WO2015178201A1

WO2015178201A1 - Scanning probe microscope and sample observation method using same

Info

Publication number: WO2015178201A1
Application number: PCT/JP2015/063159
Authority: WO
Inventors: 中田　俊彦; 馬塲　修一
Original assignee: 株式会社日立製作所
Priority date: 2014-05-22
Filing date: 2015-05-07
Publication date: 2015-11-26
Also published as: JP2017150814A

Abstract

The purpose of the present invention is to provide a method and device for obtaining a nanometer-order-resolution near-field light image having an enhanced signal-to-noise ratio, contrast, and measurement reproducibility by significantly reducing background noise in a near-field optical scanning microscope. The present invention provides a scanning probe microscope provided with a drive unit for scanning a measurement probe in relation to a sample and a scattered light detection system for selecting and detecting inelastically scattered light from among scattered light generated between the measurement probe and the sample through the irradiation of excitation light.

Description

Scanning probe microscope and sample observation method using the same

The present invention relates to a scanning probe microscope and a sample observation method using the same.

A near-field optical scanning microscope (SNOM), which is a type of scanning probe microscope, is known as a means for measuring optical properties and physical property information of a sample surface with high resolution.

And as a background art of this technical field, there is JP 2009-236895 A (Patent Document 1). This publication states that “a plasmon-enhanced near-field probe having a nanometer-order optical component function is constructed by combining a nanometer-order cylindrical structure and a nanometer-order microstructure, and is low at each measurement point on the sample. By repeatedly approaching and retracting with contact force, the optical information and unevenness information on the sample surface is measured with nanometer resolution and high reproducibility without damaging both the probe and the sample. " (See summary).

JP 2009-236895 A

Conventionally, in the near-field light scanning microscope, when the excitation light is focused on the cantilever and irradiated, not only the scattered light generated by the interaction between the near-field light excited by the excitation light and the sample but also the excitation light There are scattered light that is partly leaked from the material constituting the probe, and scattered light of excitation light scattered from the back surface of the cantilever or the sample surface. As a result, these scattered light components are superimposed on the near-field light image as background noise, which is a factor that degrades the SN ratio, contrast, and measurement reproducibility of the near-field light image.

Therefore, in Patent Document 1, CNT is used for the probe, and a metal carbide such as V, Y, Ta, and Sb that expresses photoluminescence and electroluminescence at its upper end, ZnS phosphor, and CaS phosphor. Incorporating fluorescent particles such as CdSe (core) / ZnS (outer shell) or wavelength conversion elements such as nonlinear optical crystals to form a light guide unit, the incident laser light is wavelength-converted, and after wavelength conversion A method for generating near-field light at the tip of a CNT probe is disclosed.

However, in Patent Document 1, the method of wavelength conversion by mounting fluorescent particles or a nonlinear optical crystal on the upper end of the CNT has low conversion efficiency, so that a near-field with a sufficient amount of light at the tip of the CNT probe in the nanometer order. It is difficult to obtain light, and there is an essential problem that background noise cannot be sufficiently reduced. Furthermore, there is a problem that it is difficult to stably form fluorescent particles and nonlinear optical crystals on the upper end of fine CNTs.

Therefore, an object of the present invention is to provide an apparatus and method that can solve the above-described problems and can significantly reduce background noise.

In order to achieve the above object, the present invention includes a driving unit that scans a measurement probe relative to a sample, and scattered light generated between the measurement probe and the sample by irradiation of excitation light. There is provided a scanning probe microscope comprising a scattered light detection system that selects and detects inelastic scattered light.

In another aspect of the present invention, the measurement probe is scanned relative to the sample, and the measurement probe is irradiated with excitation light, and the measurement probe and the sample are irradiated with the excitation light. Provided is a sample observation method for selecting and detecting inelastic scattered light among scattered light generated in between.

According to the present invention, the background noise can be greatly reduced, and a near-field light image having a resolution of nanometer order with improved SN ratio, contrast, and measurement reproducibility can be obtained.

