JP3754830B2 - Near-field optical microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microscope apparatus capable of observing shape / optical information of a sample surface with nanometer resolution.
[0002]
[Prior art]
In recent years, with the progress of SPM (scanning probe microscope) technology represented by STM (scanning tunneling microscope) and AFM (atomic force microscope), a probe with a pointed tip is brought closer to a distance of 100 nm or less with respect to a sample. As a result, it became possible to dramatically improve the resolution as a microscope and to observe atoms and molecules.
Regarding light, as a family of SPM, a near-field optical microscope (hereinafter abbreviated as SNOM) that examines the surface state of a sample using evanescent light that oozes out from a minute aperture at the tip of a sharp optical probe [EPO112401, Durig et al. Appl. Phys. vol. 59, p. 3318 (1986)], or photon STM (hereinafter referred to as PSTM), in which light is incident from the back of the sample via a prism under conditions of total reflection, and evanescent light oozing out from the sample surface is detected by the optical probe from the sample surface. [Reddic et al., Phys. Rev. B vol. 39, p. 767 (1989)] was also developed.
By using the SNOM, it is possible to access a very small area of 100 nm or less and detect optical information.
When observing an opaque sample using SNOM, evanescent light oozing from an optical probe having a minute aperture is irradiated from the front surface side of the sample, and reflected and scattered light from the sample is directly transmitted without passing through the optical probe. In many cases, a reflection-type oblique light detection configuration in which a detector detects the light from an oblique direction is employed. This is because when the reflected and scattered light from the sample is again passed through the micro-aperture of the optical probe, the light intensity is extremely reduced.
[0003]
In the SNOM having the reflection type oblique light detection configuration described above, the intensity of the evanescent light that oozes out from the minute aperture decreases exponentially with respect to the distance from the aperture. It is necessary to perform control so as to keep a certain distance while approaching the following distance.
As a distance control method for this,
(1) Shear force that controls the distance so that the optical probe is slightly vibrated in a direction perpendicular to the normal direction of the sample surface, and the decrease in vibration amplitude due to van der Waals force that the tip of the optical probe receives from the sample surface is made constant. method,
(2) When the optical probe and the sample have conductivity, a voltage is applied between them, and the distance control is performed so that the magnitude of the tunnel current flowing between them is constant.
(3) The optical probe is supported by an elastic body that is elastically deformable in the normal direction of the sample surface, and the elastic deformation amount of the elastic body generated by van der Waals force acting between the tip of the optical probe and the sample surface is constant. AFM method for controlling the distance so that
Etc. are often used.
[0004]
[Problems to be solved by the invention]
In the SNOM having the above-described reflective oblique light detection configuration, it is effective to reduce the size of the minute opening at the tip of the optical probe in order to improve the detection spatial resolution. However, in such a SNOM, as the size is reduced, the intensity of the evanescent light that oozes out from the minute aperture is reduced, so that the reflected scattered light intensity is also reduced, the detection signal S / N ratio is reduced, and the SNOM observation image is reduced. Image quality deteriorates.
Therefore, in order to increase the intensity of reflected and scattered light, it is effective to set the distance between the optical probe and the sample to 10 nm or more. There was a problem in that the range was 10 nm or less and it was not suitable for control at a distance (10 to 100 nm) further away.
[0005]
Therefore, in the present invention, the distance between the optical probe and the sample can be set to 10 nm or more, and the reflected signal intensity can be increased to improve the detection signal S / N ratio and the image quality of the observation image. It aims to provide a field optical microscope.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention is characterized in that a near-field optical microscope is configured as follows.
That is, the near-field optical microscope of the present invention is provided with an optical probe having a minute opening at the tip, and is arranged so as to face the sample surface close to the sample surface, and the sample surface and the optical probe are placed in the sample. The evanescent light is generated from the microscopic aperture of the optical probe to the sample surface side by the light incident from the light source, and the intensity of the scattered light of the evanescent light is detected by light. A near-field optical microscope for observing the sample surface detected by
  Distance adjusting means for adjusting the distance between the sample surface and the optical probe;
  Feedback control means for controlling the distance adjusting means so as to make the scattered light intensity constant which decreases when the scattered light is blocked by the probe tip and the sample;
  High-speed modulation means for high-speed modulating the distance between the optical probe and the sample in order to superimpose a modulation component on the scattered light intensity;
  Shape / reflectance information separating means for separating shape information and reflectance information of the sample surface from the magnitude of the modulation component of the scattered light intensity by the high-speed modulation;
  It is characterized by having.
