JP2000298132A - Near-field optical microscope and sample observation method by near-field optical microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning near-field optical microscope capable of detecting a near-field signal with a superior S/N ratio. SOLUTION: In this microscope, a slide glass 2 on which a sample 1 is placed is disposed on a total internal reflection prism 3 through a matching oil 4. The sample 1 is irradiated with a laser beam through the prism 3 to allow occurrence of a near field on a sample surface. A probe supported in a free end of a cantilever is disposed above the sample 1, while an object lens 19 is disposed above the probe. A scattered light detection body tube 222 disposed above the object lens 19 and the object lens 19 constitute a scattered light detection optical system for detecting scattered light generated by invasion of the probe into the near field. A wavelength of a light source 13 for generating the laser light irradiated on the sample 1 is variable, and the light of a wavelength causing plasmon resonance is selected according to the tip of the probe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a near-field light microscope using a scattering probe and a method for observing a sample using a near-field light microscope.

[0002]

2. Description of the Related Art A scanning probe microscope (SPM) scans a probe in an XY direction or an XYZ direction while detecting an interaction between the probe and the sample when the probe is brought close to the sample surface to 1 μm or less. A general term for a device that performs two-dimensional mapping of action, including, for example, a scanning tunneling microscope (STM), an atomic force microscope (AFM), a magnetic force microscope (MFM), and a scanning near-field light microscope (SNOM). I have.

[0003] Among them, SNOM is an optical microscope having a resolution exceeding the diffraction limit by detecting near-field light formed near the sample, particularly since the latter half of the 1980s. (Development of various characteristics of dielectric optical waveguides, measurement of emission spectra of semiconductor quantum dots, evaluation of various characteristics of semiconductor surface emitting devices, etc.) are being actively pursued. SNOM
Is a device for detecting a state of a light field (near field) near a sample by bringing a sharp probe close to the sample while irradiating the sample with light.

[0004] US Patent 5,272, issued December 21, 1993 to Betzig et al.
No. 330 introduces light into a probe whose tip is thinned to generate a localized field of light near a small aperture at the tip of the probe, which is brought into contact with the sample to illuminate a small portion of the sample. Discloses an SNOM that detects transmitted light with a photodetector arranged below a sample and performs two-dimensional mapping of transmitted light intensity.

In this SNOM, a rod-shaped probe is used, such as an optical fiber, a glass rod, or a quartz probe whose tip is thinned. As an improved version of this probe, a rod-shaped probe having a portion other than the tip covered with a metal film is already commercially available. The device using this probe has improved lateral resolution compared to a device using a probe that is not coated with metal.

[0006] Heinzelmann et al.
al.), in "J. Microscopy 177 (1995) p.115", achieved high resolution by making the photodetector movable, examining the scattering angle dependence of the signal, and using a signal at a specific angle. It shows that you can do it.

[0007] On the other hand, the AFM is the most widely used SPM as an apparatus for obtaining information on unevenness of a sample surface. AF
M detects the displacement of the cantilever, which is displaced in accordance with the force acting on the probe when the probe supported on the tip of the cantilever approaches the sample surface, for example, by an optical displacement sensor, and indirectly detects the sample. Obtain surface irregularity information. One of the AFMs is disclosed in, for example, JP-A-62-130302.

The technique of measuring the unevenness of the sample by detecting the interaction force between the sample and the tip of the probe in this AFM is also applied to other SPM devices, and keeps the distance between the sample and the probe constant. This is used as a means for performing so-called regulation.

[0009] NF van Hulst et a
l.) uses a silicon nitride AFM cantilever in “Appl. Phys. Lett. 62 (5) P.461 (1993)”
A new SNOM that detects optical information of a sample while measuring unevenness of the sample by AFM measurement has been proposed. In this device, the sample is placed on a total internal reflection prism and H
The sample is irradiated with the e-Ne laser beam from the total reflection prism side to excite the sample, and an evanescent light field is formed near the sample surface. Next, a probe supported at the tip of the cantilever is inserted into the evanescent light field, and the evanescent light, which is a localized wave, is converted into scattered light, which is a propagating wave. The light propagates through the almost transparent silicon nitride probe and exits behind the cantilever. This light is collected by a lens placed above the cantilever, enters the photomultiplier via a pinhole located at a position conjugate to the tip of the probe with respect to this lens, and is emitted from the photomultiplier. SNO
An M signal is output.

During the detection of the SNOM signal, the displacement of the cantilever is measured by an optical displacement detection sensor in the same manner as in a normal AFM measurement.
The piezoelectric scanner is feedback-controlled so as to keep this displacement at a specified constant value. Therefore, during one scan, the SNOM is determined based on the scan signal and the SNOM signal.
The measurement is performed, and the AFM measurement is performed based on the scanning signal and the feedback control signal.