FIG. 3 is a perspective view of a Si ₃ N ₄ cantilever-mounted gold-coated Si ₃ N ₄ chip and a probe fixed to the tip of each of Examples 1 to 3. FIG. 3 is a front view showing the structure of a CNT probe filled with gold nanoparticles in Examples 1 to 3. FIG. 3 is a front view showing the structure of a CNT probe with gold nanoparticles filled in the tip in Examples 1 to 3. FIG. 6 is a front view showing the structure of a CNT probe without a filler in Examples 1 to 3 and having a tip closed with carbon. FIG. 3 is a front view showing the structure of a Si probe with a sharpened tip in Examples 1 to 3. FIG. 4 is a side view showing a gold-coated Si ₃ N ₄ tip and a probe fixed to the tip end in Examples 1 to 3. FIG. 4 is a graph showing an example of a Raman spectrum of CNT in Examples 1 to 3. 1 is a block diagram illustrating a schematic configuration of a scanning probe microscope according to Embodiment 1. FIG. FIG. 6 is a graph showing the spectral transmittance of notch filters in Examples 1 to 3. It is a graph which shows the spectral transmission factor of the band pass filter in Example 1 and 2. FIG. It is a graph which shows the spectral transmission factor of the long wavelength transmission filter in Example 1 and 2. FIG. FIG. 6 is a side view showing a modified example of the gold-coated Si ₃ N ₄ tip and the probe fixed to the tip end in Examples 1 to 3. 6 is a block diagram illustrating a schematic configuration of a scanning probe microscope in Embodiment 2. FIG. 6 is a block diagram illustrating a schematic configuration of a scanning probe microscope in Embodiment 3. FIG.

Hereinafter, examples will be described with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view of a Si ₃ N ₄ cantilever-mounted gold-coated Si ₃ N ₄ chip and a measurement probe fixed to the tip of the first embodiment. The tip of the Si ₃ N ₄ cantilever 4 is formed with a triangular pyramid-shaped Si ₃ N ₄ tip 2 coated with a gold thin film 3, and a carbon nanotube (CNT: Carbon Nanotube) as a measurement probe is further provided at the tip end. The probe 1 is fixed. Here, the material of the chip 2 and the cantilever 4 is not limited to Si ₃ N ₄ , and may be Si, SiO ₂ or the like as long as it is a material that transmits laser light having a specific wavelength. The gold thin film 3 may be a film made of another material as long as it is a metal material that shields laser light depending on the film thickness, and may be, for example, an aluminum or silver film.

FIG. 2 shows an example of the structure of the CNT probe 1. The CNT probe 1 has a length of 2 to 3 μm, an outer diameter of φ20 nm, an inner diameter of φ4 nm, a multilayer CNT sharpened to a tip of about φ4 nm as a base, and filled with gold nanoparticles 10 of φ4 nm. The filler is not limited to gold nanoparticles. Depending on the wavelength of the laser light used, for example, gold nanoparticles can be used for near infrared light, silver nanoparticles can be used for visible light, and Al nanoparticles can be used for ultraviolet light.

Also, nanorods may be used instead of nanoparticles. Also, as shown in FIG. 3, when there is no problem even if the tip of the CNT is filled or the generation efficiency of near-field light is low, a structure in which the tip is closed with carbon without a filler as shown in FIG. 4 may be used. Further, the probe material is not limited to CNT, and any other material may be used as long as it is a material that induces inelastic scattering typified by Raman scattering as in CNT. For example, as shown in FIG. 5, a Si probe 15 having a sharpened tip can be used.

As shown in FIG. 6, the CNT probe 1 is fused and fixed on the ridge line of the gold-coated Si ₃ N ₄ chip 2 using three gold dots 15 formed by electron beam selective CVD (Chemical Vapor Deposition) as a binder. Is done. The dots 15 are not limited to gold, and may be carbon or tungsten. The CNT probe 1 protrudes from the tip of the gold-coated Si ₃ N ₄ chip 2 by 200 to 300 nm.