The near-field optical microscope of the present invention is characterized in that the distance adjusting means is a distance adjusting means for controlling the distance between the optical probe and the sample surface within a region of 100 nm or less..
MaIn the near-field optical microscope of the present invention, the light source includes a light source that generates a plurality of lights having different wavelengths, and the light detection unit includes a plurality of light detection units.
  A light wavelength separation means for separating a plurality of scattered lights having different wavelengths of evanescent light by the light source;
  The intensity of the plurality of scattered lights separated by the wavelength separation means is detected independently by the plurality of light detection means, and the color information of the sample surface is obtained based on the intensity of the scattered light detected independently. And color information separating means for separating.
In the near-field optical microscope of the present invention, the light detection means is constituted by a plurality of light detection means,
  A light wavelength separation means for separating light emitted by the scattered light of the evanescent light and the evanescent light exciting the sample surface;
  The scattered light of the evanescent light separated by the light wavelength separation means and the intensity of the emitted light are independently detected by the plurality of light detection means.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
  According to the present invention, the distance adjusting means for adjusting the distance between the sample surface and the optical probe described above, and the scattered light intensity that decreases when the scattered light is blocked by the probe tip and the sample are made constant. When the scattered light intensity of the evanescent light that oozes out from the minute opening at the tip of the optical probe is greater than a predetermined value by the feedback control means that controls the distance adjusting means, the optical probe is brought closer to the sample, and conversely the predetermined value If smaller, the distance between the optical probe and the sample can be set to 10 nm or more by controlling the distance between the optical probe and the sample so as to keep the optical probe away from the sample. The light intensity can be increased, the detection signal S / N ratio is improved, and the image quality of the SNOM observation image is improved.In a near-field optical microscopeThe shape information is configured by superimposing the modulation component on the scattered light intensity by the fast modulation means and separating the shape information and reflectance information of the sample surface from the size of the modulation component by the shape / reflectance information separation means. And the reflectance information can be obtained.
Further, in the present invention, the intensities of the plurality of scattered lights having different wavelengths of the evanescent light separated by the wavelength separation means are detected independently by the plurality of light detection means, and detected independently by the color information separation means. The color information on the surface of the sample is separated based on the intensity of the scattered light, and an observation image with the color information separated can be obtained.
In the present invention, the scattered light of the evanescent light is separated from the intensity of light emitted by exciting the sample surface with the light wavelength separating means, and the light intensity is detected independently by the plurality of light detecting means. In this way, it is possible to obtain an observation image of a weak light emitting portion.
[0008]
【Example】
  The following are examples of the present invention.And Reference Example 1Will be described.
[Reference example 1]
  FIG. 1 shows a near-field optical microscope of the present invention.Reference example 1It is drawing which shows the apparatus structure of this. In FIG. 1, an optical probe 101 having a minute opening with a size of 100 nm or less at the tip is brought close to a distance of 100 nm or less with respect to the surface of the sample 102. A piezoelectric element A 115 is attached to the optical probe 101 so that the distance of the optical probe 101 with respect to the sample 102 can be controlled.
An optical fiber 104 is connected to the other end of the optical probe 101 via an optical adapter 103, and laser light emitted from the laser A 105 is introduced into the optical fiber 104 through the lens A 106.
[0009]
The scattered light of the evanescent light that oozes out from the minute opening at the tip of the optical probe 101 is collected using the lens D107 and detected by the photodetector A110 through the interference filter A109 via the mirror 108.
FIG. 2 shows details of how the evanescent light that oozes out from the minute opening at the tip of the optical probe 101 is scattered. In FIG. 2, 201 is an optical probe, 202 is a metal coating film having a thickness of about 100 nm for shielding incident laser light 208, and 203 is a metal coating film 202 that does not exist only at the tip of the optical probe 201, or A microscopic aperture provided by reducing the thickness to 30 nm or less, 204 is a sample, 205 is evanescent light, 206 is scattered light of evanescent light, and 207 is a photodetector.
[0010]
Here, the optical probe 101 is manufactured as follows. For example, one end of the optical fiber is sharpened by stretching and cutting in a locally heated state or by performing chemical etching using a hydrofluoric acid buffer solution. While rotating this, a metal coating for light shielding may be performed from the lateral direction to provide a thin opening at the tip, or a fine opening may be provided so that the coating is not performed, or after performing the metal coating 202 on the whole, After coating with acrylic resin or the like so that the film thickness only becomes thin at the tip using surface tension, the fine openings may be provided by etching the metal coating.