In an aperture-type SNOM such as Betzig et al., It is desirable that a probe be metal-coated in order to obtain a high lateral resolution of an image.
However, it is not easy to mass-produce a metal-coated probe having an opening at the tip in a large amount and uniformly.
The SNOM, which is expected to have super-resolution, is required to have a resolution exceeding the resolution achievable with a normal optical microscope. To achieve this, the diameter of the opening at the tip of the probe is 0.1 μm.
Or less, and preferably 0.05 μm or less. It is extremely difficult to produce such an opening with good reproducibility.

Also, the amount of light incident on the probe through the aperture decreases in proportion to the square of the aperture radius, so that
If the aperture diameter is reduced for the purpose of increasing the lateral resolution of the SNOM image, there is a trade-off problem that the amount of detected light decreases and the S / N ratio of the detection system deteriorates.

[0013]

Therefore, instead of forming an opening at the tip of the probe, a new SNOM (scattering mode) utilizing the fact that a high-refractive-index dielectric or metal having a subwavelength structure strongly scatters near-field light is used. SNOM) has been proposed.
In this SNOM, an opening is not required at the tip of the probe, so that it is not necessary to face the above-described difficulty in making the opening and the problem of trade-off.

Kawada et al. Disclose a scattering mode SNOM in Japanese Patent Application Laid-Open No. Hei 6-137847. This SNO
M scatters the evanescent light formed on the sample surface with a needle-shaped probe and converts the scattered light into propagating light. The optical information of the sample is obtained based on the detection signal.

Kawata et al., The 42nd Japan Applied Physics Alliance Lecture Meeting (Preprints No. 3, p. 916, March 1995)
In, using a metal probe of STM for the probe, ST
While controlling the distance between the sample and the probe by M, the propagation light generated due to the evanescent light generated on the sample surface being scattered at the tip of the metal probe is observed from the lateral direction of the probe and the sample and STM is performed. It discloses an apparatus capable of performing observation and SNOM observation. The 43rd Japan Applied Physics Alliance Lecture Meeting (Preprints No. 3, p. 887, March 1996)
In this case, not only evanescent light but also multiple scattering between the tip of the metal probe and the sample of propagating light obliquely incident from above the sample is SN.
It reports that OM observation is possible.

Also, Bachelot et al.
Also, in Opt. Lett. 20 (1995) P.1924, a scattering mode SNOM due to light propagating from above without using an aperture probe is reported.

Further, Toda et al., In Japanese Patent Application No. 8-141,752.
Discloses a scattering mode SNOM using a dark field illumination system using a microcantilever for AFM.

In these scattering modes SNOM, scattered light is detected efficiently, that is, SN having a high S / N ratio.
Obtaining an OM signal (near-field signal) is very important for the purpose of obtaining more accurate observation results.

An object of the present invention is to provide a near-field signal with a good S /
An object of the present invention is to provide a scanning near-field light microscope that can detect N.

[0020]

According to one aspect of the present invention, there is provided an incident means for making light incident on a sample surface, and a tip having a size smaller than the wavelength of the light, and the tip is provided with a sample on which the light is incident. A probe disposed at a position close to the surface, a probe for scattering the light at the tip, a light detecting means for detecting scattered light due to the scattering, and relatively scanning the sample and the tip of the probe. A near-field optical microscope comprising scanning means,
A near-field light microscope characterized in that plasmon resonance is generated in the scattering.

According to another aspect of the present invention, there is provided an incidence means for making light incident on a sample surface, and a tip having a size equal to or smaller than the wavelength of the light. A probe disposed at a close position, for scattering the light at the tip, light detecting means for detecting scattered light due to the scattering, and scanning means for relatively scanning the sample and the tip of the probe. A near-field light microscope comprising: a condition including a wavelength of the light, a refractive index of the tip, and a size of the tip is a condition under which plasmon resonance occurs in the scattering. It is a field light microscope.

According to another aspect of the present invention, while relatively scanning a sample and a probe having a tip at a position close to the sample surface, light is incident on the tip, and the light is incident on the tip. This is a method of observing a sample with a near-field optical microscope by detecting scattered light due to the scattering of light, and a method of observing a sample with a near-field optical microscope characterized in that plasmon resonance occurs in the scattering.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A scattering mode near-field optical microscope according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the scattering mode near-field light microscope has a transparent silicon nitride cantilever tip 100, which is arranged above the sample 1.