As shown in FIG. 1, when excitation laser light 5a having a wavelength of 532 nm, for example, as excitation light is condensed and irradiated on the front edge of the gold-coated Si ₃ N ₄ chip 2 from the back surface of the Si ₃ N ₄ cantilever 4 As shown in FIG. 6, the surface plasmon 8 is excited on the ridgeline of the gold thin film 3. Since the intensity of the surface plasmon 8 depends on the incident angle of the excitation laser beam 5a with respect to the back surface of the Si ₃ N ₄ cantilever 4, the excitation laser beam 5a is at an angle at which the intensity of the surface plasmon 8 is the strongest (plasmon resonance). Should be incident. Note that the angle at which the strength of the surface plasmon 8 is the strongest is the thickness of the metal thin film that coats the material of the cantilever tip (Si ₃ N ₄ in this embodiment) and the measuring probe (in this embodiment, the thickness of the gold thin film). ) Etc. Similarly, it is desirable to set the thickness of the metal thin film to a thickness at which the strength of the surface plasmon 8 is the strongest.

The surface plasmon 8 propagates toward the tip of the gold-coated Si ₃ N ₄ chip 2 and the near-field light 11 localized at the tip of the chip 2 is excited. The tip of the CNT probe 1 is present in the electric field of the near-field light 11, and when the electric field is concentrated on the tip, φ4 nm (spot size), which is the same as the tip diameter, is provided at the tip of the probe. Second near-field light 6 is generated.

In particular, as shown in FIG. 2, when gold nanoparticles 10 are filled inside the CNT, the surface plasmon 8 propagates along the gold nanoparticles 10 and concentrates the electric field on the tip of the CNT probe 1, Along with the electric field concentration of the near-field light 11, a very strong near-field light 6 is excited. As shown in FIGS. 2 to 5, the near-field light 6 interacts with the surface of the sample 20 and the CNT probe 1 itself, and scattered light (propagating light) 7 is generated.

In the scattered light 7, scattered light generated from the surface of the sample 20 by the near-field light 6 and Raman scattered light generated by the interaction between the near-field light and the CNT probe 1 itself are scattered on the surface of the sample 20. This includes scattered light. In this embodiment, scattered light obtained by scattering Raman scattered light generated by the interaction between the near-field light and the CNT probe 1 itself on the surface of the sample 20 is used as the probe light. The intensity of the scattered light changes according to the magnitude relationship between the refractive index n ₀ of the region 21 constituting the sample 20 and the refractive index n ₁ of the region 22, and this is a near field obtained by scanning the CNT probe 1. It becomes the contrast of the optical image.

FIG. 7 shows an example of a Raman spectrum that is inelastically scattered light of CNTs. In FIG. 7, the vertical axis represents the Raman intensity normalized based on the intensity of the excitation light, and the horizontal axis represents the wave number representing the amount of wavelength shift from the wavelength of the excitation light. Here, the wave number representing the wavelength shift amount can be obtained by subtracting the reciprocal of the wavelength after the shift from the reciprocal of the excitation light wavelength. A spectrum called G band appearing in the vicinity of 1590 cm ⁻¹ is a spectrum unique to graphite. In particular, in the case of CNT, the G band is split into two and there are G + and G− spectra, but G + appears to be around 1593 cm ⁻¹ (G +) regardless of the diameter. The spectrum observed in the low frequency region of 100 to 300 cm ⁻¹ (186 cm ^{−1 in} FIG. 7) is a mode in which the diameter of the CNT vibrates, and is a spectrum called a radial breathing mode (RBM). . The spectrum in the vicinity of 1350 cm ⁻¹ is called a D band, and this spectrum becomes strong when the CNT has a defect such as a point defect or a crystal edge, which is a spectrum caused by the defect.

The near-field light 6 excited at the tip of the CNT probe 1 includes the above-described Raman spectrum component (inelastically scattered light) along with the component of the excitation laser beam 5a having the wavelength of 532 nm. In the present invention, among the above-described Raman spectra, the G-band spectrum having a high intensity is separated from the excitation wavelength and used as the probe light.