When the size of the minute aperture 203 is 100 nm or less and smaller than the light wavelength, the incident laser beam 208 hardly passes directly through the minute aperture 203, but as the evanescent light 205 near the distance of about 300 nm or less from the minute aperture 203. It oozes out. Since the intensity of the evanescent light 205 has a property of exponentially decaying with respect to the distance from the minute aperture 203, it can be regarded as a probe of a very narrow light localized only in the vicinity of the minute aperture 203.
[0011]
As shown in FIG. 2, the evanescent light 205 that has oozed out of the minute aperture 203 is scattered at the tip of the optical probe 201 and converted into propagating light, and directly scattered light 209 toward the photodetector 207 and once on the surface of the sample 204. The light is reflected and scattered, converted into propagating light, and detected by the photodetector 207 as scattered light 206 synthesized with the reflected scattered light 210 toward the photodetector 207.
Since the intensity and spectrum of the reflected scattered light 210 include a local uneven structure on the surface of the sample 204 and properties relating to reflection and absorption, the shape information of a minute region below the wavelength of the surface of the sample 204 is detected by detecting this. And optical information can be obtained.
Directly scattered light 209 and reflected scattered light 210 are combined and incident on the photodetector 207.
[0012]
FIG. 3 shows how the magnitude of the detection light intensity signal of the photodetector 207 changes when the distance of the optical probe 201 to the sample 204 is changed.
When the distance z is large, the detected light intensity signal has a substantially constant value as indicated by point A → B in FIG. 3, and is a signal in which periodic fluctuations due to interference between direct scattered light and reflected scattered light are superimposed. . The period of this interference differs depending on the light wavelength used and the device arrangement, that is, the angle of the light detection direction with respect to the sample surface (θ in FIG. 2) and the aperture diameter of the lens D for focusing (107 in FIG. 1). However, it is generally on the order of the wavelength of the laser beam used.
[0013]
In the near-field region where z <zn (zn to 300 nm) approaches the distance between the optical probe and the sample, the sample surface enters the region where the evanescent light intensity oozes out from the minute aperture, and the reflected scattered light intensity from the sample surface increases. The detected light intensity signal once increases as indicated by points B → C → D and takes a maximum value (D point).
When the distance further approaches 100 nm or less (z <100 nm), the scattered light is blocked by the optical probe and the sample as viewed from the photodetector, and the detected light intensity rapidly increases as indicated by points D → E → F → G. To decrease. At the point F → G, as shown in FIG. 4, the distance between the optical probe 401 and the sample 402 approaches 0 (contact point: point G), and the microscopic aperture 403 is almost blocked by the surface of the sample 401, and most of the scattered light. Is in a blocked state.
[0014]
In the present invention, as indicated by points D → E → F → G in FIG. 3, the detection light intensity decreases when the optical probe approaches the sample surface, and conversely, the detection light intensity increases when the probe moves away. Further, the distance control between the optical probe and the sample surface is performed within a region where the distance is 100 nm or less. Details of this distance control will be described with reference to FIG.
The photocurrent signal A of the photodetector A110 that has detected the evanescent light scattered light is converted into the light intensity signal A by the photocurrent voltage converter A111 and input to the error detector 112. In the error detector 112, in order to keep the light intensity signal A constant, a difference from a light intensity signal set value corresponding to a predetermined light intensity is calculated. The result is input to the low-pass filter A113 and the output signal from which the high frequency component is cut is used as a feedback signal, amplified by the amplifier A114, and then applied to the piezo element A115 as a piezo element drive signal.
This feedback signal drives the piezo element A in order to keep the distance between the optical probe and the sample surface constant so that the magnitude of the evanescent light scattered light scattered from the tip of the optical probe and the sample surface is constant. Since it is a signal, it reflects shape information such as a local uneven structure on the sample surface where the tip of the optical probe is located and optical information such as reflection / absorption.
[0015]
Here, when the light intensity signal A is larger than the light intensity signal set value, the polarity of this drive signal drives the piezo element A115 in the direction in which the optical probe 101 is brought closer to the sample 102, and the light intensity signal A is If the optical intensity signal is smaller than the set value, the piezo element A 115 is set to be driven in a direction to move the optical probe 101 away from the sample 102.
