation frequency is changed. D is a graph of the tunnel current amplitude at the defective portion,
P is the tunnel current amplitude in a portion having no defect. When there is no defect, even if the modulation frequency is changed, the tunnel current amplitude remains almost constant at a small value, indicating that there is no thermal expansion. When there is a defect, the tunnel current amplitude is larger than when there is no defect, and when the modulation frequency increases, the tunnel current amplitude decreases. This is because the thermal expansion at the defect site shortens the distance between the surface of the sample and the probe, and as the modulation frequency increases, the thermal expansion is smoothed and the modulation amplitude of the tunnel current decreases. It shows that it becomes smaller.

The period of the current waveform shown in FIG.
0.7 ms. This corresponds to the chopping cycle of the chopper 6. As a characteristic of the thermal expansion response, the curves of the increasing portion and the decreasing portion of the current are symmetric.

A two-dimensional distribution image of the current amplitude ΔI is obtained (S
4). The process of step S3 is repeated while scanning the surface of the sample 10 to obtain a two-dimensional distribution image of the current amplitude ΔI.
FIGS. 6A and 6B are schematic diagrams of a two-dimensional distribution image, and FIGS.
(A) and (b). FIGS. 6A and 7A show the two-dimensional distribution of the tunnel current amplitude ΔI at point A (modulation frequency: about 1.3 kHz) in the graph of FIG.
(B) and FIG. 7 (b) show the tunnel current amplitude ΔI at point B (modulation frequency: about 1.9 kHz) in the graph of FIG.
Shows the two-dimensional distribution of. The areas D in FIGS. 6A and 6B are centered at the same position, but the size of the D area in FIG. 6A is much larger than that in FIG. 6B. This is considered to be because if the chopping cycle is long, the heat generated by the defect diffuses and spreads to the surroundings, and the thermal expansion region modulated by the chopping frequency expands. The area D in the two-dimensional distribution image as shown in FIG. 6 is a top view image (Topo image) of the conventional STM.
graph Image) has a bright contrast that does not exist in the graph image.

For the above reasons, the resolution increases when the chopping cycle is shortened. On the other hand, if the interval is too short, the tunnel current amplitude will be small, making detection difficult.

The presence or absence of an isolated defect and its position are determined based on the above observation results (S5). As described above, (1) the tunnel current amplitude at the defect site is much larger than that at the defect-free site, and (2) the tunnel current amplitude at the defect site decreases as the modulation frequency increases, but there is no defect. (3) the presence of a bright contrast portion in the two-dimensional distribution image, (4) the contrast portion becomes smaller as the modulation frequency is increased. Indicates presence. These phenomena can be explained well because heat generated locally by non-radiative recombination at an isolated defect below the surface diffuses to the surroundings, causing a particularly large thermal expansion displacement on the surface near the defect. Therefore, the observation result is evaluated using the combination of the above (1) to (4) as a criterion, and the presence or absence and the position of the isolated defect can be determined.

As described above, according to the apparatus / method of the first embodiment of the present invention, the non-radiative recombination center in a semiconductor is directly formed on a nanoscale by using an STM probe based on the same principle as that of photoacoustic spectroscopy. Can be detected. In the conventional apparatus / method, the resolution is only about several tens of μm. However, according to the first embodiment of the present invention, detection can be performed with a much higher resolution of 10 nm or less.

In the above description, the apparatus / method according to the first embodiment of the present invention has been described as capturing only the phenomenon caused by the thermal expansion effect. It is not limited to the thermal expansion effect (for example, a phenomenon caused by light-induced deformation of a defect itself may be captured).

Specifically, the following phenomenon may occur. (1) Change in charge due to light irradiation Carriers are generated when the sample is irradiated with light. This is trapped by a defect in the band gap, and the state of charge changes each time. This can be detected by STM. This phenomenon effectively induces a change in the bias voltage, which can be detected since the current changes. (2) Sample shrinkage due to light irradiation (surface is depressed) When the sample is irradiated with light, the charged state of the defective portion changes. This is considered to be due to the fact that the defect structure becomes unstable and causes atomic displacement. (3) Displacement due to increase in staying time of a bistable defect in a metastable structure due to temperature rise due to light irradiation Bistability (a phenomenon in which two states of different structures can be taken as a (quasi) stable configuration) When the energy difference between the stable structure and the metastable structure of the defect is relatively small, the staying time in the metastable state increases as the temperature rises (the charge moves from one state to the other state). Thereby, the atomic displacement between the stable configuration and the metastable configuration causes a surface displacement, which is observed.