As shown in FIG. 7, when laser light having a wavelength of 532 nm is used as excitation light, the G band (wave number: 1593 cm ⁻¹ ) is a wavelength component of 581 nm shifted to the longer wavelength side by 49 nm. From the scattered light (propagating light) generated by the interaction between the near-field light 6, the sample 20, and the CNT probe 1 itself, the Raman spectral component of 581 nm is extracted by wavelength separation. As a result, a near-field light image equivalent to imaging the surface of the sample 20 can be obtained with light having a wavelength of 581 nm, not the excitation wavelength of 532 nm, with a resolution of 4 nm or less, which is the same as the diameter of the CNT probe tip.

Advantages obtained by wavelength-separating scattered light having a wavelength of 581 nm of the Raman spectrum component (G band) of the CNT probe 1 instead of the excitation wavelength of 532 nm are as follows. As shown in FIG. 6, when the excitation laser beam 5 a having a wavelength of 532 nm is condensed and irradiated on the front ridge line of the gold-coated Si ₃ N ₄ chip 2, 100% thereof is converted into the surface plasmon 8. Instead, a part of the light leaks from the gold thin film 3 to generate scattered light (propagating light) 12, or a component scattered from the back surface of the Si ₃ N ₄ cantilever 4 or the surface of the sample 20.

There is also scattered light generated by the interaction between the near-field light 11 and the sample. These scattered light components are superimposed on the near-field light image as background noise, and become a factor that degrades the SN ratio, contrast, and measurement reproducibility of the near-field light image. The wavelengths of these scattered light components are all 532 nm, which is equal to the excitation wavelength. On the other hand, the Raman spectral component having a wavelength of 581 nm generated in the CNT probe 1 has very high intensity as near-field light at the CNT probe tip where the electric field is concentrated, and the tip region of the probe on the surface of the sample 20 Only the information is selectively stored. Therefore, by selectively separating the Raman spectrum component having the wavelength of 581 nm from the

scattered light

7 and 12 by separating the wavelength, the background noise can be greatly reduced, and the SN ratio, contrast, and measurement reproducibility are improved. It is possible to obtain a near-field light image having a resolution of nanometer order.

FIG. 8 shows the configuration of a scanning probe microscope based on the above principle. The scanning probe microscope includes a sample holder 25 on which the sample 20 is mounted, an XY piezoelectric element stage 30 on which the sample holder 25 is mounted and which scans the sample 20 in the X and Y directions relative to the measurement probe, and the sample 20 on the tip. A Si ₃ N ₄ cantilever 4 mounted with a gold-coated Si ₃ N ₄ chip 2 to which a CNT probe 1 is fixed, a piezoelectric element actuator 34 for minutely vibrating the Si ₃ N ₄ cantilever 4 in the Z direction, and Si ₃ N ₄ Optical lever detection that detects the contact force between the CNT probe 1 and the sample 20 by detecting the deflection of the Z piezoelectric element stage 33 that scans the cantilever 4 relative to the sample 20 in the Z direction. excitation to be irradiated with the system 100, for example, the excitation laser beam 5a of a solid laser as a light source wavelength 532nm to CNT probe 1 via a _Si 3 _{N 4} cantilevers 4 back Laser light irradiation system 50, scattered light detection system 110 that collects scattered light and photoelectrically converts it, and signal processing that generates and outputs a near-field light image and a surface unevenness image from the obtained scattered light signal and XYZ displacement signal A control system 120 is provided. The drive unit includes an XY piezoelectric element stage 30 and a Z piezoelectric element stage 33 and scans the CNT probe 1 relative to the sample 20.

In the optical lever detection system 100, the back surface of the cantilever 4 is irradiated with the laser light 36 from the semiconductor laser 35, the reflected light is received by the quadrant sensor 37, and the deflection amount of the cantilever 4 is detected from the change in position of the reflected light. Further, the contact force between the CNT probe 1 and the sample 20 is detected from the deflection amount, and the Z piezoelectric element stage 33 is controlled by the control unit 80 of the signal processing / control system 120 so that the contact force always has a preset value. Feedback control. When the Si ₃ N ₄ cantilever 4 is used, it is preferable to increase the reflectance by coating an aluminum film on the laser light 36 irradiation portion on the back surface of the cantilever.