By performing the feedback control as described above, the distance between the optical probe 101 and the sample 102 can be kept constant.
Here, when the optical probe 101 is first brought closer to the sample 102 from a distance (A → B in FIG. 3, z> zn), the light intensity signal set value in the error detector 112 is a distance (A → Light intensity smaller than the light intensity corresponding to point C where the light intensity becomes minimum while the distance is reduced from point B (z> zn) to point D (z to 100 nm) (for example, light at point E in FIG. 3) Select a setting value corresponding to (strength). This is because feedback control is performed in the region of z <100 nm.
[0016]
When the light intensity signal set value input to the error detector 112 is changed while the feedback control is performed in the region of z <100 nm by the above procedure, D to E to F to G The magnitude of the light intensity signal can be freely changed between the points, and the distance between the optical probe and the sample can be freely set to a distance (z <100 nm) corresponding to the magnitude of the light intensity signal. Can keep.
First, when the optical probe is moved closer to the sample from a distance (A → B point, z> zn), the light intensity signal setting value is greater than the light intensity corresponding to the C point (for example, the B ′ point). When (light intensity) is selected, when the optical probe is brought closer to the sample, feedback control is performed not at the point (B ′ point) in the region of z <100 nm but at the point (point B) in the region of z> 100 nm. Therefore, the distance between the optical probe and the sample is increased, and the lateral resolution as a near-field optical microscope is lowered, which is not preferable.
[0017]
Now, the feedback signal output from the low-pass filter A 113 is input to the computer 116 while the distance between the optical probe and the sample is controlled by the method described above. A stage driving signal is applied from the computer 116 to the two-dimensional stage 118 to which the sample 102 is attached through the amplifier B 117, and two-dimensional relative scanning of the sample 102 with respect to the optical probe 101 is performed. The computer 116 maps the magnitude of the feedback signal at each position of the optical probe 101 with respect to the sample 102 during two-dimensional scanning, and displays it on the display 119 as a near-field optical microscope image of the sample surface.
[0018]
    [Example1]
  FIG. 5 shows an embodiment of the near-field optical microscope of the present invention.1It is drawing which shows the apparatus structure of this. In FIG. 5, the basic configuration and operation of the apparatus are as follows.Reference example 1Is almost the same.
Example1As a specific configuration, a second piezo element B501 is attached to the optical probe 101 in addition to the first piezo element A115. The modulation signal output from the oscillator 502 is amplified by the amplifier C503, and then applied to the piezo element B501 as a distance modulation signal to modulate the distance between the optical probe 101 and the sample 102 at high speed. By this distance modulation, light intensity modulation having the same frequency as the distance modulation is added to the evanescent light scattered light scattered from the tip of the optical probe 101 and the surface of the sample 102.
The light intensity signal A output from the photocurrent / voltage converter A111 is input to the low-pass filter B504 and the high-pass filter 505. In the low-pass filter B504, the low frequency component from which the high-speed modulation component is removed is input to the error detector 112, and thereafterReference example 1The same distance control between the optical probe 101 and the sample 102 is performed.
Further, the high-pass filter 505 extracts only the above high-speed modulation component, inputs it to the synchronization detector 506, performs synchronization detection using the modulation signal from the oscillator 502 as a reference signal, and outputs the amplitude of the high-speed modulation component. The modulation component amplitude signal and the feedback signal output from the low-pass filter A 113 are input to the shape / reflectance information separator 507, separated into a shape information signal and a reflectance information signal, and the result is input to the computer 116. The computer 116 maps the magnitude of the shape information signal and the reflectance information signal at each position of the optical probe 101 with respect to the sample 102 during two-dimensional scanning, and displays it on the display 119 as a near-field optical microscope image of the sample surface.
[0019]
  The principle of the separation of the shape information signal and the reflectance information signal and the signal waveform in each part of FIG. 5 will be described with reference to FIGS.
Reference example 1FIG. 6A shows the trajectory of the tip of the optical probe when scanning the optical probe 101 with respect to the surface of the sample 102 when the method for controlling the distance between the optical probe and the sample described in the above is used. As shown in the figure, it is assumed that the surface of the sample 102 includes a convex portion 601, a concave portion 602, a high reflectance portion 603, and a low reflectance portion 604.
As shown in FIG.Reference example 1In the distance control method described in the above, the convex portion 601 and the low reflectance portion 604 are controlled in the direction in which the optical probe 101 is separated from the sample 102, and the concave portion 602 and the high reflectance portion 603 are relative to the sample 102. Control is performed in the direction in which the optical probe 101 approaches. For this reason, shape information and reflectance information cannot be separated only by a feedback signal.