As shown in FIG. 2, the cantilever tip 100 includes a support portion 103, a cantilever 101 extending from the support portion 103, and a probe 102 having a pyramid-shaped sharp tip provided at the tip of the cantilever 101. Have. The tip diameter of the probe 102 is smaller than the wavelength, and the tip of the probe functions as a scatterer. The tip 102 is made of, or coated with, a high refractive index dielectric or metal. The back surface of the cantilever 101 (the surface opposite to the surface on which the probe 102 is provided) is coated with an aluminum film 104 as a highly reflective film. If the portion of the cantilever 101 near the probe 102 is transparent with respect to incident light or light used for imaging, it is easy to irradiate the probe 102 with incident light, which is preferable.

The tip of the probe 102 only needs to have a radius equal to or less than the wavelength. The length from the tip to the cantilever 101 (ie, the height of the pyramid) and the cantilever 10
The side of the contact surface with 1 (that is, the bottom surface of the pyramid) may be longer than the wavelength. Therefore, the probe provided at the tip of the cantilever 101 is not limited to the pyramid-shaped probe 102 shown in FIG. 2, and may have any shape as long as the tip has a radius equal to or less than the wavelength.

For example, as shown in FIG.
A pyramid-shaped probe base 105 and a scatterer (probe tip) 106 made of a high-refractive-index dielectric or metal and having a size equal to or smaller than the wavelength may be provided at the tip thereof. If the probe base 105 or a part of the cantilever 101 in addition to the probe base 105 is transparent to incident light or light used for imaging, the incident light can easily enter the probe scatterer 106, which is preferable.

Alternatively, as shown in FIG. 4, a probe base 107 having a flat or downwardly convex curved surface on the bottom surface, and a high-refractive-index dielectric or metal-made size smaller than the wavelength disposed on the bottom surface. Scatterer (tip of the probe) 108 may be provided. If the probe base 107 or a part of the cantilever 101 in addition to the probe base 107 is transparent to incident light or light used for imaging, the incident light can easily enter the probe scatterer 108, which is preferable.

In the following description, unless otherwise specified, the cantilever tip 100 will be described using a structure having a probe 102 typically shown in FIG.

As shown in FIG. 1, the cantilever tip 100 is supported above the sample 1 by the tip holding mechanism 35 via the ultrasonic vibrator 795. The cantilever chip 100 is vibrated at a frequency ω1 of the high-frequency power supply 796 by an ultrasonic vibrator serving as light amplitude modulation means and a high-frequency power supply 796 for driving the same.

This device has an optical lever type displacement sensor for detecting the displacement of the free end of the cantilever 101,
This displacement sensor has a semiconductor laser 7 for irradiating the cantilever 101 with light, and a two-segment photodetector 8 for receiving reflected light from the cantilever 101. The laser light emitted from the semiconductor laser 7 is applied to the cantilever 101, reflected by the aluminum film 104 provided on the back surface of the cantilever, and enters the two-part photodetector 8. The displacement of the free end of the cantilever 101 causes a change in the incident position of the reflected light on the two-segmented photodetector 8, and changes the output ratio of the light receiving unit of the two-segmented photodetector 8. Therefore, the displacement of the free end of the cantilever 101 is obtained by examining the difference between the outputs of the light receiving sections of the two-part photodetector 8, and the displacement of the probe 102 is obtained indirectly.

As shown in FIG. 5, the piezoelectric tube scanner 6 is fixed on a base 412, and a sample table 401 is fixed on the upper end of the piezoelectric tube scanner 6. A support 414 is provided at an end of the base 412, and an arm 416 extending horizontally is provided above the support 414. The total internal reflection prism 3 is fixed to the distal end of the arm 416. The internal total reflection prism 3 is arranged in the internal space of the sample table 401, and is exposed from an opening provided at the center of the upper surface of the sample table 401. .

The slide glass 2 on which the sample 1 is placed is
An appropriate amount of the matching oil 4 is dropped on the upper surface of the total internal reflection prism 3 and placed on the sample table 401. As a result, as shown in FIG. 1, the matching oil 4 is interposed between the slide glass 2 and the total internal reflection prism 3, and both are optically coupled.

The structure shown in FIG. 5 is arranged on a coarse movement stage 345 as schematically shown in FIG. The coarse movement stage 345 is driven by a coarse movement stage drive circuit 346 controlled by the computer 11, and moves the structure of FIG. 5 roughly three-dimensionally. As a result, rough positioning between the sample 1 and the probe 102 is performed, and the distance between the sample 1 and the probe 102 is roughly adjusted.