Since the CNT probe 1 is minutely vibrated in the Z direction at the resonance frequency of the cantilever 4 by the piezoelectric element actuator 34 based on the signal from the oscillator 60, the generated near-field light 6, scattered light 7, and scattered light 12 are also generated. Intensity modulated at the same frequency. In the scattered light detection system 110, the two

scattered lights

7 and 12 are converted into parallel light by the condenser lens 41, and, for example, are transmitted through the notch filter 46 and the bandpass filter 47, thereby removing the excitation wavelength component and the Raman spectrum component 43. Is selected. The Raman spectral component 43 is condensed at one point on the light receiving surface 45 of the detector 44 such as a photomultiplier tube or a photodiode by the imaging lens 42 and is photoelectrically converted. In this example, the thickness of the gold thin film 3 was set to 50 nm at which the excitation efficiency of the surface plasmon 8 was maximized.

FIG. 9 shows the spectral transmittance of the notch filter 46. The transmittance is about 0.0008% at the excitation wavelength of 532 nm, the transmittance is about 98% at the wavelength of 581 nm of the Raman spectrum component (G band) of the CNT probe 1 to be detected, and the excitation light wavelength in the scattered light. The component can be greatly attenuated.

FIG. 10 shows the spectral transmittance of the bandpass filter 47. The transmittance of the Raman spectrum component (G band) of the CNT probe 1 is about 91% at a wavelength of 581 nm, and the transmittance is 0.00002% at an excitation wavelength of 532 nm to be removed. In general, the Raman spectral component of the excitation light is a weak scattered light of nearly 6 digits, but by combining the notch filter 46 and the bandpass filter 47, an extinction ratio of nearly 12 digits can be obtained, greatly increasing the background noise. It is possible to stably obtain a near-field light image having a Raman spectrum component reduced to a very low level.

When the wavelength of 581 nm of the Raman spectral component (G band) of the CNT probe 1 fluctuates, it is possible to use a long wavelength transmission filter having the spectral transmittance shown in FIG. It is. In other words, a filter that can extract and extract a wavelength that is desired to be detected may be used as appropriate.

The wavelength-separated and intensity-modulated Raman spectrum signal output from the detector 44 is synchronously detected by the lock-in amplifier 70 of the signal processing / control system 120, and the resonance frequency component of the cantilever 4 is output. Since the Raman scattered light component (propagation light) generated by the excitation laser beam 5 a other than the tip of the CNT probe 1 is a direct current component without reacting to the minute vibration of the cantilever 4, the output of the lock-in amplifier 70. It is not included in the signal. Thereby, it is possible to selectively detect a Raman spectrum component due to near-field light while suppressing background noise.

Also, the signal SN ratio can be further improved by detecting harmonic components such as the second harmonic and the third harmonic of the resonance frequency. The Raman spectrum signal from the lock-in amplifier 70 is sent to the control unit 80 of the signal processing / control system 120 and combined with the XY signal from the XY piezoelectric element stage 30, a near-field light image is generated and output to the display 90. The At the same time, the Z signal from the Z piezoelectric element stage 33 is also combined with the XY signal by the control unit 80 to generate an uneven image on the sample surface and output to the display 90.

In this embodiment, an example in which 532 nm is used as the excitation wavelength and a wavelength component of 581 nm corresponding to the G band is detected among the Raman spectrum components of the CNT probe 1 is shown, but the present invention is not limited to this. However, it is also possible to detect a Raman spectrum component (for example, 584.54 nm or 982.83 nm) corresponding to the G band using another excitation wavelength (for example, 514.5 nm or 850 nm).

