JP2002022640A - Scanning proximity field optical microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning proximity field optical microscope improved to obtain an AFM image along with an SNOM image. SOLUTION: A scanning optical microscope comprising means for irradiating a specimen with light, a granular probe for scanning the specimen while keeping a constant distance therefrom, and means for detecting the intensity of proximity field light from the specimen is further provided with means for detecting the position of the granular probe by detecting the proximity field light therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scanning near-field optical microscope, and more particularly, to a scanning near-field optical microscope for measuring surface information and optical information of a sample.

[0002]

2. Description of the Related Art A scanning probe microscope (SPM)
This is a device that scans the probe along the sample surface and performs two-dimensional mapping of the interaction while detecting the interaction between the probe and the probe when approaching the sample surface. Representative examples include a microscope (STM), an atomic force microscope (AFM), a magnetic force microscope (MFM), and a scanning near-field optical microscope (hereinafter, SNOM).

In particular, SNOM has been used since the late 1980s as an optical microscope having a resolution exceeding the diffraction limit by detecting an evanescent wave, for observing fluorescence of a biological sample and evaluating materials and elements for photonics ( Research and development are being actively pursued for applications to various characteristics of dielectric optical waveguides, measurement of the emission spectrum of semiconductor quantum dots, and evaluation of various characteristics of semiconductor surface emitting devices.

[0004] Such a SNOM is basically an apparatus 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.

[0005] Betzi, dated December 21, 1993
U.S. Pat. No. 5,272,330 to G et al.
By introducing light into an aperture-type probe (optical fiber) whose tip is thinned, an evanescent field is generated in the vicinity of a small aperture at the tip of the probe, and the evanescent field is brought into contact with the sample. SNOM that performs two-dimensional mapping of transmitted light intensity by detecting the light generated by the contact between the nesting field and the sample with a photodetector arranged below the sample.
Is disclosed.

[0006] Van Hulst et al.
Using the M microcantilever as a SNOM probe, the tip of the probe scatters an evanescent field generated on the sample surface by a dark-field illumination optical system,
It discloses the first successful simultaneous observation of AFM and SNOM (APPI. Phys. Lett. 62 (1)
993) 461-463).

[0007] The SNOM of the type in which an evanescent field localized in the sample structure is scattered by the tip of the probe (scattering probe) having no minute aperture and converted into propagating light and detected by an external optical system has a high resolution. And the improvement of the SN ratio can be expected.

In recent years, SNOM (T. Sugiura) using fine particles trapped by laser as a scattering probe has been proposed.
et. al. Opt. Lett. V01.22,166
3 (1997)).

FIG. 1 shows a principle diagram of SNOM using minute particles laser-trapped as the scattering probe.

In this apparatus, fine particles 1 serving as a scattering probe are relatively scanned on the surface of a sample 2 while being three-dimensionally captured (trapped) by a laser trap at a focal position of an objective lens 3. The sample 2 is fixed to a cover glass 5.

The sample 2 is scanned by a piezo XY scanner 4.

In this state, the fine particles 1 are illuminated by an illuminating laser 7 for observation different from the trapping laser 6, and the scattered light (particles 1) derived from the light derives from the light. Optical signal due to generated optical near-field interaction)
Is collected by the collimator lens 8 via the objective lens 3 and detected by the photomultiplier 10, whereby the optical characteristics of the sample 2 are imaged as a SNOM image.

Since the scattered light from the minute particles 1 is detected, a normal needle-like probe (a support portion (cone portion) up to the tip)
In comparison with the SNOM using a probe having a probe, there is no influence of scattered light from portions other than the tip of the probe.

That is, the particles trapped by the laser are ideal scattering probes.

[0015]

However, with the current SNOM device using laser trapped particles, an uneven image (AFM image) of the sample surface cannot be obtained.

When an optical fiber or a micro cantilever of an AFM is used as a SNOM probe, a detection system for detecting the distance between the probe and the sample or the displacement of the probe is provided, but a laser as shown in FIG. In the SNOM device using the trapped particles, there is no probe particle displacement detection system, and the particles are only pressed against the sample surface during scanning.

When analyzing a SNOM image obtained by observation, it is important to consider whether or not the strength of an optical signal reflects information on the unevenness of the sample surface.