Embodiment 2 of the Invention Next, the apparatus / method according to the second embodiment of the present invention will be described based on the flowchart of FIG. 8 and the graph of the tunnel current amplitude ΔI when the wavelength is changed in FIG.

The sample is irradiated with intermittent light having a predetermined wavelength (S
10). Light is irradiated using the apparatus of FIG. 1 in the same manner as in the first embodiment of the invention.

The non-emission center is directly excited (S1
1). When irradiated with light of a predetermined wavelength, the GaAs sample 10
In addition to the band-to-band absorption, the non-emission center is directly excited, and exhibits a unique tunnel current amplitude characteristic.

The amplitude of the tunnel current is determined (S12). The tunnel current amplitude is obtained by using the apparatus shown in FIG. 1 in the same manner as in the first embodiment of the invention.

The wavelength of the irradiation light is scanned (S13).
A predetermined range, for example, λ = 800 nm to 1300
Steps S10 to S12 are repeated while gradually changing the wavelength of the light output from the monochromator 7 in the range of nm. In the second embodiment of the present invention, a scanning device for changing the wavelength stepwise is provided in the device of FIG. 1 (not shown).

A tunnel current amplitude-wavelength characteristic is obtained from steps S10 to S13 (S14). For example, a graph as shown in FIG. 9 is obtained. Wavelength λ from 800 nm to 1300
When scanning is performed in the range of nm, a peak of the tunnel current amplitude is observed around 1120 nm.

The peak wavelength is obtained from the tunnel current amplitude-wavelength characteristic in step S14 and analyzed (S15). This technique makes it possible to analyze the light energy absorption of various substances, and provides an unprecedented nano-resolution microspectroscopy.

According to the apparatus / method of the second embodiment of the present invention, based on the excitation wavelength dependence of the tunnel current amplitude which is considered to be derived from direct excitation of the non-emission center in addition to the interband absorption of GaAs (sample 10). Spectroscopic analysis can be performed on the nanoscale simultaneously with the acquisition of the STM image. This method has not existed before.

In the above description, the case of detecting a defect has been described as an example. However, in the first and second embodiments of the present invention, the object is not limited to the defect, and the heat is generally absorbed by a light absorbing substance. And / or any other material that causes light-induced deformation of defects and a change in charge. For example, biomolecules, chemical molecules,
It is possible to identify impurity atoms and the like by the light absorption wavelength. In addition, the bonding state and electronic state of atomic molecules can be measured on an atomic scale from the fine structure of the absorption spectrum. These features make the ST with extremely high spatial resolution
M is given an elemental analysis function that did not exist before.

The present invention can be applied to all apparatuses / methods for performing nano-scale analysis using the phenomenon of light-thermal vibration expansion.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say, this is done.

In this specification, means does not necessarily mean physical means, but also includes the case where the function of each means is realized by software.
Further, the function of one unit may be realized by two or more physical units, or the function of two or more units may be realized by one physical unit.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a nanospectroscopy microscope according to Embodiment 1 of the present invention.

FIG. 2 is a flowchart of a method for observing a light-absorbing substance, taking a non-radiative recombination center as an example according to Embodiment 1 of the present invention;

FIG. 3 is an explanatory diagram of an operation principle of the device / method according to the first embodiment of the present invention.

FIG. 4 is a modulated tunnel current waveform obtained by the device / method according to the first embodiment of the present invention.

FIG. 5 shows the tunnel current amplitude ΔI when the modulation frequency is changed, according to the device / method according to the first embodiment of the present invention.
It is a graph of.

FIG. 6 is a schematic diagram of a two-dimensional distribution image of current amplitude ΔI by the device / method according to the first embodiment of the present invention.

FIG. 7 is an example of a two-dimensional distribution image of a current amplitude ΔI by the device / method according to the first embodiment of the present invention.

FIG. 8 is a flowchart of a method of observing a light-absorbing substance using a non-radiative recombination center as an example according to Embodiment 2 of the present invention;

FIG. 9 is a graph of the tunnel current amplitude ΔI when the wavelength is changed by the device / method according to the first embodiment of the present invention.