In this embodiment, an example in which Raman scattered light (Raman spectral component) is used as inelastic scattered light has been described. However, the present invention is not limited to this. If conditions such as the measurement probe material and the excitation light irradiation method are in place, Brillouin scattering and coherent anti-Stokes Raman scattering (CARS: Coherent Anti-Stokes Raman Scattering) can be used as inelastically scattered light generated from the measurement probe. Applicable.

Also, when the energy of incident light (or scattered light) is equal to the energy of light absorption (or light emission) of CNTs, the Raman intensity becomes about 1000 times stronger. This is called the resonance Raman effect. By using excitation light having a wavelength that produces this resonance Raman effect, the intensity of the Raman spectrum component can be increased, and the background noise can be relatively greatly reduced. As a result, it is possible to obtain a near-field light image with a nanometer-order resolution with further improved SN ratio, contrast, and measurement reproducibility.

In addition, as shown in FIGS. 2 and 3, when using a probe in which metal nanoparticles are filled at the tip of the CNT, the Raman spectral component of the CNT is caused by tip enhanced near-field Raman scattering (TERS). Is further enhanced by nearly 1000 times, and it becomes possible to obtain a near-field light image having a resolution of nanometer order with improved SN ratio, contrast, and measurement reproducibility.

According to the present embodiment, as described above, the background noise can be greatly reduced by extracting the Raman spectrum component generated at the tip of the CNT probe 1 from the

scattered light

7 and 12 by wavelength separation. This makes it possible to obtain a near-field light image having a resolution of nanometer order with improved SN ratio, contrast, and measurement reproducibility.

[Modification 1 of Excitation Laser Light Irradiation System 50]
A modification of the excitation laser light irradiation system 50 of the present embodiment will be described with reference to FIG. In the present modification, the excitation laser beam 5b is not irradiated from the back surface of the Si ₃ N ₄ cantilever 4 to the ridge line of the Si ₃ N ₄ chip via the gold-coated Si ₃ N ₄ chip 2 but, for example, Si ₃ Irradiate from diagonally forward of the N ₄ cantilever 4. As a result, the near-field light 11 localized at the tip of the chip 2 is excited. The tip of the CNT probe 1 is present in the electric field of the near-field light 11, and when the electric field is concentrated on the tip, φ4 nm (spot size), which is the same as the tip diameter, is provided at the tip of the probe. Second near-field light 6 is generated. As shown in FIGS. 2 to 5, the near-field light 6 interacts with the surface of the sample 20 and the CNT probe 1 itself, and scattered light (propagating light) 7 is generated.

In this scattered light 7, scattered light generated from the surface of the sample 20 by the near-field light 6 and Raman scattered light generated by the interaction between the near-field light and the CNT probe 1 itself are scattered on the surface of the sample 20. This includes scattered light. The intensity of the scattered light 7 changes according to the magnitude relationship between the refractive index n ₀ of the region 21 constituting the sample 20 and the refractive index n ₁ of the region 22, and this is a near field obtained by scanning the CNT probe 1. It becomes the contrast of the optical image. Since the configuration and function of the scanning probe microscope are the same as those shown in FIG.

According to this modification, the background noise can be significantly reduced by extracting the Raman spectrum component generated at the tip of the CNT probe 1 from the

scattered light

7 and 12 by wavelength separation. It is possible to obtain a near-field light image having a resolution of nanometer order with improved ratio, contrast, and measurement reproducibility.

In addition, unlike the first embodiment, the present modification irradiates excitation laser light from the outside, so that Si that does not transmit laser light can be used as the material constituting the cantilever 4 and the gold coat chip 2. . When Si is used, it is only necessary to sharpen the tip of the chip, and it is not necessary to form CNT as a measurement probe on the tip of the chip. Therefore, a measurement probe that easily generates inelastically scattered light can be produced.