Therefore, when the distance control described with reference to FIG. 5 is performed, as shown in FIG. 6B, the optical probe 101 scans the surface of the sample 102 in a state where the distance between the optical probe 101 and the sample 102 is modulated at high speed.
[0020]
The feedback signal waveform is shown in FIG. 6c, and the distance modulation signal is shown in FIG. 6d. At this time, the high-speed modulation component waveform of the light intensity signal A output from the high-pass filter 505 does not change the amplitude of the modulation component in the convex portion and the concave portion as shown in FIG. It increases and the amplitude decreases in the low reflectivity part. This is because, as shown in FIG. 7, the modulation amplitude applied to the detection light intensity signal is different in the portion where the reflectance is different from the modulation of the same amplitude with respect to the distance between the optical probe and the sample surface. For example, the light intensity signal modulation amplitude (C) is smaller in the low reflectance portion than in the light reflectance signal modulation amplitude (A) in the high reflectance portion.
[0021]
Here, FIG. 7 shows the magnitude of the detected light intensity signal with respect to the distance between the optical probe and the sample surface in the portions having different reflectivities.
The distance range on the horizontal axis in FIG. 7 corresponds to the portions G to F to D (z <100 nm) in FIG. 3, and the detected light intensity signal with respect to the distance between the optical probe and the sample surface is almost equal. A portion having a linear characteristic is extracted.
At this time, the output waveform of the synchronous detector 506 is as shown in FIG. 6f, and this represents the reflectance information of the surface. Now, in the shape / reflectance information separator 507, the shape information signal (FIG. 6 g) is obtained by multiplying the feedback signal (FIG. 6 c) by multiplying the output signal (FIG. 6 f) of the synchronization detector 506 by a predetermined coefficient. Is obtained. Here, the magnitude of the predetermined coefficient is obtained by measuring a standard sample whose shape / reflectance information is known in advance.
As described above, by applying high-speed modulation to the distance between the optical probe and the sample surface and separating the modulation component superimposed on the light intensity signal by synchronous detection, the shape information and reflectance information can be obtained from the feedback signal. In the near-field optical microscope image, it was possible to obtain an image in which shape information and reflectance information were separated.
[0022]
    [Reference example 2]
  FIG. 8 shows the near-field optical microscope of the present invention.Reference example 2It is drawing which shows the apparatus structure of this.
In FIG. 8, the basic configuration and operation of the apparatus are as follows.Reference example 1Is almost the same.
Reference example 2As a configuration peculiar to the above, in addition to the laser A105, a laser B801 and a laser C802 are added as lasers for making light incident on the optical probe 101. Here, it is assumed that the lasers A (105), B (801), and C (802) have different optical wavelengths. For example, if a red semiconductor laser with a wavelength of 635 nm is used as the laser A, a solid-state laser pumped with a semiconductor laser with a wavelength of 532 nm is used as the laser B, and a blue semiconductor laser with a wavelength of 410 nm is used as the laser C, spectroscopic measurement in RGB three colors can be performed as described later. Become.
Light emitted from the laser A 105, the laser B 801, and the laser C 802 is incident on the 3 × 1 optical coupler 814 through the lens A 106, the lens B 803, and the lens C 804, respectively. The other end of the optical coupler 814 is connected to the optical probe 101 via the optical adapter 103, and light having a plurality of wavelengths is incident on the optical probe 101.
The evanescent light scattered light scattered from the tip of the optical probe 101 and the surface of the sample 102 is divided into three by beam splitters A805 and B806, and the interference filter A109 having the wavelength of the laser A105, the interference filter B807 having the wavelength of the laser B801, and the laser C802, respectively. Are detected by a photodetector A110, a photodetector B809, and a photodetector C810.
[0023]
  Photocurrent signal A, photocurrent signal B, and photocurrent signal C output from photodetector A110, photodetector B809, and photodetector C810 are respectively photocurrent voltage converter A111, photocurrent voltage converter B811, and light. The current-voltage converter C812 is input and converted into a light intensity signal A, a light intensity signal B, and a light intensity signal C. Among these, the light intensity signal A is input to the error detector 112, and thereafterReference example 1The same distance control between the optical probe 101 and the sample 102 is performed.