In FIG. 1, a piezoelectric tube scanner 6
Is driven by the control circuit 9 and the scanner drive circuit 10 controlled by the computer 11 to move the sample table 401 three-dimensionally. As a result, the sample 1 on the slide glass 2 placed on the sample table 401 is moved three-dimensionally relative to the probe 102. Thus, the probe 102 is scanned across the surface of the sample 1 and the distance between the tip of the sample 1 and the surface of the probe 102 is finely adjusted. In this specification, the scanning of the probe crossing the sample surface is also referred to as XY scanning, and the adjustment of the distance between the tip of the probe and the sample surface is also referred to as Z control. As described above with reference to FIG. 5, since the total internal reflection prism 3 is supported by the arm 416 independently of the sample table 401, the internal total reflection prism 3 moves the sample table 401 during scanning. It is kept immovable without being affected by.

This apparatus is provided with light generating means for generating light between the probe and the sample. The light generation means has localized light generation means for generating localized light that does not propagate, and propagation light generation means for generating propagation light that generates light to be propagated. Depending on various properties such as pod physical properties,
Either one is selectively operated. Here, the localized light means light that does not propagate in space, for example, evanescent light. Propagating light means light that propagates in space, for example, normal light. Hereinafter, the localized light generating means and the propagated light generating means will be described in detail.

Localized light generating means Here, in particular, the evanescent light generating means includes a laser light source 13, a filter 14, a lens 15, two mirrors 16 and 17,
It has an internal total reflection prism 3. The mirror 17 is supported by a moving / rotating mechanism (not shown) so as to be able to take two postures (positions and directions) shown by solid lines and imaginary lines in FIG. 5, and is arranged here in a posture shown by solid lines. You.

The laser light emitted from the laser light source 13 is converted into a parallel beam by a lens 15 after passing through a filter 14. The parallel laser beam is reflected by the mirror 16 and the mirror 17 in order, and then is totally reflected by the internal total reflection prism 3 on the upper surface thereof (that is, at the interface between the slide glass 2 and the sample 1 or the interface between the sample 1 and the atmosphere). .
As a result, evanescent light is generated near the surface of the sample 1. If necessary, a lens for converging a parallel laser beam may be inserted between the mirror 17 and the total internal reflection prism 3. Also, on the optical path of the parallel laser beam,
The half-wave plate 706 may be rotatably arranged. The rotation of the half-wave plate 706 changes the polarization direction of the parallel laser beam.

In addition, the propagation light generating means in FIG.
It has a laser light source 13, a filter 14, a lens 15, and two mirrors 16 and 17. As described above, the mirror 17 is supported by a moving and rotating mechanism (not shown) so as to be able to take two postures (positions and directions) shown by solid lines and imaginary lines in FIG. It is arranged in the posture shown.

The laser light emitted from the laser light source 13 passes through a filter 14 and is converted into a parallel beam by a lens 15. The parallel laser beam is reflected by the mirror 16 and the mirror 17 in order, and is applied to the sample 1 and the vicinity of the probe 102 from diagonally above, as shown in FIG. Propagation light generating means is disclosed in Japanese Patent Application No. Hei.
An optical system using a dark field illumination system as disclosed in US Pat.

As shown in FIG. 1, an objective lens 19 is arranged above the total internal reflection prism 3 with the sample 1 and the probe 102 interposed therebetween. A scattered light detection lens barrel 222 is disposed above the objective lens 19, and the scattered light detection lens barrel 222 forms a scattered light detection optical system in cooperation with the objective lens 19. The scattered light detection optical system detects scattered light generated when the probe enters evanescent light, which is localized light.

The scattered light detection lens barrel 222 includes a lens group 20,
It has a pinhole 21 and a photomultiplier tube 22. The pinhole 21 is disposed at a position optically conjugate with the tip of the probe 102 with respect to the objective lens 19 and the lens group 20, and the scattered light detection optical system is a confocal optical system. Therefore, most of the light incident on the photomultiplier tube 22 is scattered light generated near the tip of the probe 102.
As described above, since the scattered light detection optical system is a confocal optical system, the scattered light generated near the tip of the probe 102 is efficiently detected. The photomultiplier tube 22 is connected to the photomultiplier tube high-voltage power supply 23 and outputs an electric signal corresponding to the light intensity of the received scattered light. The output signal from the photomultiplier tube 22 is amplified by the amplifier 24 and taken into the computer 11 as a SNOM signal (near-field signal).

The scattered light detection optical system includes a scattered light detection lens barrel 22.
The same effect can be obtained even if the end face is arranged at the pinhole position instead of having the pinhole 21 in 2 and an optical fiber for guiding the light incident from the end face to the photomultiplier tube 22 is provided. . In this configuration, the scattered light is transmitted to the photomultiplier tube 22 via the optical fiber, so that the photomultiplier tube 22 does not need to be disposed in the scattered light detection It may be installed at any position outside 222.