FIG. 10 is a functional block diagram of a conventional scanning probe microscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanning probe microscope 2 Feedback circuit 3 Lock-in amplifier 4 Halogen lamp 5 Lens 6 Chopper 7 Monochromator 8 Optical fiber 9 Condensing lens 10 Sample

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Claims (14)

[Claims] 1. A probe provided close to a sample, and said probe and said probe receiving a tunnel current generated when said probe approaches a surface of said sample so as to keep said tunnel current constant. A negative feedback controller that controls the distance between samples, a light source, a modulator that transmits light emitted from the light source at predetermined time intervals, and a spectroscope that extracts light of a predetermined wavelength from the light emitted from the light source, A scanning probe microscope comprising: irradiating means for irradiating the sample with light emitted from the spectroscope; and an amplifier for detecting and outputting the amplitude of the tunnel current by synchronizing with a modulation signal of the modulator. 2. A detection unit for detecting a light-absorbing substance in the sample based on an output of the amplifier, wherein the detection unit performs detection using a photothermal expansion effect accompanying light absorption in the light-absorbing substance in the sample. The scanning probe microscope according to claim 1, wherein the scanning is performed. 3. The scanning probe microscope according to claim 2, wherein the detection unit determines that the tunneling current amplitude is a light absorbing substance when the tunneling current amplitude is larger than a normal tunneling current amplitude. 4. An image processing unit for generating a two-dimensional distribution image based on an output of the amplifier, wherein the detection unit determines a high contrast part in the two-dimensional distribution image as a light absorbing substance. The scanning probe microscope according to claim 2, wherein 5. The detecting section, when increasing a modulation frequency of the modulator, reduces a tunnel current amplitude,
3. The scanning probe microscope according to claim 2, wherein a portion having a high contrast in the two-dimensional distribution image is determined to be a light absorbing substance when reduced. 6. A detection unit for detecting a light-absorbing substance in the sample based on an output of the amplifier, wherein the detection unit uses a change in charge of the light-absorbing substance in the sample due to light irradiation. The scanning probe microscope according to claim 1, wherein 7. A detection unit for detecting a light-absorbing substance in the sample based on an output of the amplifier, wherein the detection unit detects the light-absorbing substance using the sample shrinkage accompanying the irradiation of the light-absorbing substance in the sample. The scanning probe microscope according to claim 1, wherein the scanning is performed. 8. A detection unit for detecting a light-absorbing substance in the sample based on an output of the amplifier, wherein the detecting unit detects that a temperature rise due to irradiation of light on the light-absorbing substance in the sample has a bistability defect. The scanning probe microscope according to claim 1, wherein the detection is performed using a displacement caused by increasing a stay time in the metastable structure. 9. The apparatus according to claim 1, wherein the spectroscope scans a wavelength to be taken out in a predetermined range.
A scanning probe microscope as described. 10. A step of irradiating a sample with modulated light of a predetermined wavelength; a step of causing a thermal expansion displacement on a surface of the sample near a light absorbing substance; Detecting and outputting the amplitude of the tunnel current by synchronizing a tunnel current generated by the thermal expansion displacement with a modulation signal when the probe approaches the surface of the sample, based on the amplitude of the tunnel current. Detecting the light absorbing substance in the sample. 11. A step of irradiating a sample with modulated light having a predetermined wavelength; a step of causing a change in charge associated with light irradiation on a surface of the sample near a light absorbing substance; And, when the probe approaches the surface of the sample, detect and output the amplitude of the tunnel current by synchronizing a tunnel current generated by a change in charge accompanying the light irradiation with a modulation signal. And a step of detecting a light absorbing substance in the sample based on an amplitude of the tunnel current. 12. A step of irradiating a sample with a modulated light having a predetermined wavelength; a step of causing sample shrinkage due to light irradiation on a surface of the sample near a light absorbing substance; Detecting the amplitude of the tunnel current by synchronizing with a modulation signal a tunnel current caused by sample shrinkage due to the light irradiation when the probe approaches the surface of the sample when the probe approaches the surface of the sample; and Detecting a light-absorbing substance in the sample based on an amplitude of the tunnel current. 13. A step of irradiating a sample with modulated light of a predetermined wavelength, wherein a temperature rise accompanying the light irradiation on a surface of the sample near a light absorbing substance causes the bistable defect to stay in a metastable structure. Causing a displacement by increasing the time; and bringing a probe close to the sample, and synchronizing a tunnel current generated by the displacement with the modulation signal when the probe approaches the surface of the sample. A method for detecting a light absorbing substance, comprising: detecting and outputting the amplitude of the tunnel current; and detecting a light absorbing substance in the sample based on the amplitude of the tunnel current. 14. irradiating a sample with modulated light having a predetermined wavelength; directly exciting a light absorbing substance of the sample; bringing a probe close to the sample; A step of detecting and outputting the amplitude of the tunnel current by synchronizing a tunnel current generated when approaching the surface with a modulation signal; and repeating the above steps while scanning the wavelength of the light within a predetermined range. A microspectroscopy method, comprising: determining amplitude and wavelength characteristics of the tunnel current.