For this purpose, the AFM together with the SNOM image is used.
It is desirable that an image be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an improved scanning near-field optical microscope which improves the above-mentioned disadvantages and obtains an AFM image together with a SNOM image is provided. The purpose is to provide.

[0020]

According to the present invention, in order to solve the above-mentioned problems, (1) means for irradiating an object with light, and a particulate probe for scanning while maintaining a constant distance from the object. A scanning optical microscope having means for detecting the intensity of near-field light from the subject, and detecting the position of the particulate probe by detecting near-field light from the particulate probe. A scanning near-field optical microscope provided with a probe position detecting means is provided.

According to the present invention, in order to solve the above problems, (2) the probe position detecting means irradiates the particulate probe with laser light or particulate probe illumination light for trapping the particulate probe. Then, by detecting the light scattered by the particulate probe,
The scanning near-field optical microscope according to (1), wherein the position of the particulate probe is detected.

According to the present invention, in order to solve the above problems, (3) the probe position detecting means detects the position of the particulate probe by a critical angle method using a triangular prism. A scanning near-field optical microscope according to (1) or (2) is provided.

That is, the present invention relates to an SNOM apparatus for irradiating an illumination laser to probe particles laser-trapped by a trapping laser and observing a sample based on scattered light information from the probe particles derived from the light. The scattered light from the light source is considered as a point light source near the focal point of the objective lens that focuses the trapping laser and the illumination laser. It is characterized by having a displacement detection system capable of measurement.

That is, in order to obtain an SNOM image, the scattered light itself from the probe particles to be detected is also used for detecting the displacement of the probe particles.

According to the present invention, for example, when the probe particle is at the focal position and when the probe particle approaches the objective lens from the focal position by using the objective lens that focuses the trapping laser and the illumination laser. And a triangular prism for detecting that the light emitted from the objective lens changes to a parallel light beam, a divergent light beam, and a convergent light beam when the light beam is displaced away from the focal position.

By using the above means, in the SNOM using the particles trapped by the laser, it is possible to detect the displacement of the probe particles during the SNOM observation. It is possible to obtain.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 2, 3, 4, and 5 are main conceptual diagrams of the SNOM device according to the embodiment of the present invention.

In the embodiment of the present invention, as shown in FIG. 2, a triangular prism 22, a photodetector (A) 23, and a conventional SNOM using fine particles trapped by a laser shown in FIG. Photodetector (B) 24
And a light branching mirror-21.

The scanner for scanning the sample 2 is a piezo XYZ scanner 25 which can be driven in the Z direction during scanning.
And

During the observation, part of the scattered light from the particles 1 trapped near the focal position of the objective lens 3 is detected by the photomultiplier 10 and used as a signal for SNOM, and the rest is transmitted to the triangular prism 22. It is designed to be incident.

FIG. 3 et seq. Show only those parts necessary for the description of the embodiment of the present invention.

Now, as shown in FIG. 3, when the particle 1 is at the focal position of the objective lens 3, the scattered light becomes a parallel light beam after passing through the objective lens 3, and the upper and lower light beams conceptually shown in FIG. Are incident on the triangular prism 22 in parallel.

At this time, the upper and lower light beams are transmitted to the triangular prism 22.
Is set so as to be incident at a critical angle on the slope of.

As a result, the upper and lower light beams are totally reflected, enter the photodetector (A) 23 and the photodetector (B) 24, and are detected as having the same intensity.

When the difference between these outputs is calculated by a signal processing system (not shown), the output is zero.
This indicates that the particle 1 is at the focal position of the objective lens 3.

Next, as shown in FIG. 4, consider a state in which the particle 1 approaches the objective lens 3 from the focal position as a result of scanning the sample 2.

At this time, the light emitted from the objective lens 3 diverges, and when looking at the upper and lower light beams incident on the triangular prism 2,
The upper beam is incident at a critical angle or more and is totally reflected, while the lower beam is incident at an angle smaller than the critical angle and is partially transmitted.

As a result, the photodetector (A) 23
And the output difference of the photodetector (B) 24 becomes negative, which indicates a state in which the particle 1 approaches the objective lens 3 from the focal position.

As shown in FIG. 5, when the particle 1 is displaced away from the focal position, the light emitted from the objective lens 3 is converged, and the upper and lower light beams incident on the triangular prism 2 are shown in FIG. This is the opposite condition.