In FIG. 1, the cantilever tip 100 is
The projection image of the longitudinal axis of the cantilever 101 on the prism upper surface is arranged in parallel with the projected image of the incident light on the prism 3 on the prism upper surface. But,
The cantilever tip 100 may be arranged in any direction as long as the Mie scattering generated when the probe 102 enters the evanescent light and the scattered light generated strongly in the traveling direction of the parallel laser beam can be detected. Good. In particular, if the two projected images are arranged in an orthogonal positional relationship, strongly generated scattered light can be detected efficiently and a high S / S
N can detect scattered light.

This device has a microscope eyepiece tube 28 and a microscope illumination lens tube 25, both of which are optically coupled to the objective lens 19 by a half mirror prism 30 arranged above the objective lens 19. Yes, microscope eyepiece tube 2
Numeral 8 cooperates with the objective lens 19 to form an optical microscope, and a microscope illumination lens barrel 25 cooperates with the objective lens 19 to form an illumination optical system. The optical microscope is used not only for various optical observations of the sample 1 but also for specifying an observation position of the sample 1, positioning the probe 102 at the observation position, and irradiating the cantilever 101 with laser light from the displacement sensor. Used for confirmation. In addition, if the observation place can be specified and the irradiation position of the laser beam for the displacement sensor can be confirmed, the stereo microscope, loupe,
Other means such as an electron microscope may be used.

The microscope eyepiece tube 28 is provided with a CCD camera 32 for acquiring an image.
The image acquired by the camera 32 is sent to the CCD camera control unit 33 and displayed on the monitor television 34. The microscope illumination lens barrel 25 is connected to an illumination light source 27 via an optical fiber 26.

The illumination light emitted from the illumination light source 27 is applied to the sample 1 via the optical fiber 26, the microscope illumination lens barrel 25, the lens 31, the half mirror prism 30, and the objective lens 19. The light from the sample 1 is
9. The light enters the eyepiece microscope lens barrel 28 via the half mirror prism 30, the lens 31, the half mirror prism 370, and the mirror prism 371, and is imaged on the light receiving surface of the CCD camera 32. The image acquired by the CCD camera 32 is displayed on a monitor television 34.

In this apparatus, the AFM is simultaneously performed with the SNOM measurement.
A measurement is made. In other words, SNOM during one scan
Information acquisition and AFM information acquisition are performed. AFM measurement has various modes depending on the manner of Z control between the tip of the probe and the sample surface. For example, there are a dynamic mode in which a micro vibration is applied to the cantilever so that the probe vibrates in a direction perpendicular to the sample surface, and a contact mode in which the probe is brought into contact with the sample by supporting the cantilever in a static posture. .

In the dynamic mode, the ultrasonic vibrator 7
95, the cantilever tip 100 is vibrated so that the probe 102 provided at the tip of the cantilever 101 vibrates at a constant amplitude in a direction substantially perpendicular to the surface of the sample 1. When the probe 102 is sufficiently brought close to the surface of the sample 1 (that is, to a distance where an atomic force acts), the vibration amplitude of the probe 102 is attenuated. This attenuated probe 10
The probe 102 is subjected to XY scanning while performing Z control (that is, controlling the distance between the probe and the sample) so as to keep the vibration amplitude of No. 2 constant.

On the other hand, in the contact mode, the probe 102
Is sufficiently brought close to (or brought into contact with) the surface of the sample 1 (that is, to the distance where the atomic force acts). At this time, the cantilever 101 is elastically deformed by the attraction or repulsion generated between the sample and the probe, and the probe 102 is displaced in the Z direction. In order to keep the displacement of the probe 102 constant, Z
The probe 102 is scanned in XY while controlling (that is, controlling the distance between the probe and the sample).

While the probe 102 is scanned across the surface of the sample, Z control between the tip of the probe and the surface of the sample is performed.
This Z control is performed by the control circuit 9 according to the signal of the displacement sensor.
The control signal is generated by controlling the piezoelectric tube scanner 6 by the scanner drive circuit 10 based on the control signal. During scanning, the control signal generated from the control circuit 9 for Z control is AFM.
The information is taken into the computer 11 as information, and processed together with the XY scanning signal generated therein. As a result, an AFM image expressing irregularities on the sample surface is formed. During scanning, the output signal from the photomultiplier tube 22 is converted into SNOM information (near field information) by the computer 11.
And processed together with the XY scanning signal generated therein. As a result, an SNOM image expressing optical information on the sample surface is formed. AFM image and SNOM
The images are displayed together on the monitor 12.

In the dynamic mode, the amplitude of the scattered light intensity can be imaged by passing the received scattered light intensity signal through a lock-in amplifier synchronized with the vibration of the cantilever. In addition, as shown in FIG. 7, it is also possible to obtain an angle-dependent emphasized image by detecting signals of a plurality of angle components, performing arithmetic processing by a computer, and imaging the result.