A second embodiment of the present invention will be described with reference to FIG. In the first embodiment, scattered light on the surface of the sample 20 of the near-field light 6 at the tip of the CNT probe 1 is detected. In this embodiment, the sample 20 of the near-field light 6 at the tip of the CNT probe 1 is detected. Of the scattered light on the surface, the scattered light component 7 transmitted through the sample 20 is detected. In the scattered light detection system 110, the two

scattered lights

7 and 12 pass through the transparent sample holder 26 and become parallel light by the condenser lens 41. Then, the parallel light passes through the notch filter 46 and the band pass filter 47, so that the Raman spectrum component 43 is selected. The light of the selected Raman spectral component 43 is condensed by the imaging lens 42 at one point on the light receiving surface 45 of the detector 44 such as a photomultiplier tube or a photodiode, and subjected to photoelectric conversion.

Modification 1 of the excitation laser beam irradiation system 50 can also be incorporated in this embodiment. The XY piezoelectric element stage 31 that places the sample holder 26 and scans the sample 20 in the XY direction has a structure in which a hole is opened in the center in order to transmit the transmitted scattered light. The configurations and functions of the other excitation laser beam irradiation system 50, optical lever detection system 100, and signal processing / control system 120 are the same as those in the first embodiment, and thus description thereof is omitted.

According to the present embodiment, as in the first embodiment, the Raman spectrum component generated at the tip of the CNT probe 1 is extracted from the

scattered light

7 and 12 by wavelength separation, thereby greatly reducing the background noise. Thus, it is possible to obtain a near-field light image having a nanometer-order resolution with improved SN ratio, contrast, and measurement reproducibility.

Further, according to the present embodiment, since the scattered light is not blocked by the cantilever 4, the XY piezoelectric element stage 31, and the piezoelectric element actuator 34, the detection solid angle can be increased, and imaging can be performed with higher contrast than in the first embodiment. The SN ratio and measurement reproducibility of the optical image can be further improved.

A third embodiment of the present invention will be described with reference to FIG. In the first and second embodiments, the excitation laser light irradiation system 50 irradiates the CNT probe 1 with

excitation laser light

5a and 5b having a constant wavelength, and the scattered light detection system 110 provides two scattered light 7 And 12 are transmitted through the notch filter 46 and the band pass filter 47 to extract the Raman spectrum component 43, and then received by the detector 44.

In the present embodiment, in order to generate inelastically scattered light of a measurement probe optimum for measuring a sample surface with high sensitivity and high accuracy, excitation laser light 5c having an arbitrary wavelength is generated using a wavelength variable solid-state laser as a light source. The excitation laser beam irradiation system 51 that emits light is used, and the notch filter 46 can be replaced with a notch filter having a different light blocking wavelength region according to the excitation wavelength. Further, in the scattered light detection system 110, the two

scattered lights

7 and 12 are guided not to the band pass filter but to the spectroscope 48 so that inelastic scattered light to be detected can be selected from a plurality of scattered lights. Thereby, it becomes the structure which can select a Raman spectrum component flexibly according to an excitation wavelength.

Also, the control unit 81 of the signal processing / control system 120 executes wavelength control of the wavelength tunable laser and control of the Raman spectrum component extracted by the spectroscope 48. For example, it is possible to monitor the intensity of a specific Raman spectral component while changing the excitation wavelength and search for an excitation wavelength at which the resonance Raman effect occurs. Other configurations and functions are the same as those of the first embodiment, and thus description thereof is omitted. By observing the surface of the sample 20 using an excitation wavelength that causes a resonance Raman effect, it is possible to perform measurement with higher sensitivity while reducing background noise.

In the present embodiment, the spectroscopic optical system having the spectroscope 48 can acquire the Raman spectrum of the sample 20 itself excited by the Raman spectrum component of the CNT probe 1, and the surface of the sample 20 can be nano-sized. It becomes possible to perform Raman spectroscopic imaging with meter resolution. Modification 1 of the excitation laser beam irradiation system 50 can also be incorporated in this embodiment.