The light intensity signal B and the light intensity signal C are input to the color information separator 813, and together with the feedback signal output from the low-pass filter A113, the color information signal A representing the reflectance at the wavelength of the laser A105 and the wavelength of the laser B801. Is separated into a color information signal B representing the reflectance at the wavelength of the laser C 802, and this result is input to the computer 116. The computer 116 maps the magnitudes of the color information signals A, B, and C at each position of the optical probe 101 with respect to the sample 102 during two-dimensional scanning, and displays them on the display 119 as a near-field optical microscope image of the sample surface.
[0024]
  The principle of the separation of each color information signal and the signal waveform in each part of FIG. 8 will be described with reference to FIG.
Reference example 1FIG. 9A shows the trajectory of the tip of the optical probe when the optical probe 101 is scanned with respect to the surface of the sample 102 when the method for controlling the distance between the optical probe and the sample described in the above is used. As shown in the figure, it is assumed that the surface of the sample 102 includes a high reflectivity portion 901, a low reflectivity portion 902, a different color portion A903, and a different color portion B904.
Here, it is assumed that the high reflectance portion 901 and the low reflectance portion 902 are portions having different reflectances at the same ratio with respect to the respective light wavelengths of the lasers A (105), B (801), and C (802). . In addition, the portion A903 having a different color has a low reflectance with respect to the light wavelengths of the laser A and the laser B (the reflectance is normal with respect to the light wavelength of the laser C), and the portion B904 having a different color is the light wavelength of the laser B The reflectance is low with respect to the light wavelength of the laser C, and the reflectance is high with respect to the light wavelength of the laser A (the reflectance is normal for the light wavelength of the laser A).
[0025]
  As shown in FIG.Reference example 1In the distance control method described in the above, when light having the wavelength of laser A is used for distance control, the high reflectivity portion 901 performs control in the direction in which the optical probe 101 approaches the sample 102, and the wavelength of laser A is controlled. Control is performed in the direction in which the optical probe 101 moves away from the sample 102 in the low reflectance portion 902 showing a low reflectance with respect to the light and in the portion A903 having a different color, and in the portion B904 having a different color, control between the two is performed. Done. For this reason, each color information cannot be separated only by the feedback signal.
Therefore, the distance control and signal detection described in FIG. 8 are performed, and the feedback signal waveform at this time is shown in FIG. 9b, the light intensity signal B in FIG. 9c, and the light intensity signal C in FIG. In the color information separator 813, the feedback signal (FIG. 9b) is inverted to obtain the color information signal A (FIG. 9e). Further, by subtracting the feedback signal (FIG. 9b) from the light intensity signal B (FIG. 9c) and the light intensity signal C (FIG. 9d) by multiplying each by a predetermined coefficient, the color information signal B (FIG. 9f), the color information Signal C (FIG. 9g) is obtained. Here, the magnitude of the predetermined coefficient is obtained by measuring a standard sample whose color information is known in advance.
As described above, the evanescent light scattered light intensity is independently detected for a plurality of lights having different wavelengths, and the feedback signal is obtained by performing control so that the light intensity of one wavelength is constant. The color information signals can be separated from the light intensity signals of other wavelengths and the color information in the near-field optical microscope image.
[0026]
    [Reference example 3]
  FIG. 10 shows the near-field optical microscope of the present invention.Reference example 3It is drawing which shows the apparatus structure of this. In FIG. 10, the basic configuration and operation of the apparatus are as follows.Reference example 1Is almost the same.
Reference example 3As a configuration peculiar to the optical probe 101, local emission (fluorescence, phosphorescence, etc.) from a portion where the surface of the sample 102 is locally excited by evanescent light oozing from the tip of the optical probe 101 is evanescent from the tip of the optical probe 101 or the surface of the sample 102. Simultaneously with the scattered light, the light is condensed using the lens D107, divided into two by the beam splitter C1001 via the mirror 108, one is detected by the photodetector A110 through the interference filter A109 having the wavelength of the laser A105, and the other is The light is detected by a photodetector D1003 through a bandpass filter 1002 that matches the emission wavelength.
The photocurrent signal A and the photocurrent signal D output from the photodetector A110 and the photodetector D1003, respectively, are input to the photocurrent voltage converter A111 and the photocurrent voltage converter D1004, and the light intensity signal A and the light intensity signal, respectively. Converted to D (light emission intensity signal). Among these, the light intensity signal A is input to the error detector 112, and thereafterReference example 1The same distance control between the optical probe 101 and the sample 102 is performed.