As a result, the photo detector (A) 23
And the output difference of the photodetector (B) 24 becomes positive, which indicates a state in which the particles 1 are displaced away from the focal position.

As described above, by calculating the output difference between the photodetector (A) 23 and the photodetector (B) 24 by a signal processing system (not shown), the displacement of the particle 1 can be measured simultaneously during SNOM observation. can do.

Normally, it is desirable to standardize the output difference between the photodetector (A) 23 and the photodetector (B) 24 by dividing by the sum of the outputs of the photodetector (A) 23 and the photodetector (B) 24.

When the surface of the sample 2 has large irregularities and the particles 1 exceed the depth of focus of the objective lens 3 during scanning, the displacement signal of the particles 1 is zero, or the displacement signal is a certain amount. The voltage is applied in the Z direction of the piezo XYZ scanner 25 by a control circuit (not shown) so that the displacement can be adjusted.

In the drawings used for the description, the sample 2 is transparent, and the objective lens 3, the cover glass 5, the sample 2, and the particle 1 are arranged from above.
Is applicable even when the sample 2 is opaque.

In this case, the objective lens 3, the particles 1, and the sample 2 are taken from above.

As described above, the SNOM apparatus using the laser trapped particles having the components as described above has an effect that an AFM image of the same part as the SNOM image can be obtained at the same time by mapping the displacement signal of the particles.

When the irregularities on the surface of the sample are large, the voltage applied to the piezo XYZ scanner 25 and the sensitivity of the piezo XYZ scanner 25 are controlled by the control circuit so that the displacement signal of the particles becomes zero or constant. And an AFM image can be obtained by calculating the displacement.

In the present specification described in the above-described embodiment, in addition to claims 1 to 3 described in the claims, the inventions shown as supplementary notes 1 and 2 below will be described. include.

(Supplementary Note 1) The probe position detecting means has a triangular brhythm for refracting scattered light from the particulate probe and a plurality of photodetectors for detecting scattered light refracted by the triangular prism. Detecting the position of the particulate probe by detecting a difference between signals from the plurality of photodetectors.
The near-field optical microscope according to 1.

(Supplementary note 2) The observation of the same part of the subject by near-field light and the detection of the surface shape of the subject are simultaneously performed based on a signal from the probe position detecting means. 3. The near-field optical microscope according to any one of Items 1 to 3 and Appendix 1.

[0052]

As described above, according to the present invention,
A scanning near-field optical microscope improved so that an AFM image can be obtained together with an SNOM image can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the principle of a conventional SNOM as a comparative example shown in comparison with a configuration according to the present invention.

FIG. 2 is a main configuration diagram of an embodiment of the present invention.

FIG. 3 is a diagram for explaining an example of a use mode in the embodiment of the present invention.

FIG. 4 is a diagram for explaining an example of a use mode in the embodiment of the present invention.

FIG. 5 is a diagram for explaining an example of a use mode in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... particle, 2 ... sample, 3 ... objective lens, 4 ... piezo XY scanner, 5 ... cover glass, 6 ... trapping laser, 7 ... illumination laser, 8 ... collimator lens, 9 ... pinhole, 10 ... photomulti Pliers, 11: Optical splitting mirror, 12: Optical splitting mirror, 13: Optical filter, 21: Optical splitting mirror, 22: Triangular prism, 23: Photodetector (A), 24: Photodetector (B), 25: Piezo XYZ scanner.

Claims (3)

[Claims] 1. A scanning device comprising: means for irradiating an object with light; a particulate probe for scanning while maintaining a predetermined distance from the object; and means for detecting the intensity of near-field light from the object. A scanning near-field optical microscope, comprising: a probe-type optical microscope; and a probe position detecting means for detecting a position of the particulate probe by detecting near-field light from the particulate probe. 2. The probe position detecting means irradiates the particulate probe with laser light or particulate probe illumination light that traps the particulate probe, and detects light scattered by the particulate probe. The scanning near-field optical microscope according to claim 1, wherein the position of the particulate probe is detected. 3. The method according to claim 1, wherein the probe position detecting means detects the position of the particulate probe by a critical angle method using a triangular prism.
2. A scanning near-field optical microscope according to item 1.