According to the present embodiment, the background noise can be greatly reduced by extracting the Raman spectral component generated at the tip of the CNT probe 1 from the

scattered light

7 and 12 by wavelength separation. It is possible to obtain a near-field light image having a resolution of nanometer order with improved ratio, contrast, and measurement reproducibility. In addition, it is possible to easily search for an excitation wavelength at which the resonance Raman effect occurs. Therefore, the intensity of the Raman spectrum component used as the probe light can be increased by using excitation light having a wavelength that causes the resonance Raman effect in the measurement probe, and the background noise can be significantly reduced relatively. Become. As a result, it is possible to obtain a near-field light image with a nanometer-order resolution with further improved SN ratio, contrast, and measurement reproducibility.

In all the embodiments described above, the

excitation laser beams

5a, 5b, and 5c are all monochromatic light. However, the present invention is not limited to this, and the excitation wavelengths for three wavelengths of red, green, and blue are used. It is also possible to perform color near-field imaging by simultaneously acquiring three Raman spectral components corresponding to each wavelength by combining laser light and a spectroscope. Furthermore, when near infrared light is used for the excitation laser light, the cantilever and the tip can be changed to Si. Further, the other configurations are not limited to the configurations of all the above-described embodiments, and it is needless to say that the configurations can be appropriately changed as long as the configurations exhibit the effects of the present invention.

1 ... CNT probe 2 ... gold coated _Si 3 _{N 4} tip 3 ... gold thin film 4 ... _Si 3 _{N 4}

cantilevers

5a, 5b, 5c ... pumping

laser light

6,11 ...・ Near-

field light

7, 12 ... Scattered light (propagating light)
8 ... surface plasmon 10 ... gold nanoparticles 15 ... Si probe 20 ...

sample

25, 26 ... sample holder 30 ... XY piezoelectric element stage 33 ... Z piezoelectric element stage 34 ... Piezoelectric actuator 41 ... Condensing lens 42 ... Imaging lens 43 ... Raman spectral component 44 ... Detector 48 ...

Spectrometers

50 and 51 ... Excitation laser light irradiation System 60: Oscillator 70: Lock-in

amplifier

80, 81 ... Control unit 90 ... Display 100 ... Optical lever detection system 110 ... Scattered light detection system 120 ... Signal processing / control system

Claims

A drive unit that scans the measurement probe relative to the sample;
A scattered light detection system that selects and detects inelastic scattered light among scattered light generated between the measurement probe and the sample by irradiation of excitation light;
A scanning probe microscope.
The scanning probe microscope according to claim 1, wherein the scattered light detection system includes a filter that selectively allows the inelastic scattered light to pass through.
The scanning probe according to claim 1, further comprising a laser beam irradiation system that irradiates the back surface of the cantilever provided with the measurement probe with the excitation light and generates inelastic scattered light on the measurement probe. microscope.
The scanning probe microscope according to claim 1, further comprising a laser beam irradiation system that irradiates the measurement probe with the excitation light and generates inelastic scattered light on the measurement probe.
The scanning probe microscope according to claim 3 or 4, wherein the measurement probe includes a carbon nanotube.
The scanning probe microscope according to claim 5, wherein the carbon nanotube has metal nanoparticles.
The scanning probe microscope according to claim 3, wherein the measurement probe is made of Si.
3. The scanning probe microscope according to claim 1, wherein the scattered light detection system selects inelastic scattered light that has passed through the sample.
The scanning probe microscope according to claim 1, wherein the scattered light detection system includes a spectroscopic optical system that splits the scattered light.
Scan the measuring probe relative to the sample,
Irradiate the measurement probe with excitation light,
A sample observation method for selecting and detecting inelastic scattered light among scattered light generated between the measurement probe and the sample by irradiation of the excitation light.
The sample observation method according to claim 1, wherein the selection of the inelastic scattered light is performed by a filter.
The sample observation method according to claim 10, wherein the excitation light is applied to a back surface of a chip having the measurement probe, and the inelastic scattered light is generated on the measurement probe.
The sample observation method according to claim 10, wherein the excitation light is applied to the measurement probe, and the inelastic scattered light is generated on the measurement probe.
The sample observation method according to claim 10, wherein the inelastically scattered light transmitted through the sample is selected.
The scanning probe microscope according to claim 10, wherein the inelastic scattered light is selected by splitting the scattered light.