The light intensity signal D (light emission intensity signal) and the feedback signal output from the low pass filter A 113 are input to the computer 116. The computer 116 maps the magnitude of the feedback signal and the emission intensity signal at each position of the optical probe 101 with respect to the sample 102 during two-dimensional scanning, and displays it on the display 119 as a near-field optical microscope image of the sample surface.
[0027]
  A signal waveform in each part of FIG. 10 will be described with reference to FIG.
Reference example 1FIG. 11A shows the trajectory of the tip of the optical probe when scanning the optical probe 101 with respect to the surface of the sample 102 when the method for controlling the distance between the optical probe and the sample described in the above is used. As shown in the figure, it is assumed that the surface of the sample 102 includes a convex portion 1102 and a light emitting portion 1101.
As shown in FIG.Reference example 1In the distance control method described in the above, when light of the wavelength of laser A is used for distance control, the convex portion 1102 is controlled in a direction in which the optical probe 101 moves away from the sample 102 as shown in the locus of the tip of the optical probe. The
[0028]
A feedback signal waveform when the distance control and signal detection described in FIG. 10 are performed is shown in FIG. 11b, and a light intensity signal D (light emission intensity signal) is shown in FIG. 11c.
As described above, the evanescent light scattered light intensity and the local light emission intensity of the excitation light are independently detected, and the former light intensity is controlled to be constant, so that the former has an uneven portion and emits light. It was possible to stably control the distance between the optical probe and the sample even in a sample in which a portion and a non-light emitting portion were mixed, and a near-field optical microscope image of a weak light emitting portion could be obtained.
[0029]
  As above, the example1Then, the method of separating the shape information and reflectance information of the sample surface,Reference example 2Then, the method of separating the color information of the sample surface,Reference example 3Then, although the method of performing stable distance control with respect to weak light emission by local evanescent light excitation has been shown separately, it is also included in the concept of the present invention to use a combination of these methods.
In addition, the above embodiment1 and Reference Examples 1 to 3In the description, the method for controlling the distance between the optical probe and the sample in the near-field optical microscope and the method for separating a plurality of pieces of information such as the shape information and optical information on the sample surface have been described. The present invention can also be applied to a microfabrication apparatus and an information storage apparatus applying the above.
[0030]
【The invention's effect】
  As described above, according to the present invention, when the scattered light intensity of the evanescent light that oozes out from the minute opening at the tip of the optical probe is larger than the predetermined value by the distance adjusting means and the feedback control means, If the optical probe is brought closer and conversely smaller than the predetermined value, the distance between the optical probe and the sample is set to 10 nm or more by controlling the distance between the optical probe and the sample so that the optical probe is moved away from the sample. This makes it possible to increase the intensity of reflected and scattered light, thereby improving the detection signal S / N ratio and improving the image quality of the SNOM observation image.In a near-field optical microscopeThe shape information is configured by superimposing the modulation component on the scattered light intensity by the fast modulation means and separating the shape information and reflectance information of the sample surface from the size of the modulation component by the shape / reflectance information separation means. And the reflectance information can be obtained.
Further, in the present invention, the intensities of the plurality of scattered lights having different wavelengths of the evanescent light separated by the wavelength separation means are detected independently by the plurality of light detection means, and detected independently by the color information separation means. The color information on the surface of the sample is separated based on the intensity of the scattered light, and an observation image with the color information separated can be obtained.
In the present invention, the scattered light of the evanescent light is separated from the intensity of light emitted by exciting the sample surface with the light wavelength separating means, and the light intensity is detected independently by the plurality of light detecting means. In this way, it is possible to obtain an observation image of a weak light emitting portion.
[Brief description of the drawings]
FIG. 1 shows a near-field optical microscope of the present invention.Reference example 1It is a figure which shows the apparatus structure of.
FIG. 2 is an explanatory diagram of scattering of evanescent light that oozes out from a minute opening at the tip of an optical probe.
FIG. 3 is a characteristic diagram of a detected light intensity signal with respect to a distance between an optical probe and a sample.
FIG. 4 is an explanatory diagram of a state in which the distance between the optical probe and the sample approaches 0, the minute aperture is blocked by the sample surface, and the scattered light is blocked.
FIG. 5 shows an embodiment of the near-field optical microscope of the present invention.1It is a figure which shows the apparatus structure of.
6 is a diagram for explaining the principle of shape / reflectance information separation and signal waveforms in each part of FIG. 5; FIG.