As described above, the light incident on the sample surface by the light generating means is scattered by the probe 102. Precisely, the tip of the probe 102 in the cantilever tip shown in FIG. 2 and the probe base 105 or 10 in the cantilever tip shown in FIG.
The light is scattered by the scatterer 106 or 108 provided at the end of 7. In the following description, the tip of the probe 102 and the scatterers 106 and 108 that actually function as scatterers will be simply referred to as scatterers. This scattering can be substantially regarded as Mie scattering, and the intensity efficiency greatly depends on the size and refractive index of the scatterer and the wavelength of the incident light.

This will be described using a scatterer of gold particles as an example. Assuming now that the diameter of the gold particle is infinitesimal, it is known that the wavelength dependence of the scattered light intensity becomes as shown in FIG. 8 under the incident light having a constant intensity. The scattered light intensity has a peak because plasmon resonance occurs. As can be seen from this graph, the scattering efficiency of gold particles having an infinitesimal diameter is maximized when the wavelength of the incident light is about 550 nm.

The wavelength of the incident light giving this peak, that is, the plasmon resonance wavelength changes according to the change in the size of the gold particles. 9 to 14 each show a diameter of 2
00nm, 160nm, 100nm, 80nm, 40n
The wavelength dependence of the scattered light intensity due to m, 10 nm gold particles is shown. As can be seen from these graphs, the peak position of the plasmon resonance shifts to the longer wavelength side as the diameter of the gold particle increases. Similar results have been obtained in experiments using colloidal gold particles.

Further, even if the refractive index of the scatterer changes, the plasmon resonance wavelength changes. 15 to 20 show that the diameters are 200 nm, 160 nm, 100 nm, and 80 nm, respectively.
The wavelength dependence of the scattered light intensity due to silver particles of nm, 40 nm, and 10 nm is shown. As can be seen by comparing the graphs of FIGS. 15 to 20 and the graphs of FIGS. 9 to 14,
The wavelength dependence of the scattered light intensity in the scattering by silver particles is
The plasmon resonance peak is located on the short wavelength side as compared with the wavelength dependence of the scattered light intensity in the scattering by the gold particles having the same diameter.

Although the above description has been made using metal fine particles, plasmon resonance occurs even if the scatterer can be handled by Mie scattering, even if it has a shape other than fine particles. For example, the scattering of the incident light by the scatterers 102, 106, and 108 described above can be approximately handled by Mie scattering. Plasmon resonance occurs.

In the present invention, the scatterers 102, 106, 10
In this case, plasmon resonance is generated at the time of scattering by the light emitting device 8, thereby improving the scattering efficiency and detecting the SNOM signal, that is, the near-field signal with high S / N.

Hereinafter, several specific methods for generating plasmon resonance during scattering by the scatterers 102, 106, and 108 will be described.

<First Method> In the first method, plasmon resonance is generated according to the scatterers 102, 106 and 108 by using a variable wavelength light source as the laser light source 13 in the above-mentioned light generating means. Second, light of a wavelength is selected. Examples of such a variable wavelength light source include a variable wavelength dye laser, a titanium sapphire laser, and a semiconductor laser.

In this method, the scattering efficiency is maximized by using light having a wavelength at which plasmon resonance occurs.
As a result, a near-field signal is detected with the best S / N achieved by improving the signal strength.

<Second Technique> A second technique is to select the sizes of the scatterers 102, 106, and 108 so that plasmon resonance is generated according to the wavelength of the laser light source 13 of the light generating means. is there. In this case, the wavelength of the laser light source 13 of the light generating means does not need to be variable, and therefore, a single-line oscillation Ar laser may be used as the laser light source 13. Alternatively, a multi-line oscillation Ar laser may be used as the laser light source 13, and a single wavelength may be selected by a frequency selection line filter. In this configuration, there are several wavelengths of the oscillation line (for example, 514.5 nm, 488 nm,
Since there are many weak oscillation lines in addition to the main oscillation line of 459 nm), the size of the plasmon-resonant scatterer increases by the wavelength.

In this method, the scattering efficiency is maximized by selecting the size of the scatterer that generates plasmon resonance according to the wavelength. As a result, a near-field signal is detected with the best S / N achieved by improving the signal strength.

<Third Method> A third method is to select the refractive indices of the scatterers 102, 106 and 108 according to the wavelength of the laser light source 13 of the light generating means so that plasmon resonance is generated. is there. In this case, the wavelength of the laser light source 13 of the light generating means does not need to be variable, and therefore, a single-line oscillation Ar laser may be used as the laser light source 13. Alternatively, a multi-line oscillation Ar laser may be used as the laser light source 13, and a single wavelength may be selected by a frequency selection line filter. In this configuration, there are several wavelengths of the oscillation line (for example, 514.5 nm, 488 nm,
In addition to the main oscillation line of 459 nm, there are many weak oscillation lines), so that the refractive index that the plasmon-resonant scatterer can take becomes wider by the wavelength.