FIG. 7 is a characteristic diagram of a detection light intensity signal with respect to a distance between an optical probe and a sample in a portion having a different reflectance.
FIG. 8 shows the near-field optical microscope of the present invention.Reference example 2It is a figure which shows the apparatus structure of.
9 is a diagram for explaining the principle of color information separation and signal waveforms in each part of FIG. 8;
FIG. 10 shows the near-field optical microscope of the present invention.Reference example 3It is a figure which shows the apparatus structure of.
11 is a diagram for explaining signal waveforms in each part of FIG. 10;
[Explanation of symbols]
          101: Optical probe
          102: Sample
          103: Optical adapter
          104: Optical fiber
          105: Laser A
          106: Lens A
          107: Lens D
          108: Mirror
          109: Interference filter A
          110: Photodetector A
          111: Photocurrent voltage converter A
          112: Error detector
          113: Low-pass filter A
          114: Amplifier A
          115: Piezo element A
          116: Computer
          117: Amplifier B
          118: Two-dimensional stage
          119: Display
          201: Optical probe
          202: Metal coating film
          203: Micro aperture
          204: Sample
          205: Evanescent light
          206: Scattered light of evanescent light
          207: Photodetector
          208: Incident laser light
          209: Direct scattered light
          210: Reflected scattered light
          401: Optical probe
          402: Sample
          403: Micro opening
          501: Piezo element B
          502: Oscillator
          503: Amplifier C
          504: Low-pass filter B
          505: High pass filter
          506: Synchronous detector
          507: Shape / reflectance information separator
          601: convex portion
          602: concave portion
          603: High reflectivity part
          604: Low reflectance portion
          801: Laser B
          802: Laser C
          803: Lens B
          804: Lens C
          805: Beam splitter A
          806: Beam splitter B
          807: Interference filter B
          808: Interference filter C
          809: Photodetector B
          810: Photodetector C
          811: Photocurrent voltage converter B
          812: Photocurrent voltage converter C
          813: Color information separator
          814: Optical coupler
          901: High reflectivity part
          902: Low reflectance portion
          903: A part with different colors
          904: Part B with a different color
          1001: Beam splitter C
          1002: Band pass filter
          1003: Photodetector D
          1004: Photocurrent voltage converter D
          1101: Light emitting part
          1102: Convex part

Claims (4)

An optical probe having a microscopic aperture at the tip is disposed, and the microscopic aperture is disposed so as to be opposed to and close to the sample surface, and the sample surface and the optical probe are relatively two-dimensionally scanned in the in-plane direction of the sample. Then, the evanescent light is generated from the microscopic aperture of the optical probe to the sample surface side by the light incident from the light source, the intensity of the scattered light of the evanescent light is detected by the light detection means, and the sample surface is observed. A near-field optical microscope,
Distance adjusting means for adjusting the distance between the sample surface and the optical probe;
Feedback control means for controlling the distance adjusting means so as to make the scattered light intensity constant which decreases when the scattered light is blocked by the probe tip and the sample;
High-speed modulation means for high-speed modulating the distance between the optical probe and the sample in order to superimpose a modulation component on the scattered light intensity;
Shape / reflectance information separating means for separating shape information and reflectance information of the sample surface from the magnitude of the modulation component of the scattered light intensity by the high-speed modulation;
A near-field optical microscope characterized by comprising: The near-field optical microscope according to claim 1, wherein the distance adjusting unit is a distance adjusting unit that performs distance control between the optical probe and the sample surface within a region of 100 nm or less. The light source is constituted by a light source that generates a plurality of lights having different wavelengths, and the light detection means is constituted by a plurality of light detection means,
A light wavelength separation means for separating a plurality of scattered lights having different wavelengths of evanescent light by the light source;
The plurality of scattered light intensities separated by the wavelength separation means are detected independently by the plurality of light detection means, and the color information of the sample surface is obtained based on the independently detected scattered light intensities. Color information separating means for separating;
The near-field optical microscope according to claim 1, wherein the near-field optical microscope is provided. The light detection means is constituted by a plurality of light detection means,
A light wavelength separation means for separating light emitted by the scattered light of the evanescent light and the evanescent light exciting the sample surface;
3. The proximity according to claim 1, wherein the scattered light of the evanescent light separated by the light wavelength separation means and the intensity of the light emission are detected independently by the plurality of light detection means. Field optical microscope.

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