In the present method, the scattering efficiency is maximized by selecting the refractive index of the scatterer that generates plasmon resonance according to the wavelength. As a result, a near-field signal is detected with the best S / N achieved by improving the signal strength.

<Fourth Method> In a fourth method, a wavelength required for sample measurement is selected by using a wavelength-variable dye laser, a titanium sapphire laser, a semiconductor laser, or the like as the laser light source 13 in the above-described light generating means. Along with
The size or refractive index of the scatterers 102, 106 and 108 is selected so that plasmon resonance is generated according to the selected wavelength.

In this method, the wavelength required for the measurement of the sample is selected, and the scattering efficiency is maximized by selecting the size or the refractive index of the scatterer so that plasmon resonance is generated even at the selected wavelength. Is done. As a result, a near-field signal is detected with the best S / N achieved by improving the signal intensity while using light having a wavelength suitable for sample measurement.

<Fifth Method> In the fifth method, the wavelength required for sample measurement is selected by using a wavelength-variable dye laser, titanium sapphire laser, semiconductor laser, or the like as the laser light source 13 in the above-described light generating means. Along with
Scatterers 102, 106, 1 according to the resolution required for measurement
08, and the refractive indices of the scatterers 102, 106, and 108 are selected according to the selected wavelength and the scatterer tip diameter so that plasmon resonance is generated.

In this method, the wavelength required for the measurement of the sample is selected, the tip diameter of the scatterer is selected according to the resolution required for the measurement, and plasmon resonance occurs at the selected wavelength and the tip diameter of the scatterer. Thus, by choosing the refractive index of the scatterer, the scattering efficiency is maximized. As a result, while using light having a wavelength suitable for sample measurement, the best S achieved by improving the signal intensity is achieved by the resolution required for sample measurement.
/ N detects a near-field signal.

The present invention is not limited to the above-described embodiment, but includes all embodiments carried out without departing from the gist thereof.

The scanning near-field light microscope according to the present invention can be described as follows.

(1) an incident means for incident light on the sample surface;
A probe having a tip having a size equal to or smaller than the wavelength, the tip being set close to the sample, and scattering the incident light at the tip;
Light detection means for detecting scattered light, displacement detection means for detecting displacement of the probe or the support member of the probe, scanning means for relatively scanning the sample and the probe, and signals from the displacement detection means A scanning near-field light microscope having control means for controlling the distance or the probe pressure between the probe and the sample, signal acquisition means, and imaging means based on the incident light. The scattered light generated at the tip of the needle has a wavelength that causes plasmon resonance.

(2) an inputting means for inputting light to the sample surface;
A probe having a tip having a size equal to or smaller than the wavelength, the tip being set close to the sample, and scattering the incident light at the tip;
Light detection means for detecting scattered light, displacement detection means for detecting displacement of the probe or the support member of the probe, scanning means for relatively scanning the sample and the probe, and signals from the displacement detection means A scanning near-field optical microscope having control means for controlling the distance or the probe pressure between the probe and the sample based on the signal, a signal capturing means, and an imaging means, wherein the probe is The scattered light generated by the incident light has a tip diameter such that plasmon resonance occurs.

(3) Incident means for impinging light on the sample surface;
A probe having a tip having a size equal to or smaller than the wavelength, the tip being set close to the sample, and scattering the incident light at the tip;
Light detection means for detecting scattered light, displacement detection means for detecting displacement of the probe or the support member of the probe, scanning means for relatively scanning the sample and the probe, and signals from the displacement detection means A scanning near-field optical microscope having control means for controlling the distance or the probe pressure between the probe and the sample based on the signal, a signal capturing means, and an imaging means, wherein the probe is A scanning near-field optical microscope, wherein the scattered light generated by the incident light has a refractive index such that plasmon resonance occurs.

(4) Incident means for impinging light on the sample surface;
A probe having a tip having a size equal to or smaller than the wavelength, the tip being set close to the sample, and scattering the incident light at the tip;
Light detection means for detecting scattered light, displacement detection means for detecting displacement of the probe or the support member of the probe, scanning means for relatively scanning the sample and the probe, and signals from the displacement detection means A scanning near-field optical microscope having a control means for controlling the distance or the probe pressure between the probe and the sample based on the signal, a signal acquisition means, and an imaging means. It is characterized by having a probe that causes plasmon resonance at a wavelength.

(5) Incident means for impinging light on the sample surface;
A probe having a tip having a size equal to or smaller than the wavelength, the tip being set close to the sample, and scattering the incident light at the tip;
Light detection means for detecting scattered light, displacement detection means for detecting displacement of the probe or the support member of the probe, scanning means for relatively scanning the sample and the probe, and signals from the displacement detection means A scanning near-field optical microscope having a control means for controlling the distance or the probe pressure between the probe and the sample based on the signal, a signal acquisition means, and an imaging means. It has a wavelength and a probe tip diameter, and scattered light undergoes plasmon resonance at the probe tip.

[0077]

According to the present invention, plasmon resonance is generated at the time of scattering by a probe, thereby improving the scattering efficiency, thereby enabling a near-field signal to be detected with good S / N. A field light microscope is provided.

[Brief description of the drawings]

FIG. 1 schematically shows the entire configuration of a scattering mode scanning near-field light microscope according to the present invention.

FIG. 2 is a perspective view of a cantilever tip used in the scanning near-field light microscope of FIG.

FIG. 3 is a perspective view of another cantilever chip applicable to the scanning near-field light microscope of FIG. 1;

FIG. 4 is a perspective view of still another cantilever tip applicable to the scanning near-field light microscope of FIG. 1;

FIG. 5 is a perspective view of a structure around a total internal reflection prism shown in FIG. 1;

FIG. 6 shows a state in which a parallel laser beam is applied to a sample from obliquely above as a propagation light.

FIG. 7 shows a configuration example of a scattered light detection lens barrel used to obtain an angle-dependent emphasized image.

FIG. 8 is a graph showing the wavelength dependence of the scattered light intensity by various virtual metal particles having an infinitesimal diameter.

FIG. 9 is a graph showing the wavelength dependence of the intensity of light scattered by gold particles having a diameter of 200 nm.

FIG. 10 is a graph showing the wavelength dependence of the intensity of scattered light by a gold particle having a diameter of 160 nm.

FIG. 11 is a graph showing the wavelength dependence of the intensity of scattered light by a gold particle having a diameter of 100 nm.

FIG. 12 is a graph showing the wavelength dependence of the intensity of light scattered by gold particles having a diameter of 80 nm.

FIG. 13 is a graph showing the wavelength dependence of the intensity of light scattered by gold particles having a diameter of 40 nm.

FIG. 14 is a graph showing the wavelength dependence of the intensity of light scattered by gold particles having a diameter of 10 nm.

FIG. 15 is a graph showing the wavelength dependence of the intensity of light scattered by silver particles having a diameter of 200 nm.

FIG. 16 is a graph showing the wavelength dependence of the intensity of light scattered by silver particles having a diameter of 160 nm.

FIG. 17 is a graph showing the wavelength dependence of the intensity of light scattered by silver particles having a diameter of 100 nm.

FIG. 18 is a graph showing the wavelength dependence of the intensity of light scattered by silver particles having a diameter of 80 nm.

FIG. 19 is a graph showing the wavelength dependence of the intensity of light scattered by silver particles having a diameter of 40 nm.

FIG. 20 is a graph showing the wavelength dependence of the intensity of light scattered by silver particles having a diameter of 10 nm.

[Explanation of symbols]

 3 Total Internal Reflection Prism 6 Piezoelectric Tube Scanner 7 Semiconductor Laser 8 Bipartite Photodetector 11 Computer 13 Laser Light Source 19 Objective Lens 20 Lens Group 21 Pinhole 22 Photomultiplier Tube 102 Probe 222 Scattered Light Detection Barrel

Claims (3)

[Claims] 1. An incident means for incident light on a sample surface,
A tip having a size equal to or smaller than the wavelength of the light, the tip is disposed at a position close to the sample surface on which the light is incident,
In a near-field optical microscope including a probe that scatters the light at the tip, a light detection unit that detects scattered light due to the scattering, and a scanning unit that relatively scans the sample and the tip of the probe. A near-field optical microscope, wherein plasmon resonance is generated in the scattering. 2. An incident means for injecting light onto a sample surface, and a tip having a size equal to or smaller than the wavelength of the light, wherein the tip is disposed at a position close to the sample surface on which the light is incident.
In a near-field optical microscope including a probe that scatters the light at the tip, a light detection unit that detects scattered light due to the scattering, and a scanning unit that relatively scans the sample and the tip of the probe. A near-field optical microscope, wherein conditions including the wavelength of the light, the refractive index of the tip, and the size of the tip are conditions under which plasmon resonance occurs in the scattering. 3. A sample and a probe having a tip at a position close to the surface of the sample are relatively scanned, light is incident on the tip, and scattered light due to scattering of the light at the tip is detected. A method of observing the sample with a near-field light microscope, wherein plasmon resonance occurs in the scattering.